CA1263796A - Method for converting si-h containing polycarbosilanes to new and useful preceramic polymers and ceramic materials - Google Patents
Method for converting si-h containing polycarbosilanes to new and useful preceramic polymers and ceramic materialsInfo
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Abstract
ABSTRACT
A method of forming preceramic polymers using a polycarbosilane having repeat units of the formula [RSi(H)-(CH2)q] (where R is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, q is an integer 1 or greater), by reacting it with alkali metal silylamides in a weight ratio of polycarbo-silane:silylamide of 10:1. or less is disclosed.
Preferably, the alkali metal silylamide is a poly-meric alkali metal silylamide of the formula [(R1SiHNH)a(R1SiN)b(R1SiHNM)c]m where a + b + c = 1;
R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl-or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and n and m are integers greater than 1. Novel preceramic polymers formed by this method are also disclosed.
A method of forming preceramic polymers using a polycarbosilane having repeat units of the formula [RSi(H)-(CH2)q] (where R is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, q is an integer 1 or greater), by reacting it with alkali metal silylamides in a weight ratio of polycarbo-silane:silylamide of 10:1. or less is disclosed.
Preferably, the alkali metal silylamide is a poly-meric alkali metal silylamide of the formula [(R1SiHNH)a(R1SiN)b(R1SiHNM)c]m where a + b + c = 1;
R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl-or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and n and m are integers greater than 1. Novel preceramic polymers formed by this method are also disclosed.
Description
This application is a division of Applicatisn No.
514,060, filed July 17, lg86.
The present invention relates to a process for preparing silicon-containing preceramic po]ymers useful for making silicon carbide and silicon nitride/silicon carbide ceramics and for their pyrolysis to such ceramic materials.
There is a great deal of interest in preceramic polymer materials, which can be pyrolyzed to yield silicon carbide, silicon nitride and other silicon-based ceramic materials. R.W.
Rlce, Amer Ceram. Soc. ~ull., 62: 889-892 (1983). Applications for such polymers include, among others:
1. formation into complex shapes and subsequent pyrolysis to give a ceramic material of the same shape;
514,060, filed July 17, lg86.
The present invention relates to a process for preparing silicon-containing preceramic po]ymers useful for making silicon carbide and silicon nitride/silicon carbide ceramics and for their pyrolysis to such ceramic materials.
There is a great deal of interest in preceramic polymer materials, which can be pyrolyzed to yield silicon carbide, silicon nitride and other silicon-based ceramic materials. R.W.
Rlce, Amer Ceram. Soc. ~ull., 62: 889-892 (1983). Applications for such polymers include, among others:
1. formation into complex shapes and subsequent pyrolysis to give a ceramic material of the same shape;
2. spinning into continuous fibers whose subsequent pyrolysis yields ceramic fibers;
3. as a matrix material for carbon or ceramic fibers, or as a binder for ceramic powders ~with subsequent pyrolysis to form a ceramic body);
4. oxidation-resistant coatings on otherwise oxidizable materials (such as carbon/carbon composites) - after the polymer coating is made, it can be pyrolyzed to give the resistant ceramic coating;
5. infiltration of porous ceramic bodies such as ones obtained from reaction-sintered silicon nitride by the polymer itself (if liquid) or by a solution of the polymer, with subsequent pyrolysis to form a ceramic, resulting in better strength, oxidation resistance, etc., of the body; and
6. formation of thin films of the ceramic material for electronics applications.
~63~9~
For instance, Penn et al., J. APD1 ~ PO1Vmer SCi . 27 :
3751-61 (1982) describe the preparation oE silicon carbide-silicon nitride fibers from a polycarbosilazane precursor. Tris(N-methylamino) methylsilane monomer was formed by reaction of monomethylamine and methyltrichlorosilane in dry petroleum ether and a polycarbosilazane resin was formed by passiing the monomer over glass Raschig rings at 520C. The brittle polymer was soluble ln methylene cllloride nnd chloroform, etc. This product was spun into fibers, crosslinked in air and then pyrolyzed to give ceramic fibers.
Other polymer precursors for forming silicon carbide and silicon nitride ceramics have been described in ~.S. Pat. Nos.
3,108,985; 3,853,567; 3,892,583; 4,310,651 and ~1,312,970. These linear or crosslinked polymers and processes for producing ceramic materials have generally been found to be deficient in one or more ways.
S. Yajima, mer, Cer~m. Soc, ~ull,, 62: 893-898; 903 (1983) discloses using (CH3)2SiClz as a starting material Eor a preceramic polymer for the preparation of SiC-containing ceramics. The polymer of Yajima is prepared by sodium metal condensation of (CH3)2SiC12 to result in a polysilane, -[(CH3)2Si]n- (n is approximately 30). This polysilane can then form either a "Mark I" polymer or a "Mark III" polymer depending upon the treatment used. Heating in an autoclave under argon at 100 kPa at 450-470C for 14 hours results in a Mark I polymer while adding a few percent of a polyborodiphenylsiloxane and heating under nitrogen at ambient pressure at 350C for 10 hours results in the Mark III
polymer. In either case, the poly-silicon backbone is converted to a polymeric chain in which the main repeat unit is:
'11 263796 ~H3 -[~li~Cll2]~ (I) H
The Mark I polymer also contains some -[(C}l3)2SiCH2]-units. The Mark III polymer contains some Si-Si bonds in the form -[(CH3)2Si-Sl(C~l3)2]n((n=2-8) units and a low percentage of [(C6H5)2SiO] units These preceramic polymers can be processed to give ceramic fibers containing SiC, some free carbon and some SiO2. However, there are problems associated with these polycarbosilane-derived ceramics. They have a tendency to crystalli~e below 1200C, they have a detrimental SiO2 content as a result of an oxidative cure step, and free carbon and a relatively low ceramic yield is obtained upon their pyrolysis for a commercial product. While the ceramic yield for the Mark III polymer is 68%t the yield for the Mark I polymer is only 54%.
It would be useful to have a polymer precursor that is formed from readily available and relatively cheap starting materials, that is stable at room temperature, is soluble in organic solvents and whose pyrolysis can typically provide a high yield of ceramic products. It would also be useful to be be able to form a ceramic material upon pyrolysis which contains substantially no fr0e silicon, carbon or SiO2.
SummarY of Invention We have now found that reaction of a metal amide with an organosilicon polymer containing Si-H repeat units yields new polymeric organosilicon compounds which are useful preceramic materials. Upon pyrolysis these typically give ceramic yields significantly better than the original polysiloxane compound.
Preferably, the metal amide is a polymeric alkali metal silylamide of the formula ~63796 [(RlSiHNtl)a(RlSiN)b(RlSiHNM)c]m (where a + b + c ~
l); Rl is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1). This alkali metal poly(silylamide) may be preformed and added to the Si-H containing organosilicon polymer. Alternativelyj one may prepare the alkali metal silylamide in situ, in the presence of the organosilicon compound.
Preferably the organosilicon polymer is a polysilane compound of the formula [(RSiH)X(RSi)y]n, (where x + y -1, n is an integer greater than 1, R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, or a tri(lower)alkyl- or di(lower)alkylsilyl group), or a polycarbosilane polymer containing repeat units of the formula [RaSi(H)-(CH2)q],i.e., Rla -lsi-(cH2)q- (II) (where q is an integer 1 or greater, Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms).
The present invention is more especially concerned with the aforementioned polycarbosilanes.
~263796 Aryl-substituted polymers of the type ~RaSi(}l)-(Cll2)q], and [RSill]n (e.g., where R, or Ra is phenyl), react in the same way as the above described polycarbosilanes and organopolysllanes to give new polycarbosllane/organopolysilazane, organopolysilane/organopolysilazane and hybrid polymers, respectively.
In one embodiment of the present invention, the polymeric alkali metal silylamide is generated by treating the ammonolysis product of RlSiHX2 (Rl is as derined above and X is a halogen) with a basic catalyst capable of deprot~nating the hydrogen from a nitrogen atom adjacent to a silicon atom. The silylamide thus formed can react with the organosilicon compound, for example, the [RaSi(ll)-(CH2)q] already present. With either the preEormed polysilylamide or the in situ silylamide procedure, the reaction mixture containing the organosllicon polymer having Si-l~ repeat units and the polysilylamide i9 stirred at room temperature and preferably heated at reflux in a suitable solvent such as tetrahydrofuran to complete the reaction. The resulting solution is then coolsd and quenched with an organic halide or a silicon halide to produce the preceramic organosilicon polymers of the present invention. The polymers formed by either method can then be pyrolyzed to yield ceramic materials in high yield.
Brief Description of Drawings Figure 1 is a proton N~R spectrum comparing a polymer formed by adding already preformed polysilylamide (III-37~ with a 1:1 by weight physical mixture of polycarbosilane and preformed polysilylamde.
Figure 2 is a proton N~R spectrum comparing a polymer formed by adding already preformed polysilylamide (III-7) with a polymer formed with polysilylamide generated in situ (III-42).
~63796 Figure 3 is a thermogravimetric analysis (TG~) curve of polymer III-7.
Figure 4 is a TGA curve of polymer III-42.
Detailed DescriPtion Or the Invention We have discovered that the reaction of a metal amide with an organosilicon polymer containing Si-H repeat units (referred to as an Si-H containing organosilicon polymer) results in novel preceramic polymers. Most preferably, the metal amide is a polymeric alkali metal silylamide oE the f~mula [(RlSiHNH)a(RlSiN)b(RlSiHNM)C]m (where a ~ b ~ c -l; Rl is a lower alXyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, a i~ , substituted or unsubstituted lower aryl group having Erom 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1). However, as will be discussed below other metal amides can be used in the present invention.
The Si-H containing organosilicon polymer is preferably a polysilane compound of the formula [(RSi~l)x(RSi)y]nl (where x ~ y - 1, n is an integer greater than 1, R is a lower alkyl group havlng from 1 to about G carbon atoms, ~ lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, or a tri(lower)alkyl- or di(lower)alkylsilyl group), or a polycarbosilane polymer containing repeat units of the formula [RaSi(H)-(CH2~q],i.e., ~2~i37~6 Ra ~$i~(CH2)q~ (II) H
(where q is an integer 1 or greater, Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms).
In accord with the present invention, treatment of, Eor example, organopolysilaries witll an alka~i metal amide will provide higher molecular weight preceramic materials and improve the ceramic yield. Preferably, one uses organic alkali metal amides for treating the organopolysilane. Organic alkali metal amides are well known to the person of ordinary skill in the art. Examples include: potassium piperidide, ~ K, potassium ethylamide, C2H5NIIK, and potassium diisopropylamide, (i-C3H~)2NK, corresponding lithium, sodiuin, rubidium and cesium derivatives and the like. Polymeric secondary ~mines may be partially deprotonated by a strong base to give polymers containing metal amide functions. Such products also may be used to react with [(CH3SiH)X(CH3Si)y in this invention. Examples of such polymeric amines are: poly(ethyleneimine), [CH2CH2NH]n, or Ciba-Geigy ChimassorbTM94~ polymer, L N ~ CH2)6 ~ N ~ N
,~ ~ P~ l . P~ ~j/
The reaction of CH3SiHC12 with an alkali metal will produce methylsilicon compounds of the formula ~Z63796 [(CH3SiH)X(CH3Si)y]n, where x + y = l; and n is an integer greater than 1 (hereinafter such compounds will be reEerred to as "methylpolysilanes"). The ceramic product obtained when this compound is pyrolyzed contains an excess of "Eree" silicon, rather than the ideal lSi:lC composition.
Further, depending upon the particular process used to obtain the methylpolysilane, other deficiencies can arise. A ceramic yield of less than 50% after pyrolysis typically represents an unacceptable preceramic polymer. Of the above described methylpolysilanes, those with xay which on pyrolysis gave a reasonable ceramic yield, had only a limited solubility in organic solvents, thus limiting further processing.
Additionally, conversion of these polymers to ceramic fibers appears to require a photolysis-oxidation cure step. A
methylpolysilane of the above-described formula, in which the crosslinking of the product is not as excessive (x>y) and, which is, therefore, more soluble in organic solvents, on the o~her hand provides an unacceptably low ceramic yield on pyrolysis, e.g., 12-27% in various runs. Consequently, alkali metal condensation of CH3SiHC12 does not give a very useful preceramic polymer which can be used to form SiC and other Si/C
ceramic materials.
After extensive research we have now found that or.ganopolysilnnes such as the methylpolysilnnes ol~tnined in the above reactions, upon treatment with catalytic quantities of alkali metal amides in accord with the present invention, yield preceramic polymers of higher molecular weight which upon pyrolysis give significantly higher ceramic yields. Such polymers, when prepared as described herein, are soluble in organic solvents.
The resulting products obtained when the organic alkali metal amides were used with the methylpolysilanes were white solids ~ Z63796 g with a higher molecular weight than the starting material. The ceramic yields obtained on pyrolysis to 1000C typically are 50 to 60%, or more More l~reEernbly, one utilizes nn nlkaLi metnl. si].yl~mide.
Common alkali metal silylamides that can be used in the practice of the present invention include: [R2R3R4Si]2NM wherein R2, R3 and R4 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstitut:ed vinyl group, a suhstituted or unsubstituted allyl group, a substltuted or unsubstituted lower aryl group havlng from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R2, R3 and R4 may be the same or diffarent; and ~ is an alkali metal or one-half equivalent of an alkaline earth metal. Common alkali metal silylamides include: [(CH3)3Si]2NK, i(CH3)2(CH2-CH)si]2NK~
The alkali metal silylamide can also be partially deprotonated cyclo-[R5R6SiNH]m containing ~R5R6SiNM] units wherein R5 and R6 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubstituted allyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R5 and R6 may be the same or different; M is as defined above and m is an integer greater than 1. For example, the reaction products of one molar equivalent of KH with one of cyclo-[(CH3)2SiNH]3 or of one molar equivalent of KH with one of cyclo-~(CH3)(CH2 CH)SiNH]3, and the like. The person skilled in the art can select other alkali metal silylamides to use, including the lithium, sodium, rubidium and cesium derivatives. Treatment of either the organoploysilane or the . .
-~Z63~796 polycarbosilane with the alkali metal silylamides generally increases the ceramic yield in the pyrolysis of the resulting preceramic polymer.
Polycarbosllane polymers that are used in the prcsent invention preferably contain a multiplicity of repeat units of the formula [RaSl(}l)-(C112)q] (where q and Ra are as defined above)(hereinafter polymers containing such repeat units are referred to as "polycarbosilanes"). The reaction oE these polycarbosilanes with an alkall metal silylamide results in novel preceramlc polymers. Typlcally, the pyrolysls of thls new polymer glves a black ceramlc solid in a yield that is about 10 to 50% greater than the parent polycarbosilane.
Tl~e polycarbosllane polymer should contnin n~ lenst 25 mole % of repeat unlts of the formula II, l.e. ~RaSl(H)-(CH2)q], ln addition to other repeat units, such as [Ra2Si(C112)q]
(e.g. the Ya;ima polymers). Preferably the polycarbosilane polymer contains at least 35 mole ~ of repeat units of formula II. More preferably, the polymer contains at least 50 mole repeat units of formula II.
The polymer may also contain a mixture of repeat units of the above described formula, e.g., both [RaSi(H)~(CH2)q]
and Ra'Si(H)~(CH2)q'] (Ra' and q' are defined the same as Ra and q, respectively, but Ra' may be difEerent than Ra and q'may be different than q). Ra is preEerably a lower alkyl group, more preferably Ra is CH3. Preferably q is equal to 1 - 3, more preferably it is equal to one.
The polycarbosilane and alkali metal silylamide are typically added in a weight ratio of polycarbosllane: alkall metal sllylamide of about 10:1 or less. Preferably this ratio is about 5:1 or less. More preferably the ratio is about 3:1 or less. Most preferably the ratio is about 1:1.
Preferably the polymeric silylamide used has the formula ~Z637~6 ~(RlSiHNII)a(RlSiN)b(RlSiHNM)c]m. These polysilylamide compounds have been described in U.S.
Patent 4,482,669, issued November 13, 1984.
R preferably is a ~ower alkyl group, more preferably CH3. This patent describes the formation of novel preceramic polysilazanes by treatment of the mainly cyclic ammonolysis product of, for example, CH3SiHC12 with catalytic quantities of a base, for example, KH in organic solvents, for example, tetrahydrofuran, THF. After these compounds are treated with an electrophile such as methyl iodide, CH3I, polymers having the general formula [(cH3siHNH~a(cH3si)b(cH3siHNcH3)c]m are obtained. Prior to the addition of CH3I, a reactive "living"
polymer intermediate, an alkali metal silylamide of the type [(CH3SiHNH)a(CH3SiN)b(CH3SiHNM)C]m is obtained This intermediate species can react with electrophiles other than CH3I, e.g , with diverse chlorosiianes. Pyrolysis of such CH3I-treated polysilazanes typically yields a ceramic material contalning SiC, Si3N4 and "free" carbon.
The use of the polymeric alkali metal silylamide of the l ~(RlSiHNH) (RlSiN)b(R SiHNM)C]m in embodiment of the present invention upgrades the Si-H containing organosilicon polymer, for example, the organopolysilanes and the polycarbosilanes to new polymers which give a high ceramic yield on pyrolysis. When this alkaii metal silylamide, [(RlSiHNH)a(RlSiN)b(RlSiHN~)C]m, is reacted with an Si-H containing organosilicon polymer, the reaction product after treatment with a suitable electrophile such as an organic or a silyl halide, incorporates both starting materials. When this reaction product is pyrolyzed, the ceramic yield is significantly greater than that of the "parent" organosili~on polymer.
12~3796 The weight ratio of Si-iI containing polymer to alkali metal silylamide can vary widely. For example, mole ratios of organopolysilane: polymeric alkali metal silylamlde Erom about 4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically provide useful results. Weight ratios of polycarbosilane:
polymeric alkali metal silylamide from about lO to about l; and preferably from 5:1 to 1:1 typically provide useful results.
IIowever, in both cases other ratios can be used depending on the particular starting materials and their pyrolysis characteristics.
The organosilicon polymers thus formed by reaction of the organosillcon polymer containing Si-II repeat units witI
preformed ~(RlSiHNII)a(RlSiN)b(RlSi}lNM)C]m, followed by treatment with an electrophile, henceforth will be referred to as "graft" polymers.
; Polysilanes of type (RSiH)n (i.e., the general case where y - 0, x 1) also react with the polymeric silylamides, [~RlSiHNH)a(RlSiN)b(RlSiHNMC]m. Thus, a reaction of (C6H5SiH)n with [(cH3siNH)a(cH3siN)b(cH3sil~NK)c]m ( 1 1 m ratio) in THF at room temperature gave a new organosilicon polymer which was found to be an effective ceramic precursor, giving a Si3N4/SiC/C ceramic product in high yield upon pyrolysis to 1000C.
Additionally, use of the reaction product of organopolysilanes or polycarbosilanes with the polymeric alkali metal silylamide results in a product that is self-curing as the temperature is raised in the production of ceramic material.
Consequently, with these polymers it is possible to avoid the formation of SiO2 which results when an oxidative cure step is used. This again is an improvement over pyrolysis of the precursor silane compound alone.
~263796 In this system, R or Ra is preferably a lower alkyl, more preferably, R or Ra is C113. However, R or Ra need not be the same and, as aforesaid, mixtures of Si-11 containing organosilicon compounds and/or repeat units, e.g., [(RSiH)x(Rsi)y]n and [(R, SiH)x,(R Si.)y,]n"
[RaSi(H)~(CH2)q] and lRa Si(H)~(CH2)q~]~ and [(RSiH)X(RSi)y]n and [RaSi(1-1)~(C1i2)q] can be used to obtain further flexibility in tailoring the properties of the aforesaid product. Mixed polymers of the type [(RSi~1)a(RSi)b(RR Si)C~m (where a, b, c, m and R are as defined above, and R is defined as is R above and R may be the same or di~ferent th~n R) cnn be used ~s well.
YreEerably, R-R -C113, Ra-Ra ~CH3, Ra-R C113.
Further, these aforesaid mixtures of compounds can be used to obtain additional flexibility in tailoring the properties of the aforesaid product.
_ As metnioned, also included in this invention is the case of [(RSiH)X(RSi)y]n, where x-l, y-O, with R as defined above, where [(RSiH)]n may be a linear or a mixture of cyclic species, or a hybrid of both types. For example, [PhSiH]n (Ph is a phenyl group), cf, Aitken, C. et al., J. Organoll1et. Chem., 279:Cll-Cl3 (1985), reacts in the same way as the above-described organopolysilanes to provide new organopolysilane/organopolysilazane hybrid polymers. These mixtures will be particularly useful in attempts to avoid excess free silicon or carbon. The case of aryl-substituted repeat units of [RaSi(H)~(CH2)q] for example, where Ra is a phenyl or substituted phenyl group, and Ra can be a lower aryl group, is also included.
Mixtures of alkali metal polysilazanes, i.e., [(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m and [(Rl Si11N11)a,(Rl SiN)b,(Rl Si11NE)C,]m, (where E
12~3796 is the moiety introduced by reaction with an electrophile, e.g., a lower alkyl group of 1 to 6 carbon atorns, preferably CH3, or a silyl group), also may be used.
The preceramic product obtained by using alkali metal silylamides, even in only catalytic amounts, differs from the starting organosilicon compound. This difference is confirmed by proton NMR spectra. A typical organopolysilane starting material when R - CH3 shows an observed proton NMR integration ratio, SiCH3/SiH, ranging from 3.27 through 3.74 (see Table 1). In contrast, the similar ratio for products obtained when the starting material is reacted with an alkali metal silylamide, range from 8.รด to 14.
This difference in products apparently arises because both Si-H and Si-Si bonds are reactive towards nucleophilic reagents. Although not wishing to be bound by theory, it is believed that when alkali metal silylamides are used the following processes result:
(R3Si)2NM + ,SiH ~siN(siR3)2 + MH (1) (R3Si)2NM + ,SiH > (R3si)2NH + SiM ~2) (R3Si)2NM ~-~Si-Si ~(R3si)2N-si~ + SiM~ (3) In each of the above reactions a new reactive nucleophile is generated. In the first reaction, this nucleophile is MH, while in the second and third reactions, the nucleophile is a silyl alkali metal compound. Thus, nucleophilic attack on the [CH3SiH)X(CH3Si)y]n system will recur during these reactions and some of these oligomeric species, which comprise the starting materials, are linked together, resulting in products of higher molecular weight. There are other processes that are possible as well: e.g., ~2637~
(R3Si)2NK + -Si ~li (R3Si)2NSi~ K
H ll ~ Si: + Kll Thus, not only anionic species but also s:ilylenes can be involved as intermediates.
The "graft" polymer is Eormed by combining the already formed polymeric alkali metal silylamide with the Si-H
containing organosilicon polymer, for example, the organopolysilane in varying proportions in an organic solvent.
Thereafter, the mixture is stirred at room temperature for sufficient time for the two compounds to reac~. Al~y or~nnic solvent in whlch both polymer systems are soluble without reaction can be used. Such organic solvents include, for example, T~F, diethyl ether, glycol ethers, alkanes, arenes and comblnations thereof. The mixture may be heated above room temperature, and can be refluxed to speed up the completion of the reaction. After refluxing, the mixture is quenched with an electrophile, E-X, to form the organosilicon "graft" polymer.
The electrophile can be an alkyl halide, sulfate, or sulfonate;
a halosilane; or the like. Typically, CH3I or a chlorosilane is used, although other equivalent electrophiles wel].-known to those skilled in the art can also be used. E is preferably a lower alkyl group or silyl group; X preferably a halide, sulfate or sulfonate.
The organosilicon polymer formed by the present ("graft") process with the organopolysilane is typically obtained in yields greater than 85% based on weight of the starting materials with a variable molecular weight, typical values being in the 1800-2500 g/mol range. This preceramic organosilicon polymer can then by pyrolyzed under inert atmosphere conditions to result in a ceramic material in high yield. Typically, ~Z~379G
pyrolysis under nitrogen gives ceramic products in a yield of 70-83%.
The organosilicon polymers formed by the present ("graft") process typically give ceramic yields lO~ to 50~ greater (based on welght of the starting materials) than the polycarbosilane (See Table 2) and have a variable molecular weight.
Figure ] is a proton NMR spectrum comparing a l:l by weight physical mixture of the polycarbosilane and the polysilazane and a "graft" polymer formed by reacting the polycarbosilane with a preformed silyamide. The NMR spectrum shows that a new polymer is obtained when the polycarbosilane and the .silylamide are heated together in solution and then quenched with methyl iodide. First, the CH3Si/HSi integrated ratio differ, 9.4 in the former, 8.7 in the latter. Secondly, ths CH3Si_ NH proton (at ~ 5.06) to CH3Si_ (at ~ 4.50) proton ratio has changed from about 2 in the physical mixture to about 1 in the reaction mixture.
These preceramic organosilicon polymers can then by pyrolyzed under nitrogen or an inert atmosphere to result in ceramic materials in high yield. Typically, pyrolysis under nitrogen gives ceramlc products in a yield o~ G/~-~8~.
What is referred to herein as an "in situ" polymer is obtained by carrying out the cyclo-(RlSiHNH)n/MH reaction in solution in the presence of the Si-H containing organosilicon polymer. In this method, the methylpolysilane or polycarbosilane is added to an organic solvent. Afterwards, the cyclo-(RlSiHNH)n mixture (generated by reacting in solution anhydrous ammonia with RlSiHX2, where Rl is the same as defined earlier and X is a halogen) is added.
One then adds to the solution a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom. See U.S. Patent No. 4,482,669. The reaction ~Z63t7~6 mixture gradually changes color and hydrogen is evolved. The resulting solutlon is then stirred at room tem~erature Eor sufficient time for the silylamide intermediates and the Si-11 containing organosilicon polymer to react. It can be heated above room temperature, and can be heated at reflux to speed the completion of the reaction. AEterwards, the reaction mixture is allowed to cool to room temperature, if required, and quenched with an electrophile such as C113I or a halosilane, such as a chlorosilane, to produce the organosilicon "in situ" polymer.
The molecular weight of the "in situ" polymer is variable. For example, typLcal values of the polymer Eormed usin~ an organopolysilane are between 1600 g/mole to 2750 g/mole. On pyrolysis this material provides a high yield of a black ceramic material.
On pyrolysis the polycarbosilane-derived material provides a yield of a black ceramic material, that is typically lO~ to 50%
greater than that obtained on pyrolysis of the polycarbosilane (see Table 2).
The organosilicon polymer formed by either of the above "graft" or "in situ" methods usually is separated from solution. The solvent is removed by using techniques well known to a person of ordinary skill in the art. One standard method is distillation, preferably trap-to-trap distillation. The polymer, typLcally a white powder that is soluble in an organic solvent, is thereby obtained. One may also combine trap-to-trap distillation with centrifuging, followed by trap-to-trap distillation to separate the polymer from solution.
The "in situ" preceramic polymer differs physically from the "graft" preceramic polymer. Major differences are observed in their proton NMR spectra and in the form of their thermogravimetric analysis (TGA~ curves.
Figure 2 shows the proton NMR spectrum of a graft polymer lZ~3796 and that of an "i situ" polymer. Both polymers have similar starting molar ratios of [(Cll3SiH)x(CH3Si)y]:
(CH3SiHNH), [1.5:1 and 1.45:1, respectively], in terms of initial reactants used. However, in the " i situ" polymer the intensity ratio of the ~ 5.1, 4.7 to the ~ 4.0 proton signals is 12, while in the "graft" polymer this ratio is 1.
The signals around ~ 5.l and 4.7 are due to the Cll3SillN
proton while those around b 4.0 are due to CH3Si_ protons which are attached to silicon atoms not bound to nitrogen.
Accordingly, this difference in ratio demonstrates that the two polymers have different structures.
Although not wishing to be bouncl by theory, it appears likely that in the "i situ" preparation, intermediates formed, for example, by the action of Kll on (CH3SiHNII)n cyclics also react with the Si-H containing organosilicon polymer, for example, the organopolysilane [(CH3SiH)X(CH3Si)y]n before the polymeric alkali metal silylamide which is the starting reactant in the "graft" procedure has a chance to be formed to its usual extent. This results in either less of the original CH3SiHNH protons being lost and/or more of the Si-H
containing organosilicon system being reacted.
The TGA curve of the "graft" polymer is shown in Figure 3, while that of the "i situ" polymer is shown in Figure 4. These two curves differ as well. In the "graft" polymer, the curves show that there is a small weight loss between 100C and 200 D C
which begins at about 100C. In contrast, with the "in situ"
polymer, the initial small weight loss occurs only at higher temperatures, approximately beginning at 175C. Both types of polymers are useful as preceramic materials.
~2~3796 Table 2 TGA Ceramic Yield of Preceramic Polymer Wt ratio of Polycarbo- Ceramic Compound silane: Alkali Metal Yield (Example) Sil~lamide 100:0 58~ B.(2) 1:1 84~ 37 D.(3)(a)(i) 5:1 67~ III-57 D.(3)(a)(ii) ;
1:1 88~ III-39 D.(3)(b)(i) 5:1 64% III-59 D.(3)(b)(ii) 1:1 86% III-38 E.(2)(a)(i) 5:1 80~ III-56 E.(2)(a)(ii) 1:1 86~ III-40 E. (2)(b)~i) 5:1 66% III-58 E. (2)(b)(ii) ~263796 The use of the alkali metal silylamide of the formula [(RlSiHNH)a~RlSiN)b(RlSiHNM)C]m not only improves the ceramic yield oE the organopolysilanes, but, more significantly, when this alkali metal silylamide is reacted with organopolysilane of the formula [(RSill)x(RSi)y]n in the appropriate stoichiometry, the reaction product of [(RSiH)X(RSi) ]n and [(RlSiHNH)a(R~SiN)b(RlSiHNM)C]m (where m and n are integers greater than l), after treatment with a suitable electrophile such as an organic or a silyl halide, incorporates both starting materials. When this reacti.on product is pyrolyzed, the excess silicon normally obtained in the pyrolysis of the organopolysilane alone and the excess carbon normally obtained in the pyrolysis of the quenched polymeric alkali metal silylamide alone combine so that there is no substantial excess of either element in the ceramic product. Consequentiy, one can obtain a ceramic material with less than about 0.1~ of free silicon and less than about O.l~ of free carbon, i.e., a ceramic material containing substantially no free carbon and no free silicon. The exact combination oE the two compounds necessary to result in the desired stoichiometry can readily be calculated by a person of ordinary skill in the art on the basis of the results of the analyses of the ceramic products obtained in the pyrolysis of the separate polymers. Mole ratios of organopolysilane : polymeric alkali metal silylamide from about 4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically provide useful results. However, other ratios can be used depending on the particular starting materials and their pyrolysis characteristics.
The excess of free carbon, which can be a problem with the starting polycarbosilanes, can be dealt with by using a ternary system of: (1) the polycarbosilane; (2) the polysilazane (as the ~6~796 polymeric silylamide, eitller preformed or generated i situ) and (3) a polysilane whose pyrolysis alone gives a ceramic product which contains an excess of silicon. Examples of such polysilanes are organopolysilanes as described above, for example, those which are produced by the sodium condensation of methyldichlorosilane. In these reactions the organopolysilane is preferably as defined above, i.e [(RSiH)X(RSi)y]n.
More preferably R is a lower alkyl group, most preferably R is CH3. Using an appropriate mixture of the three polymers (which can be calculated from the results oE the analyse.s of the ceramic products of the pyrolysis oE each individual polymer, e.g., the CH3I- quenched polymer in the case of the polymeric silylamide), one can obtain a ceramic product which contains a minimal excess of either element, carbon or silicon. Such hydrid ternary preceramic polymers are soluble in organic solvents and, depending on component ratios used, are of variable molecular weight. Their pyrolysis gives black ceramic products in high (generally > 80%) yield.
Physical blends of Si-H containing organosilicon polymers, for example the organopolysilane, or the polycnrbosilane polymers containing repeat units of ~RaSi(H)~(CH2)q]~ for example, the Yajima polycarbosilane with the "quenched"
[(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m organosilazane polymer of U.S. Patent No. 4,482,669 can be used since these react when they are heated together. ~len approximately equal molar quantities of the polymers where R, or Ra ~ CH3, - CH3, q - 1 and E ~ CH3, were mixed and finely ground together and then subjected to pyrolysis to 1000C, ceramic yields was obtained which were approximately the average of the ceramic yields when the organopolysilane and the organosilazane polymers were pyrolyzed separately, and were significantly ~63796 higher than that which resulted when the polycarbosilane was pyrolyzed separately ~see Table 2).
When polycarbosilane/orgosilazane mixtures were heated, in the absence of a solvent at 200C under nitrogen, white foamy solids were obtalned WhiCIl were insoluble in nollpolar organic solvents, thus demonstrating ~hat a reaction had occurred below 200C and prior to pyrolysis. When organosilane/
organosilazane mixtures were heated, either in the absence of a solvent at 100C under nitrogen or in a toluene solution at rcflux, white powders were obtained which were insoluble in nonpolar organic solvents, again demonstrating that a reaction occurred.
Ternary blends of the polycarbosilane, the [(CH3SiH)X(CH3Si)y]n liquid polysilazane and the [ (cH3siHN~l)a(cH3siN)b(cH3siHNcH3)c]m . ~ polysilazane behaved similarly. An obvious reaction occurred when such a mixture had been heated to 200C, since the originally soluble mixture became insoluble in organic solvents.
The comblned polymers obtained by the "graft," "i situ" and physical blend methods can be converted to black ceramic fibers. Pyrolysis of pressed bars of the combined polymers to 1000C provides a black solid product. In other experiments, silicon carbide powder was dispersed in a toluene solution containing 25~ by weight of the combined organosilane/organosilazane polymers. The solvent was evaporated and the residue, a fine pow'aer of silicon carbide k with combined polymer binder was pressed into bars and pyrolyzed at 1000C. A ceramic bar was obtained showing a low weight loss and slightly shrunken size.
Similarly, when silicon carbide powder was dispersed in toluene solutions of the combined polycarbosilane/organosilazane polymers. The solvent was evaporated and the residue, a fine powder of silicon carbide with combined polymer binder, was pressed into bars and pyrolyzed at 1000C. A ceramic bar was obtained showing a low weight loss and slightly shrunken size.
The invention will be further illustrated by the examples that follow:
A. General All glassware was Elame-dried under vacuum or under a stream of nitrogen prior to use. Tetrahydrofuran t~llF) and benzene were distilled from sodium and benzophenone ketyl. ~lexane was distilled from LiAlH4. Solvents were deoxygenated by bubbling nitrogen through them prior to use. Methyldichlorosilane, CH3SiHC12, and dimethyldichlorosilane, (CH3)2SiC12, were commercial products. The polycarbosilane was purchased from Dow Corning Corporation. Its characterization is reported below. The ammonolysis of CH3SiHC12 in ether and in THF
solution has been described in U.S. Patent No. 4,482,699 (D.
Seyferth and G.H. Wiseman), as has the reaction of ammonolysis products, [CH3SiHNH]m, wIth KH to give the polymeric silylamide, [(CH3SiHNH)a(CH3SiN)b(Cll3SillNK)c)]m Poly(methydrosiloxane), [CH3Si(H)O]n was purchased from Petrarch (Catalog #PS 122) and was used as recieved. Piperdine, diisopropylamine, and propylamine were purchased and were distilled from CaO before use. Reagent grade sodium shot was further purified by creating a dispersion in refluxing xylene and allowing this to cool, with stirring. This served to remove most of the oxide coating. Anhydrous ammonia was dried further by passing it through a KOH column.
lH NMR spectra were recorded on a JEOL-FX-9OQ spectrometer operating at 90 MHz. Elemental analyses were performed by Galbraith Laboratories, Knoxville, Tennessee. Molecular weights :' ..
~,%63796 were determined bymeasuring the free~ing point depression of a weighed sample of benzene caused by a weighed sample of product. Thermal analyses were performed using a Perkin-Elmer TGS-2 Thermogravimetric Analyzer interfacsd with a System 7/4 Thermal Analysis Controller on a DuPont 950 TGA cormected to a DuPont thermal analysis system. Samples were heated, under argon, from 25-1000C at a rate of 10C/min. Large scale pyrolyses were carried out in fused silica boats using a Lindberg 59344 tube furnace (25-].000C, 10C/min) under argon atmosphere. scanning electron~icrographs were obtained using an AM~ lnstrument, operating at 20 KV.
B. Preparation of Organosilicon Compounds 1. Preparation of ~(CH3SiH)X~_3~yln (all operations under nitro~en) - - i i ~_~ a. In THF Medium.
A 500 ml, three-necked, round-bottomed flask equipped with a stir-bar, a dropping funnel and a reflux condenser was charged with 50.5 g (2-.20 g atom) of Na metal. The flask was attached to a Schlenk manifold, evacuated and refilled with nitrogen three times. THF (200 ml) was added and the dropping funnel was charged with 65 ml (0.625 mol) of CH3SiHC12. The silane was added to the stirred Na suspension during the course of 45 min., after which time the reaction mixture was cloudy and slightly warm. The mixture was stirred for 16 hours at room temperature ~:. and 48 hours at reflux; it then was cooled to room temperature.
llexane (60 ml) was added. The mixture was transferred by cannula to a heavy-walled centrifuge bottle and centrifuged.
The supernatant layer was transferred to a 1 liter round-bottomed flask (under nitrogen). THF (50 ml) and hexane (30 ml) were added to the resldual solid and the resulting ~LZ63796 suspension was centrifuged. The supernatant layers were combined and solvents were removed by t.rap-to-trap distillation in vacuum until the residual liquid volume was about 100 ml.
This liquid was cannulated into a 250 ml single-necked flask and the remaining solvent was removed in vacuo to leave 13.2 g (0.30 mol, 48% yield) of a white, glassy solid. On being heated in a sealed capillary (in vacuo~ this solid soEtened around 40C and "melted" between 130-140C with gas evolution, leaving a thick gum There was no further change up to 300C except For a gradual increase in viscosity. The product was poorly soluble in hexane, only somewhat soluble in benzene (precluding measurement of its cryoscopic molecular weight in this solvent) and quite soluble in THF.
NMR ~90 MHz, in CDC13): ~ 0.10-0.61 (m, SiCH3, 7.5H) and 3.55-3.90 (m, SiH, 1ll). Based on the reasonable assumption that every Si atom bearing a H substituent also bears a CH3 substituent, the integrated CH3Si and SiH intensities lead to a constitution [(CH3SiH)o 4(CH3Si)o 6]n Anal. Calcd for CSiH3 4: C, 27.60; H, 7.87.
Found: C, 27.18; H, 7.17.
IR (KBr, Nujol): 2170(sh), 2100(s, Si-H), 1408(m), 1260(m, Si-CH3), 1249(s, Si-CH3), 1060(br), lOl9(s), 931(s), 865(vs, Si-CH3), 770(vs), 685(vs), cm~l.
TGA(25-1000C, 10C/min.): 60% yield of a gray-black ceramic solid. A tube furnace pyrolysis of 3.20 g of this material to 1500C gave 1.52 g (48%) of a gray ceramic powder.
~_263~96 Anal. of the Ceramic Powder. Found: C, 22.56; Si, 78.42; H, 0.01; N, 0.009~ (SiC requires C, 29.94; Si, 70.06%; actual composition: SiC + 0.49 Si). X-ray powder difEraction (d A): 1.315(s) (~ -SiC), 1.542(s) (~ -SiC), l.91(m) (Si), 2.181(m), (~ -SiC), 2.52(vs) (a -SiC), 3-13(m) si) .
A mass spectral analysis of the pyrolysis gas in another experiment showed the following: no gaseous products were observed up to 385C, then fragment ions corresponding well with the reported fragmentation oE Cll35iH3. At 445c, CH3Sill3 was still observed and a peak at m/z ~ 16 (CH4) began to grow in. By 5~0C, when weight loss was about over, only the methane peak was observable. ..
b. In Hexane/T~lF Medium `~ In a dry box, a 1 liter three-necked, round-bottomed flask equipped with a stir-bar, a dropping funnel and a reflux condenser was charged with 75.0 g (3.26 mol) of sodium metal.
The flask was attached to a Schlenk manifold, evacuated and flushed with nitrogen. THF (70 ml) and hexane (420 ml) were added and the dropping funnel was charged with 150 ml (1.44 mol) of methyldichlorosilane. Methyldichlorosilane was added slowly into the flask over a 3 hour period. The reaction solution turned purple and by the end of the addition was at gentle reflux. The reaction mixture was stirred at room temperature for 2 hours and then heated at reflux for 16 hours. After it ~~ had been cooled to room temperature, the reaction mixture (except for the large NaCl crystals) was transferred via cannula into a heavy-walled glass bott].e. The mixture was centrifuged and the clear, colorless supernatant layer transferred by cannula into a 1 liter round-bottomed flask equipped with a ~ ~637~6 stir-bar. Hexane (200 ml) and THF (20 ml) were added to the remaining solids, the mixture again was centrifuged, and the supernatant liquid combined with the supernatant solution previously separated. Solvent was removed by trap-to-trap distillation until the volume of the residue was about 100 ml, and the remaining liquid was transferred by cannula into a weighed 250 ml round-bottomed flask. Remaining solvent was removed by trap-to-trap distillation at approximately 0.05 mm Hg at room temperature to give 51.2 g (81%, 1.16 mol) of a cloudy white oil.
H NMR (90 MHz, C6D6):~ 0.37 (broad, SiCH3, 3.74H) 3.92 (broad, Si}l, l H).
NMR integration of the product gave a constitution of [(CH3SiH)o 8(CH3Si)0,2]n.
IR (thin film, cm l): 2967(s), 2900(s), 2800(w), 2099(vs), \~ 1410~s), 1385(w), 1249(s), 1055(br), 933(s), 865(vs), 770(vs), 685(br), 650(sh), 585(w).
Molecular weight (cryoscopic in benzene): 600 g/mol.
Anal, (material from another similar preparation). Calcd. for CSiH3 76; C, 27.39; H, 8.55; Si, 64.05. Found: C, 27.49; H, 8.98; Si, 61.58%.
TGA (25-1000C, 10C/min): 20% yield of a gray-black ceramic solid. Pyrolysis of a sample from another preparation in a tube furnace gave a gray-black ceramic solid in 36% yield (by weight).
Anal. of Ceramic. Found: C, 22.93; Si, 75.99%.
~-~ The pure liquid obtained by this procedure is very air-sensitive, particularly when its effective surface area is high, as when in contact with a fritted funnel or a paper or cloth towel (in which cases spontaneous inflammation may occur).
Other, si~ilar reactions have given 62-75% yields of (CH3SiH)X(CH3Si)y. Molecular weight determinations of ~Z63'796 several preparations ranged from 520-740 g/mol. All products had very similar lH NMR spectra, but with different SiCH3:SiH ratios. Physical data of these products are listed in Table 1.
~v .
~,Z63796 PHYSICAL DATA FOR ~(CH3SiH)x(Cll3S~ _ POLYM~RS
Sample # Polymer M.W.a SiCl13:Sillb Cer~micC x y Yield (%) Yield (~) _ YFY III-l 81 600 3.74:1 20 0.80 0.20 YFY II-40 74 740 3.56:1 16 0.84 0.16 YFY II-25 73 650 3.51:1 26 0.85 0.15 YFY II-12 , 66 520 3.27:1 16 0.91 0.09 YFY I-73 73 680 3.48:1 27 0.86 0.14 aCryoscopic in benzene.
b lH NMR integration ratio.
CUnder nitrogen gas, 25-1000C, 10C/min (TGA) ;, ~Z63796 For the purposs of simplifying calculation, an average formula weight value 44 was assigned for the unit (CII3Si~I)X(CII3Si)y Therefore, in each o~ the following experiments, the number of moles of the reaction unit (CH3SiH) was calculated from the weight of the polymer used divided by 44.
The product formed in the TIIF solution,gives a 60~ ceramic yield, but lt is of limlted solubility in organic solvents and its conversion to ceramic fibers requires a curing step of photolysis/oxidation. Preparation of the [(CH3SiH)X(CH3Si)y]n in a hexane/TllF mixture of ~pI)roxiIlln~oly 6 to 7:1. ros~ o(I 1Il sn~isfnc~ory yi.olds of n soluble produet. I-Iowever, pyrolysls of this material resulted in very low eeramie yields, ranging from 16 to 27~. -' ; , .2. Characteri~zation of the Polycarbosilane.
The polyearbosilane, a white solid, was purchased from Dow Corning Corporation. The following data were eolleeted on it:
H NMR (90 MHz, C6D6): ~ 4.52 (broad, SiH, lH) 0.26 (broad, SiCH3 and SiC_2Si, 8.6H~
IR (KBr, Nu~ol, em 1): 2104(s), 1253(s), 1014(s, broad), 845(s, broad), 734(s).
Moleeular ~eight (eryoseopie in benzene): 1210 g/mol TGA (25-1000C, 10C/min): 58~ yield of a blaek eeramie solid.
Tl/2 - 510C
C. Catalytie Reaetions of ~(CH3SiH~X(CH3Si~yl_ 1. Potassium Bis(trimethvlsilvl~amide - Catalyzed Conversion of ~(CH3SiH~x(CH3Si~yln ~,Z6~796 In a dry box, a 50 ml round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap ("standard apparatus") was charged with 0.1 g of KH (0.0025 mol). THF (20 ml) was added to the flask to suspend the KH. To the KH suspension was added 0.44 g of [(CH3)3Si]2Nll (0.0027 mol). Reaction occurred immediately with hydrogen gas evolution. The solution was stirred at room temperature for 20 mlnutes and then heated at reflux for 20 minutes. The slightly yellow solution was allowed to cool to room temperature.
Another 100 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with 2.2 g of [(CH3Slll)x(CH3Sl)y]n (0.05 mol, x - 0.85, y - 0.15). THF (20 ml) was added to the flask to dissolve the polymer. The [(CH3)3Si]2NK solution previously described was slowly added to the reaction flask by syringe. Addition of each drop resulted in formation of a transient orange color which quickly disappeared. The orange color perslsted after 1 ml of the solution had been added.
After 10 ml (ca. 2.5 mol~) of the solution of [(CH3)3Si]2NK had been added, the reaction mixture turned deep red and a small amount of white precipitate was present.
CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stlrred at room temperature for one hour. The solvent was removed under reduced pressure to give a white solid which was extracted with two 50 ml portions of hexane. The extracts were centrifuged, and the clear, colorless supernatant layer was transferred via cannula into a weighed 100 ml round-bottomed flask equipped with a stir-bar. Solvent was removed by trap-to-trร p distillation to give 1.51 g (68~, by weight) of a white powder ("usual work-รนp"). The reaction product is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.2 (broad, SiH, 1 H) 0.47 (broad, SiCH3, 8.8 H) ~,2~3796 Molecular weight (cryoscopic in benzene): 1000 g/mol TGA (25-1000C, 10C/min~: 63~ yield of a black ceralnic solid, T1~2 ~ 300Ca aTl/2 ~ temperature at which one-half oE the total weight loss has occurred.
2. Potassium Bis(vinvldimethylsilvl)amide - CatalYzed Conversion of ~(CH3SiH)xtCH3Si~yln According to the procedure described previously, the reaction between 0.46 g (0.0025 mol) of [(CH2-CII)Si(CH3)2]2NH and 0.1 g (0.0025 mol) of KII in 20 ml oE THF was carrled out under nitrogen. The resulting solution was added to a separate flask which was charged with 2.2 g (0.05 mol) of [(CH3siH)x(cH3si)y]n (x ~ 0.85, y = 0.15) and 20 ml of THF. After 9 ml (ca. 2.5 mol%) of the [(CH2-CH)Si(CH3)2]2NK solution had been added, the deep red reaction mixture started to form small amounts of white precipitate. CH3I (0.5 ml, 7.9 mmol) was added and the resulting solution was stirred at room temperature for one hour. The usual work-up followed. A white powder (2.01 g, 91~) was obtained which is very soluble in hexane, benzene, and TIIF.
H NMR (90 MHz, C6D6): ~ 4.08 (broad, SiH, llI) 0.47 (broad, SiCH3, 12 H) Molecular weight (cryscopic in benzene): 850 g/mol TGA (25-1000C, 10C/min): 61% yield of black ceramic solid, Tl/2 ~ 400C.
3. Monopotassium Derivative of HexamethylcYclotrisilazane -Catalvzed Conversion of ~(CH3SiH?x(CH3Si)yln_ According to the procedure described previously, the reaction between 0.55 g (0.0025 mol) of [(CH3)2SiNH]3 and 0.1 g (0.0025 mol) of KH in 20 ml of THF was carried out under nitrogen. The resulting solution was added to a separate flask ~2~3796 which was charged with 2 2 g (0.05 mol) of [(CH3SiII)X(CH3Si)y]n (x ~ 0.85, y 0.15) and 20 ml of THF. After 10 ml (ca. 2.5 mol~) of the potassium silylamide solution had been added, the reaction mixture turned deep red and a small amount of white solid precipitated. CH3I (0.5 ml,
~63~9~
For instance, Penn et al., J. APD1 ~ PO1Vmer SCi . 27 :
3751-61 (1982) describe the preparation oE silicon carbide-silicon nitride fibers from a polycarbosilazane precursor. Tris(N-methylamino) methylsilane monomer was formed by reaction of monomethylamine and methyltrichlorosilane in dry petroleum ether and a polycarbosilazane resin was formed by passiing the monomer over glass Raschig rings at 520C. The brittle polymer was soluble ln methylene cllloride nnd chloroform, etc. This product was spun into fibers, crosslinked in air and then pyrolyzed to give ceramic fibers.
Other polymer precursors for forming silicon carbide and silicon nitride ceramics have been described in ~.S. Pat. Nos.
3,108,985; 3,853,567; 3,892,583; 4,310,651 and ~1,312,970. These linear or crosslinked polymers and processes for producing ceramic materials have generally been found to be deficient in one or more ways.
S. Yajima, mer, Cer~m. Soc, ~ull,, 62: 893-898; 903 (1983) discloses using (CH3)2SiClz as a starting material Eor a preceramic polymer for the preparation of SiC-containing ceramics. The polymer of Yajima is prepared by sodium metal condensation of (CH3)2SiC12 to result in a polysilane, -[(CH3)2Si]n- (n is approximately 30). This polysilane can then form either a "Mark I" polymer or a "Mark III" polymer depending upon the treatment used. Heating in an autoclave under argon at 100 kPa at 450-470C for 14 hours results in a Mark I polymer while adding a few percent of a polyborodiphenylsiloxane and heating under nitrogen at ambient pressure at 350C for 10 hours results in the Mark III
polymer. In either case, the poly-silicon backbone is converted to a polymeric chain in which the main repeat unit is:
'11 263796 ~H3 -[~li~Cll2]~ (I) H
The Mark I polymer also contains some -[(C}l3)2SiCH2]-units. The Mark III polymer contains some Si-Si bonds in the form -[(CH3)2Si-Sl(C~l3)2]n((n=2-8) units and a low percentage of [(C6H5)2SiO] units These preceramic polymers can be processed to give ceramic fibers containing SiC, some free carbon and some SiO2. However, there are problems associated with these polycarbosilane-derived ceramics. They have a tendency to crystalli~e below 1200C, they have a detrimental SiO2 content as a result of an oxidative cure step, and free carbon and a relatively low ceramic yield is obtained upon their pyrolysis for a commercial product. While the ceramic yield for the Mark III polymer is 68%t the yield for the Mark I polymer is only 54%.
It would be useful to have a polymer precursor that is formed from readily available and relatively cheap starting materials, that is stable at room temperature, is soluble in organic solvents and whose pyrolysis can typically provide a high yield of ceramic products. It would also be useful to be be able to form a ceramic material upon pyrolysis which contains substantially no fr0e silicon, carbon or SiO2.
SummarY of Invention We have now found that reaction of a metal amide with an organosilicon polymer containing Si-H repeat units yields new polymeric organosilicon compounds which are useful preceramic materials. Upon pyrolysis these typically give ceramic yields significantly better than the original polysiloxane compound.
Preferably, the metal amide is a polymeric alkali metal silylamide of the formula ~63796 [(RlSiHNtl)a(RlSiN)b(RlSiHNM)c]m (where a + b + c ~
l); Rl is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1). This alkali metal poly(silylamide) may be preformed and added to the Si-H containing organosilicon polymer. Alternativelyj one may prepare the alkali metal silylamide in situ, in the presence of the organosilicon compound.
Preferably the organosilicon polymer is a polysilane compound of the formula [(RSiH)X(RSi)y]n, (where x + y -1, n is an integer greater than 1, R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, or a tri(lower)alkyl- or di(lower)alkylsilyl group), or a polycarbosilane polymer containing repeat units of the formula [RaSi(H)-(CH2)q],i.e., Rla -lsi-(cH2)q- (II) (where q is an integer 1 or greater, Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms).
The present invention is more especially concerned with the aforementioned polycarbosilanes.
~263796 Aryl-substituted polymers of the type ~RaSi(}l)-(Cll2)q], and [RSill]n (e.g., where R, or Ra is phenyl), react in the same way as the above described polycarbosilanes and organopolysllanes to give new polycarbosllane/organopolysilazane, organopolysilane/organopolysilazane and hybrid polymers, respectively.
In one embodiment of the present invention, the polymeric alkali metal silylamide is generated by treating the ammonolysis product of RlSiHX2 (Rl is as derined above and X is a halogen) with a basic catalyst capable of deprot~nating the hydrogen from a nitrogen atom adjacent to a silicon atom. The silylamide thus formed can react with the organosilicon compound, for example, the [RaSi(ll)-(CH2)q] already present. With either the preEormed polysilylamide or the in situ silylamide procedure, the reaction mixture containing the organosllicon polymer having Si-l~ repeat units and the polysilylamide i9 stirred at room temperature and preferably heated at reflux in a suitable solvent such as tetrahydrofuran to complete the reaction. The resulting solution is then coolsd and quenched with an organic halide or a silicon halide to produce the preceramic organosilicon polymers of the present invention. The polymers formed by either method can then be pyrolyzed to yield ceramic materials in high yield.
Brief Description of Drawings Figure 1 is a proton N~R spectrum comparing a polymer formed by adding already preformed polysilylamide (III-37~ with a 1:1 by weight physical mixture of polycarbosilane and preformed polysilylamde.
Figure 2 is a proton N~R spectrum comparing a polymer formed by adding already preformed polysilylamide (III-7) with a polymer formed with polysilylamide generated in situ (III-42).
~63796 Figure 3 is a thermogravimetric analysis (TG~) curve of polymer III-7.
Figure 4 is a TGA curve of polymer III-42.
Detailed DescriPtion Or the Invention We have discovered that the reaction of a metal amide with an organosilicon polymer containing Si-H repeat units (referred to as an Si-H containing organosilicon polymer) results in novel preceramic polymers. Most preferably, the metal amide is a polymeric alkali metal silylamide oE the f~mula [(RlSiHNH)a(RlSiN)b(RlSiHNM)C]m (where a ~ b ~ c -l; Rl is a lower alXyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, a i~ , substituted or unsubstituted lower aryl group having Erom 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1). However, as will be discussed below other metal amides can be used in the present invention.
The Si-H containing organosilicon polymer is preferably a polysilane compound of the formula [(RSi~l)x(RSi)y]nl (where x ~ y - 1, n is an integer greater than 1, R is a lower alkyl group havlng from 1 to about G carbon atoms, ~ lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, or a tri(lower)alkyl- or di(lower)alkylsilyl group), or a polycarbosilane polymer containing repeat units of the formula [RaSi(H)-(CH2~q],i.e., ~2~i37~6 Ra ~$i~(CH2)q~ (II) H
(where q is an integer 1 or greater, Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms).
In accord with the present invention, treatment of, Eor example, organopolysilaries witll an alka~i metal amide will provide higher molecular weight preceramic materials and improve the ceramic yield. Preferably, one uses organic alkali metal amides for treating the organopolysilane. Organic alkali metal amides are well known to the person of ordinary skill in the art. Examples include: potassium piperidide, ~ K, potassium ethylamide, C2H5NIIK, and potassium diisopropylamide, (i-C3H~)2NK, corresponding lithium, sodiuin, rubidium and cesium derivatives and the like. Polymeric secondary ~mines may be partially deprotonated by a strong base to give polymers containing metal amide functions. Such products also may be used to react with [(CH3SiH)X(CH3Si)y in this invention. Examples of such polymeric amines are: poly(ethyleneimine), [CH2CH2NH]n, or Ciba-Geigy ChimassorbTM94~ polymer, L N ~ CH2)6 ~ N ~ N
,~ ~ P~ l . P~ ~j/
The reaction of CH3SiHC12 with an alkali metal will produce methylsilicon compounds of the formula ~Z63796 [(CH3SiH)X(CH3Si)y]n, where x + y = l; and n is an integer greater than 1 (hereinafter such compounds will be reEerred to as "methylpolysilanes"). The ceramic product obtained when this compound is pyrolyzed contains an excess of "Eree" silicon, rather than the ideal lSi:lC composition.
Further, depending upon the particular process used to obtain the methylpolysilane, other deficiencies can arise. A ceramic yield of less than 50% after pyrolysis typically represents an unacceptable preceramic polymer. Of the above described methylpolysilanes, those with xay which on pyrolysis gave a reasonable ceramic yield, had only a limited solubility in organic solvents, thus limiting further processing.
Additionally, conversion of these polymers to ceramic fibers appears to require a photolysis-oxidation cure step. A
methylpolysilane of the above-described formula, in which the crosslinking of the product is not as excessive (x>y) and, which is, therefore, more soluble in organic solvents, on the o~her hand provides an unacceptably low ceramic yield on pyrolysis, e.g., 12-27% in various runs. Consequently, alkali metal condensation of CH3SiHC12 does not give a very useful preceramic polymer which can be used to form SiC and other Si/C
ceramic materials.
After extensive research we have now found that or.ganopolysilnnes such as the methylpolysilnnes ol~tnined in the above reactions, upon treatment with catalytic quantities of alkali metal amides in accord with the present invention, yield preceramic polymers of higher molecular weight which upon pyrolysis give significantly higher ceramic yields. Such polymers, when prepared as described herein, are soluble in organic solvents.
The resulting products obtained when the organic alkali metal amides were used with the methylpolysilanes were white solids ~ Z63796 g with a higher molecular weight than the starting material. The ceramic yields obtained on pyrolysis to 1000C typically are 50 to 60%, or more More l~reEernbly, one utilizes nn nlkaLi metnl. si].yl~mide.
Common alkali metal silylamides that can be used in the practice of the present invention include: [R2R3R4Si]2NM wherein R2, R3 and R4 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstitut:ed vinyl group, a suhstituted or unsubstituted allyl group, a substltuted or unsubstituted lower aryl group havlng from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R2, R3 and R4 may be the same or diffarent; and ~ is an alkali metal or one-half equivalent of an alkaline earth metal. Common alkali metal silylamides include: [(CH3)3Si]2NK, i(CH3)2(CH2-CH)si]2NK~
The alkali metal silylamide can also be partially deprotonated cyclo-[R5R6SiNH]m containing ~R5R6SiNM] units wherein R5 and R6 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubstituted allyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R5 and R6 may be the same or different; M is as defined above and m is an integer greater than 1. For example, the reaction products of one molar equivalent of KH with one of cyclo-[(CH3)2SiNH]3 or of one molar equivalent of KH with one of cyclo-~(CH3)(CH2 CH)SiNH]3, and the like. The person skilled in the art can select other alkali metal silylamides to use, including the lithium, sodium, rubidium and cesium derivatives. Treatment of either the organoploysilane or the . .
-~Z63~796 polycarbosilane with the alkali metal silylamides generally increases the ceramic yield in the pyrolysis of the resulting preceramic polymer.
Polycarbosllane polymers that are used in the prcsent invention preferably contain a multiplicity of repeat units of the formula [RaSl(}l)-(C112)q] (where q and Ra are as defined above)(hereinafter polymers containing such repeat units are referred to as "polycarbosilanes"). The reaction oE these polycarbosilanes with an alkall metal silylamide results in novel preceramlc polymers. Typlcally, the pyrolysls of thls new polymer glves a black ceramlc solid in a yield that is about 10 to 50% greater than the parent polycarbosilane.
Tl~e polycarbosllane polymer should contnin n~ lenst 25 mole % of repeat unlts of the formula II, l.e. ~RaSl(H)-(CH2)q], ln addition to other repeat units, such as [Ra2Si(C112)q]
(e.g. the Ya;ima polymers). Preferably the polycarbosilane polymer contains at least 35 mole ~ of repeat units of formula II. More preferably, the polymer contains at least 50 mole repeat units of formula II.
The polymer may also contain a mixture of repeat units of the above described formula, e.g., both [RaSi(H)~(CH2)q]
and Ra'Si(H)~(CH2)q'] (Ra' and q' are defined the same as Ra and q, respectively, but Ra' may be difEerent than Ra and q'may be different than q). Ra is preEerably a lower alkyl group, more preferably Ra is CH3. Preferably q is equal to 1 - 3, more preferably it is equal to one.
The polycarbosilane and alkali metal silylamide are typically added in a weight ratio of polycarbosllane: alkall metal sllylamide of about 10:1 or less. Preferably this ratio is about 5:1 or less. More preferably the ratio is about 3:1 or less. Most preferably the ratio is about 1:1.
Preferably the polymeric silylamide used has the formula ~Z637~6 ~(RlSiHNII)a(RlSiN)b(RlSiHNM)c]m. These polysilylamide compounds have been described in U.S.
Patent 4,482,669, issued November 13, 1984.
R preferably is a ~ower alkyl group, more preferably CH3. This patent describes the formation of novel preceramic polysilazanes by treatment of the mainly cyclic ammonolysis product of, for example, CH3SiHC12 with catalytic quantities of a base, for example, KH in organic solvents, for example, tetrahydrofuran, THF. After these compounds are treated with an electrophile such as methyl iodide, CH3I, polymers having the general formula [(cH3siHNH~a(cH3si)b(cH3siHNcH3)c]m are obtained. Prior to the addition of CH3I, a reactive "living"
polymer intermediate, an alkali metal silylamide of the type [(CH3SiHNH)a(CH3SiN)b(CH3SiHNM)C]m is obtained This intermediate species can react with electrophiles other than CH3I, e.g , with diverse chlorosiianes. Pyrolysis of such CH3I-treated polysilazanes typically yields a ceramic material contalning SiC, Si3N4 and "free" carbon.
The use of the polymeric alkali metal silylamide of the l ~(RlSiHNH) (RlSiN)b(R SiHNM)C]m in embodiment of the present invention upgrades the Si-H containing organosilicon polymer, for example, the organopolysilanes and the polycarbosilanes to new polymers which give a high ceramic yield on pyrolysis. When this alkaii metal silylamide, [(RlSiHNH)a(RlSiN)b(RlSiHN~)C]m, is reacted with an Si-H containing organosilicon polymer, the reaction product after treatment with a suitable electrophile such as an organic or a silyl halide, incorporates both starting materials. When this reaction product is pyrolyzed, the ceramic yield is significantly greater than that of the "parent" organosili~on polymer.
12~3796 The weight ratio of Si-iI containing polymer to alkali metal silylamide can vary widely. For example, mole ratios of organopolysilane: polymeric alkali metal silylamlde Erom about 4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically provide useful results. Weight ratios of polycarbosilane:
polymeric alkali metal silylamide from about lO to about l; and preferably from 5:1 to 1:1 typically provide useful results.
IIowever, in both cases other ratios can be used depending on the particular starting materials and their pyrolysis characteristics.
The organosilicon polymers thus formed by reaction of the organosillcon polymer containing Si-II repeat units witI
preformed ~(RlSiHNII)a(RlSiN)b(RlSi}lNM)C]m, followed by treatment with an electrophile, henceforth will be referred to as "graft" polymers.
; Polysilanes of type (RSiH)n (i.e., the general case where y - 0, x 1) also react with the polymeric silylamides, [~RlSiHNH)a(RlSiN)b(RlSiHNMC]m. Thus, a reaction of (C6H5SiH)n with [(cH3siNH)a(cH3siN)b(cH3sil~NK)c]m ( 1 1 m ratio) in THF at room temperature gave a new organosilicon polymer which was found to be an effective ceramic precursor, giving a Si3N4/SiC/C ceramic product in high yield upon pyrolysis to 1000C.
Additionally, use of the reaction product of organopolysilanes or polycarbosilanes with the polymeric alkali metal silylamide results in a product that is self-curing as the temperature is raised in the production of ceramic material.
Consequently, with these polymers it is possible to avoid the formation of SiO2 which results when an oxidative cure step is used. This again is an improvement over pyrolysis of the precursor silane compound alone.
~263796 In this system, R or Ra is preferably a lower alkyl, more preferably, R or Ra is C113. However, R or Ra need not be the same and, as aforesaid, mixtures of Si-11 containing organosilicon compounds and/or repeat units, e.g., [(RSiH)x(Rsi)y]n and [(R, SiH)x,(R Si.)y,]n"
[RaSi(H)~(CH2)q] and lRa Si(H)~(CH2)q~]~ and [(RSiH)X(RSi)y]n and [RaSi(1-1)~(C1i2)q] can be used to obtain further flexibility in tailoring the properties of the aforesaid product. Mixed polymers of the type [(RSi~1)a(RSi)b(RR Si)C~m (where a, b, c, m and R are as defined above, and R is defined as is R above and R may be the same or di~ferent th~n R) cnn be used ~s well.
YreEerably, R-R -C113, Ra-Ra ~CH3, Ra-R C113.
Further, these aforesaid mixtures of compounds can be used to obtain additional flexibility in tailoring the properties of the aforesaid product.
_ As metnioned, also included in this invention is the case of [(RSiH)X(RSi)y]n, where x-l, y-O, with R as defined above, where [(RSiH)]n may be a linear or a mixture of cyclic species, or a hybrid of both types. For example, [PhSiH]n (Ph is a phenyl group), cf, Aitken, C. et al., J. Organoll1et. Chem., 279:Cll-Cl3 (1985), reacts in the same way as the above-described organopolysilanes to provide new organopolysilane/organopolysilazane hybrid polymers. These mixtures will be particularly useful in attempts to avoid excess free silicon or carbon. The case of aryl-substituted repeat units of [RaSi(H)~(CH2)q] for example, where Ra is a phenyl or substituted phenyl group, and Ra can be a lower aryl group, is also included.
Mixtures of alkali metal polysilazanes, i.e., [(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m and [(Rl Si11N11)a,(Rl SiN)b,(Rl Si11NE)C,]m, (where E
12~3796 is the moiety introduced by reaction with an electrophile, e.g., a lower alkyl group of 1 to 6 carbon atorns, preferably CH3, or a silyl group), also may be used.
The preceramic product obtained by using alkali metal silylamides, even in only catalytic amounts, differs from the starting organosilicon compound. This difference is confirmed by proton NMR spectra. A typical organopolysilane starting material when R - CH3 shows an observed proton NMR integration ratio, SiCH3/SiH, ranging from 3.27 through 3.74 (see Table 1). In contrast, the similar ratio for products obtained when the starting material is reacted with an alkali metal silylamide, range from 8.รด to 14.
This difference in products apparently arises because both Si-H and Si-Si bonds are reactive towards nucleophilic reagents. Although not wishing to be bound by theory, it is believed that when alkali metal silylamides are used the following processes result:
(R3Si)2NM + ,SiH ~siN(siR3)2 + MH (1) (R3Si)2NM + ,SiH > (R3si)2NH + SiM ~2) (R3Si)2NM ~-~Si-Si ~(R3si)2N-si~ + SiM~ (3) In each of the above reactions a new reactive nucleophile is generated. In the first reaction, this nucleophile is MH, while in the second and third reactions, the nucleophile is a silyl alkali metal compound. Thus, nucleophilic attack on the [CH3SiH)X(CH3Si)y]n system will recur during these reactions and some of these oligomeric species, which comprise the starting materials, are linked together, resulting in products of higher molecular weight. There are other processes that are possible as well: e.g., ~2637~
(R3Si)2NK + -Si ~li (R3Si)2NSi~ K
H ll ~ Si: + Kll Thus, not only anionic species but also s:ilylenes can be involved as intermediates.
The "graft" polymer is Eormed by combining the already formed polymeric alkali metal silylamide with the Si-H
containing organosilicon polymer, for example, the organopolysilane in varying proportions in an organic solvent.
Thereafter, the mixture is stirred at room temperature for sufficient time for the two compounds to reac~. Al~y or~nnic solvent in whlch both polymer systems are soluble without reaction can be used. Such organic solvents include, for example, T~F, diethyl ether, glycol ethers, alkanes, arenes and comblnations thereof. The mixture may be heated above room temperature, and can be refluxed to speed up the completion of the reaction. After refluxing, the mixture is quenched with an electrophile, E-X, to form the organosilicon "graft" polymer.
The electrophile can be an alkyl halide, sulfate, or sulfonate;
a halosilane; or the like. Typically, CH3I or a chlorosilane is used, although other equivalent electrophiles wel].-known to those skilled in the art can also be used. E is preferably a lower alkyl group or silyl group; X preferably a halide, sulfate or sulfonate.
The organosilicon polymer formed by the present ("graft") process with the organopolysilane is typically obtained in yields greater than 85% based on weight of the starting materials with a variable molecular weight, typical values being in the 1800-2500 g/mol range. This preceramic organosilicon polymer can then by pyrolyzed under inert atmosphere conditions to result in a ceramic material in high yield. Typically, ~Z~379G
pyrolysis under nitrogen gives ceramic products in a yield of 70-83%.
The organosilicon polymers formed by the present ("graft") process typically give ceramic yields lO~ to 50~ greater (based on welght of the starting materials) than the polycarbosilane (See Table 2) and have a variable molecular weight.
Figure ] is a proton NMR spectrum comparing a l:l by weight physical mixture of the polycarbosilane and the polysilazane and a "graft" polymer formed by reacting the polycarbosilane with a preformed silyamide. The NMR spectrum shows that a new polymer is obtained when the polycarbosilane and the .silylamide are heated together in solution and then quenched with methyl iodide. First, the CH3Si/HSi integrated ratio differ, 9.4 in the former, 8.7 in the latter. Secondly, ths CH3Si_ NH proton (at ~ 5.06) to CH3Si_ (at ~ 4.50) proton ratio has changed from about 2 in the physical mixture to about 1 in the reaction mixture.
These preceramic organosilicon polymers can then by pyrolyzed under nitrogen or an inert atmosphere to result in ceramic materials in high yield. Typically, pyrolysis under nitrogen gives ceramlc products in a yield o~ G/~-~8~.
What is referred to herein as an "in situ" polymer is obtained by carrying out the cyclo-(RlSiHNH)n/MH reaction in solution in the presence of the Si-H containing organosilicon polymer. In this method, the methylpolysilane or polycarbosilane is added to an organic solvent. Afterwards, the cyclo-(RlSiHNH)n mixture (generated by reacting in solution anhydrous ammonia with RlSiHX2, where Rl is the same as defined earlier and X is a halogen) is added.
One then adds to the solution a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom. See U.S. Patent No. 4,482,669. The reaction ~Z63t7~6 mixture gradually changes color and hydrogen is evolved. The resulting solutlon is then stirred at room tem~erature Eor sufficient time for the silylamide intermediates and the Si-11 containing organosilicon polymer to react. It can be heated above room temperature, and can be heated at reflux to speed the completion of the reaction. AEterwards, the reaction mixture is allowed to cool to room temperature, if required, and quenched with an electrophile such as C113I or a halosilane, such as a chlorosilane, to produce the organosilicon "in situ" polymer.
The molecular weight of the "in situ" polymer is variable. For example, typLcal values of the polymer Eormed usin~ an organopolysilane are between 1600 g/mole to 2750 g/mole. On pyrolysis this material provides a high yield of a black ceramic material.
On pyrolysis the polycarbosilane-derived material provides a yield of a black ceramic material, that is typically lO~ to 50%
greater than that obtained on pyrolysis of the polycarbosilane (see Table 2).
The organosilicon polymer formed by either of the above "graft" or "in situ" methods usually is separated from solution. The solvent is removed by using techniques well known to a person of ordinary skill in the art. One standard method is distillation, preferably trap-to-trap distillation. The polymer, typLcally a white powder that is soluble in an organic solvent, is thereby obtained. One may also combine trap-to-trap distillation with centrifuging, followed by trap-to-trap distillation to separate the polymer from solution.
The "in situ" preceramic polymer differs physically from the "graft" preceramic polymer. Major differences are observed in their proton NMR spectra and in the form of their thermogravimetric analysis (TGA~ curves.
Figure 2 shows the proton NMR spectrum of a graft polymer lZ~3796 and that of an "i situ" polymer. Both polymers have similar starting molar ratios of [(Cll3SiH)x(CH3Si)y]:
(CH3SiHNH), [1.5:1 and 1.45:1, respectively], in terms of initial reactants used. However, in the " i situ" polymer the intensity ratio of the ~ 5.1, 4.7 to the ~ 4.0 proton signals is 12, while in the "graft" polymer this ratio is 1.
The signals around ~ 5.l and 4.7 are due to the Cll3SillN
proton while those around b 4.0 are due to CH3Si_ protons which are attached to silicon atoms not bound to nitrogen.
Accordingly, this difference in ratio demonstrates that the two polymers have different structures.
Although not wishing to be bouncl by theory, it appears likely that in the "i situ" preparation, intermediates formed, for example, by the action of Kll on (CH3SiHNII)n cyclics also react with the Si-H containing organosilicon polymer, for example, the organopolysilane [(CH3SiH)X(CH3Si)y]n before the polymeric alkali metal silylamide which is the starting reactant in the "graft" procedure has a chance to be formed to its usual extent. This results in either less of the original CH3SiHNH protons being lost and/or more of the Si-H
containing organosilicon system being reacted.
The TGA curve of the "graft" polymer is shown in Figure 3, while that of the "i situ" polymer is shown in Figure 4. These two curves differ as well. In the "graft" polymer, the curves show that there is a small weight loss between 100C and 200 D C
which begins at about 100C. In contrast, with the "in situ"
polymer, the initial small weight loss occurs only at higher temperatures, approximately beginning at 175C. Both types of polymers are useful as preceramic materials.
~2~3796 Table 2 TGA Ceramic Yield of Preceramic Polymer Wt ratio of Polycarbo- Ceramic Compound silane: Alkali Metal Yield (Example) Sil~lamide 100:0 58~ B.(2) 1:1 84~ 37 D.(3)(a)(i) 5:1 67~ III-57 D.(3)(a)(ii) ;
1:1 88~ III-39 D.(3)(b)(i) 5:1 64% III-59 D.(3)(b)(ii) 1:1 86% III-38 E.(2)(a)(i) 5:1 80~ III-56 E.(2)(a)(ii) 1:1 86~ III-40 E. (2)(b)~i) 5:1 66% III-58 E. (2)(b)(ii) ~263796 The use of the alkali metal silylamide of the formula [(RlSiHNH)a~RlSiN)b(RlSiHNM)C]m not only improves the ceramic yield oE the organopolysilanes, but, more significantly, when this alkali metal silylamide is reacted with organopolysilane of the formula [(RSill)x(RSi)y]n in the appropriate stoichiometry, the reaction product of [(RSiH)X(RSi) ]n and [(RlSiHNH)a(R~SiN)b(RlSiHNM)C]m (where m and n are integers greater than l), after treatment with a suitable electrophile such as an organic or a silyl halide, incorporates both starting materials. When this reacti.on product is pyrolyzed, the excess silicon normally obtained in the pyrolysis of the organopolysilane alone and the excess carbon normally obtained in the pyrolysis of the quenched polymeric alkali metal silylamide alone combine so that there is no substantial excess of either element in the ceramic product. Consequentiy, one can obtain a ceramic material with less than about 0.1~ of free silicon and less than about O.l~ of free carbon, i.e., a ceramic material containing substantially no free carbon and no free silicon. The exact combination oE the two compounds necessary to result in the desired stoichiometry can readily be calculated by a person of ordinary skill in the art on the basis of the results of the analyses of the ceramic products obtained in the pyrolysis of the separate polymers. Mole ratios of organopolysilane : polymeric alkali metal silylamide from about 4:1 to about 1:4, and preferably from 2.5:1 to 1:2 typically provide useful results. However, other ratios can be used depending on the particular starting materials and their pyrolysis characteristics.
The excess of free carbon, which can be a problem with the starting polycarbosilanes, can be dealt with by using a ternary system of: (1) the polycarbosilane; (2) the polysilazane (as the ~6~796 polymeric silylamide, eitller preformed or generated i situ) and (3) a polysilane whose pyrolysis alone gives a ceramic product which contains an excess of silicon. Examples of such polysilanes are organopolysilanes as described above, for example, those which are produced by the sodium condensation of methyldichlorosilane. In these reactions the organopolysilane is preferably as defined above, i.e [(RSiH)X(RSi)y]n.
More preferably R is a lower alkyl group, most preferably R is CH3. Using an appropriate mixture of the three polymers (which can be calculated from the results oE the analyse.s of the ceramic products of the pyrolysis oE each individual polymer, e.g., the CH3I- quenched polymer in the case of the polymeric silylamide), one can obtain a ceramic product which contains a minimal excess of either element, carbon or silicon. Such hydrid ternary preceramic polymers are soluble in organic solvents and, depending on component ratios used, are of variable molecular weight. Their pyrolysis gives black ceramic products in high (generally > 80%) yield.
Physical blends of Si-H containing organosilicon polymers, for example the organopolysilane, or the polycnrbosilane polymers containing repeat units of ~RaSi(H)~(CH2)q]~ for example, the Yajima polycarbosilane with the "quenched"
[(RlSiHNH)a(RlSiN)b(RlSiHNE)C]m organosilazane polymer of U.S. Patent No. 4,482,669 can be used since these react when they are heated together. ~len approximately equal molar quantities of the polymers where R, or Ra ~ CH3, - CH3, q - 1 and E ~ CH3, were mixed and finely ground together and then subjected to pyrolysis to 1000C, ceramic yields was obtained which were approximately the average of the ceramic yields when the organopolysilane and the organosilazane polymers were pyrolyzed separately, and were significantly ~63796 higher than that which resulted when the polycarbosilane was pyrolyzed separately ~see Table 2).
When polycarbosilane/orgosilazane mixtures were heated, in the absence of a solvent at 200C under nitrogen, white foamy solids were obtalned WhiCIl were insoluble in nollpolar organic solvents, thus demonstrating ~hat a reaction had occurred below 200C and prior to pyrolysis. When organosilane/
organosilazane mixtures were heated, either in the absence of a solvent at 100C under nitrogen or in a toluene solution at rcflux, white powders were obtained which were insoluble in nonpolar organic solvents, again demonstrating that a reaction occurred.
Ternary blends of the polycarbosilane, the [(CH3SiH)X(CH3Si)y]n liquid polysilazane and the [ (cH3siHN~l)a(cH3siN)b(cH3siHNcH3)c]m . ~ polysilazane behaved similarly. An obvious reaction occurred when such a mixture had been heated to 200C, since the originally soluble mixture became insoluble in organic solvents.
The comblned polymers obtained by the "graft," "i situ" and physical blend methods can be converted to black ceramic fibers. Pyrolysis of pressed bars of the combined polymers to 1000C provides a black solid product. In other experiments, silicon carbide powder was dispersed in a toluene solution containing 25~ by weight of the combined organosilane/organosilazane polymers. The solvent was evaporated and the residue, a fine pow'aer of silicon carbide k with combined polymer binder was pressed into bars and pyrolyzed at 1000C. A ceramic bar was obtained showing a low weight loss and slightly shrunken size.
Similarly, when silicon carbide powder was dispersed in toluene solutions of the combined polycarbosilane/organosilazane polymers. The solvent was evaporated and the residue, a fine powder of silicon carbide with combined polymer binder, was pressed into bars and pyrolyzed at 1000C. A ceramic bar was obtained showing a low weight loss and slightly shrunken size.
The invention will be further illustrated by the examples that follow:
A. General All glassware was Elame-dried under vacuum or under a stream of nitrogen prior to use. Tetrahydrofuran t~llF) and benzene were distilled from sodium and benzophenone ketyl. ~lexane was distilled from LiAlH4. Solvents were deoxygenated by bubbling nitrogen through them prior to use. Methyldichlorosilane, CH3SiHC12, and dimethyldichlorosilane, (CH3)2SiC12, were commercial products. The polycarbosilane was purchased from Dow Corning Corporation. Its characterization is reported below. The ammonolysis of CH3SiHC12 in ether and in THF
solution has been described in U.S. Patent No. 4,482,699 (D.
Seyferth and G.H. Wiseman), as has the reaction of ammonolysis products, [CH3SiHNH]m, wIth KH to give the polymeric silylamide, [(CH3SiHNH)a(CH3SiN)b(Cll3SillNK)c)]m Poly(methydrosiloxane), [CH3Si(H)O]n was purchased from Petrarch (Catalog #PS 122) and was used as recieved. Piperdine, diisopropylamine, and propylamine were purchased and were distilled from CaO before use. Reagent grade sodium shot was further purified by creating a dispersion in refluxing xylene and allowing this to cool, with stirring. This served to remove most of the oxide coating. Anhydrous ammonia was dried further by passing it through a KOH column.
lH NMR spectra were recorded on a JEOL-FX-9OQ spectrometer operating at 90 MHz. Elemental analyses were performed by Galbraith Laboratories, Knoxville, Tennessee. Molecular weights :' ..
~,%63796 were determined bymeasuring the free~ing point depression of a weighed sample of benzene caused by a weighed sample of product. Thermal analyses were performed using a Perkin-Elmer TGS-2 Thermogravimetric Analyzer interfacsd with a System 7/4 Thermal Analysis Controller on a DuPont 950 TGA cormected to a DuPont thermal analysis system. Samples were heated, under argon, from 25-1000C at a rate of 10C/min. Large scale pyrolyses were carried out in fused silica boats using a Lindberg 59344 tube furnace (25-].000C, 10C/min) under argon atmosphere. scanning electron~icrographs were obtained using an AM~ lnstrument, operating at 20 KV.
B. Preparation of Organosilicon Compounds 1. Preparation of ~(CH3SiH)X~_3~yln (all operations under nitro~en) - - i i ~_~ a. In THF Medium.
A 500 ml, three-necked, round-bottomed flask equipped with a stir-bar, a dropping funnel and a reflux condenser was charged with 50.5 g (2-.20 g atom) of Na metal. The flask was attached to a Schlenk manifold, evacuated and refilled with nitrogen three times. THF (200 ml) was added and the dropping funnel was charged with 65 ml (0.625 mol) of CH3SiHC12. The silane was added to the stirred Na suspension during the course of 45 min., after which time the reaction mixture was cloudy and slightly warm. The mixture was stirred for 16 hours at room temperature ~:. and 48 hours at reflux; it then was cooled to room temperature.
llexane (60 ml) was added. The mixture was transferred by cannula to a heavy-walled centrifuge bottle and centrifuged.
The supernatant layer was transferred to a 1 liter round-bottomed flask (under nitrogen). THF (50 ml) and hexane (30 ml) were added to the resldual solid and the resulting ~LZ63796 suspension was centrifuged. The supernatant layers were combined and solvents were removed by t.rap-to-trap distillation in vacuum until the residual liquid volume was about 100 ml.
This liquid was cannulated into a 250 ml single-necked flask and the remaining solvent was removed in vacuo to leave 13.2 g (0.30 mol, 48% yield) of a white, glassy solid. On being heated in a sealed capillary (in vacuo~ this solid soEtened around 40C and "melted" between 130-140C with gas evolution, leaving a thick gum There was no further change up to 300C except For a gradual increase in viscosity. The product was poorly soluble in hexane, only somewhat soluble in benzene (precluding measurement of its cryoscopic molecular weight in this solvent) and quite soluble in THF.
NMR ~90 MHz, in CDC13): ~ 0.10-0.61 (m, SiCH3, 7.5H) and 3.55-3.90 (m, SiH, 1ll). Based on the reasonable assumption that every Si atom bearing a H substituent also bears a CH3 substituent, the integrated CH3Si and SiH intensities lead to a constitution [(CH3SiH)o 4(CH3Si)o 6]n Anal. Calcd for CSiH3 4: C, 27.60; H, 7.87.
Found: C, 27.18; H, 7.17.
IR (KBr, Nujol): 2170(sh), 2100(s, Si-H), 1408(m), 1260(m, Si-CH3), 1249(s, Si-CH3), 1060(br), lOl9(s), 931(s), 865(vs, Si-CH3), 770(vs), 685(vs), cm~l.
TGA(25-1000C, 10C/min.): 60% yield of a gray-black ceramic solid. A tube furnace pyrolysis of 3.20 g of this material to 1500C gave 1.52 g (48%) of a gray ceramic powder.
~_263~96 Anal. of the Ceramic Powder. Found: C, 22.56; Si, 78.42; H, 0.01; N, 0.009~ (SiC requires C, 29.94; Si, 70.06%; actual composition: SiC + 0.49 Si). X-ray powder difEraction (d A): 1.315(s) (~ -SiC), 1.542(s) (~ -SiC), l.91(m) (Si), 2.181(m), (~ -SiC), 2.52(vs) (a -SiC), 3-13(m) si) .
A mass spectral analysis of the pyrolysis gas in another experiment showed the following: no gaseous products were observed up to 385C, then fragment ions corresponding well with the reported fragmentation oE Cll35iH3. At 445c, CH3Sill3 was still observed and a peak at m/z ~ 16 (CH4) began to grow in. By 5~0C, when weight loss was about over, only the methane peak was observable. ..
b. In Hexane/T~lF Medium `~ In a dry box, a 1 liter three-necked, round-bottomed flask equipped with a stir-bar, a dropping funnel and a reflux condenser was charged with 75.0 g (3.26 mol) of sodium metal.
The flask was attached to a Schlenk manifold, evacuated and flushed with nitrogen. THF (70 ml) and hexane (420 ml) were added and the dropping funnel was charged with 150 ml (1.44 mol) of methyldichlorosilane. Methyldichlorosilane was added slowly into the flask over a 3 hour period. The reaction solution turned purple and by the end of the addition was at gentle reflux. The reaction mixture was stirred at room temperature for 2 hours and then heated at reflux for 16 hours. After it ~~ had been cooled to room temperature, the reaction mixture (except for the large NaCl crystals) was transferred via cannula into a heavy-walled glass bott].e. The mixture was centrifuged and the clear, colorless supernatant layer transferred by cannula into a 1 liter round-bottomed flask equipped with a ~ ~637~6 stir-bar. Hexane (200 ml) and THF (20 ml) were added to the remaining solids, the mixture again was centrifuged, and the supernatant liquid combined with the supernatant solution previously separated. Solvent was removed by trap-to-trap distillation until the volume of the residue was about 100 ml, and the remaining liquid was transferred by cannula into a weighed 250 ml round-bottomed flask. Remaining solvent was removed by trap-to-trap distillation at approximately 0.05 mm Hg at room temperature to give 51.2 g (81%, 1.16 mol) of a cloudy white oil.
H NMR (90 MHz, C6D6):~ 0.37 (broad, SiCH3, 3.74H) 3.92 (broad, Si}l, l H).
NMR integration of the product gave a constitution of [(CH3SiH)o 8(CH3Si)0,2]n.
IR (thin film, cm l): 2967(s), 2900(s), 2800(w), 2099(vs), \~ 1410~s), 1385(w), 1249(s), 1055(br), 933(s), 865(vs), 770(vs), 685(br), 650(sh), 585(w).
Molecular weight (cryoscopic in benzene): 600 g/mol.
Anal, (material from another similar preparation). Calcd. for CSiH3 76; C, 27.39; H, 8.55; Si, 64.05. Found: C, 27.49; H, 8.98; Si, 61.58%.
TGA (25-1000C, 10C/min): 20% yield of a gray-black ceramic solid. Pyrolysis of a sample from another preparation in a tube furnace gave a gray-black ceramic solid in 36% yield (by weight).
Anal. of Ceramic. Found: C, 22.93; Si, 75.99%.
~-~ The pure liquid obtained by this procedure is very air-sensitive, particularly when its effective surface area is high, as when in contact with a fritted funnel or a paper or cloth towel (in which cases spontaneous inflammation may occur).
Other, si~ilar reactions have given 62-75% yields of (CH3SiH)X(CH3Si)y. Molecular weight determinations of ~Z63'796 several preparations ranged from 520-740 g/mol. All products had very similar lH NMR spectra, but with different SiCH3:SiH ratios. Physical data of these products are listed in Table 1.
~v .
~,Z63796 PHYSICAL DATA FOR ~(CH3SiH)x(Cll3S~ _ POLYM~RS
Sample # Polymer M.W.a SiCl13:Sillb Cer~micC x y Yield (%) Yield (~) _ YFY III-l 81 600 3.74:1 20 0.80 0.20 YFY II-40 74 740 3.56:1 16 0.84 0.16 YFY II-25 73 650 3.51:1 26 0.85 0.15 YFY II-12 , 66 520 3.27:1 16 0.91 0.09 YFY I-73 73 680 3.48:1 27 0.86 0.14 aCryoscopic in benzene.
b lH NMR integration ratio.
CUnder nitrogen gas, 25-1000C, 10C/min (TGA) ;, ~Z63796 For the purposs of simplifying calculation, an average formula weight value 44 was assigned for the unit (CII3Si~I)X(CII3Si)y Therefore, in each o~ the following experiments, the number of moles of the reaction unit (CH3SiH) was calculated from the weight of the polymer used divided by 44.
The product formed in the TIIF solution,gives a 60~ ceramic yield, but lt is of limlted solubility in organic solvents and its conversion to ceramic fibers requires a curing step of photolysis/oxidation. Preparation of the [(CH3SiH)X(CH3Si)y]n in a hexane/TllF mixture of ~pI)roxiIlln~oly 6 to 7:1. ros~ o(I 1Il sn~isfnc~ory yi.olds of n soluble produet. I-Iowever, pyrolysls of this material resulted in very low eeramie yields, ranging from 16 to 27~. -' ; , .2. Characteri~zation of the Polycarbosilane.
The polyearbosilane, a white solid, was purchased from Dow Corning Corporation. The following data were eolleeted on it:
H NMR (90 MHz, C6D6): ~ 4.52 (broad, SiH, lH) 0.26 (broad, SiCH3 and SiC_2Si, 8.6H~
IR (KBr, Nu~ol, em 1): 2104(s), 1253(s), 1014(s, broad), 845(s, broad), 734(s).
Moleeular ~eight (eryoseopie in benzene): 1210 g/mol TGA (25-1000C, 10C/min): 58~ yield of a blaek eeramie solid.
Tl/2 - 510C
C. Catalytie Reaetions of ~(CH3SiH~X(CH3Si~yl_ 1. Potassium Bis(trimethvlsilvl~amide - Catalyzed Conversion of ~(CH3SiH~x(CH3Si~yln ~,Z6~796 In a dry box, a 50 ml round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap ("standard apparatus") was charged with 0.1 g of KH (0.0025 mol). THF (20 ml) was added to the flask to suspend the KH. To the KH suspension was added 0.44 g of [(CH3)3Si]2Nll (0.0027 mol). Reaction occurred immediately with hydrogen gas evolution. The solution was stirred at room temperature for 20 mlnutes and then heated at reflux for 20 minutes. The slightly yellow solution was allowed to cool to room temperature.
Another 100 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with 2.2 g of [(CH3Slll)x(CH3Sl)y]n (0.05 mol, x - 0.85, y - 0.15). THF (20 ml) was added to the flask to dissolve the polymer. The [(CH3)3Si]2NK solution previously described was slowly added to the reaction flask by syringe. Addition of each drop resulted in formation of a transient orange color which quickly disappeared. The orange color perslsted after 1 ml of the solution had been added.
After 10 ml (ca. 2.5 mol~) of the solution of [(CH3)3Si]2NK had been added, the reaction mixture turned deep red and a small amount of white precipitate was present.
CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stlrred at room temperature for one hour. The solvent was removed under reduced pressure to give a white solid which was extracted with two 50 ml portions of hexane. The extracts were centrifuged, and the clear, colorless supernatant layer was transferred via cannula into a weighed 100 ml round-bottomed flask equipped with a stir-bar. Solvent was removed by trap-to-trร p distillation to give 1.51 g (68~, by weight) of a white powder ("usual work-รนp"). The reaction product is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.2 (broad, SiH, 1 H) 0.47 (broad, SiCH3, 8.8 H) ~,2~3796 Molecular weight (cryoscopic in benzene): 1000 g/mol TGA (25-1000C, 10C/min~: 63~ yield of a black ceralnic solid, T1~2 ~ 300Ca aTl/2 ~ temperature at which one-half oE the total weight loss has occurred.
2. Potassium Bis(vinvldimethylsilvl)amide - CatalYzed Conversion of ~(CH3SiH)xtCH3Si~yln According to the procedure described previously, the reaction between 0.46 g (0.0025 mol) of [(CH2-CII)Si(CH3)2]2NH and 0.1 g (0.0025 mol) of KII in 20 ml oE THF was carrled out under nitrogen. The resulting solution was added to a separate flask which was charged with 2.2 g (0.05 mol) of [(CH3siH)x(cH3si)y]n (x ~ 0.85, y = 0.15) and 20 ml of THF. After 9 ml (ca. 2.5 mol%) of the [(CH2-CH)Si(CH3)2]2NK solution had been added, the deep red reaction mixture started to form small amounts of white precipitate. CH3I (0.5 ml, 7.9 mmol) was added and the resulting solution was stirred at room temperature for one hour. The usual work-up followed. A white powder (2.01 g, 91~) was obtained which is very soluble in hexane, benzene, and TIIF.
H NMR (90 MHz, C6D6): ~ 4.08 (broad, SiH, llI) 0.47 (broad, SiCH3, 12 H) Molecular weight (cryscopic in benzene): 850 g/mol TGA (25-1000C, 10C/min): 61% yield of black ceramic solid, Tl/2 ~ 400C.
3. Monopotassium Derivative of HexamethylcYclotrisilazane -Catalvzed Conversion of ~(CH3SiH?x(CH3Si)yln_ According to the procedure described previously, the reaction between 0.55 g (0.0025 mol) of [(CH3)2SiNH]3 and 0.1 g (0.0025 mol) of KH in 20 ml of THF was carried out under nitrogen. The resulting solution was added to a separate flask ~2~3796 which was charged with 2 2 g (0.05 mol) of [(CH3SiII)X(CH3Si)y]n (x ~ 0.85, y 0.15) and 20 ml of THF. After 10 ml (ca. 2.5 mol~) of the potassium silylamide solution had been added, the reaction mixture turned deep red and a small amount of white solid precipitated. CH3I (0.5 ml,
7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. Work-up as above followed. A
whlte powder (1.95 g, 89~) was obtained. The reaction product is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.60 (quartet, SiH, 0.7 H) 4.18 (broad, SiH, 1 H) 0.48 (broad, SiCI13, 14 II) Molecular weight (cryoscopic in benzene): 750 g/mol TGA (25-1000C, 10C/min): 56~ yield of a black ceramic solid, Tl/2 300~C.
4. Monopotassium Derivative of sym-TrimethYltrivinYlcYclotri-silazane- Catalyzed Conversion of ~3 S ~ x ( CH3 S i ~ yln Essentially the same procedures were used in the reaction of [(CH3)(CH2-CH)SiNH]3 (0.66 g, 0.0025 mol) with ~I (0.1 g, 0.0025 mol) in 20 ml of THF solution. The resulting solution was added to a 100 ml three-necked round-bottomed flask which was charged with 2.2 g (0.05 mol) of ~(CH3SiH)x(CH35i)y]n (x - 0.85, y - 0.15) and 40 ml of THF. After 6 ml (ca. 1.5 mol~) of the solution had been added, the deep red color of the reaction mixture persisted and a small amount of white solid precipitated. CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. Work-up as above followed. A white powder (1.79 g, 81.4%) was obtained. The reaction product is soluble in hexane, benzene and THF.
1~63796 H NMR (90 ~l~, C6D6): 5 4.16 (broad, SiH, 1 Il) 0.49 (broad, SiCil3, 8.9 H) Molecular weight (cryoscopic in benzene): 910 g/mol TGA (25-lOOO~C, 10C/min): 67~ yield of a black ceramic solid, Tl/2 = 410C.
5. Potassium Piperidide - Catalvzed Conversion of ~ (CH3SiH)x(CH3~Lyl~
In a dry box, a 50 ml round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with 0.1 g of Kll (0.0025 mol). TIIF (20 ml) was added to the flask to suspend the Kll. To the Kll suspension was added 0.25 ml of piperidine. Reaction occurred immediately with hydrogen gas evolution. The solution was stirred at room temperature for one hour and then heated at reflux for one hour. The slightly yellow solution was allowed to cool to room temperature.
Another 100 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with l.l g of [(CH3SiH)X(CH3Si)y]n (0.025 mol, x - 0.8, y - 0.2). THF (20 ml) was added to the flask to dissolve the polymer. The potassium piperidide solution previously described was added slowly to the reaction flask by syringe. Addition of each drop resulted in formation of a transient orange color which quickly disappeared. The orange color persisted aEter 10 ml of the solution had been added.
AEter 20 ml (ca. 10 mol~) of the solution of cyclo-C5HlONK
had been added, the reaction mixture was stirred at room temperature for one hour. The reaction solution turned deep red and a small amount of white precipitate was present. CH3I
(0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. The solvent was removed by trap-to-trap distillation at reduced pressure to give ~263796 a white solid which was extracted with two 35 ml portions of hexane. The extracts were centrifuged, and the clear, colorless supernatant layer was transferred via cannul.a into a weighed 100 ml round-bottomed flask equipped with a stir-bar. Solvent was removed by trap-to-trap distillation to give 1.03 g (67~, by weight) of white powder which is soluble in hexane, benzene, and TIIF.
H NMR (90 MHz, C6D6): 6 4 09 (broad, Sill, 1 }l) 0.47 (~road, SiCl13, ~.7 Il) Molecular weight (cryoscopic in benzene): 840 g/mol TGA (25-1000C, 10C/min): 57~ yield of a brownish-black ceramic solid Tl/2 ~ 350OC.
6. Potassium n-Propylamide - Catalyzed Conversion of ~(CH3SiH)x(c~13si)~ln Essentially the same procedure was used in the reaction of 0.30 g (0.0025 mol) of n-C3H7NH2 with 0.1 g (0.0025 mol) of Kll in 20 ml of THF as that described in Section C.(5). In this case, 20 ml of the n-C3H7NIIK solution (ca. lO mol~) was used to react with l.l g (0.025 mol) of [(CH3SiH)X(CH3Si)y]n (x ~ 0.8, y 0.2) in 20 ml of THF. After the addition was completed, the reaction solution turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white precipitate was present. CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. The usual work-up left 0.95 g (73% by weight) of a white solid which is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6) 6 4.08 ~broad, SiH, l H) 0.51 (broad, SiCH3, 13.6 H) Molecular weight (cryoscopic in benzene) : 840 g/mol ~L2637~i TGA (25-1000C, 10C/min): 57% yield of a brownish-black ceramic solid Tl/2 ~ 300C
7. Potassium Diisovropylamide - Catalyzed Conversion of l(cH3siH)-(cll3si)yl-Essential].y the same procedure was used in the reaction of 0.30 g (0.0025 mol) oE (iso-C3H7)2NII wlth 0.1 g (0.0025 ol) oE ~l in 20 ml o~ Tlll as ~llat described in Section C.(5).
In this case, 20 ml of the (iso-C31l7)2NK solution (ca. 10 mol~) was used to react with 1.1 g (0.025 mol) of [(CH3SlH)X(CH3Si)y]n (x ~ 0.8, y ~ 0.2) in the 20 ml of THF. After the addition was completed, the reaction solution turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white preclpltate was present. CH3I (0.5 ml, 7.9 mmol) was added, and the resultlng solution was stirred at room temperature for one hour. Work-up as above left 1.03 g (79% by weight) of a white solid which i5 soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 3.99 (broad, SiH, 1 H) 0.47 (broad, SiCH3, 8.7 H) Molecular weight (cryoscopic in benzene): 750 g/mol TGA (25-lOOO~C, lOrC/min): 34% yield of a brownish-black solid Tl/2 = 280C
D. "Graft Procedure"
1. Reactions of ~(CH3SiHNH)a(CH3SiN)b(CH3SiHNK)clm Livin~ Polymer 3 ~ x~CH3Sl)yln a ~(CH3SiH~x1__3Si)yln Prepared in 7:1 Hexane/THF
i. Using cyclo-~CH3SiHNH]m Pre~ared in Diethyl Ether 1~6~796 The same general procedures were used for all of these reactions. In a dry box, a 250 ml round-bottomed Elask equipped with a stir-bar, reflux condenser and a serum cap was charged with a weighed smount of Ktl (ca. 3. 3 mol~) based on (CH35itlNtl) ) . THF (100 ml) was added to suspend the KH.
(CH3SiHNH)m, prepared in ether solution, was added into the flask by syringe (a vigorous reaction occurred and a large amount of H2 gas was evolved which was vented o.tt oE the flask tllrougll nn oil bu~bler. A~ter ~lle addition wns Llnislled, the reaction mixture was stirred at room temperature for 1 hour and then heated at reflux for l hour.
A separate 250 ml flask equipped with a septum, reflux condenser and stir-bar was charged with a weighed amount oE
[(CH3siH)X(cH3si)y]n (x - 0.85, y - 0.15). TilF (60 ml) was added by syringe to give a clear, colorless solution.
The living polymer solution previously described was cannulated slowly into the reaction flask. The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the volatiles were removed by trap-to-trap distillation.
The product was treated with 200 ml of hexane and the insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leaving a white solid. Physical data for these reaction products are given in the Tables 3, 4, 5, and 6. All of these polymers are very soluble in hexane, benzene, and THF.
b. Using cyclo- ~C113SitlNtll~ Prepared in TIIF
According to the procedure described previously, the reactions between KH and (CH3SiHNH)m (prepared in THF
12~3796 solution) were carried out under nitrogen. The living polymer solution then was added to the THF solution of [(C113Si~)x(CH3Si)y]n (x = 0.8, y = 0.2). The resulting orange solution was stirred at room temperature for one hour and then heated at reElux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added. Work-up as described in the previous experiment left a white solid. Physical data for these reaction produc~s are ~iven in ~lle Tn~lcs 3, 4, 5, nnd G.
.~
_ 12637~6 PREPARATION OF TIIE MIXED POLYMERS
Sample ~ YFY YFY YFY YFY YFY YFY
III-7 III-ll III-14 II-29 II-30 II-30-1 Solvent for (CH3sillNH)m PreparationTHF THF THF Ether Ether Ether Weight of [(CH3siH)x10.1 g6.6 g 3.3 g 2.4 g 1.1 g 2.2 g (CH3sl)y~n i'-~:.
Moles of [(CH3siH)x0.23 0.15 0.075 0.055 0.025 0.05 (CH3Si)y)n (A) Weight of (CH3slllNH)m 8.85 g8.85 g 8.85 g 2.4 g 2.08 g 1.22 g Moles of (C1~3SiHNH)m ;~ ~ (B)0.15 0.15 0.15 0.041 0.035 0.021 Mole Ratio A:B 1.5:1 1:1 1:2 1.34:1 1:1.41 2.42:1 Yield (%) 85 88 87 90 95 88 lZ63796 --~o--CERAMIC YIELD AND MOLECULAR WEIGHT DATA OF MIXED POLYMERS
Sample #d Ceramica 1/2 MolcularC
Yield (~) _ (C) Wei~llt(g/mol) YFY III-ll 78 420 2600 aUnder nitrogen, 25-1000C, 10C/min (TGA) bTemperature at which l/2 of total weight loss had cccurred . . ~
CCryoscopic in benzene dFor detalls of preparation, see Table 4 lZ63796 l_ NMR SPECTRAL DATA- OF THE MIXED POLYMERS
Sample #c (CH3SiHNH) (Cll3SiH) (Cll3SiHNH) Integration and SiC113_ Ratio=
YFY III-7 5.12 (b) 4.12 (b) 1.56, 1.22, 1:1:14.4 4.G7 (b) 0.88, 0.46 (b), 0.24 Y~Y III-ll 5.14 (b) 4 07 (b) 1.56, 1.22, 1.75:1:7 4.67 (b) 0.88, 0.41 (b), 0.24 YFY III-14 5.19 (b) 4.08 (b) 1.55, 1.23, 3:1:18 4.71 (b) 0.89, 0 45 (b), 0.26 YIY II-29 5.17 (b) 4 o5 (b) 1.35, 2:1:14.6 4.72 (b) 3.56 (b) 0.52 (b), 0.27 YFY II-30 5.17 (b) 4 03 (b) 1.41, 1.34, 2.13:1 13.8 4.71 (b) 3.56 (b) 1.22, 0.46 (b), 0.27 YFY II-30-1 5.15 (b) 4.12 (b) 1.23, 1.9:1:16.1 4.72 (b) 3.57 (b) 0.46 (b) 0.26 . _ . ... _ _ a90 MHz, in C6D6, chemical shift in ppm.
b(CH3SiHNH)/(CH3Si_)/(C_3Si)+(N_) proton integration CFor details of preparation, see Table 4 12~37!~6 PROPOSED FORMULAS AND TIIEIR ANALYTICAL DATA FOR TIIE MIXED POLYMERS
Proposed Formula (CH3SiH)x(CH35i)y(CH3SiHNII)a(C~13SiN)b Sample f~f Polymera Totalg Ceramic Total Anal. Accounted Anal. Accounted Calcd. Found ForFound For YFY III-7 x, 0.163 C, 24.46 C, 25.75 96.8 C, 20.59 97,27b y, 0.437 ~1, 7.11 Il, 7.69 Il, 0.78 a, 0.163 Si, 57.02 Si,53.42 Si, 62.79 `- b, 0.238 N, 11.41 N, 9.94 N, 13.11 YFY III-ll x, 0.116 C, 23.78 C, 24.79 98.49 C, 19.28 101.0C
y, 0.384 H, 6.97 H, 7.34 H, 0.99 a, 0.203 Si, 55.41 Si,53.17 Si, 63.47 b, 0.297 N, 13.85 N, 13.19 N, 17.26 YFY III-14 x, 0.09 C, 22.65 C, 24.21 100.46 C, 18.27 90.44 y, 0.24 H, 6.85 H, 7.85 H, 0.55 a, 0.27 Si, 52.81 Si, 51.89 Si, 58.65 b, 0.40 N, 17.69 N, 16.51 N, 12.97 YFY III-29 x, 0.087 C, 24.26 C, 24.03 87.06 C, 19.68 95.0ld y, 0.482 H, 6.94 H, 7.97 H, 0.19 `- a, 0.174 Si, 56.56 Si, 43.56 Si, 58.71 b, 0.256 N, 12.17 N, 11.50 N 16.43 YFY III-30 x, 0.112 C, 22.73 C, 24.56 90.53 C, 17.31 95.39e y, 0.303 H, 8.76 H, 6.97 H, 0.20 a, 0.239 Si, 53.00 Si, 44.56 Si, 57.87 b, 0.346 N, 15.50 N, 14.44 N, 20.01 ~2~3796 -43~
YFY II-30-1 x, O.062C, 25.33 C, 23.35 79.45 C, 19.97 90.36 y, 0.646H, 6.98 Il, 6.88il, 0.65 a, 0.122Si, 59.06 Si, 41.53Si, 58.44 b, 0.172N, 8.62 N, 7.69N, 11.30 -aCalculated on the basis of NMR integratlon bCalcd- compo5ition (Si3N4~ Si3N4 -~ 6.6 SiC -~ 0.74 C
this repre3ents only 2.2 % by weight free carbon CCalcd. composltion: Si3N4 + 4.4 SiC + 0.85 C
(equivalent to 3.1~ by weight Eree carbon) dCalcd. composition (assuming % Si is in error):
Si3N4 + 4.8 SiC + 0.84 C
(equivalent to 2.9~ by weight free carbon) eCalcd. composition (same assumption): Si3N4 + 3.3 SiC + 0.78C
~equivalent to 3.3% by weight free carbon) For details of preparation, see Table 4 gAnalytical difficulties, probably due to formation of ceramic material ~Z6;~796 b. ~(CiI3Sil-I)X(CII3Si) ln PrePared in THF
i. U~in~ cvclo~ H35iHNII)Im PreDared in Diethyl Ether In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.01 g (0.25 mmol) of KII. TIIF (100 ml) was added to suspend the ~I.
To the KH suspension, (CII3SiHNIl)m (1.57 g, 0.027 mol, prepared in ether solution), was added by syringe (a vigorous reaction occurred and a large amount of H2 gas was evo].ved whlch was vented out of the flask through an oil bubbler).
After the addition was finished, the reaction mixture was stirred at room temperature for 1 hour and then at reflux for 1 hour.
A separate flask equipped with a septum, reflux condenser and stir-bar wa5 charged with 1.1 g (0.025 mol) of [(CII3SiH)X(CH3Si)y]n (x ~ 0.46, y ~ 0.54). TIIF (60 ml) was added by syringe to give a clear, colorless solution.
The living polymer solution described above was carmulated slowly into the reaction flask. The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the solvent was removed by trap-to-trap distillation, leaving a white solid (2.5 g, 94% by weight). The reaction product is soluble in hexane, benzene, and TIIF.
11 NMR (90 MHz, C6D6) ~ 5.20, 4.74 (broad, SiCH3HNH, 1.25H) 4.07 (broad, SiCH3_, lH) 1.59,1.23 (broad, SiCH3HNH, lH) 0.46, 0.26 (broad, SiCH3, 11 H) Molecular weight (cryoscopic in benzene): 1700 g/mol TGA (25-1000C, 10C/min): 76~ yield of a black ceramic solid, Tl/2 - 400C.
~263~796 ii. Uslng cyclo-~C113SillNIllm Prepared in THF
According to the procedure described previously, the reactions between KH (0.1 g, 2.5 mmol) and (C113SillNII)m (2.9 ~, 0.051 mol, prepared ln Tlll solu~lon) were carried out uncler nitrogen. The living polymer solution then was added to the THF
solution of [(CH3SiH)X(CH3Si)y]n (2-2 g, 0-05 mol~ x =
0.46, y - 0.54). The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of C113I was added. Work-up as described in the previous experiment left a white solid (4.65 g, 91% by weight). The reaction product is soluble in hexane, benzene, and THF.
11 NMR (90 Mllz, C6D6): ~ 5.15, 4.71 (broad,SiCH3llNII, 2 H) 4.50, 3.93 (broad, SiCH3_, 1 H) 1.58, 1.23 (broad, SiCH3HNH, 1 H) 0.47, 0.25 (broad, SiC_3,16 H) Molecular weight (cryoscopic in benzene): 2700 g/mol TGA (25-1000C, 10C/min): 80~ yield of a black ceramic solid, Tl/2 420C.
2. Reaction of Polymeric ~(C6_5SiH~ln with Poly(phenylsllylene), [C6H5SiH]n, molecular weight 860, was prepared by the method of Aitken, et al., J. Organomet.
Chem., supra.
The polymeric silylamide was prepared by the usual method, in this case by adding 1.0 g (3.0 mmol) of cyclo-(CH3SiHNH)m (mol. wt 330), obtained by ammonolysis of CH3SiHC12 in diethyl ether, to a suspension of 0.02 g (0.5 mmol) of KH in 10 ml of THF at room temperature. The mixture was stirred at room temperature for two hours. This solution then was added, under dry nitrogen, to 1.0 g of (C6H5SiH)X (1.2 mmol) in 20 ml of THF in a 100 ml three-necked flask equipped with reflux condenser topped with a nitrogen inlet tube, two rubber septa and a magnetic stir-bar, at room temperature. The reaction mixture turned orange upon addition of a few drops of the polysilylamide solution. (The final color was re~.) After the reaction mixture llad been stirrecl at room tcmperature fcr three days, 0.1 g of methyl iodide was added. One-half of the THF was removed in vacuo and 20 ml of hexane was added. Centrifugati.on gave a clear supernatant solution which was evaporated in vacuo to leave an ofE-white powder, 1.90 g (95~ yield).
Analvsis: Found: C, 45.54; Il, 6.08; N, 12.31; Si, 36.37%.
lH NMR (C6D6): ~ 0.2-1.4 (broad, SiCH3, 0.58H) ... 4.6-5.8 (broad, SiH, 0.16 H) 6.5-7.7 (broad, SiC6H5, lH).
Molecular weight (cryoscopic in benzene): 1470 g/mol TGA (25-1000C, 10/min): 78% yleld of a black ceramic solid.
Pyrolysis of a larger sample in a tube furnace to 1000C gave a black ceramic solid in 74% yield.
Analysis: Found: C, 39.93; H, 0.54; N, 15.41; Si, 44.29~.
From these data a composition 1 Si3N4 + 2.75 SiC + 9.4 C may be calculated.
A similar preparation in which the polysilylamide/poly(phenylsilylene) mole ratio used was 5 gave a soluble white powder, molecular weight 2360, as a product whose ` pyrolysis to 1000C gave an 86% ceramic yield.
3. Reactions of ~(cH3siHNH)a(cH3siN~b~cH3siHNK)clm Living Polymer with PolycarbosiTa-ne .
a, Using Cyclo-(CH35iHNH)m Prepared in Diethvl_Ether.
i. Polycarbosilane/[CH35iHNH]m in l:l weight ratio (III-37).
~263796 In a dry box, a 250 ml round-bottomed flask equiped with a stir-bar, reflux condenser and a serum cap was charged with 0.15 g ~3.75 mmol) of K~l (4.4 molG, based on (C113SillNII)). THF (50 ml) was added to suspend the KH. (CH3SillNHjm (5 g, 0.085 mol, in 80 ml of TIIF), prepared by C113SiUC12 ammonolysis in ether solution, was added into the flask by syringe. A vigorous reaction occurred and a large amount of H2 gas was evolved whlch was vented out oE the flask through an oi:L bubbler. After the additlon was finished, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 5.0 g of polycarbosilane. TIIF (50 ml) was added by syringe to give a clear solution. The living polymer solution previously described was cannulated slow].y into the reaction flask. The `~ resulting clear solution was stirred at room temperature for two hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added, the mixture was refluxed for 2 hours and the solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by c~ntrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leavlng 9.6 g (969~ yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 5.02, 4.55 (broad, SiH, lH) ~- 1.56, 1.23, 0.88 (SiCH3NH) 0.25, O.la (broad, SiCH3, SiC1129.4U, for the total area of SiC_3 SiCH2 and SiCH3NH)-Molecular weight (cryoscopic in benzene): 1550 g/mol ~ Z63796 -4~-TGA (25-1000C, 10C/min): 8~1% yield of a black ceramic solid.
Tl/2 - 640C. (Tl/2 = temperature at which one-halE of weight loss has occurred.) Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
Analysis: Found: C, 32.00; H, 7.47; Si, 48.25; N, 11.87 Tot~l: 99.59%
Ceramic ~nalysis: Large scale pyrolysis of the sample under N2 to give 77~ yield of a black ceramic solid (25-1000C, 10/C/min).
Found: C, 25.54; Il, 0.62; Si, 53.04; N, 15.55 Total: 94.75~
Composition:l SiC + 0.2 Si3N4 + 0.7C
(equivalent to 10.5 weight % of free carbon) ! ii. Polycarbosilane/lCll3SillNHln in 5:1 Weight Ratio (III-57).
According to the procedure descrlbed previously, the reaction between 0.05 g (1.25 mmol) KH and 1.0 g (0.017 mol) (CH3SiHNH)m (prepared in ether solution) in 100 ml of THF
was carried out under nitrogen. The living polymer solution then was added to the THF (50 ml) solution of the polycarbosilane (5.0 g). The resulting solution was stirred at room temperature for 16 hours. To the reaction mixture 0.5 ml (7.9 mmol) of CH31 was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left 5.8 g (97% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, ~nd TIIF.
H NMR (90 MHz, C6D6: ~ 5.00, 4.55 (broad, Si_, 1l-l) 1.22, 0.88 (SiCH3N_) 0.30 (broad, SiCH3 and SiCH2 9H, for the total area of SiCH3, SICH2 and SiCH3NH) --~19--Molecular weight (cryoscopic in benzene): 1100 g/mol TGA (25-1000C, 10C/min): 67~ yield of a black ceramic solid.
Tl/2 ~ 520C.
Melting point (sealed capillary under vacuum): Softens at 220C, melts at 240C (to a thick gum), no further change up to 300C.
b. Usin~ CYC10 (CH3SiHNH?m Pre~ared in T~IF.
i. Polycarbosilane/~Cll3SiHNIIm in 1:1 weight ratio (III-39~ - -In a dry box, a 250 ml round-bottomed flask equipped with a stLr-bar, reflux condenser and a serum cap was charged with 0.15 g (3.75 mmol) of KH (4.4 mol~, based on (CH3SiHNH)). THF (50 ml) was added to suspend the KH (CH3SiHNII)m (5.0 g, 0.085 mol, in 80 ml of THF), prepared by ammonolysis of CH3SiHC12 i in THF solution, was added into the flask by syringe. A
vigorous reactlon occurred and a large amount of H2 gas was evolved which was vented out of the flask through an oil bubbler. After the addition was finished, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 5.0 g of polycarbosilane. THF (50 ml) was added by syringe to give a clear solution. The living polymer solution previously described was cannulated slowly into the reaction flask. The resulting solution was stirred at room temperature for two hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added, the mixture was heated a few hours, and the solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation. The hexane was removed from the lZ6379~i supernatant solution by trap-to-trap distillation, leaving 9.7 g (97% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene and THF.
H NMR (90 MHz, C6D6) ~ 5.33, 4.58 (broad, Sl}l, lH) 1.37, 1.25, 0.91 (SiCH3NH) 0.29, 0.22 (broad, SiCH3, SiCH2, 9.9H, for the total area of SiCH3 SiC_2 and SlCl13NH)-Molecular weight (cryscopic ln benzene): 2360 g/mol TGA (25-1000C, 10C/min): 88% yield of a black ceramic solid Tl/2 - 670C.
Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
Analysls: Found: C, 31.88; ~l, 7.52; Sl, 49.16; N, 11.69 Total: 100.25%
Ceramic Ana~ : Large scale pyrolysis oE the sample under argon gave an 80% yleld of a black ceramic solid (25-1000C, 10C/min).
Found: C, 24.03; Il, 0.77; Sl, 60.72; N, 14.72 Total: 100.24%
Composition: lSiC + 0.2 Si3N4 + 0.45 C
(equivalent to 7.5 weight ~ of free carbon) ii. Polvcarbosilane/LC~3SiHNHlm in 5:1 Weight Ratio (III-59).
, According to the procedure described previously, the reactions between 0.005 g (1.25 mmol) KH and 1.0 g (0.017 mol) (CH3SiHNH)m (prepared in THF solution) in 100 ml of THF were carried out under nitrogen. The living polymer solution then was added to the THF (50 ml) solution of polycarbosilane (5.0 g). The resulting solution was stirred at room temperature 126379~
overnight. To the reaction mixture 0.5 ml (7.9 mmol) of CH3I
was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left 5.9 g (98% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and TIIF.
lH NMR (90 MHz, C6D6): ~ 5.07, 4.55 (broad, SiH, l11) 1.24, 0.89 (SiCH3NII) 0.28 (broad, SiCH3, SiCl-12 7.5}1, Eor the total area of SiCH3 SiCH2 and SiC113NH).
Molecular weight (cryoscopic in benzene): 970 g/mol.
TGA (25-1000C, 10C/min): 64% yield of a black ceramic solid Tl/2 - 530C.
Melting point (sealed capillary under vacuum): Softens at 240C, melts at 265C, no further change up to 300C.
E. "In-Situ Procedure"
1. Reaction of a Mixture of CX~lic [CH3SiHNIIlm and iH-~(c~-l3si)yl ~ th K~ Cat.~].Yst ~
a. Using cYclo- ~C113SillN11)]m Prepared in Diethyl Ether In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.10 g of KH (0.0025 mol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged with 2.0 g of cyclic (CH3SiNHN)m (0.034 mol), prepared by ammonolysis of CH3SiHC12 in ether solution, and 2.2 g of [(CH3SiH)X(CH3Si)y]n (0.05 mol, x ~ 0.74, y = 0.26), and lO0 ml of THF. The mixed polymer solution was transferred by cannula into the KH suspension. The reaction mixture gradually changed color to light orange and hydrogen gas was slowly evolved. The resulting solution was stirred at room temperature for 14 hours and then heated at reflux for l hour.
~2~;3~79~
The light orange color of the solution persisted. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation.
The clear, colorless supernatant layer was transferred via cannula into a weighed 250 ml round-bottomed flask The hexane was removed by trap-to-trnp dis~illation Lenvin~ 3.8 ~ (91% ~y weight) of A white powder. The latter is soluble in TllF, benzene, and hexane.
H NMR (90 Mtlz, C6D6):~ 5.19, 4.70, 3.97 (broad, SiH, 1 H) 1.30, 0.47, 0.26 (broad, SiCH3 and NH
3.6 H) Molecular weight (cryoscopic): 1650 g/mol TGA (25-1000C, 10C/min): 62% yield of a black ceramic solid, Tl/2 - 380C
Anal, of Polymer Product: Found: C, 23.56; tl, 7.37; N, 14.51 Si, 50.89%
A sample of the ceramic product obtained in a tube furnace pyrolysis was analyzed:
Found: C, 19.30; N, 19.58;
SL, 57.94; 0, 2.05%
From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.68 C + 0.07 SiO2 (equivalent to 7.9~ by weight free carbon) b. ~sing cyclo-[Cll3SillNtl]m Prepared in TtlF
According to the procedure described above, the reaction between 0.1 g of K~l (0.0025 mol), 2.0 g of cyclic ~IZ6;~79~
(CH3SiHNH)m (prepared in THF solution), and 2.2 g of [(C113SiH)x(CH3Si)y]n (x = 0.74, y ~ 0.26) was carried out under nitrogen. The resulting reaction mixture also gradually changed color to light orange with slow evolution of hydrogen gas. The solution was stirred at room temperature for 14 hours and then 0.5 ml (7.9 mmol) of C113I was added. Work-up as described in the previous experiment left a white, soluble solid (3.75 g, B9%).
H NMR (90 ~-lz, C6D6):~ 5.13, 4.72, 3.98 (broad,SiH, 1 Il) 1.29, 0.48, 0.26 (broad, SiCH3 and Nll, 3 7 H) Molecular weight : 2750 g/mol TCA (25-1000C, 10C/min): 73~ yield of a black ceramic solid, Tl/2 360 C.
Anal. of Polymer Product: Found: C, 24.16; H, 7.14; N, 15.26;
Si, 51.20~
A sample of the ceramic product obtained in a tube furnace pyrolysis was analy7ed:
Found: C, 19.81; N, 19.77;
Si, 58.14; 0, 1.67 From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.7 C + 0.05 SiO2 (equivalent to 8.1~ by weight free carbon) ~- 2. Reactions of a Mixture of Cyclic [CH3SiHNH13 and Polvcarbosilane with KH Catalvst.
~263796 a. Usin~ CYC10 ICH3SiHNHIm Prepared Erom Diethyl Ether.
i. Polycarbosilane/~CII3SiIINHlm in 1:1 weight ratio (III-38).
In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.15 g of ~I (3.75 mmol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged wtih 5.0 g of (CH3SiHNH)m (0.085 mol), prepared in ether solution, and 5.0 g of polycarbosilane, and 150 ml of TIIF. The mixed polymer solution was transferred by cannula into the ~I suspension in THF. The reaction mixture gradually turned clear and hydrogen gas slowly evolved. The resulting solution was stirred at room temperature for 2 hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the mixture was heated for several hours. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation. The clear, colorless supernatant layer was transferred via a cannula into a weighed 250 ml round-bottomed flask. The hexane was removed by trap-to-trap distillation leaving 9.7 g (97% yi.eld by weight) of a white powder. The white powder is soluble in THF, benzene, and hexane.
H NMR (9OMHZ,C6D6) ~ 5.10, 4.55 (broad 5:H, lH) 1.56, 1.22, 0.88 (SiCH3NH) - 0.26, 0.19, (broad SiCH3, and `~ SiCH2 9.1H, for total area of SiCH2 and SiCH3N~I) Molecular weight (cryoscopic in ben~ene): 2150 g/mol TGA (25-1000C, 10C/min): 86~ yield of a black ceramic solid Tl/2 ~ 670C.
~263796 _~)rj_ Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
AnalysLs: Found: C, 31.87; 11, 7.55; Si, 48.93; N, 11.70 Total: 100.05%
Ceramic Analvsis: Large scale pyrolysis of the sample under N2 to give 74% yield of a black ceramic solid (25-1000C, 10C/min).
Found: C, 24.79; H, 0.70; Si; 56.79; N, 15.80 Total: 97.38%
Composition:l SlC ~ 0.2 Si3N4 ~ 0.6 C
(equivalent to 9.6 weight % of free carbon) ii. Polycarbosilane/~C1l351l-lNI{~n~ in 5;1 wei~ht ratio (III-56).
According to the procedure described previously, the reactions between 0.05 g of Kll (1.25 mmo].), 1.0 g oE
[CH3SiHNH]m (prepared in ether solution), and 5.0 g of polycarbosilane was carried out under nitrogen. The resulting 1 reaction mixture also gradually turned clear with slow evolution of hydrogen gas. The solution was stirred at room temperature for 3 hours and then heated ar reflux for 2 hours. The solution was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of C}13I was added and the mixture refluxed for several hours.
Work-up as described in the previous experiment left a white solid (5.8 g, 97% yield by weight). The white powder is soluble in THF, benzene and hexane.
H NMR (90 MHz, C6D6): ~ 5 03, 4.54 (broad, Si_, ].H) 1.23, 0.88 (SiCH3NI-I) 0.24 (broad, SiC_3, and '~ SiC_2, 8.3H, for the total area of SiCH3, SiC_2 and SiCH3N_) Molecular weight (cryoscopic in benzene): 1670 g/mol.
TGA (25-1000C, 10C/min): 80% yield of a black ceramic solid Tl/2 - 610C-~263796 Me]ting point (sealed capillary under vacuum): SoEten at 235C, melts at 260C, no further change up to 275C.
b. Usin~ CYC10 ~Cil3SillNH~m Prepared Erom Tlll~.
i. Polvcarbosilane/~CH3SiHNHlm in 1:1 wei~ht ratio (III-40).
In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condensor ancl a serum cap WAa chnr~ed wlth 0.15 g oE Kll (3.75 m~ol). Tl-IF (50 ml) was added to suspend the Ktl.
A separate 250 ml Schlenk flask was charged with 5.0 g of ICH3SillNH]m (0.085 mol), prepared in THF solution, and 5.0 g of polycarbosilane, and 150 ml of THF. The mixed polymer solution was transferred by cannula into the K}l suspension. The reaction mixture gradually turned clear and hydrogen gas slowly ~: evolved. The resulting solution was stirred at room temperature for 24 hours and then 0.5 ml (7.9 mmol) of CH3I was added and the mixture was refluxed for 2 hours. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane snd the insoluble residue removed by centrifugation. The clear, colorless supernatant layer was transferred via a cannula into a weighed 250 ml round~bottomed flask. The hexane was removed by trap-to-trap distillation leaving 9.8 g (98% yield by weight) of a white powder. The white powder is soluble in THF, benzene, and hexane.
H NMR (90 MHรฆ, C6D6): ~ 5.21, 4.57 (broad, SiH, lH) ~;~ 1.25 (broad, SiCH3NH) ~ 0.34, 0.30 (broad, SiC_3, and SiCH2, 8.8H, for the total area of SiCH3, SiC_2 and SiCH3N_).
Molecular weight (cryoscopic in benzene): 2560 g/mol.
. ~
lZ63796 TGA (25-1000C, 10C/min): 86~ yield of a black ceramic solid Tl/2 ~ 670C.
Melting point (sealed capillary under vacuum): Does not melt at temperature up to 320C.
Analysis: Found: C, 31.04; Il, 7.36; Si, 50.16; N, 11.62 Total: 100.18%
Ceramic Analysis: Large scale pyrolysis of the sample under argon gave a 78% yield of a black ceramic solid (25-1000C, 10C/min) Found: C, 23.36; H, 0.85; Si, 59.95; N, 15.94 Total: 100.10%.
Composition: lSiC + 0.2 Si3N4 + 0.5 C
(equivalent to 7.9 weight % of free carbon) ii. Polvcarbosilane/~C113~ 3 in 5:1 wei~ht ratio (III-58).
According to the procedure described previously, the reaction between 0.05 g of KH (1.25 mmol), 1.0 g of [CH3SiHNH]m (prepared in THF solution), and 5.0 g of polycarbosilane was carried out under nitrogen. The resulting reaction mixture also gradually turned clear with slow evolution of hydrogen gas. The solution was stirred at room temperature for 14 hours and 0.5 ml (7.9 mmol) of CH3I was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left a white solid (5.9 g, 98~ yield by weight). The white powder is soluble in THF, benzene, and hexane.
11 NMR (90 MHz, C6D6): ~ 5.07,4.55 (broad, SiH, lH) 1.24, 0.88 (SiCH3NH) 0.28 (broad, SiCH3, and SiC_2, 8.1H, for the total area of SiC_3, SiCH2 and SiCH3NH).
~Z63796 -5~-Molecular weight (cryoscopic in benzene): 1100 g/mol TGA ~25-1000C, 10C/min): 66~ yield of a black ceramic solid Tl/2 - 530 C.
Meltlng polnt (sealed capillAry un~er vacuum): Softens at 240C, rnelcs at 260~C, no further change up to 275C.
eaction of th Orgallosilicon Comvound with Partially Del:~ro_ nated Polymerizatioll ~roduct oE
Cyclo-~(CII3)2SiNIIl~n.
o]ylneri7A~on oL Cvclo-i(CII3)2SiNIllm.
~ 100 ml, three-necked, round-bottome~ Elask equipped with a stir-bar, a thermometer, and two gas inlet tubes was charged with 45.0 ml (41.4 g, 0.188 mol) of [(CH3)2SiNII]3 and 2.07 g (0.052 mol, 5~ by weight) oE NH4Br. After flushing the system with nitrogen, a constant stream of nitrogen was maintained. The reaction mixture was then lleated at 160C for
whlte powder (1.95 g, 89~) was obtained. The reaction product is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 4.60 (quartet, SiH, 0.7 H) 4.18 (broad, SiH, 1 H) 0.48 (broad, SiCI13, 14 II) Molecular weight (cryoscopic in benzene): 750 g/mol TGA (25-1000C, 10C/min): 56~ yield of a black ceramic solid, Tl/2 300~C.
4. Monopotassium Derivative of sym-TrimethYltrivinYlcYclotri-silazane- Catalyzed Conversion of ~3 S ~ x ( CH3 S i ~ yln Essentially the same procedures were used in the reaction of [(CH3)(CH2-CH)SiNH]3 (0.66 g, 0.0025 mol) with ~I (0.1 g, 0.0025 mol) in 20 ml of THF solution. The resulting solution was added to a 100 ml three-necked round-bottomed flask which was charged with 2.2 g (0.05 mol) of ~(CH3SiH)x(CH35i)y]n (x - 0.85, y - 0.15) and 40 ml of THF. After 6 ml (ca. 1.5 mol~) of the solution had been added, the deep red color of the reaction mixture persisted and a small amount of white solid precipitated. CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. Work-up as above followed. A white powder (1.79 g, 81.4%) was obtained. The reaction product is soluble in hexane, benzene and THF.
1~63796 H NMR (90 ~l~, C6D6): 5 4.16 (broad, SiH, 1 Il) 0.49 (broad, SiCil3, 8.9 H) Molecular weight (cryoscopic in benzene): 910 g/mol TGA (25-lOOO~C, 10C/min): 67~ yield of a black ceramic solid, Tl/2 = 410C.
5. Potassium Piperidide - Catalvzed Conversion of ~ (CH3SiH)x(CH3~Lyl~
In a dry box, a 50 ml round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with 0.1 g of Kll (0.0025 mol). TIIF (20 ml) was added to the flask to suspend the Kll. To the Kll suspension was added 0.25 ml of piperidine. Reaction occurred immediately with hydrogen gas evolution. The solution was stirred at room temperature for one hour and then heated at reflux for one hour. The slightly yellow solution was allowed to cool to room temperature.
Another 100 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser and a no-air rubber serum cap was charged with l.l g of [(CH3SiH)X(CH3Si)y]n (0.025 mol, x - 0.8, y - 0.2). THF (20 ml) was added to the flask to dissolve the polymer. The potassium piperidide solution previously described was added slowly to the reaction flask by syringe. Addition of each drop resulted in formation of a transient orange color which quickly disappeared. The orange color persisted aEter 10 ml of the solution had been added.
AEter 20 ml (ca. 10 mol~) of the solution of cyclo-C5HlONK
had been added, the reaction mixture was stirred at room temperature for one hour. The reaction solution turned deep red and a small amount of white precipitate was present. CH3I
(0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. The solvent was removed by trap-to-trap distillation at reduced pressure to give ~263796 a white solid which was extracted with two 35 ml portions of hexane. The extracts were centrifuged, and the clear, colorless supernatant layer was transferred via cannul.a into a weighed 100 ml round-bottomed flask equipped with a stir-bar. Solvent was removed by trap-to-trap distillation to give 1.03 g (67~, by weight) of white powder which is soluble in hexane, benzene, and TIIF.
H NMR (90 MHz, C6D6): 6 4 09 (broad, Sill, 1 }l) 0.47 (~road, SiCl13, ~.7 Il) Molecular weight (cryoscopic in benzene): 840 g/mol TGA (25-1000C, 10C/min): 57~ yield of a brownish-black ceramic solid Tl/2 ~ 350OC.
6. Potassium n-Propylamide - Catalyzed Conversion of ~(CH3SiH)x(c~13si)~ln Essentially the same procedure was used in the reaction of 0.30 g (0.0025 mol) of n-C3H7NH2 with 0.1 g (0.0025 mol) of Kll in 20 ml of THF as that described in Section C.(5). In this case, 20 ml of the n-C3H7NIIK solution (ca. lO mol~) was used to react with l.l g (0.025 mol) of [(CH3SiH)X(CH3Si)y]n (x ~ 0.8, y 0.2) in 20 ml of THF. After the addition was completed, the reaction solution turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white precipitate was present. CH3I (0.5 ml, 7.9 mmol) was added, and the resulting solution was stirred at room temperature for one hour. The usual work-up left 0.95 g (73% by weight) of a white solid which is soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6) 6 4.08 ~broad, SiH, l H) 0.51 (broad, SiCH3, 13.6 H) Molecular weight (cryoscopic in benzene) : 840 g/mol ~L2637~i TGA (25-1000C, 10C/min): 57% yield of a brownish-black ceramic solid Tl/2 ~ 300C
7. Potassium Diisovropylamide - Catalyzed Conversion of l(cH3siH)-(cll3si)yl-Essential].y the same procedure was used in the reaction of 0.30 g (0.0025 mol) oE (iso-C3H7)2NII wlth 0.1 g (0.0025 ol) oE ~l in 20 ml o~ Tlll as ~llat described in Section C.(5).
In this case, 20 ml of the (iso-C31l7)2NK solution (ca. 10 mol~) was used to react with 1.1 g (0.025 mol) of [(CH3SlH)X(CH3Si)y]n (x ~ 0.8, y ~ 0.2) in the 20 ml of THF. After the addition was completed, the reaction solution turned orange and was stirred at room temperature for one hour.
The solution turned deep red and a small amount of white preclpltate was present. CH3I (0.5 ml, 7.9 mmol) was added, and the resultlng solution was stirred at room temperature for one hour. Work-up as above left 1.03 g (79% by weight) of a white solid which i5 soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 3.99 (broad, SiH, 1 H) 0.47 (broad, SiCH3, 8.7 H) Molecular weight (cryoscopic in benzene): 750 g/mol TGA (25-lOOO~C, lOrC/min): 34% yield of a brownish-black solid Tl/2 = 280C
D. "Graft Procedure"
1. Reactions of ~(CH3SiHNH)a(CH3SiN)b(CH3SiHNK)clm Livin~ Polymer 3 ~ x~CH3Sl)yln a ~(CH3SiH~x1__3Si)yln Prepared in 7:1 Hexane/THF
i. Using cyclo-~CH3SiHNH]m Pre~ared in Diethyl Ether 1~6~796 The same general procedures were used for all of these reactions. In a dry box, a 250 ml round-bottomed Elask equipped with a stir-bar, reflux condenser and a serum cap was charged with a weighed smount of Ktl (ca. 3. 3 mol~) based on (CH35itlNtl) ) . THF (100 ml) was added to suspend the KH.
(CH3SiHNH)m, prepared in ether solution, was added into the flask by syringe (a vigorous reaction occurred and a large amount of H2 gas was evolved which was vented o.tt oE the flask tllrougll nn oil bu~bler. A~ter ~lle addition wns Llnislled, the reaction mixture was stirred at room temperature for 1 hour and then heated at reflux for l hour.
A separate 250 ml flask equipped with a septum, reflux condenser and stir-bar was charged with a weighed amount oE
[(CH3siH)X(cH3si)y]n (x - 0.85, y - 0.15). TilF (60 ml) was added by syringe to give a clear, colorless solution.
The living polymer solution previously described was cannulated slowly into the reaction flask. The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the volatiles were removed by trap-to-trap distillation.
The product was treated with 200 ml of hexane and the insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leaving a white solid. Physical data for these reaction products are given in the Tables 3, 4, 5, and 6. All of these polymers are very soluble in hexane, benzene, and THF.
b. Using cyclo- ~C113SitlNtll~ Prepared in TIIF
According to the procedure described previously, the reactions between KH and (CH3SiHNH)m (prepared in THF
12~3796 solution) were carried out under nitrogen. The living polymer solution then was added to the THF solution of [(C113Si~)x(CH3Si)y]n (x = 0.8, y = 0.2). The resulting orange solution was stirred at room temperature for one hour and then heated at reElux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added. Work-up as described in the previous experiment left a white solid. Physical data for these reaction produc~s are ~iven in ~lle Tn~lcs 3, 4, 5, nnd G.
.~
_ 12637~6 PREPARATION OF TIIE MIXED POLYMERS
Sample ~ YFY YFY YFY YFY YFY YFY
III-7 III-ll III-14 II-29 II-30 II-30-1 Solvent for (CH3sillNH)m PreparationTHF THF THF Ether Ether Ether Weight of [(CH3siH)x10.1 g6.6 g 3.3 g 2.4 g 1.1 g 2.2 g (CH3sl)y~n i'-~:.
Moles of [(CH3siH)x0.23 0.15 0.075 0.055 0.025 0.05 (CH3Si)y)n (A) Weight of (CH3slllNH)m 8.85 g8.85 g 8.85 g 2.4 g 2.08 g 1.22 g Moles of (C1~3SiHNH)m ;~ ~ (B)0.15 0.15 0.15 0.041 0.035 0.021 Mole Ratio A:B 1.5:1 1:1 1:2 1.34:1 1:1.41 2.42:1 Yield (%) 85 88 87 90 95 88 lZ63796 --~o--CERAMIC YIELD AND MOLECULAR WEIGHT DATA OF MIXED POLYMERS
Sample #d Ceramica 1/2 MolcularC
Yield (~) _ (C) Wei~llt(g/mol) YFY III-ll 78 420 2600 aUnder nitrogen, 25-1000C, 10C/min (TGA) bTemperature at which l/2 of total weight loss had cccurred . . ~
CCryoscopic in benzene dFor detalls of preparation, see Table 4 lZ63796 l_ NMR SPECTRAL DATA- OF THE MIXED POLYMERS
Sample #c (CH3SiHNH) (Cll3SiH) (Cll3SiHNH) Integration and SiC113_ Ratio=
YFY III-7 5.12 (b) 4.12 (b) 1.56, 1.22, 1:1:14.4 4.G7 (b) 0.88, 0.46 (b), 0.24 Y~Y III-ll 5.14 (b) 4 07 (b) 1.56, 1.22, 1.75:1:7 4.67 (b) 0.88, 0.41 (b), 0.24 YFY III-14 5.19 (b) 4.08 (b) 1.55, 1.23, 3:1:18 4.71 (b) 0.89, 0 45 (b), 0.26 YIY II-29 5.17 (b) 4 o5 (b) 1.35, 2:1:14.6 4.72 (b) 3.56 (b) 0.52 (b), 0.27 YFY II-30 5.17 (b) 4 03 (b) 1.41, 1.34, 2.13:1 13.8 4.71 (b) 3.56 (b) 1.22, 0.46 (b), 0.27 YFY II-30-1 5.15 (b) 4.12 (b) 1.23, 1.9:1:16.1 4.72 (b) 3.57 (b) 0.46 (b) 0.26 . _ . ... _ _ a90 MHz, in C6D6, chemical shift in ppm.
b(CH3SiHNH)/(CH3Si_)/(C_3Si)+(N_) proton integration CFor details of preparation, see Table 4 12~37!~6 PROPOSED FORMULAS AND TIIEIR ANALYTICAL DATA FOR TIIE MIXED POLYMERS
Proposed Formula (CH3SiH)x(CH35i)y(CH3SiHNII)a(C~13SiN)b Sample f~f Polymera Totalg Ceramic Total Anal. Accounted Anal. Accounted Calcd. Found ForFound For YFY III-7 x, 0.163 C, 24.46 C, 25.75 96.8 C, 20.59 97,27b y, 0.437 ~1, 7.11 Il, 7.69 Il, 0.78 a, 0.163 Si, 57.02 Si,53.42 Si, 62.79 `- b, 0.238 N, 11.41 N, 9.94 N, 13.11 YFY III-ll x, 0.116 C, 23.78 C, 24.79 98.49 C, 19.28 101.0C
y, 0.384 H, 6.97 H, 7.34 H, 0.99 a, 0.203 Si, 55.41 Si,53.17 Si, 63.47 b, 0.297 N, 13.85 N, 13.19 N, 17.26 YFY III-14 x, 0.09 C, 22.65 C, 24.21 100.46 C, 18.27 90.44 y, 0.24 H, 6.85 H, 7.85 H, 0.55 a, 0.27 Si, 52.81 Si, 51.89 Si, 58.65 b, 0.40 N, 17.69 N, 16.51 N, 12.97 YFY III-29 x, 0.087 C, 24.26 C, 24.03 87.06 C, 19.68 95.0ld y, 0.482 H, 6.94 H, 7.97 H, 0.19 `- a, 0.174 Si, 56.56 Si, 43.56 Si, 58.71 b, 0.256 N, 12.17 N, 11.50 N 16.43 YFY III-30 x, 0.112 C, 22.73 C, 24.56 90.53 C, 17.31 95.39e y, 0.303 H, 8.76 H, 6.97 H, 0.20 a, 0.239 Si, 53.00 Si, 44.56 Si, 57.87 b, 0.346 N, 15.50 N, 14.44 N, 20.01 ~2~3796 -43~
YFY II-30-1 x, O.062C, 25.33 C, 23.35 79.45 C, 19.97 90.36 y, 0.646H, 6.98 Il, 6.88il, 0.65 a, 0.122Si, 59.06 Si, 41.53Si, 58.44 b, 0.172N, 8.62 N, 7.69N, 11.30 -aCalculated on the basis of NMR integratlon bCalcd- compo5ition (Si3N4~ Si3N4 -~ 6.6 SiC -~ 0.74 C
this repre3ents only 2.2 % by weight free carbon CCalcd. composltion: Si3N4 + 4.4 SiC + 0.85 C
(equivalent to 3.1~ by weight Eree carbon) dCalcd. composition (assuming % Si is in error):
Si3N4 + 4.8 SiC + 0.84 C
(equivalent to 2.9~ by weight free carbon) eCalcd. composition (same assumption): Si3N4 + 3.3 SiC + 0.78C
~equivalent to 3.3% by weight free carbon) For details of preparation, see Table 4 gAnalytical difficulties, probably due to formation of ceramic material ~Z6;~796 b. ~(CiI3Sil-I)X(CII3Si) ln PrePared in THF
i. U~in~ cvclo~ H35iHNII)Im PreDared in Diethyl Ether In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.01 g (0.25 mmol) of KII. TIIF (100 ml) was added to suspend the ~I.
To the KH suspension, (CII3SiHNIl)m (1.57 g, 0.027 mol, prepared in ether solution), was added by syringe (a vigorous reaction occurred and a large amount of H2 gas was evo].ved whlch was vented out of the flask through an oil bubbler).
After the addition was finished, the reaction mixture was stirred at room temperature for 1 hour and then at reflux for 1 hour.
A separate flask equipped with a septum, reflux condenser and stir-bar wa5 charged with 1.1 g (0.025 mol) of [(CII3SiH)X(CH3Si)y]n (x ~ 0.46, y ~ 0.54). TIIF (60 ml) was added by syringe to give a clear, colorless solution.
The living polymer solution described above was carmulated slowly into the reaction flask. The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the solvent was removed by trap-to-trap distillation, leaving a white solid (2.5 g, 94% by weight). The reaction product is soluble in hexane, benzene, and TIIF.
11 NMR (90 MHz, C6D6) ~ 5.20, 4.74 (broad, SiCH3HNH, 1.25H) 4.07 (broad, SiCH3_, lH) 1.59,1.23 (broad, SiCH3HNH, lH) 0.46, 0.26 (broad, SiCH3, 11 H) Molecular weight (cryoscopic in benzene): 1700 g/mol TGA (25-1000C, 10C/min): 76~ yield of a black ceramic solid, Tl/2 - 400C.
~263~796 ii. Uslng cyclo-~C113SillNIllm Prepared in THF
According to the procedure described previously, the reactions between KH (0.1 g, 2.5 mmol) and (C113SillNII)m (2.9 ~, 0.051 mol, prepared ln Tlll solu~lon) were carried out uncler nitrogen. The living polymer solution then was added to the THF
solution of [(CH3SiH)X(CH3Si)y]n (2-2 g, 0-05 mol~ x =
0.46, y - 0.54). The resulting orange solution was stirred at room temperature for one hour and then heated at reflux for one hour. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of C113I was added. Work-up as described in the previous experiment left a white solid (4.65 g, 91% by weight). The reaction product is soluble in hexane, benzene, and THF.
11 NMR (90 Mllz, C6D6): ~ 5.15, 4.71 (broad,SiCH3llNII, 2 H) 4.50, 3.93 (broad, SiCH3_, 1 H) 1.58, 1.23 (broad, SiCH3HNH, 1 H) 0.47, 0.25 (broad, SiC_3,16 H) Molecular weight (cryoscopic in benzene): 2700 g/mol TGA (25-1000C, 10C/min): 80~ yield of a black ceramic solid, Tl/2 420C.
2. Reaction of Polymeric ~(C6_5SiH~ln with Poly(phenylsllylene), [C6H5SiH]n, molecular weight 860, was prepared by the method of Aitken, et al., J. Organomet.
Chem., supra.
The polymeric silylamide was prepared by the usual method, in this case by adding 1.0 g (3.0 mmol) of cyclo-(CH3SiHNH)m (mol. wt 330), obtained by ammonolysis of CH3SiHC12 in diethyl ether, to a suspension of 0.02 g (0.5 mmol) of KH in 10 ml of THF at room temperature. The mixture was stirred at room temperature for two hours. This solution then was added, under dry nitrogen, to 1.0 g of (C6H5SiH)X (1.2 mmol) in 20 ml of THF in a 100 ml three-necked flask equipped with reflux condenser topped with a nitrogen inlet tube, two rubber septa and a magnetic stir-bar, at room temperature. The reaction mixture turned orange upon addition of a few drops of the polysilylamide solution. (The final color was re~.) After the reaction mixture llad been stirrecl at room tcmperature fcr three days, 0.1 g of methyl iodide was added. One-half of the THF was removed in vacuo and 20 ml of hexane was added. Centrifugati.on gave a clear supernatant solution which was evaporated in vacuo to leave an ofE-white powder, 1.90 g (95~ yield).
Analvsis: Found: C, 45.54; Il, 6.08; N, 12.31; Si, 36.37%.
lH NMR (C6D6): ~ 0.2-1.4 (broad, SiCH3, 0.58H) ... 4.6-5.8 (broad, SiH, 0.16 H) 6.5-7.7 (broad, SiC6H5, lH).
Molecular weight (cryoscopic in benzene): 1470 g/mol TGA (25-1000C, 10/min): 78% yleld of a black ceramic solid.
Pyrolysis of a larger sample in a tube furnace to 1000C gave a black ceramic solid in 74% yield.
Analysis: Found: C, 39.93; H, 0.54; N, 15.41; Si, 44.29~.
From these data a composition 1 Si3N4 + 2.75 SiC + 9.4 C may be calculated.
A similar preparation in which the polysilylamide/poly(phenylsilylene) mole ratio used was 5 gave a soluble white powder, molecular weight 2360, as a product whose ` pyrolysis to 1000C gave an 86% ceramic yield.
3. Reactions of ~(cH3siHNH)a(cH3siN~b~cH3siHNK)clm Living Polymer with PolycarbosiTa-ne .
a, Using Cyclo-(CH35iHNH)m Prepared in Diethvl_Ether.
i. Polycarbosilane/[CH35iHNH]m in l:l weight ratio (III-37).
~263796 In a dry box, a 250 ml round-bottomed flask equiped with a stir-bar, reflux condenser and a serum cap was charged with 0.15 g ~3.75 mmol) of K~l (4.4 molG, based on (C113SillNII)). THF (50 ml) was added to suspend the KH. (CH3SillNHjm (5 g, 0.085 mol, in 80 ml of TIIF), prepared by C113SiUC12 ammonolysis in ether solution, was added into the flask by syringe. A vigorous reaction occurred and a large amount of H2 gas was evolved whlch was vented out oE the flask through an oi:L bubbler. After the additlon was finished, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 5.0 g of polycarbosilane. TIIF (50 ml) was added by syringe to give a clear solution. The living polymer solution previously described was cannulated slow].y into the reaction flask. The `~ resulting clear solution was stirred at room temperature for two hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added, the mixture was refluxed for 2 hours and the solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by c~ntrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leavlng 9.6 g (969~ yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and THF.
H NMR (90 MHz, C6D6): ~ 5.02, 4.55 (broad, SiH, lH) ~- 1.56, 1.23, 0.88 (SiCH3NH) 0.25, O.la (broad, SiCH3, SiC1129.4U, for the total area of SiC_3 SiCH2 and SiCH3NH)-Molecular weight (cryoscopic in benzene): 1550 g/mol ~ Z63796 -4~-TGA (25-1000C, 10C/min): 8~1% yield of a black ceramic solid.
Tl/2 - 640C. (Tl/2 = temperature at which one-halE of weight loss has occurred.) Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
Analysis: Found: C, 32.00; H, 7.47; Si, 48.25; N, 11.87 Tot~l: 99.59%
Ceramic ~nalysis: Large scale pyrolysis of the sample under N2 to give 77~ yield of a black ceramic solid (25-1000C, 10/C/min).
Found: C, 25.54; Il, 0.62; Si, 53.04; N, 15.55 Total: 94.75~
Composition:l SiC + 0.2 Si3N4 + 0.7C
(equivalent to 10.5 weight % of free carbon) ! ii. Polycarbosilane/lCll3SillNHln in 5:1 Weight Ratio (III-57).
According to the procedure descrlbed previously, the reaction between 0.05 g (1.25 mmol) KH and 1.0 g (0.017 mol) (CH3SiHNH)m (prepared in ether solution) in 100 ml of THF
was carried out under nitrogen. The living polymer solution then was added to the THF (50 ml) solution of the polycarbosilane (5.0 g). The resulting solution was stirred at room temperature for 16 hours. To the reaction mixture 0.5 ml (7.9 mmol) of CH31 was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left 5.8 g (97% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, ~nd TIIF.
H NMR (90 MHz, C6D6: ~ 5.00, 4.55 (broad, Si_, 1l-l) 1.22, 0.88 (SiCH3N_) 0.30 (broad, SiCH3 and SiCH2 9H, for the total area of SiCH3, SICH2 and SiCH3NH) --~19--Molecular weight (cryoscopic in benzene): 1100 g/mol TGA (25-1000C, 10C/min): 67~ yield of a black ceramic solid.
Tl/2 ~ 520C.
Melting point (sealed capillary under vacuum): Softens at 220C, melts at 240C (to a thick gum), no further change up to 300C.
b. Usin~ CYC10 (CH3SiHNH?m Pre~ared in T~IF.
i. Polycarbosilane/~Cll3SiHNIIm in 1:1 weight ratio (III-39~ - -In a dry box, a 250 ml round-bottomed flask equipped with a stLr-bar, reflux condenser and a serum cap was charged with 0.15 g (3.75 mmol) of KH (4.4 mol~, based on (CH3SiHNH)). THF (50 ml) was added to suspend the KH (CH3SiHNII)m (5.0 g, 0.085 mol, in 80 ml of THF), prepared by ammonolysis of CH3SiHC12 i in THF solution, was added into the flask by syringe. A
vigorous reactlon occurred and a large amount of H2 gas was evolved which was vented out of the flask through an oil bubbler. After the addition was finished, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 5.0 g of polycarbosilane. THF (50 ml) was added by syringe to give a clear solution. The living polymer solution previously described was cannulated slowly into the reaction flask. The resulting solution was stirred at room temperature for two hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added, the mixture was heated a few hours, and the solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation. The hexane was removed from the lZ6379~i supernatant solution by trap-to-trap distillation, leaving 9.7 g (97% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene and THF.
H NMR (90 MHz, C6D6) ~ 5.33, 4.58 (broad, Sl}l, lH) 1.37, 1.25, 0.91 (SiCH3NH) 0.29, 0.22 (broad, SiCH3, SiCH2, 9.9H, for the total area of SiCH3 SiC_2 and SlCl13NH)-Molecular weight (cryscopic ln benzene): 2360 g/mol TGA (25-1000C, 10C/min): 88% yield of a black ceramic solid Tl/2 - 670C.
Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
Analysls: Found: C, 31.88; ~l, 7.52; Sl, 49.16; N, 11.69 Total: 100.25%
Ceramic Ana~ : Large scale pyrolysis oE the sample under argon gave an 80% yleld of a black ceramic solid (25-1000C, 10C/min).
Found: C, 24.03; Il, 0.77; Sl, 60.72; N, 14.72 Total: 100.24%
Composition: lSiC + 0.2 Si3N4 + 0.45 C
(equivalent to 7.5 weight ~ of free carbon) ii. Polvcarbosilane/LC~3SiHNHlm in 5:1 Weight Ratio (III-59).
, According to the procedure described previously, the reactions between 0.005 g (1.25 mmol) KH and 1.0 g (0.017 mol) (CH3SiHNH)m (prepared in THF solution) in 100 ml of THF were carried out under nitrogen. The living polymer solution then was added to the THF (50 ml) solution of polycarbosilane (5.0 g). The resulting solution was stirred at room temperature 126379~
overnight. To the reaction mixture 0.5 ml (7.9 mmol) of CH3I
was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left 5.9 g (98% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and TIIF.
lH NMR (90 MHz, C6D6): ~ 5.07, 4.55 (broad, SiH, l11) 1.24, 0.89 (SiCH3NII) 0.28 (broad, SiCH3, SiCl-12 7.5}1, Eor the total area of SiCH3 SiCH2 and SiC113NH).
Molecular weight (cryoscopic in benzene): 970 g/mol.
TGA (25-1000C, 10C/min): 64% yield of a black ceramic solid Tl/2 - 530C.
Melting point (sealed capillary under vacuum): Softens at 240C, melts at 265C, no further change up to 300C.
E. "In-Situ Procedure"
1. Reaction of a Mixture of CX~lic [CH3SiHNIIlm and iH-~(c~-l3si)yl ~ th K~ Cat.~].Yst ~
a. Using cYclo- ~C113SillN11)]m Prepared in Diethyl Ether In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.10 g of KH (0.0025 mol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged with 2.0 g of cyclic (CH3SiNHN)m (0.034 mol), prepared by ammonolysis of CH3SiHC12 in ether solution, and 2.2 g of [(CH3SiH)X(CH3Si)y]n (0.05 mol, x ~ 0.74, y = 0.26), and lO0 ml of THF. The mixed polymer solution was transferred by cannula into the KH suspension. The reaction mixture gradually changed color to light orange and hydrogen gas was slowly evolved. The resulting solution was stirred at room temperature for 14 hours and then heated at reflux for l hour.
~2~;3~79~
The light orange color of the solution persisted. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation.
The clear, colorless supernatant layer was transferred via cannula into a weighed 250 ml round-bottomed flask The hexane was removed by trap-to-trnp dis~illation Lenvin~ 3.8 ~ (91% ~y weight) of A white powder. The latter is soluble in TllF, benzene, and hexane.
H NMR (90 Mtlz, C6D6):~ 5.19, 4.70, 3.97 (broad, SiH, 1 H) 1.30, 0.47, 0.26 (broad, SiCH3 and NH
3.6 H) Molecular weight (cryoscopic): 1650 g/mol TGA (25-1000C, 10C/min): 62% yield of a black ceramic solid, Tl/2 - 380C
Anal, of Polymer Product: Found: C, 23.56; tl, 7.37; N, 14.51 Si, 50.89%
A sample of the ceramic product obtained in a tube furnace pyrolysis was analyzed:
Found: C, 19.30; N, 19.58;
SL, 57.94; 0, 2.05%
From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.68 C + 0.07 SiO2 (equivalent to 7.9~ by weight free carbon) b. ~sing cyclo-[Cll3SillNtl]m Prepared in TtlF
According to the procedure described above, the reaction between 0.1 g of K~l (0.0025 mol), 2.0 g of cyclic ~IZ6;~79~
(CH3SiHNH)m (prepared in THF solution), and 2.2 g of [(C113SiH)x(CH3Si)y]n (x = 0.74, y ~ 0.26) was carried out under nitrogen. The resulting reaction mixture also gradually changed color to light orange with slow evolution of hydrogen gas. The solution was stirred at room temperature for 14 hours and then 0.5 ml (7.9 mmol) of C113I was added. Work-up as described in the previous experiment left a white, soluble solid (3.75 g, B9%).
H NMR (90 ~-lz, C6D6):~ 5.13, 4.72, 3.98 (broad,SiH, 1 Il) 1.29, 0.48, 0.26 (broad, SiCH3 and Nll, 3 7 H) Molecular weight : 2750 g/mol TCA (25-1000C, 10C/min): 73~ yield of a black ceramic solid, Tl/2 360 C.
Anal. of Polymer Product: Found: C, 24.16; H, 7.14; N, 15.26;
Si, 51.20~
A sample of the ceramic product obtained in a tube furnace pyrolysis was analy7ed:
Found: C, 19.81; N, 19.77;
Si, 58.14; 0, 1.67 From this analysis one may calculate a ceramic composition:
1 SiC + 0.37 Si3N4 + 0.7 C + 0.05 SiO2 (equivalent to 8.1~ by weight free carbon) ~- 2. Reactions of a Mixture of Cyclic [CH3SiHNH13 and Polvcarbosilane with KH Catalvst.
~263796 a. Usin~ CYC10 ICH3SiHNHIm Prepared Erom Diethyl Ether.
i. Polycarbosilane/~CII3SiIINHlm in 1:1 weight ratio (III-38).
In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.15 g of ~I (3.75 mmol). THF (50 ml) was added to suspend the KH.
A separate 250 ml Schlenk flask was charged wtih 5.0 g of (CH3SiHNH)m (0.085 mol), prepared in ether solution, and 5.0 g of polycarbosilane, and 150 ml of TIIF. The mixed polymer solution was transferred by cannula into the ~I suspension in THF. The reaction mixture gradually turned clear and hydrogen gas slowly evolved. The resulting solution was stirred at room temperature for 2 hours and then heated at reflux for 24 hours. The reaction mixture was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I was added and the mixture was heated for several hours. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane and the insoluble residue removed by centrifugation. The clear, colorless supernatant layer was transferred via a cannula into a weighed 250 ml round-bottomed flask. The hexane was removed by trap-to-trap distillation leaving 9.7 g (97% yi.eld by weight) of a white powder. The white powder is soluble in THF, benzene, and hexane.
H NMR (9OMHZ,C6D6) ~ 5.10, 4.55 (broad 5:H, lH) 1.56, 1.22, 0.88 (SiCH3NH) - 0.26, 0.19, (broad SiCH3, and `~ SiCH2 9.1H, for total area of SiCH2 and SiCH3N~I) Molecular weight (cryoscopic in ben~ene): 2150 g/mol TGA (25-1000C, 10C/min): 86~ yield of a black ceramic solid Tl/2 ~ 670C.
~263796 _~)rj_ Melting point (sealed capillary under vacuum): Does not melt at temperatures up to 320C.
AnalysLs: Found: C, 31.87; 11, 7.55; Si, 48.93; N, 11.70 Total: 100.05%
Ceramic Analvsis: Large scale pyrolysis of the sample under N2 to give 74% yield of a black ceramic solid (25-1000C, 10C/min).
Found: C, 24.79; H, 0.70; Si; 56.79; N, 15.80 Total: 97.38%
Composition:l SlC ~ 0.2 Si3N4 ~ 0.6 C
(equivalent to 9.6 weight % of free carbon) ii. Polycarbosilane/~C1l351l-lNI{~n~ in 5;1 wei~ht ratio (III-56).
According to the procedure described previously, the reactions between 0.05 g of Kll (1.25 mmo].), 1.0 g oE
[CH3SiHNH]m (prepared in ether solution), and 5.0 g of polycarbosilane was carried out under nitrogen. The resulting 1 reaction mixture also gradually turned clear with slow evolution of hydrogen gas. The solution was stirred at room temperature for 3 hours and then heated ar reflux for 2 hours. The solution was allowed to cool to room temperature and 0.5 ml (7.9 mmol) of C}13I was added and the mixture refluxed for several hours.
Work-up as described in the previous experiment left a white solid (5.8 g, 97% yield by weight). The white powder is soluble in THF, benzene and hexane.
H NMR (90 MHz, C6D6): ~ 5 03, 4.54 (broad, Si_, ].H) 1.23, 0.88 (SiCH3NI-I) 0.24 (broad, SiC_3, and '~ SiC_2, 8.3H, for the total area of SiCH3, SiC_2 and SiCH3N_) Molecular weight (cryoscopic in benzene): 1670 g/mol.
TGA (25-1000C, 10C/min): 80% yield of a black ceramic solid Tl/2 - 610C-~263796 Me]ting point (sealed capillary under vacuum): SoEten at 235C, melts at 260C, no further change up to 275C.
b. Usin~ CYC10 ~Cil3SillNH~m Prepared Erom Tlll~.
i. Polvcarbosilane/~CH3SiHNHlm in 1:1 wei~ht ratio (III-40).
In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condensor ancl a serum cap WAa chnr~ed wlth 0.15 g oE Kll (3.75 m~ol). Tl-IF (50 ml) was added to suspend the Ktl.
A separate 250 ml Schlenk flask was charged with 5.0 g of ICH3SillNH]m (0.085 mol), prepared in THF solution, and 5.0 g of polycarbosilane, and 150 ml of THF. The mixed polymer solution was transferred by cannula into the K}l suspension. The reaction mixture gradually turned clear and hydrogen gas slowly ~: evolved. The resulting solution was stirred at room temperature for 24 hours and then 0.5 ml (7.9 mmol) of CH3I was added and the mixture was refluxed for 2 hours. The solvent was removed by trap-to-trap distillation. The product was extracted with 200 ml of hexane snd the insoluble residue removed by centrifugation. The clear, colorless supernatant layer was transferred via a cannula into a weighed 250 ml round~bottomed flask. The hexane was removed by trap-to-trap distillation leaving 9.8 g (98% yield by weight) of a white powder. The white powder is soluble in THF, benzene, and hexane.
H NMR (90 MHรฆ, C6D6): ~ 5.21, 4.57 (broad, SiH, lH) ~;~ 1.25 (broad, SiCH3NH) ~ 0.34, 0.30 (broad, SiC_3, and SiCH2, 8.8H, for the total area of SiCH3, SiC_2 and SiCH3N_).
Molecular weight (cryoscopic in benzene): 2560 g/mol.
. ~
lZ63796 TGA (25-1000C, 10C/min): 86~ yield of a black ceramic solid Tl/2 ~ 670C.
Melting point (sealed capillary under vacuum): Does not melt at temperature up to 320C.
Analysis: Found: C, 31.04; Il, 7.36; Si, 50.16; N, 11.62 Total: 100.18%
Ceramic Analysis: Large scale pyrolysis of the sample under argon gave a 78% yield of a black ceramic solid (25-1000C, 10C/min) Found: C, 23.36; H, 0.85; Si, 59.95; N, 15.94 Total: 100.10%.
Composition: lSiC + 0.2 Si3N4 + 0.5 C
(equivalent to 7.9 weight % of free carbon) ii. Polvcarbosilane/~C113~ 3 in 5:1 wei~ht ratio (III-58).
According to the procedure described previously, the reaction between 0.05 g of KH (1.25 mmol), 1.0 g of [CH3SiHNH]m (prepared in THF solution), and 5.0 g of polycarbosilane was carried out under nitrogen. The resulting reaction mixture also gradually turned clear with slow evolution of hydrogen gas. The solution was stirred at room temperature for 14 hours and 0.5 ml (7.9 mmol) of CH3I was added and the mixture was refluxed for 2 hours. Work-up as described in the previous experiment left a white solid (5.9 g, 98~ yield by weight). The white powder is soluble in THF, benzene, and hexane.
11 NMR (90 MHz, C6D6): ~ 5.07,4.55 (broad, SiH, lH) 1.24, 0.88 (SiCH3NH) 0.28 (broad, SiCH3, and SiC_2, 8.1H, for the total area of SiC_3, SiCH2 and SiCH3NH).
~Z63796 -5~-Molecular weight (cryoscopic in benzene): 1100 g/mol TGA ~25-1000C, 10C/min): 66~ yield of a black ceramic solid Tl/2 - 530 C.
Meltlng polnt (sealed capillAry un~er vacuum): Softens at 240C, rnelcs at 260~C, no further change up to 275C.
eaction of th Orgallosilicon Comvound with Partially Del:~ro_ nated Polymerizatioll ~roduct oE
Cyclo-~(CII3)2SiNIIl~n.
o]ylneri7A~on oL Cvclo-i(CII3)2SiNIllm.
~ 100 ml, three-necked, round-bottome~ Elask equipped with a stir-bar, a thermometer, and two gas inlet tubes was charged with 45.0 ml (41.4 g, 0.188 mol) of [(CH3)2SiNII]3 and 2.07 g (0.052 mol, 5~ by weight) oE NH4Br. After flushing the system with nitrogen, a constant stream of nitrogen was maintained. The reaction mixture was then lleated at 160C for
8 hours during which time N~13 gas slowly evolved. The reaction mixture was allowed to cool to room temperature, and then dissolved in 300 ml of diethyl ether. The solution was cannulated into a 500 ml, three-necked, round-bottomed flask equipped with a cold condenser (dry ice-acetone) and two no-air rubber serum caps. The solution was cooled to 0C. An excess of anhydrous ammonia was bubbled into the reaction mixture during about 1 hour. The reaction mixture was filtered with a Schlenk fr'tted filter. The solvent was removed by trap-to-trap distilLation to leave a viscous oil. The latter was then distilled under reduced pressure (0.05 mmHg) and the low boiling compounds ~starting material and oligomers) were collected from 100C to 250C. A very viscous gum remained (20.2 g, 49~ by weight).
H N~R (90 MHz, C6D6): ~ 0.42 (broad, SiCH3, lH) 0.23 (broad, SiCH3, 1.2H) ~Z63796 Molecular weight (cryoscopic in benzene): 5100 g/mol.
TGA (25-1000C, 10C/min): 100~ weight loss occurred at 630C.
2. Reaction of Metallated Polymer from Sectlon F.(l) with ~(C}13SiH~x(CH3Si)yln (IV-40~
In a dry box, a lO0 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.1 g (2.25 ~mnol) o~ ~I (5~ by weigllt). TIIF (lO ml) was added to suspend the KH. A solution of the polymer from L.a. (above) (2.0 g in 30 ml of THF) was added to the flask by cannulation.
After the addition was finished, the reaction mixture was heated at reflux for 1.5 hours. The solution gradually turned clear while H2 gas was slowly evolved.
A separate lO0 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 2.2 g of [(CH3SiH~X(CH3Si)y]n (x-0.81, y=0.19). TIIF (30 ml) was added by syringe to give a clear solution. The KH/polymer product solution of Section L.a. previously described was cannulated slowly into the raction flask. Addition of each drop resulted in formation of an orange color which quickly disappeared. To the resulting solutlon 0.5 ml (7.9 mmol) of CH3I was added and the solvent was removed by trap-to-trap distillation. The product was extracted with 80 ml oE hexane and the insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leaving 3.6 g (89% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and T}IF.
11 NMR (90 MHz, C6D6):~ 5.12, 4.68, 4.09 (broad, SiH, 1 H) 1.17 (broad, NH) 0.47, 0.27 (broad, SiC_3, 17.5 H, for the total area of SiCH3 and N_) lZ6~796 Molecular weight (cryoscopic in benzene): 1500 g/mol Pyrolysis of this polymer to 1000C left a black ceramic material.
3. Reaction of the Polycarbosilarle with the Product of Section F.(l).
In a dry box, a 100 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.1 g (2.25 mmol) of ~l (5% by weight). THF (10 ml) was added to suspend the KH. A solution of the polymer prepared in Section (a) above (2.0 g in 30 ml of THF) was added into the flask by cannulation. After the additLon was finished, the reaction mixture was heated at reflux temperature for 2 hours. The solution gradually turned clear while H2 gas slowly evolved, forming the polysilylamide.
A separate 100 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 2.0 g of polycarbosilane. THF (30 ml) was added by syringe to give a clear solution. The polysilylamide solution was cannulated slowly into the reaction flask. The reaction mixture was then heated at reflux for 4 hours. The resulting yellow solution was treated with 0.5 ml (7.9 mmol) of CH3I, the mixture was refluxed for 2 hours and the solvent was removed by t~ap-to-trap distillation. The product was extracted with 80 ml of hexane and th~ insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap ~_ distillation, leaving 3.7 g (93% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and THF.
lH NMR (90 MHz, C6D6) ~ 4.60 (broad, SiH, lH) 0.43, 0.33, 0.23, 0.16, 0.13, 0.11 (multiplet, SiCH3, SiC_2, and NH, 13.8H, for the ~i3796 total area oE SiC_3, SiCH2, and N_).
Molecular weight (cryoscopic in ben~ene): 1570 g/mol.
~yrolysis (to 1000C) gave a black ceramic material.
G. Reactions of ~(C113SillNtl)a(CH3SiN)b-(CH3SiHNK)Clm Livin~ PolYmer-with-Polvcarbosilane MiCH~ CH3Siyl_ Or~anopo 1YS ilane 1. Polycarbosilanbe/OrganopolYsilane,/PolYmeric Silylamide in l:l:2 Weight Ratio.
a. PolYcarbosilane/Polysilane Mixture Added to ~he Polymeric SilYlamide Solution.
A 250 ml round-bottomed flask equipped with a stir-bar, reflux condensor and a serum c~p was charged wi~h 0.13 g (3.25 mmol) of KH (4.3 mol ~, based on (CH3SiHNH) unit). THF (50 ml) was added to suspend the ~1. Then 5.15 g (0.088 mol of CH3SiHNH unit) of (CH3SiHNH)moligomer (via ammonolysis of CH3SiHCl2 in the THF) in 75 ml of THF was added. A vigorous reaction occurred with brisk evolution of 112. ~fter the addition was completed, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml flask equipped as above was charged with 2.58 g of the polycarbosilane and 2.58 g of l(CH3Sill)x(CH3Si)y]1l (liquid polysilane, preparcd by sodium condensation of CH3SiHCl2 in 7:l hexane/THF) and 50 ml of THF. To the resulting clear solution was added very slowly by cannula the polymeric silylamide solution prepared above. The resulting clear orange solution was stirred at room temperature for 2 hours and then at reflux for 24 hours.
Subsequently, 0.5 ml of CH3I was added, the mixture was refluxed for 2 hours and then the solvent was removed at reduced pressure. To the residue was added 150 ml of hexane to extract ~63796 the product. Centrifugation removed insoluble salts. The hexane extracts were evaporated at reduced pressure, leaving
H N~R (90 MHz, C6D6): ~ 0.42 (broad, SiCH3, lH) 0.23 (broad, SiCH3, 1.2H) ~Z63796 Molecular weight (cryoscopic in benzene): 5100 g/mol.
TGA (25-1000C, 10C/min): 100~ weight loss occurred at 630C.
2. Reaction of Metallated Polymer from Sectlon F.(l) with ~(C}13SiH~x(CH3Si)yln (IV-40~
In a dry box, a lO0 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.1 g (2.25 ~mnol) o~ ~I (5~ by weigllt). TIIF (lO ml) was added to suspend the KH. A solution of the polymer from L.a. (above) (2.0 g in 30 ml of THF) was added to the flask by cannulation.
After the addition was finished, the reaction mixture was heated at reflux for 1.5 hours. The solution gradually turned clear while H2 gas was slowly evolved.
A separate lO0 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 2.2 g of [(CH3SiH~X(CH3Si)y]n (x-0.81, y=0.19). TIIF (30 ml) was added by syringe to give a clear solution. The KH/polymer product solution of Section L.a. previously described was cannulated slowly into the raction flask. Addition of each drop resulted in formation of an orange color which quickly disappeared. To the resulting solutlon 0.5 ml (7.9 mmol) of CH3I was added and the solvent was removed by trap-to-trap distillation. The product was extracted with 80 ml oE hexane and the insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap distillation, leaving 3.6 g (89% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and T}IF.
11 NMR (90 MHz, C6D6):~ 5.12, 4.68, 4.09 (broad, SiH, 1 H) 1.17 (broad, NH) 0.47, 0.27 (broad, SiC_3, 17.5 H, for the total area of SiCH3 and N_) lZ6~796 Molecular weight (cryoscopic in benzene): 1500 g/mol Pyrolysis of this polymer to 1000C left a black ceramic material.
3. Reaction of the Polycarbosilarle with the Product of Section F.(l).
In a dry box, a 100 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap was charged with 0.1 g (2.25 mmol) of ~l (5% by weight). THF (10 ml) was added to suspend the KH. A solution of the polymer prepared in Section (a) above (2.0 g in 30 ml of THF) was added into the flask by cannulation. After the additLon was finished, the reaction mixture was heated at reflux temperature for 2 hours. The solution gradually turned clear while H2 gas slowly evolved, forming the polysilylamide.
A separate 100 ml round-bottomed flask equipped with a septum, reflux condenser and stir-bar was charged with 2.0 g of polycarbosilane. THF (30 ml) was added by syringe to give a clear solution. The polysilylamide solution was cannulated slowly into the reaction flask. The reaction mixture was then heated at reflux for 4 hours. The resulting yellow solution was treated with 0.5 ml (7.9 mmol) of CH3I, the mixture was refluxed for 2 hours and the solvent was removed by t~ap-to-trap distillation. The product was extracted with 80 ml of hexane and th~ insoluble residue removed by centrifugation. The hexane was removed from the supernatant solution by trap-to-trap ~_ distillation, leaving 3.7 g (93% yield by weight) of a white solid. The polymer is very soluble in hexane, benzene, and THF.
lH NMR (90 MHz, C6D6) ~ 4.60 (broad, SiH, lH) 0.43, 0.33, 0.23, 0.16, 0.13, 0.11 (multiplet, SiCH3, SiC_2, and NH, 13.8H, for the ~i3796 total area oE SiC_3, SiCH2, and N_).
Molecular weight (cryoscopic in ben~ene): 1570 g/mol.
~yrolysis (to 1000C) gave a black ceramic material.
G. Reactions of ~(C113SillNtl)a(CH3SiN)b-(CH3SiHNK)Clm Livin~ PolYmer-with-Polvcarbosilane MiCH~ CH3Siyl_ Or~anopo 1YS ilane 1. Polycarbosilanbe/OrganopolYsilane,/PolYmeric Silylamide in l:l:2 Weight Ratio.
a. PolYcarbosilane/Polysilane Mixture Added to ~he Polymeric SilYlamide Solution.
A 250 ml round-bottomed flask equipped with a stir-bar, reflux condensor and a serum c~p was charged wi~h 0.13 g (3.25 mmol) of KH (4.3 mol ~, based on (CH3SiHNH) unit). THF (50 ml) was added to suspend the ~1. Then 5.15 g (0.088 mol of CH3SiHNH unit) of (CH3SiHNH)moligomer (via ammonolysis of CH3SiHCl2 in the THF) in 75 ml of THF was added. A vigorous reaction occurred with brisk evolution of 112. ~fter the addition was completed, the reaction mixture was stirred at room temperature for 2 hours.
A separate 250 ml flask equipped as above was charged with 2.58 g of the polycarbosilane and 2.58 g of l(CH3Sill)x(CH3Si)y]1l (liquid polysilane, preparcd by sodium condensation of CH3SiHCl2 in 7:l hexane/THF) and 50 ml of THF. To the resulting clear solution was added very slowly by cannula the polymeric silylamide solution prepared above. The resulting clear orange solution was stirred at room temperature for 2 hours and then at reflux for 24 hours.
Subsequently, 0.5 ml of CH3I was added, the mixture was refluxed for 2 hours and then the solvent was removed at reduced pressure. To the residue was added 150 ml of hexane to extract ~63796 the product. Centrifugation removed insoluble salts. The hexane extracts were evaporated at reduced pressure, leaving
9.12 g (89~ yield, by weight) of a white solid which was Eound to be soluble in hexane, benzene and THF.
H NMR (90 MHz, CDC13): ~ 5.18, 4.67 (broad, SiH, 1 H) 1.39, 1.22 (SiCH3NH) 0.48, 0.27 (broad, SiCH3 and SiCH2, 6.2H for total SiC_3, SiCH2 and SiCH3NH) Molecular weight (cryoscopic in benzene): 1730 g/mol TGA (25-1000C, 10C/min): 86% yield of a black ceramic solid, T1~2=630C
Melting point (sealed capillary under vacuum): does not melt up to 300C.
Ceramic analysis: Large scale pyrolysis oE the sample under argon (25-1000C, 10C/min): 77~ yield of a black ceramic ~olid.
b. Alternate Mode of Addition A solution of [CH3SiHNH)a(CH3SiN)b-(CH3SiHNK)C]m (prepared by reaction of 0.12.g (3.0 mmol) of KH and 5.27 g (0.090 mol of (CH3SiHNH) unit) of the CH3SilIC12 ammonolysis product (prepared in THF) in 50 ml of THF was cannulated into a 250 ml flask containing 2.63 g of [(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The resulting clear orange solution was stirred under nitrogen at room temperature for one hour. To this solution then was added 2.63 g of the polycarbosilane in 50 ml of THF. This reaction mixture was stirred at room temperature for 2 hours and at reflux for 24 hours. After addition of 0.5 ml of CH3I, the further procedure followed as described in K.l.(a). The product polymer was a white, soluble solid (9.14 g, 87~ yield).
~Zรงj3796 H N~R (C6D6): ~ 5.19, 4.72 (broad, Si_, 1 H) 1.39, 0.98 ~SiCH3NH) 0.27 (broad, SiC_3 and SiC}I2, 5.4H for the total SiCH3, SiCH2 and SiCH3NH) Molecular weight: 1790 g/mol TGA (25-1000C, 10C/min): 85~ yield of a black ceramic solid.
2. Same ComDonents as in G.(l) in 1:1:1 Wei~ht Ratio A solution of the polymerl.c silylamide was prepared as described above (3.20 g oE CH3SlllC12 ammonolysis product, 0.1 g of KH in 100 ml of THF). This solution was added, under nitrogen wlth stirring, to a mixture of 3.02 g of the polycarbosilane and 3.08 g of the liquid [(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The further procedure followed that described in G.(l)(a). The product polymer was isolated as a soluble white solid (8.40 g, 90% yield).
1~ NMR (C6D6): ~ 5.20, 4;81 (broad, SiH, lH) 1.40 (SiCH3N_) 0.47, 0.27 (broad, SiCH3 and SiC_2, 6.3H for total SiCH3 SiCH2 and SiCH3NH) Molecular weight: 970 g/mol TGA (25-1000C, 10C/mln): 84~ yield of a black ceramic solid.
Melting point (sealed, evacuated capillary): softens at 310C, melts 340-350C.
Analysis found: C, 32.64; H, 7.83; N, 9.07; Si, 48.82.
Ceramic analysis: Large scale pyrolysis of sample under argon (25-1000C): black ceramic in 72% yield.
Analysis found: C, 26.15; N, 12.37; Si, 61.48.
Composition: lSiC -1- 0.14 Si3N~ 0./13C
3. Same Components as in G.(l) in 1;2:1 Wei~ht Ratio A solution of the polymeric silylamide was prepared as described in G.(l)(a) (3.0 g of CH3SiHC12 ammonolysis product, 0.1 g of ~-l in 100 ml of TIIF). This solution was cannulated, slowly with stirring under nitrogen, to a mixture of 3.0 g of the polyc~rbosilane and 6.0 g of the [(CH3siH)x(cH3si)y]n liquid polysilane in 50 ml of THF. The further procedure followed that described in K.l.(a).
The white, solid product pol.ylner wns obta:Lned in 92% yi.eld (11.l g). It was found to be very soluble in hexane, benzene and TlIF.
~1 NMR (C6D6): ~ 5.12, 4.79, 4.19(broad SiH, lH) 1.40 (SiCH3N_) 0.30, 0.25 (broad, SiCH3 and .~ . SiCH2, 3.9H for total SiCH3 SiCH2 and SiCH3N~I) Molecular weight: 615 g/mol.
TGA (25-1000C, 10C/min): 74% yield of a black solid.
Melting point: ~sealed evacuated capillary): softens at melts at 260-270C.
Ceramic analysis: ~arge scale pyrolysis of sample under argon (25-1000C); 74% yield of a black ceramic.
Analysis found: C, 26.60; N, 8.23; Si, 65.17.
Compositon: lSiC + 0.08 Si3N4 ~ 0.18 C.
, , H. Physical Blends 1. Experiments with Polymer Blends (a) ~(CH3SiH)x(CH3Si) ln/~(CH3SiHNH~a (cH3~iN)bTcH3~iHN~H3)clm Blend Prepared at Room Temperature ~2~3796 In a dry box, 1.1 g (0.025 mol) of [(CH3Sill)x(CH3Si)y]n (x ~ 0.~6, y ~ 0.54) (Tl-IF
preparation) and 1.45 g (0.025 mol) of [(CH3SiHNH)o 39 -(CH3SiH)o 61]m (THF preparation) were finely ground together. The TGA curve of the physical blend polymer was measured. TGA (25-1000C, 10C/min): 70~ yield of a black ceramic solid. (average value of the two individual polymers) (b) A Blend Heated Neat to 100C
In a dry box, 1.1 g (0.025 mo]) of [(C~l3Si~l)x(Cll3Si)y]n (x - 0.46, y ~ 0.54) and 1.45 g (0.025 mol) of [(CH3SillNII)0~3g(C~l3SiN)0~61]m (TIIF
preparation) were finely ground together. The solid mixture was transferred to a 100 ml round-bottomed flask and then was heated in an oil bath at 100C for 30 minutes. The heat-treated mixed polymer is insoluble in THF, benzene, and hexane. TGA
(25-1000C, 10C/min): 67% yield of a black ceramic solid.
(c) _ Blend Heated in Toluene at Reflux The polymer mix~ure prepared ~IS ln ~He pL-ovLous cxperillle was dissolved in 20 ml of toluene in a 50 ml three-necked, round-bottomed flask. The solution was heated in reflux for one hour. The solution ~radually turned cloudy. Solvent was removed by trap-to-trap distillation to give a white powder which is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10/min): 75% yield of a black ceramic solid.
2. Experiments with Phvsical Polvmer Blends of Polvcarbosilane and ~CH3SiHNH~a(CH3SiN)b(CH3SiHNCH3)Clm.
a. ~sing ~ (cH3siHNH~a~!3siN)b~3siHNcH3)clm Prepared in Ether SoIution (IV-Z0~.
~Z6~79~
1. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g oE
[( 3Si}lNH)a(cll3siN)b(cH3siHNc~l3)c]m were finely ground together. The TGA curve of the physical blend polymer was measured.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
The solid polymer blend was then dissolved in hexane. The solvent was slowly removed by trap-to-trap distillation to give a homogeneous mixture. The TGA curve oE the mixture was again measured.
TGA (25-1000C, 10C/min): 78~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was dissolved in 10 ml of toluene and added to a 50 ml three-necked, round-bottomed flask. The solution was heated at reflux for 3 hours and the solution remained clear. Solvent was removed by trap-to-trap distillation to give a white powder which is soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 79% of a black ceramic solid.
iii. A Blend }leated Neat at 200C.
The polymer prepared as in the previous experiment was transferred to a 50 ml round-bottomed flask and was then heated in a sand bath at 200C for 2 hours. The finely ground powder turned to a foamy solid at the end of heating. The heat-treated mixed polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 20C/min): 82% of a black ceramic solid.
Using the same general procedure as outlined above, the polymer blends between polycarbosilane with different quantities of [(cH3siHNH)a(cH3siN)b(cH3siHNcH3)c]m (ether '~ Z63796 preparation) were prepared. The ceramic yields of these polymer blends produced are tabulated in Table 7.
b. Usin~
~C113SiltNll~atCI-13SiN)b(Cl135illNc113)clm--Prepared in THF Solutio-n (IV-27).
i. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g of [(C~3siHNll)a(cH3siN)l~(cl13sillNcll3)clm were finely ground together. The TGA curve oE the physical blend polymer was measured.
TGA (25-1000C, 10C/min): 77~ of a black ceramic solid.
The solid polymer blend then was dissolved in hexane. The solvent was slowly removed by trap-to-trap distillation to give a homogeneous mixture. The TGA curve of the mixture was again measured.
TGA (25-1000C, 10C/min): 80~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was dissolved in 10 ml of toluene and added to a 50 ml three-necked, round-bottomed flask. The solution was heated at reflux for 3 hours and the solution remained clear. Solvent was removed by trap-to-trap distillation to give a white powder which is soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
~_, iii. A Blend Heated Neat at 200C.
The polymer blend prepared as in the previous experiment was transferred to a 100 ml round-bottomed flask and was then heated in a sand bath at 200C for 2 hours. The heat- treated mixed ~2~3796 polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 86~ of a black ceramic solid.
Using the same general procedure as outlined above, the polymer blends between polycarbosilane with diEferent quantities of [(CH3SiHNH)a(CH35iN)b(cH3si~lNcH3)c]m (THF
preparation) were prepared. The ceramic yield of these polymer blends produced are tabulated in Table 7.
c. Ternarv Blends i. Mixed at ~oom Temperature In a dry box, 2.0 g of the polycarbosilane, 2.0 g of the liquid [(CH3SiH)X(CH3Si)y]n oreanopolysilane and 4.0 of the l(CH3SiHNH)a(CH3SiN)b(CH3SiHNCH3)C]m polysilazane (prepared in THF solution) were combined to give a nonhomogeneous mixture which was dissolved in 40 ml of hexane.
This solution was stirred at room temperature for one hour and ~LZ63796 ~ t~ ~ W. ~ W~ ~
~h t~ tc~ ; .
O ~r @ ~ ( n n ~ ~ a ~ ~ ~ r~ D * K:
~r wQ wQ w~ w _ o ~_,, I ~ o j.~
~Z63796 then was evaporated at reduced pressure. A homogeneous white powder remained. This material was Einely ground under nitrogen and examined by thermal analysis. TGA (25-1000C, 10C/min): 77~ yield of a black ceramic.
ii. At Refluxin~ Toluene Temperature The polymer mixture prepared in L.3.(a) was dissolved in 40 ml of toluene in a 100 ml flask equipped with a reflux condenser and a nitrogen inlet tube. The solution was heated at reflux under nitrogen for 3 hours. Subsequent removal of solvent at reduced pressure left a white powder which was soluble in hexane, benzene and THF. The powder was finely ground and examined by thermal analysis.
TGA (25-1000C, 10C/min): 76% yield of a black ceramic.
iil. Neat at 200 In a dry box 4 g of the polymer blend prepared in H.(2)(c)(i) was charged into a 250 ml flask equipped with a reflux condenser and a nitrogen inlet tube. The flask was heated in a sand bath at 200C for 2 hours. The resulting hard, solid product now was insoluble in hexane, benzene and THF. It was finely ground and examined by thermal analysis.
TGA (25-1000C, 10C/,min): 85~ yield of a black ceramic.
I. Ceramic Preparations -- 1. Or~anopolysilane-derived Ceramic Preparations a. Preparation of Ceramic Fibers i. From Mixed Polvmer Prepared as in Example D.(l)(a)(i) (a) In a dry box, an approximately 1 g sample o$ the polymer was dissolved in toluene (ca. 10 ml). The solution was concentrated ~Z6~79~
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 foot long were pulled with a glass rod dipped into the gummy mass. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube in a tube furnace and flushed with nitrogen. The polymer fibers then were pyrolyzed at 10C/mln to lOOO^C. Thls produced black ceramic fibers.
ii. From Mixed Polymer Prepared as ln Example D.tl)(b)(ii) (b) The same procedure was used in preparation Or polymer fibers in this polymer. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube in a tube furnace and flushed with nitrogen. The polymer fibers then were pyrolyzed at 10C/min to 1000C. This produced black ceramic fibers.
b. Preparation of Ceramic Bars bv Polymer PyrolYsis The two organosilicon polymers used for these experiments were prepared as described earlier.
i. Mixed Polymer Prepared as in Example D.(l)(a)(ii) The polymer (3.0 g) was loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs. for 5 minutes. The polymer bar was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C, heating at 10C/min. A black, irregular-shaped foam product was obtained with a loss of 24~ of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii) ~,Z63796 The polymer bar (3.0 g) was prepared by the same procedures used in the preparation of polymer bar above. The polymer bar was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C, heating At 10C/min. A black, irregular-shaped foam product was obtained with a loss of 26% oE
the original weight.
c. Preparation of SiC Powder Composites i. Mlxed Polymer Prepared as in Example D.(l)(a)(l) In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20~ by weight) of mixed polymer were combined in a 100 ml round-bottomed flask. The flask was removed from the dry box, charged with 10 ml of toluene, and the ceramic powder was dispersed ultrasonically for one hour. The toluene was removed on a rotary evaporator and the ceramic powder/polymer residue was further dried under vacuum for about 30 minutes. The residue was removed from the flask and lightly ~round in a mortar and pestle to produce a fine powder. The powde~ were loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes. The bar of ceramic powder was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C
heating at 10C/min. A slightly shrunk ceramic product was formed with a loss of 6% of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii~
In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20% by weight) of mixed polymer were combined in a 100 ml round-bottomed flask. The flask was removed from the dry box, char~ed with 10 ml of toluene, and the ceramic powder was 1263~96 dispersed ultrasonically for one hour. The toluene was removed on a rotary evaporator leaving a gray residue. The ceramic powder/polymer was further dried under vacuum for about 30 minutes The residue was removed from the flask and lightly ground with a mortar and pestle to produce a fine powder. The powder were loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and unlaxlally pressed at 5000 lbs for 5 minutes. The bar of cernmic powder was then bagged and isostatically pressed at 40,000 psi for one minute. The sample wa.s placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to lOOO~C, heating at 10C/min. A slightly shrunk ceramic product was formed with a loss of 6% of the original weight.
This invention has been described in detail with reference to the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration oE
this disclosure, may make modifications and improvements without departing from the spirit and scope of the invention as described in the claims.
2. PolYcarbosilane-derived Ceramic a. PreDaration of Ceramic Fibers.
i. From Mixed Polvmer Prepared as in D.(3~(a~(i) In a dry box, approximately 1 g of sample III-37 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to ~Z63796 -7~-1000C. This produced black ceramic fibers. S~M micrographs of the ceramic fibers were obtained.
ii. From Mixed Polvmer Prepared as in D.(4)(a)(i) In a dry box, approximately 1 g of sample III-39 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a Eused silica crucible which was in turn placed in a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to 1000C.
This produced black ceramic fibers. SEM micrograpl-s of the ceramic fibers were obtained.
iii. From Mixed Polvmer Prepared as in D.(3)(a~
In a dry box, approximately 1 g of sample III-40 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a fused silica crucible which was in turn placed i.n a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to 1000C. This produced black ceramic fibers. S~M micrographs of the ceramic fibers were obtained.
b. Preparation of Ceramic Bars.
i. From Mixed Polvmer Prepared as in D.(3~(a)(i~.
The polymer (III-37, 2.28 g) was loaded into a 3.9 cm x 1.3 ~;263796 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes, The polymer bar was thetl bagged and isostatically pressed at 40,000 psi for one minute, The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min, A black, rectangular-shaped bar was obtained with a loss of 32% of the original weight. SEM
micrographs of the ceramic bar was obtained, ii. From Mixed Polymer Prepared as in D.(3)(b~(i).
The polymer (III-38, 2,57 g) was loaded into a 3,9 cm x 1.3 cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000 lbs Eor 5 minutes, The poLymer bar w~s thell bagge<l and isostatically pressed at 40,000 psi for one minute. The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min, A black, rectangu].ar shaped bar was obtained with a loss of 29% of the original weight, SEM
micrographs of the ceramic bar was obtained, iii, From Mixed Polymer Prepared as in E,(2)(a~
The polymer (III-39, 2,36 g) was loaded into a 3.9 cm x 1,3 cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes. The polymer bar was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heatlng at 10C/min. A black, rectangular shaped bar was obtained with a loss of 27~ of the original weight, SEM
micrographs of the ceramic bar was obtained, iv. From Mixed Polymer Prepared as in E.(2)(b)(i).
The polymer (III-40, 2,07 g~ was loaded into a 3,9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 ~.Z6~3796 lbs for 5 minutes. The polymer bar was then bagged and lsostatically pressed at 40,000 psi for one minute. The sample was placed in the ~uartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min A black, rectangular shaped bar was obtained with a loss of 24~ of the original weight. SEM
micrographs of the ceramic bar was obtained.
This invention has been described in detail including the preferred embodiments thereof. ~owever, it will be appreciated that those skilled in the art, upon consideration of this disclosure, may make modificatlons and improvements without departing fro~ the spirit and scope of the invention as set forth ln the claims.
.
H NMR (90 MHz, CDC13): ~ 5.18, 4.67 (broad, SiH, 1 H) 1.39, 1.22 (SiCH3NH) 0.48, 0.27 (broad, SiCH3 and SiCH2, 6.2H for total SiC_3, SiCH2 and SiCH3NH) Molecular weight (cryoscopic in benzene): 1730 g/mol TGA (25-1000C, 10C/min): 86% yield of a black ceramic solid, T1~2=630C
Melting point (sealed capillary under vacuum): does not melt up to 300C.
Ceramic analysis: Large scale pyrolysis oE the sample under argon (25-1000C, 10C/min): 77~ yield of a black ceramic ~olid.
b. Alternate Mode of Addition A solution of [CH3SiHNH)a(CH3SiN)b-(CH3SiHNK)C]m (prepared by reaction of 0.12.g (3.0 mmol) of KH and 5.27 g (0.090 mol of (CH3SiHNH) unit) of the CH3SilIC12 ammonolysis product (prepared in THF) in 50 ml of THF was cannulated into a 250 ml flask containing 2.63 g of [(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The resulting clear orange solution was stirred under nitrogen at room temperature for one hour. To this solution then was added 2.63 g of the polycarbosilane in 50 ml of THF. This reaction mixture was stirred at room temperature for 2 hours and at reflux for 24 hours. After addition of 0.5 ml of CH3I, the further procedure followed as described in K.l.(a). The product polymer was a white, soluble solid (9.14 g, 87~ yield).
~Zรงj3796 H N~R (C6D6): ~ 5.19, 4.72 (broad, Si_, 1 H) 1.39, 0.98 ~SiCH3NH) 0.27 (broad, SiC_3 and SiC}I2, 5.4H for the total SiCH3, SiCH2 and SiCH3NH) Molecular weight: 1790 g/mol TGA (25-1000C, 10C/min): 85~ yield of a black ceramic solid.
2. Same ComDonents as in G.(l) in 1:1:1 Wei~ht Ratio A solution of the polymerl.c silylamide was prepared as described above (3.20 g oE CH3SlllC12 ammonolysis product, 0.1 g of KH in 100 ml of THF). This solution was added, under nitrogen wlth stirring, to a mixture of 3.02 g of the polycarbosilane and 3.08 g of the liquid [(CH3SiH)X(CH3Si)y]n polysilane in 50 ml of THF. The further procedure followed that described in G.(l)(a). The product polymer was isolated as a soluble white solid (8.40 g, 90% yield).
1~ NMR (C6D6): ~ 5.20, 4;81 (broad, SiH, lH) 1.40 (SiCH3N_) 0.47, 0.27 (broad, SiCH3 and SiC_2, 6.3H for total SiCH3 SiCH2 and SiCH3NH) Molecular weight: 970 g/mol TGA (25-1000C, 10C/mln): 84~ yield of a black ceramic solid.
Melting point (sealed, evacuated capillary): softens at 310C, melts 340-350C.
Analysis found: C, 32.64; H, 7.83; N, 9.07; Si, 48.82.
Ceramic analysis: Large scale pyrolysis of sample under argon (25-1000C): black ceramic in 72% yield.
Analysis found: C, 26.15; N, 12.37; Si, 61.48.
Composition: lSiC -1- 0.14 Si3N~ 0./13C
3. Same Components as in G.(l) in 1;2:1 Wei~ht Ratio A solution of the polymeric silylamide was prepared as described in G.(l)(a) (3.0 g of CH3SiHC12 ammonolysis product, 0.1 g of ~-l in 100 ml of TIIF). This solution was cannulated, slowly with stirring under nitrogen, to a mixture of 3.0 g of the polyc~rbosilane and 6.0 g of the [(CH3siH)x(cH3si)y]n liquid polysilane in 50 ml of THF. The further procedure followed that described in K.l.(a).
The white, solid product pol.ylner wns obta:Lned in 92% yi.eld (11.l g). It was found to be very soluble in hexane, benzene and TlIF.
~1 NMR (C6D6): ~ 5.12, 4.79, 4.19(broad SiH, lH) 1.40 (SiCH3N_) 0.30, 0.25 (broad, SiCH3 and .~ . SiCH2, 3.9H for total SiCH3 SiCH2 and SiCH3N~I) Molecular weight: 615 g/mol.
TGA (25-1000C, 10C/min): 74% yield of a black solid.
Melting point: ~sealed evacuated capillary): softens at melts at 260-270C.
Ceramic analysis: ~arge scale pyrolysis of sample under argon (25-1000C); 74% yield of a black ceramic.
Analysis found: C, 26.60; N, 8.23; Si, 65.17.
Compositon: lSiC + 0.08 Si3N4 ~ 0.18 C.
, , H. Physical Blends 1. Experiments with Polymer Blends (a) ~(CH3SiH)x(CH3Si) ln/~(CH3SiHNH~a (cH3~iN)bTcH3~iHN~H3)clm Blend Prepared at Room Temperature ~2~3796 In a dry box, 1.1 g (0.025 mol) of [(CH3Sill)x(CH3Si)y]n (x ~ 0.~6, y ~ 0.54) (Tl-IF
preparation) and 1.45 g (0.025 mol) of [(CH3SiHNH)o 39 -(CH3SiH)o 61]m (THF preparation) were finely ground together. The TGA curve of the physical blend polymer was measured. TGA (25-1000C, 10C/min): 70~ yield of a black ceramic solid. (average value of the two individual polymers) (b) A Blend Heated Neat to 100C
In a dry box, 1.1 g (0.025 mo]) of [(C~l3Si~l)x(Cll3Si)y]n (x - 0.46, y ~ 0.54) and 1.45 g (0.025 mol) of [(CH3SillNII)0~3g(C~l3SiN)0~61]m (TIIF
preparation) were finely ground together. The solid mixture was transferred to a 100 ml round-bottomed flask and then was heated in an oil bath at 100C for 30 minutes. The heat-treated mixed polymer is insoluble in THF, benzene, and hexane. TGA
(25-1000C, 10C/min): 67% yield of a black ceramic solid.
(c) _ Blend Heated in Toluene at Reflux The polymer mix~ure prepared ~IS ln ~He pL-ovLous cxperillle was dissolved in 20 ml of toluene in a 50 ml three-necked, round-bottomed flask. The solution was heated in reflux for one hour. The solution ~radually turned cloudy. Solvent was removed by trap-to-trap distillation to give a white powder which is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10/min): 75% yield of a black ceramic solid.
2. Experiments with Phvsical Polvmer Blends of Polvcarbosilane and ~CH3SiHNH~a(CH3SiN)b(CH3SiHNCH3)Clm.
a. ~sing ~ (cH3siHNH~a~!3siN)b~3siHNcH3)clm Prepared in Ether SoIution (IV-Z0~.
~Z6~79~
1. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g oE
[( 3Si}lNH)a(cll3siN)b(cH3siHNc~l3)c]m were finely ground together. The TGA curve of the physical blend polymer was measured.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
The solid polymer blend was then dissolved in hexane. The solvent was slowly removed by trap-to-trap distillation to give a homogeneous mixture. The TGA curve oE the mixture was again measured.
TGA (25-1000C, 10C/min): 78~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was dissolved in 10 ml of toluene and added to a 50 ml three-necked, round-bottomed flask. The solution was heated at reflux for 3 hours and the solution remained clear. Solvent was removed by trap-to-trap distillation to give a white powder which is soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 79% of a black ceramic solid.
iii. A Blend }leated Neat at 200C.
The polymer prepared as in the previous experiment was transferred to a 50 ml round-bottomed flask and was then heated in a sand bath at 200C for 2 hours. The finely ground powder turned to a foamy solid at the end of heating. The heat-treated mixed polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 20C/min): 82% of a black ceramic solid.
Using the same general procedure as outlined above, the polymer blends between polycarbosilane with different quantities of [(cH3siHNH)a(cH3siN)b(cH3siHNcH3)c]m (ether '~ Z63796 preparation) were prepared. The ceramic yields of these polymer blends produced are tabulated in Table 7.
b. Usin~
~C113SiltNll~atCI-13SiN)b(Cl135illNc113)clm--Prepared in THF Solutio-n (IV-27).
i. At Room Tem~erature.
In a dry box, 1.0 g of polycarbosilane and 1.0 g of [(C~3siHNll)a(cH3siN)l~(cl13sillNcll3)clm were finely ground together. The TGA curve oE the physical blend polymer was measured.
TGA (25-1000C, 10C/min): 77~ of a black ceramic solid.
The solid polymer blend then was dissolved in hexane. The solvent was slowly removed by trap-to-trap distillation to give a homogeneous mixture. The TGA curve of the mixture was again measured.
TGA (25-1000C, 10C/min): 80~ of a black ceramic solid.
ii. At Refluxin~ Toluene Temperature.
The mixed polymer prepared as in the previous experiment was dissolved in 10 ml of toluene and added to a 50 ml three-necked, round-bottomed flask. The solution was heated at reflux for 3 hours and the solution remained clear. Solvent was removed by trap-to-trap distillation to give a white powder which is soluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 76% of a black ceramic solid.
~_, iii. A Blend Heated Neat at 200C.
The polymer blend prepared as in the previous experiment was transferred to a 100 ml round-bottomed flask and was then heated in a sand bath at 200C for 2 hours. The heat- treated mixed ~2~3796 polymer is insoluble in THF, benzene, and hexane.
TGA (25-1000C, 10C/min): 86~ of a black ceramic solid.
Using the same general procedure as outlined above, the polymer blends between polycarbosilane with diEferent quantities of [(CH3SiHNH)a(CH35iN)b(cH3si~lNcH3)c]m (THF
preparation) were prepared. The ceramic yield of these polymer blends produced are tabulated in Table 7.
c. Ternarv Blends i. Mixed at ~oom Temperature In a dry box, 2.0 g of the polycarbosilane, 2.0 g of the liquid [(CH3SiH)X(CH3Si)y]n oreanopolysilane and 4.0 of the l(CH3SiHNH)a(CH3SiN)b(CH3SiHNCH3)C]m polysilazane (prepared in THF solution) were combined to give a nonhomogeneous mixture which was dissolved in 40 ml of hexane.
This solution was stirred at room temperature for one hour and ~LZ63796 ~ t~ ~ W. ~ W~ ~
~h t~ tc~ ; .
O ~r @ ~ ( n n ~ ~ a ~ ~ ~ r~ D * K:
~r wQ wQ w~ w _ o ~_,, I ~ o j.~
~Z63796 then was evaporated at reduced pressure. A homogeneous white powder remained. This material was Einely ground under nitrogen and examined by thermal analysis. TGA (25-1000C, 10C/min): 77~ yield of a black ceramic.
ii. At Refluxin~ Toluene Temperature The polymer mixture prepared in L.3.(a) was dissolved in 40 ml of toluene in a 100 ml flask equipped with a reflux condenser and a nitrogen inlet tube. The solution was heated at reflux under nitrogen for 3 hours. Subsequent removal of solvent at reduced pressure left a white powder which was soluble in hexane, benzene and THF. The powder was finely ground and examined by thermal analysis.
TGA (25-1000C, 10C/min): 76% yield of a black ceramic.
iil. Neat at 200 In a dry box 4 g of the polymer blend prepared in H.(2)(c)(i) was charged into a 250 ml flask equipped with a reflux condenser and a nitrogen inlet tube. The flask was heated in a sand bath at 200C for 2 hours. The resulting hard, solid product now was insoluble in hexane, benzene and THF. It was finely ground and examined by thermal analysis.
TGA (25-1000C, 10C/,min): 85~ yield of a black ceramic.
I. Ceramic Preparations -- 1. Or~anopolysilane-derived Ceramic Preparations a. Preparation of Ceramic Fibers i. From Mixed Polvmer Prepared as in Example D.(l)(a)(i) (a) In a dry box, an approximately 1 g sample o$ the polymer was dissolved in toluene (ca. 10 ml). The solution was concentrated ~Z6~79~
under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 foot long were pulled with a glass rod dipped into the gummy mass. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube in a tube furnace and flushed with nitrogen. The polymer fibers then were pyrolyzed at 10C/mln to lOOO^C. Thls produced black ceramic fibers.
ii. From Mixed Polymer Prepared as ln Example D.tl)(b)(ii) (b) The same procedure was used in preparation Or polymer fibers in this polymer. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube in a tube furnace and flushed with nitrogen. The polymer fibers then were pyrolyzed at 10C/min to 1000C. This produced black ceramic fibers.
b. Preparation of Ceramic Bars bv Polymer PyrolYsis The two organosilicon polymers used for these experiments were prepared as described earlier.
i. Mixed Polymer Prepared as in Example D.(l)(a)(ii) The polymer (3.0 g) was loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs. for 5 minutes. The polymer bar was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C, heating at 10C/min. A black, irregular-shaped foam product was obtained with a loss of 24~ of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii) ~,Z63796 The polymer bar (3.0 g) was prepared by the same procedures used in the preparation of polymer bar above. The polymer bar was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C, heating At 10C/min. A black, irregular-shaped foam product was obtained with a loss of 26% oE
the original weight.
c. Preparation of SiC Powder Composites i. Mlxed Polymer Prepared as in Example D.(l)(a)(l) In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20~ by weight) of mixed polymer were combined in a 100 ml round-bottomed flask. The flask was removed from the dry box, charged with 10 ml of toluene, and the ceramic powder was dispersed ultrasonically for one hour. The toluene was removed on a rotary evaporator and the ceramic powder/polymer residue was further dried under vacuum for about 30 minutes. The residue was removed from the flask and lightly ~round in a mortar and pestle to produce a fine powder. The powde~ were loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes. The bar of ceramic powder was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to 1000C
heating at 10C/min. A slightly shrunk ceramic product was formed with a loss of 6% of the original weight.
ii. Mixed Polymer Prepared as in Example D.(l)(a)(ii~
In a dry box, 2.4 g of fine -SiC powder and 0.6 g (20% by weight) of mixed polymer were combined in a 100 ml round-bottomed flask. The flask was removed from the dry box, char~ed with 10 ml of toluene, and the ceramic powder was 1263~96 dispersed ultrasonically for one hour. The toluene was removed on a rotary evaporator leaving a gray residue. The ceramic powder/polymer was further dried under vacuum for about 30 minutes The residue was removed from the flask and lightly ground with a mortar and pestle to produce a fine powder. The powder were loaded into a 3.9 cm x 1.3 cm x 3.7 cm rectangular steel die and unlaxlally pressed at 5000 lbs for 5 minutes. The bar of cernmic powder was then bagged and isostatically pressed at 40,000 psi for one minute. The sample wa.s placed in a quartz tube in a tube furnace and pyrolyzed under nitrogen to lOOO~C, heating at 10C/min. A slightly shrunk ceramic product was formed with a loss of 6% of the original weight.
This invention has been described in detail with reference to the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration oE
this disclosure, may make modifications and improvements without departing from the spirit and scope of the invention as described in the claims.
2. PolYcarbosilane-derived Ceramic a. PreDaration of Ceramic Fibers.
i. From Mixed Polvmer Prepared as in D.(3~(a~(i) In a dry box, approximately 1 g of sample III-37 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a fused silica crucible which was in turn placed in a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to ~Z63796 -7~-1000C. This produced black ceramic fibers. S~M micrographs of the ceramic fibers were obtained.
ii. From Mixed Polvmer Prepared as in D.(4)(a)(i) In a dry box, approximately 1 g of sample III-39 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a Eused silica crucible which was in turn placed in a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to 1000C.
This produced black ceramic fibers. SEM micrograpl-s of the ceramic fibers were obtained.
iii. From Mixed Polvmer Prepared as in D.(3)(a~
In a dry box, approximately 1 g of sample III-40 was dissolved in toluene (ca. 10 ml). The solution was concentrated under vacuum until a fibrous, gummy material was obtained.
Fibers approximately 1 ft long were pulled with a glass rod dipped into the gummy solid. The fibers were quickly placed in a fused silica crucible which was in turn placed i.n a quartz tube furnace and flushed with argon. The polymer fibers then were converted into ceramics by pyrolyzing them at 10C/min to 1000C. This produced black ceramic fibers. S~M micrographs of the ceramic fibers were obtained.
b. Preparation of Ceramic Bars.
i. From Mixed Polvmer Prepared as in D.(3~(a)(i~.
The polymer (III-37, 2.28 g) was loaded into a 3.9 cm x 1.3 ~;263796 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes, The polymer bar was thetl bagged and isostatically pressed at 40,000 psi for one minute, The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min, A black, rectangular-shaped bar was obtained with a loss of 32% of the original weight. SEM
micrographs of the ceramic bar was obtained, ii. From Mixed Polymer Prepared as in D.(3)(b~(i).
The polymer (III-38, 2,57 g) was loaded into a 3,9 cm x 1.3 cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000 lbs Eor 5 minutes, The poLymer bar w~s thell bagge<l and isostatically pressed at 40,000 psi for one minute. The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min, A black, rectangu].ar shaped bar was obtained with a loss of 29% of the original weight, SEM
micrographs of the ceramic bar was obtained, iii, From Mixed Polymer Prepared as in E,(2)(a~
The polymer (III-39, 2,36 g) was loaded into a 3.9 cm x 1,3 cm x 3,7 cm rectangular steel die and uniaxially pressed at 5000 lbs for 5 minutes. The polymer bar was then bagged and isostatically pressed at 40,000 psi for one minute. The sample was placed in the quartz tube furnace and pyrolyzed under argon to 1000C, heatlng at 10C/min. A black, rectangular shaped bar was obtained with a loss of 27~ of the original weight, SEM
micrographs of the ceramic bar was obtained, iv. From Mixed Polymer Prepared as in E.(2)(b)(i).
The polymer (III-40, 2,07 g~ was loaded into a 3,9 cm x 1.3 cm x 3.7 cm rectangular steel die and uniaxially pressed at 5000 ~.Z6~3796 lbs for 5 minutes. The polymer bar was then bagged and lsostatically pressed at 40,000 psi for one minute. The sample was placed in the ~uartz tube furnace and pyrolyzed under argon to 1000C, heating at 10C/min A black, rectangular shaped bar was obtained with a loss of 24~ of the original weight. SEM
micrographs of the ceramic bar was obtained.
This invention has been described in detail including the preferred embodiments thereof. ~owever, it will be appreciated that those skilled in the art, upon consideration of this disclosure, may make modificatlons and improvements without departing fro~ the spirit and scope of the invention as set forth ln the claims.
.
Claims (96)
1. A method for preparing preceramic organo-silicon polymers, wherein the method comprises:
(a) mixing a polycarbosilane containing Si-H repeat units with at least a catalytic amount of an alkali metal amide or a silylamide in an organic solvent;
b) allowing the mixture of step (a) to react at room temperature or above; and (c) quenching the reaction mixture with a reactive electrophile, thereby forming said pre-ceramic organosilicon polymer;
said polycarbosilane having a plurality of repeat units of the formula [RaSi(H)-(CH2)q] where Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater.
(a) mixing a polycarbosilane containing Si-H repeat units with at least a catalytic amount of an alkali metal amide or a silylamide in an organic solvent;
b) allowing the mixture of step (a) to react at room temperature or above; and (c) quenching the reaction mixture with a reactive electrophile, thereby forming said pre-ceramic organosilicon polymer;
said polycarbosilane having a plurality of repeat units of the formula [RaSi(H)-(CH2)q] where Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater.
2. The method of claim 1 wherein the poly-carbosilane contains at least about 25 mole % of repeat units of the formula [RaSi(H)-(CH2)q].
3. The method of claim 2 wherein Ra is a lower alkyl group.
4. The method of claim 2 wherein Ra is CH3.
5. The method of claim 1 wherein the alkali metal amide is a polymeric alkali metal silylamide of the formula [(R1SiHNH)a(R1SiN)b(R1SiHNM)c]m, where a + b + c = 1, R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubsti-tuted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(]ower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1.
6. The method of claim 5 wherein the reaction mixture is quenched with an electrophile, E-X, where E is selected from the group consisting of lower alkyl groups and silyl groups and X is selected from the group consisting of halogen, sulfate and sulfon-ate.
7. The method of claim 5 wherein R1 is a lower alkyl group.
8. The method of claim 7 wherein the poly-meric alkali metal silylamide has the formula [(CH3SiHNH)a(CH3SiN)b-(CH3SiHNK)c]m.
9. The method of claim 7 wherein Ra is CH3.
10. The method of claim 7 wherein the pre-ceramic polymer is pyrolyzed under an inert gas stream to form a ceramic material.
11. The ceramic material formed by the method of claim 10.
12. A preceramic polymer formed by the method of claim 5.
13. The method of claim 1 wherein the alkali metal amide is an alkali metal silylamide.
14. The method of claim 13 wherein the alkali metal silylamide is [R2R3R4Si]2NM wherein R2, R3 and R4 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubsti-tuted allyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R2, R3 and R4 may be the same or different; and M is an alkali metal or one-half equivalent of an alkaline earth metal.
15. The method of claim 14 wherein [R2R3R4Si]2NM is selected from [(CH3)2(CH2=CH)Si]2NM
and [(CH3)3Si]2NM.
and [(CH3)3Si]2NM.
16. The method of claim ] wherein the alkali metal silylamide is partially deprotonated cyclo-[R5R6SiNH)m containing [R5R6SiNM] units wherein R5 and R6 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubsti-tuted allyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R5 and R6 may be the same or different; M is an alkali metal. or one-half equivalent of an alkaline earth metal and m is an integer greater than 1.
17. The method of claim 16 wherein cyclo-[R5R6SiNH]m is selected from [(CH3)2SiNH]m and [(CH3)(CH2=CH)SiN]m.
18. The method of claim 1. wherein the silyl-amide is a diorganocyclopolysilazane that is either partially or completely ring-opened.
19. The method of claim 18 where the diorgano-cyclopolysilazane comprises units having the formula [R1R11SiNH]m where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl. group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkyl amino group; R11 is defined as R1, and may be the same or different, and m is an integer greater than 1.
20. The method of claim 5 wherein the pre-ceramic product is pyrolyzed in an inert atmosphere for a sufficient time and at a sufficient temperature to form a ceramic material.
21. The method of claim 1 wherein the weight ratio of polycarbosilane:silylamide is about 10:1 or less.
22. A method for preparing a preceramic organosilicon polymer, wherein the method comprises:
(a) generating a polysilylamide in the presence of a polycarbosilane wherein -the polysilyl-amide is generated by reacting the ammonolysis product of an R1SiHX2 where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl. group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group and X is a halogen, in the presence of a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom to generate the polysilylamide in situ;
said polycarbosilane having a plurality of repeat units of the formula [RaSi(H)-(CH2)q] where Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater;
(b) allowing the in situ generated poly-silylamide and the polycarbosilane sufficient time to react with each other at room temperature; and (c) quenching the mixture with an organic halide or halosilane to produce the organosilicon preceramic polymer.
(a) generating a polysilylamide in the presence of a polycarbosilane wherein -the polysilyl-amide is generated by reacting the ammonolysis product of an R1SiHX2 where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl. group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group and X is a halogen, in the presence of a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom to generate the polysilylamide in situ;
said polycarbosilane having a plurality of repeat units of the formula [RaSi(H)-(CH2)q] where Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater;
(b) allowing the in situ generated poly-silylamide and the polycarbosilane sufficient time to react with each other at room temperature; and (c) quenching the mixture with an organic halide or halosilane to produce the organosilicon preceramic polymer.
23. The method of claim 22 wherein the poly-carbosilane contains at least about 25 mole % of repeat units of the formula [RaSi(H)-(CH2)q].
24. The method of claim 22 wherein Ra is a lower alkyl group.
25. The method of claim 22 wherein Ra is CH3.
26. The method of claim 22 wherein the pre-ceramic polymer is pyrolyzed under an inert gas stream for a sufficient time and at a sufficient temperature to form a ceramic product.
27. The ceramic material formed by the method of claim 26.
28. A preceramic polymer formed by the method of claim 22.
29. A ceramic material formed by pyrolyzing a physical mixture of a polycarbosilane and a polymer of the formula [(R1SiHNH)a(R1SiN)b(R1SiHNE)c]m, where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl-or di(lower)alkylsilyl group or a di(lower)alkylamino group, n and m are integers greater than 1, and E is a moiety introduced by reaction of an electrophile, E-X, with [(R1SiNH)a(R1SiN)b(R1SiNM)c]m where M is an alkali metal or one-half equivalent of an alkaline earth metal, said polycarbosilane having a plurality of repeat units of the formula [RaSi(H)-(CH2)q] where Ra is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer I or greater.
30. The ceramic material of claim 29 wherein E
is introduced by an electrophile selected from the group consisting of lower alkyl halides and halo-silanes.
is introduced by an electrophile selected from the group consisting of lower alkyl halides and halo-silanes.
31. A method for preparing novel. preceramic organosilicon polymers, wherein the method comprises:
(a) admixing with a silylamide in an organic solvent a polycarbosilane having at least 25 mole % of repeat units of -the formula [RSi(H)-(CH2)q]
where R is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, or a substituted or unsubsti-tuted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater, wherein the weight ratio of polycarbosilane:silyl-amide is about 10:1 or less;
(b) allowing the admixture of step (a) to react at room temperature or above; and (c) quenching the reaction mixture with a reactive electrophile, when a metal silylamide is used, thereby forming said organosilicon polymer.
(a) admixing with a silylamide in an organic solvent a polycarbosilane having at least 25 mole % of repeat units of -the formula [RSi(H)-(CH2)q]
where R is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having 3 to about 6 carbon atoms, or a substituted or unsubsti-tuted lower aryl group having from 6 to about 10 carbon atoms, and q is an integer 1 or greater, wherein the weight ratio of polycarbosilane:silyl-amide is about 10:1 or less;
(b) allowing the admixture of step (a) to react at room temperature or above; and (c) quenching the reaction mixture with a reactive electrophile, when a metal silylamide is used, thereby forming said organosilicon polymer.
32. The method of claim 31 wherein the metal silylamide has the formula [(R1SiHNH)a(R1SiN)b-(R1SiHNM)c]m, where a + b + c = 1, R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)-alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and m is an integer greater than 1.
33. The method of claim 31 wherein R is a lower alkyl group.
34. The method of claim 33 wherein R is CH3.
35. The method of claim 31 wherein q is 3 or less.
36. The method of claim 31 wherein q is one.
37. The method of claim 32 wherein R1 is a lower alkyl group.
38. The method of claim 37 wherein R is a lower alkyl group.
39. The method of claim 32 wherein R1 is CH3.
40. The method of claim 39 wherein R is CH3.
41. The method of claim 31 wherein the ratio of polycarbosilane to alkali metal silylamide is about 5:1 or less.
42. The method of claim 41 wherein the ratio is about 3:1 or less.
43. The method of claim 41 wherein the ratio is about 1:1.
44. The method of claim 41 wherein the re-action mixture is quenched with an electrophile.
45. The method of claim 44 wherein the elec-trophile is E-X, where E is selected from the group consisting of organic groups and silyl groups and X
is selected from the group consisting of halogen, sulfate and sulfonate.
is selected from the group consisting of halogen, sulfate and sulfonate.
46. The method of claim 45 wherein the mixture is allowed to react by stirring at room temperature.
47. The method of claim 45 wherein the mixture is heated above room temperature.
48. The method of claim 46 wherein the elec-trophile quenching the reaction is an organic halide or a halosilane.
49. The method of claim 48 wherein the organic halide is a lower alkyl halide.
50. The method of claim 49 wherein the lower alkyl halide is CH3I.
51. The method of claim 48 wherein the halo-silane is a chlorosilane.
52. A preceramic polymer containing Si, C and N formed by the method of claim 31.
53. A preceramic polymer containing Si, C and N formed by the method of claim 32.
54. A preceramic polymer containing Si, C and N formed by the method of claim 34.
55. The method of claim 31 wherein the silyl-amide is [R2R3R4Si]2NM wherein R2, R3 and R4 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R2, R3 and R4 may be the same or different; and M is an alkali metal or one-half equivalent of an alkaline earth metal.
56. The method of claim 55 wherein [R2R3R4Si]2NM is selected from [(CH3)2(CH2=CH)Si]2NM
and [(CH3)3Si]2NM.
and [(CH3)3Si]2NM.
57. The method of claim 31 wherein the silyl-amide is partially deprotonated cyclo-[R5R6SiNH]m containing [R5R6SiNM] units wherein R5 and R6 are each a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkoxy group having from 1 to about 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group, R5 and R6 may be the same or different; M is an alkali metal or one-half equivalent of an alkaline earth metal and m is an integer greater than 1.
58. The method of claim 57 wherein cyclo-[R5R6SiNH]m is selected from [(CH3)2SiNH]m and [(CH3)(CH2=CH)SiN]m.
59. The method of claim 31 wherein R is a lower aryl group.
60. The method of claim 31 wherein the silyl-amide is derived from a diorganocyclopolysilazane that is either partially or completely ring-opened.
61. The method of claim 60 where the diorgano-cyclopolysilazane comprises units having the formula [R1R11SiNH]m where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; R11 is defined as R1 and may be the same or different, and m is an integer greater than 1.
62. The method of claim 61 wherein the di-organocyclopolysilazane is reacted with a few mole percent based on available NH groups of a base to produce a polymeric silyalamide containing a few mole percent of [R1R11SiNM] units where M is an alkali metal or one-half equivalent of an alkaline earth metal.
63. The method of claim 61 wherein R11 is the same as R1 .
64. The method of claim 63 wherein R11 and R1 are CH3I.
65. A preceramic polymer formed by the method of claim 40.
66. A preceramic polymer formed by the method of claim 60.
67. A preceramic polymer formed by the method of claim 61.
68. A method for preparing an organosilicox preceramic polymer, wherein the method comprises:
(a) generating a polysilylamide in the presence of a polycarbosilane of the formula: -[RSi-(H)-(CH2)9]n-, where q is an integer 1 or greater; R
is H, a lower alkyl group having from 1 to about 6 carbon atoms, a lower cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubsti-tuted lower aryl group having from 6 to about 10 carbon atoms, and n is an integer greater than 1;
wherein the polysilylamide is generated by reacting the ammonolysis product of an R1SiHX2, where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di-(lower)alkylsilyl group or a di(lower)alkylamino group and X is a halogen, in the presence of a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom to generate the polysilylamide in situ;
(b) allowing the in situ generated poly-silylamide and the polycarbosilane sufficient time to react with each other at room temperature; and (c) quenching the mixture with an organic halide or halosilane to produce the organosilicon preceramic polymer.
(a) generating a polysilylamide in the presence of a polycarbosilane of the formula: -[RSi-(H)-(CH2)9]n-, where q is an integer 1 or greater; R
is H, a lower alkyl group having from 1 to about 6 carbon atoms, a lower cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubsti-tuted lower aryl group having from 6 to about 10 carbon atoms, and n is an integer greater than 1;
wherein the polysilylamide is generated by reacting the ammonolysis product of an R1SiHX2, where R1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di-(lower)alkylsilyl group or a di(lower)alkylamino group and X is a halogen, in the presence of a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom to generate the polysilylamide in situ;
(b) allowing the in situ generated poly-silylamide and the polycarbosilane sufficient time to react with each other at room temperature; and (c) quenching the mixture with an organic halide or halosilane to produce the organosilicon preceramic polymer.
69. The method of claim 68 wherein the mixture of in situ generated polysilylamide and polycarbo-silane reaction mixture is heated in solution above room temperature for a sufficient time to cause a reaction to occur.
70. The method of claim 68 wherein R is a lower alkyl.
71. The method of claim 70 wherein R is CH3.
72. The method of claim 71 wherein R1SiHX2 is CH3SiHCl2.
73. The method of claim 68 wherein the organic halide is lower alkyl halides.
74. The method of claim 73 wherein the lower alkyl halide is CH3I.
75. A preceramic polymer formed by the method of claim 68.
76. A preceramic polymer formed by the method of claim 73.
77. A preceramic polymer formed by the method of claim 74.
78. The method of claim 31 wherein an organo-polysilane of the formula [(RaSiH) (RaSi)y]n,where x + y = 1, n is an integer greater than 1, Ra is a lower alkyl group having from about 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms or a tri(lower)alkyl- or di(lower)alkylsilyl group is added to create a ternary preceramic poly-mer.
79. The method of claim 78 wherein the organo-polysilane is added in sufficient quantity so that the excess silicon obtained on pyrolysis of the organopolysilane can react with excess carbon from the pyrolysis of the polycarbosilane and the silyl-amide, thereby reducing the amount of free carbon.
80. The method of claim 79 wherein Ra is a lower alkyl group.
81. The method of claim 80 wherein Ra is CH3.
82. The method of claim 32 wherein an organo-polysilane of the formula [(RaSiH)x(RaSi)y]n, where x + y = 1, n is an integer greater than 1, Ra is a lower alkyl group having from about 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms or a tri(lower)alkyl- or di(lower)alkylsilyl group is added to create a ternary preceramic poly-mer.
83. The method of claim 82 wherein the organo-polysilane is added in sufficient quantity so that the excess silicon obtained on pyrolysis of the organopolysilane can react with excess carbon from the pyrolysis of the polycarbosilane and the silyl-amide, thereby reducing the amount of free carbon.
84. The method of claim 83 wherein Ra is a lower alkyl group.
85. The method of claim 84 wherein Ra is CH3.
86. The method of claim 68 wherein an organo-polysilane of the formula [(RaSiH)x(RaSi)y]n , where x + y = 1, n is an integer greater than 1, Ra is a lower alkyl group having from about 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms or a tri(lower)alkyl- or di(lower)alkylsilyl group is added to create a ternary preceramic poly-mer.
87. The method of claim 86 wherein the organo-polysilane is added in sufficient quantity so that the excess silicon obtained on pyrolysis of the organopolysilane can react with excess carbon from the pyrolysis of the polycarbosilane and the silyl-amide, thereby reducing the amount of free carbon.
88. The method of claim 87 wherein Ra is a lower alkyl group.
89. The method of claim 88 wherein Ra is CH3.
90. A preceramic polymer formed by the method of claim 78.
91. A preceramic polymer formed by the method of claim 83.
92. A preceramic polymer formed by the method of claim 85.
93. A preceramic polymer formed by the method of claim 87.
94. A preceramic polymer formed by the method of claim 89.
95. The method of claim 55, wherein the substituted vinyl group is a substituted or unsubsti-tuted alkyl group.
96. The method of claim 57, wherein the substituted vinyl group is a substituted or unsubsti-tuted allyl group.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000581792A CA1263796A (en) | 1985-07-18 | 1988-10-31 | Method for converting si-h containing polycarbosilanes to new and useful preceramic polymers and ceramic materials |
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/756,353 US4645807A (en) | 1985-07-18 | 1985-07-18 | Method for forming new preceramic polymers for SiC and Si3 N4 /SiC systems |
| US781,934 | 1985-09-30 | ||
| US06/781,934 US4650837A (en) | 1985-09-30 | 1985-09-30 | Method for converting Si-H containing polycarbosilanes to new and useful preceramic polymers and ceramic materials |
| CA000514060A CA1263797A (en) | 1985-07-18 | 1986-07-17 | Method for forming new preceramic polymers for sic and si3n4/sic systems |
| CA000581792A CA1263796A (en) | 1985-07-18 | 1988-10-31 | Method for converting si-h containing polycarbosilanes to new and useful preceramic polymers and ceramic materials |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000514060A Division CA1263797A (en) | 1985-07-18 | 1986-07-17 | Method for forming new preceramic polymers for sic and si3n4/sic systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1263796A true CA1263796A (en) | 1989-12-05 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000581792A Expired CA1263796A (en) | 1985-07-18 | 1988-10-31 | Method for converting si-h containing polycarbosilanes to new and useful preceramic polymers and ceramic materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1263796A (en) |
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1988
- 1988-10-31 CA CA000581792A patent/CA1263796A/en not_active Expired
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