CA1304875C - Method for converting organosilicon polymers containing sih repeat units and organopolysilazane precursors to new and useful polymers and silicon nitride enriched ceramic materials - Google Patents

Abstract

ABSTRACT
A method for preparing preceramic polymers is disclosed. This method includes the steps of reacting in solution anhydrous ammonia with a mixture of R1SiHX2 (where R1 and X are as described above) and R2SiX3 (where R2 as described above) can be used to form a different and useful preceramic polymer by reacting it with an organosilicon polymer containing Si-H repeat units. The Si-H containing organosilicon polymer is preferably selected from the group consisting of organopolysilanes of the formula [(RSiH)X(RSi)y]n (where 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, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and n is greater than 1), a polycarbosilane having 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 from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, q is an integer 1 or greater), and a polysiloxane having repeat units of the formula [RbSi(H)O]n (where Rb is 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, and n is an integer greater than 1).
Novel preceramic polymers formed by this method are also disclosed.

Description

4*` `j 1304~75 pct 36503 Docket No. 36503 The present invention relates to a process for preparing silicon-containing preceramic polymers that is particularly useful for making silicon nitride and silicon nitride/silicon carbide and silicon oxynitride ceramics and for their pyrolysis to such ceramic materials.
There is a great deal of interest in preceramic polymer ; materials, which can ba pyrolyzed to yield silicon carbide, silicon nitride, silicon oxynitrida and other silicon-based cera~ic materials. R.W. Rlce, mer~ Ce~ oc,,_Bull~, 62: 889-892 tl983).
Applications for such polymers include, among others:
1. formation into complex shapes and subsequent pyrolysis to give a ceramic material of the same shape, I-j 2. spinning into contlnuous fibers whose subsequent pyrolysis I 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 otherwisc oxidlzable materials (such as carbon/carbon composites) - after the polymer coating is made, it can be pyrolyzed to gi~e the resistant ceramiclcoating . S. infiltration of porous ceramic bodies such as ones obtained ;~
~ from reaction-sintered silicon nitr~de by the polymer itself (if -~

!

.

~:~04~37S

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 c~ramic material for electronics applications.
For instance, Penn et al., ~ pl. Polvmer Sci.. 27: 3751-61 (1982) describe tha preparation of silicon carbide-silicon nitride fibers from a polycarbosilazane precursor. Tris(N methylamino) methylsilane monomer was formed by reaction o~ monomethylamine and methyltrichlorosilane in dry petroleum ether and a polycarbosilazane resin was formed by passing the monomer over glass Raschig rings at 520C. The brittle polymer was soluble in methylene chloride and 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 U.S. Pat. Nos. 3,108,935;
3,853,567; 3,892,583; 4,310,651 and 4,312,970. These linear or crosslinked polymers and processes :Eor producing ceramic materials have generally been found to be deficient in one or more ways.
S. Yajima, Amer. Ceram. Soc. Bull , ~2: 893-898; 903 (1983) discloses using (CH3)2SiC12 as a starting material for a preceramic polymer for the preparation of SiC-containing cer~mics.
The polymer of Ya~ima is prepared by sodium metal condensation of (CH3)2SiC12 to result i~ a polysilane, -[(~H3)2Si]n- (n is approximately 30). This polysilane can then iorm 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 polyborodiph~nylsiloxane and heating under nitrogen at ambient pressure at 350C for 10 hours results in the Mark III polymer. In either case, the polysilicon backbone is ;

~ -2-~3~7S

converted to a polymeric chain in which the main repeat unit is:

ICsH3 [- i-CH2]- (I) The Mark I pol~mer also contains some -[(CH3)2SiCH2]- units. The Mark III polymer contains some Si-Si bonds in the form -[(CH3)2si-si(cH3)2]n((n-2-8) units and a low percentage of [(C6H5~2SiO] units. l'hese preceramic polymers can be processed to give ceramic fibers containing SiC, some free carbon and some Si02. However, there are problems associated with these polycarbosilane-derived ceramics. They have a tendency to crystallize below 1200C, they have a 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~, the yield for the Mark I
polymer is only 54%.
Silicon oxynitrides are another important group of ceramics. This ceramic material has most of the same advantages as sillcon nitride, but is expected to have a better oxidation stability. These are high refractory materials able to withstand temperatures up to about 1500C before decomposing. Although K. Okamura et al, Chem. Lett, (1984): 2059-2060 (See also K. Okamura et al, Fifth Int. Conf, on Composite Materials, July 29 - August 1, 1985, Proceedings: 535-S42), reported obtaining silicon oxynitride fibers after pyrolysis under ammonia, of SiO2-containing polycarbosilanes ~having CH3Si(H)CH2] as the major repeat unit), this was an expensive and inef~icient process.
U.S. Patent 4,482,669 issued November 13, 1984, describes organopolysilazane preceramic polymers whose pyrolysis gives a mixture of silicon carbide and silicon nitride wherein, generally, neither component is in large excess over the other. These polymers were obtained by the reaction of a base (such as an alkali metal hydride, amide, etc.) with the ammonolysis product of a dihalosilane, for s ~xampla, CH3S~HC12 whlch result3 in a pol~m~rization proc~3~
balieved to in~lude th~ Dyt~r~ UiLLI ~ (DHCD) reactiDn ~hown in ~q. A.

ba~s / N ~

2 -~L-~- ~ ~ 2 ~2 ~/si Si / (A) H H N

The action of a catalytic smount of the bs3a on thos~ cyclic oligom~r~ link3 thom toge~h~r ~ia such cy~lodl~ilazan~ units l~to sh~t-lik~ array. Tr~atm~nt of, for ex~mple, th~ CH3SL~C12 a~onolysis product by th~ bas~, usually KH (0.5-4 mol percen~ ba~t on CH3SiH~H uni~s), providas a polysil~zana inten~adiate of ~ypo [(CH3s~H~l)a~cH3s~N)b(cH3slxNK)cln~ l.o. a nll~in~"
poly~ar which ~ill con~ains re~ctive 3ilylamlds functlons. Thl~
~li~ing" poly~ilazano $n~rm~dlat~ can b~ ~ra~sd wit~ a suit2bl~
alec~rophlle, such a3 CH3I or 8 chloro~ilan~, to "nautralizo~ th~
r~acti~ silyl~ida functlon~. Ulti~at~ly, on pyrDlyYia in a~ in~rr ga~ s~rea~ (N2 or Ar~ to lOOO~C, the yield o~cer~ic re~iduo i~
high (80-85~, A ~ical compo~it~o~ o such a c~ra~ic matari~l is 0.9 Si3N~ + 1.3 51C ~ 0.75 C or, o~ n welg~t ~ b~s, 67 Si~Nh, 283 S~C and.5~ C.

U.S. Patents Nos. 4,645,807 issued February 24, 1987 and 4,650,837 issued March 17, 1987, deæcribe methods for converting organosilicon polymers containing Si-H repeat units to new and useful preceramic polymers and ceramic materials.
The preceramic polymers, which are prepared by reacting either ~; an organopolysilane or a polycarbosilane with a silylamide result in preceramic polymers whose pyrolysis gives a mixture of silicon carbide and silicon nitride ceramic materials, which are generally rich in silicon carbide.
It would be useful to have a polymer precursor that is formed from readily available and relatively inexpensive starting materials, that is stable at room temperature, is fusible and/or soluble in..... ~... ,.............. ~

D

~3~'1L875 organic solvents and whose pyrolysis can provide a high yield of ceramic products. It would also be useful to be able to ha~e such a polymer precursor which forms a ceramic material upon pyrolysis that i~ rich in the silicon nitride component.
Summary of the Invention We have found that reaction of a polymeric silylamide, which is the intermediate formed from the dehydrocylodimerization reaction (DHCD) of the coammonolysis product of [RlSiHX2] and [R2SiX3~ where R1, R and X are as defined above, with an organosilicon pol~mer containing Si-~ repeat units yields new polymeric organosilicon compounds which are useful preceramic materials. Upon pyrolysis these "hybrid" polymers typically qive ceramic yields significantly better than obtained for the original organosilicon polymer compound alone. The polymeric silylamide may be preformed and added to the Si-H containing organosilicon polymer.
Alternatively, one may prepare the silylamide in situ, in the presence of the organosilicon compound.
The above polymeric silylamide is generated by treating the coammonolysis product of R1SiHX2 and R2SiX3 (R and R are as defined above) with a basic catalyst capable of deprotonating the hydrogen from a nitrogen atom adjacent to a silicon atom also referred to as dehydrocylodimerization. With either preformed polysilylamide or an ln situ silylamide procedure, the reaction mixture containing the organosilicon polymer having Si-H repeat llnits and the polysilylamide is 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 cooled and quenched typically with an organic halide or a silicon halide to produce the preceramic organosilicon polymers of the present invention. Preferably the organosilicon polymer is a polysilane compound of the formula ~13~487S

[(RSiH)X(RSi)y3n, (where x ~ y ~ 1, n i~ 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), a poly-carbosilane polymer containing repeat units o the formula [RaSi(H~-(CH2)q], i.e., a~
~~i~(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 Prom 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms or a substituted or un-substituted lower aryl group having from 6 to about 10 carbon atoms), or an organohydrogen-siloxane polymer containing repeat units of formula [RbSi(H)o]n/ i.e., ~ Rb -~i-O- (III) ~where n is an integer 1 or greater, Rb is a lower alkyl group having from 1 to about 6 carbon ~toms, a 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 or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms).
Aryl-substituted polymers of the type [RaSi(H)-(CH2)q~, '[RSiH]n and [RbSi(H)o]n (e.g., where R, Ra or Rb is phenyl), react in the same way as ths above described polycarbosilanes, organopolysilanes and polysiloxanes to give new polycarbosilane/organopolysilazane, organopoly-silane/organopolysilazane and polysiloxane/organopoly-silazane hybrid polymers, respectively.

~ ~, : "

~L3~a~S

The polymer~ formed by thi~ method can then bepyrolyzed to yield cera~ic materials in high yield.
~çtailed Descrip~ion of the Inven~ion The following description of the invention includes not only the method ~or preparing preceramic polymers by reacting a polymeric silylamide with an organosilicon polymer, to which the present application is directed, but also a method for preparing preceramic organosilicon polymers comprising thP ~teps of reacting in solution anhydrous ammonia with a mixture of RlSiHX2 and RSiX3, thereby forming a mixture of precursor polymers; and reacting the precursor polymers in the presence of a basic catalyst capable of deprotonating the NH ~unctions in the precursor polymers to form the preceramic polymer. The latter method is being made the subject o~ a divisional application.
We have now discovered that by using the coam-monolysis product of a mixture of a dihalosilane and a trihalosilane, one can obtain a preceramic polymer whose pyrolysis results in a ceramic material richer in silicon nitride than the polymer obtained by using the. ammonolysis product of the corresponding dihalosilane alone. ........

r~ ~ 7 --~13~
.

Additionally, the coammonolysls product i9 often more soluble than the ammonolysis product of the corresponding trihalosllane, and because an important requirement for a useful preceramic poly~er is that it be processable, i.e., fusible, and/or soluble ln organic solvents, the coammonolysis product is preferable.
Preferably, the dihalosllane is of the formula R15iHX2, wherein Rl is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group hav~ng from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having ~rom 2 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, while X is a halogen, preferably, fluorine, chlorine, bromine or iodine. More preferably, Rl is a lower alkyl group. Nost preferably, Rl is CH3. X is preferably chlorine.
Preferably, the trihalosilane has the formula RSiX3, wherein R is hydrogen, 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, or a substituted or unsubstituted lower aryl group having from S to about 10 carbon atoms and X is a halogen, preferably, fluorine, chlorine, bromine or iodine. Nore preferably, R is a hydrogen or a lower alkyl group.
Still more preferably R is hydrogen or CH3. Most preferably, R ls hydrogen. X is preferably chlorine.
The coammonolysis reaction is carried out in any organic solvent in which ~he two reactants are soluble. Solvents which may be used include ethers such as dialkyl ethers, particularly diethyl ether (Et20); cyclic ethers such as tetrahydropyran, l,~-dioxane, preferably tetrahydrofuran (THF); glycol ethers; aliphatic hydrocarbons such as pentane, hexane; and aromatic hydrocarbons such as benzene, toluene, xylenes. Other useful solvents are well known to the person of ordinary skill in the art, based upon this disclosure. The RlSiHX2/RSiX3 mixture is then reacted with sm=onia in such a sol~ent to tffoct ~he coa:monolysis teaotion.

:, .',, ~304~S17~;

In a pref0rred embodiment of the present invention, the coammonolysis product is treated with catalytic quantities oE a base capable of deprotonating the NH functions in the resultant coammonolysis product, for example, KH, in an organic solvent. A
dehydrocyclodimerization reaction (DHCD) takes place, which results in a preceramic polymer that gives high ceramic yields upon pyrolysis. Preferably, the base is an alkali me~al, an alkal$ metal hydride, an alkaline earth metal hydride, an alkali metal amid0, an alkaline earth metal amide, a complex alkali metal hydride, e.g. KB
(sec-Bu)3H, LiAlH4, etc., alkali and alkaline earth metal silylamides, an alkali metal organic compound and the like. More preferably, the base is KH. Only small amounts of the base are necessary (0.1-10 mole percent based upon the NH containing repeat unit) because the reaction is catalytic.
The coammonolysis product is reacted with the base in any organic solvent, in which the coammonolysis product is soluble without reaction. Such organic solvents include ethers, such as dialkyl ethers, preferably diethyl ether; cyclic ethers, for example, preferably, THF; glycol ethers, aliphatic hydrocarbons such as alkanes, arenes ? and combinations thereof.
The temperature at which this reaction takes place generally ranges from about -10C to about +30C. After the reaction is complete, the mixture may be quenched with an electrophile, EX, capable of reaction with residual silylamide functions. E is any organic group, preferably, a lower alkyl group or silyl group; X is preferably a halide, sulfate or sulfonate. The electrophile can be an alkyl halide, sulfate or sulfonatz; a halosilane; or the like.
Typically, CH3I or a chlorosilane is used although other equivalent electrophiles well-known to those skilled in the art can also be used. This quenching limits the reactivity of the "living" polymer intermediate.

l3l~a7s The preceramic polymer produced by the DHCD reaction typically is a white solid, which is produced ln virtually quantitative yield.
When Rl was CH3, X was Cl and R was H, the proton NMR spectra of the products showed an increase in the SiCH3/SiH + NH proton ratio, while the relative SiH/NH ratio was unchanged. This indicates that a hydrogen loss had taken place.
In the DHCD reactions, the molecular weight of the qolid product was greater than that of the starting coammonolysis product, thus a polymerization reaction had occurred. The conversion of the oils which typically are formed in the coammonolysis reactions to the solids of the present invention results in a material that is more easily handled.
Pyrolysis of the white solid obtained in these base-catalyzed, DHCD reactions under argon from 50 to 950C, typically produces black ceramic residues. The ceramic yields were generally excellent. These ceramic materials have a rich silicon nitride content.
Relatively pure silicon nitride material can be formed when the preceramic polymer is pyrolyzed in a stream of = onia rather than of an inert gas such as nitrogen or argon. The ammonia reacts with the polymer at higher temperatures to cleave methyl groups from silicon, so that essentially all carbon is lost. For example, where ~1 is CH3 and R is H, the pyrolysis of the preceramic polymer derived from the DHCD product of the 1:1 co = onolysis (in THF) product to 1000C in a stream of ammonia produced a white ceramic residue in high yield containing only 0.29~ by weight C, with the remainder being silicon nitride. When both Rl and R were C~3, the pyrolysi~ of the preceramic polymer derived from the DHCD product of the 6:1 coammonolysis (in Et20) product to 1000C in a stream of ammonia produced a white ceramic residue containing only 0.36~ by wei~ht of carbon. Similarly, pyrolysis of a 3:1 CH3SiHC12:C2H5SiC13 (co = onolysis product in Et20) KH-catalyzed DHCD (in THF) product to 1000C in a stream of ammonia produced an essentially pure white residue with a very faint brown `` ~30~'7S

tinge. However, alkenyl groups appear to be more intimately involved with the pyrolysis chemistry. Pyrolysis oE a control ammonolysis product of CH2-~HSiC13 to 1000C in a stream of ammonia produced a brown ceramic residue, while pyrolysis of a 3:1 CH3SiHC12:CH2-CHSiC13 (coammonolysis in THF) KH-catalyzed DHCD (in THF) product in a stream of ammonia produced a ceramic that was black with touches of white and brown.
A wide range of RlSiHX2:RSiX3 ratios can be used in preparing the coammonolysis product, the mole ratio can be for example from about 20:1 to 1:20, it preferably ranges from about 8:1 to 1:7. Generally, the higher the mole % of dihalosilane used, the more soluble is the coammonolysis product. However, this product generally forms a ceramic material in lower yields. In addition, at a high mole % oi trihalosilane, the DHCD reaction has less effect.
The DHCD reaction at high mole ~ of trihalosilane should be limited to the soluble reaction product. For certain halosilanes, however, the coammonolysis product obtained with high levels of trihalosilane has properties that are quite useful without a subsequent DHCD
reaction. ~hen a DHCD reaction is contemplated, the mole ratio of RlSiHX2:RSi~3 is preferably from about 8:1 to about 1:6, more preferably from about 8:1 to about 1.2, even more preferably about 6:1 to about 1:1. A higher mole ratLo of dihalo~ilane to trihalosilane, such as about 6:1 to 3:1, provides a coammonolysis product that is typically soluble, which, when sub;ected to a DHCD
reaction, results in a preceramic polymer that provides excellent yields of ceramic material. However, a ratio of about 2:1 to 1:2, preferably about 1:1, produces a preceramic polymer whose pyrolysis in an inert atmosphere, typically, results in a greater percent of silicon nitride in the ceramic material than obtained on using the higher mole ratio of dihalosilane. Thus, depending upon the desired end product and reaction sequences, the mole ratio of dihalosilane:trihalosilane will vary. The particular ratio to use in a given situation can readily be determined empirically by the desired end use based upon the present disclosure.

~3~L875 For example, ammonolysis of HSiCl3 alone gives mostly insoluble, highly cross-linked products. The highest yield oP
soluble products (47~) was obtained when the HSiC13 ammonolysls was carried out at -20C (at 0C the yield of soluble product was 17%, at -78C it was 20%). However, these lnitially soluble silazanes become insoluble after the solvent is removed. Since the main requirement of a preceramic polymer is that it must be processable, i.e., uslble and/or soluble in organic solvents, ammonolysis of HSiCl3 alone is not satisfactory.
When R is H, and Rl is CH3 and X is Cl, the preferred ratio of RlSiHX2:RSiX3 ranges from about 8:1 to about 1:4; more preferably, the ratio is about 6:1 to about 1:2 when a DHCD reaction is used; more preferably about 6:1 ~o about 3:1 when one is concerned with the solubility of the starting materials; and about 3:1 to about 1:2, more preferably about l:l when one is interested in the resultant weight percent of the ceramic residue obtained after pyrolysis in an inert atmosphere; and l:l to about 1:4, most preferably about 1:3 when the coammonolysis product without a DHCD
reaction is desired.
In either Et20 or THF, the 6:1 and 3:1 ratios used in the co = onolysis produced polysilazane oils with molecular weights in the range 390-401 g/mol and 480 g/mol, respectively. When a l:l reactant ratio was used, waxes of somewhat higher (764-778 g/mol) molecular weights were obtained in both solvents. In the l:l reaction carried out in Et20 the yield of soluble product was only 40%, but in THF it wa~ nearly quantitativ~.
The oils produced in the 6:1 and 3:1 reactions in Et20 are stable on long-t~rm storage at room temperature in the absence of moisture (e.g., in an inert atmosphere box). However, the waxy product of 1:1 reactions in (Et20) and all the coammonolysis products prepared in THF formed gels (i.e., became insoluble) after 3-4 weeks at room temperature, even when stored in a nitrogen-filled dry box. (See Tables l and 2).

. ' ............. ' :
, ' ., ;'""'`''', '''''''''"' '"' " ' ''' ~

~30487S

T~BLE l COAMMONOLYSIS OF METHYLDI_HLOROSILANE 4ND
TRICHL~ ILA~E I~ DIETHYL ETHER MEDIUM.
DEHY~ROCYCLODIMERIZATION OF THE PRODUCTS~

CH3~Ç12 Ceramlc HSiC13 _ Yield by ReactionMolar Ratio . Product Yield~%)_~W TGA. ~ -6 oil 74 390 33 Coammonolysis in Et20 3 oil 79 484 41 1 wax 40 778 72 . _ 6 solid 1001300 85 DHCD Reaction, 1~ KH in THF 3 solid 99 1250 88 1 solid 931630 87 .,, !

~3~ '7S

CoAMyç~LoLysIs oE ~ETHx~D~yL8a~
TRICHLOROSI19E~ i~ T~E_~enI~.
DEHYDROCYCLODIMERIZATION QF ~E_PRoDUCTS.

CH3SiH 2 Ceramic HSiC13 _ Yield Reaction _ MoLsr RatiQ_ Product Yield(~) M~ b~ TÇA~
6 oil 91 401 28 Co = onolysis in THF 3 oil 85 482 67 1 wax 94 764 78 _ _ _ _ 6 solid 961094 82 DHCD Reaction, 1% XH in THF 3solid97 942 82 1 solid 931620 86 ., .. ~

~30~a7s The integrated proton NMR spectra of the various coammonolysis products establish their approximate constitutions:

Ç~3sl~cl2~ 3 ~io Ap~roximflte Eorm la 6:1 [CH3SiHNH]l.o[Hsi(NH)l.5]o.l7 3:1 [CH3SiHNH]l.o[Hsi(NH)l.5]o.33 1:1 [CH3SiHNH]l.o[Hsi(NH)l.5]o.37 These formulas carry no structural implications, they merely are average formulations. The HSiC13 component probably introduces both SiNHSi bridglng and SiNH2 terminal groups into the structure. From these approximate formulas one can calculate expected % C, H, N and Si compositions and, in general, the agreement of observed % C, H and N for the 6:1 and 3:1 products with these values is good (+ 0.55~). (Analyses were not obtained of the wa~es prepared in the 1:1 reactions).
The pyrolysis of these coammonolysis products was studied.
The 6 CH3SiHC12:1 HSiC13 ammonolysis product gives low ceramic yields on pyrolysis. Pyrolysis of the 3:1 products gives incr ased ceramic yields, whi:Le pyrolysis of the most highly cross-linked 1:1 ammonolysis products gives quite good ceramic yields*, 72~ for the product prepared in Et20, 78% for that prepared in THF.

*Ceramic yield is defined as wei~ht of residue x_100 _ weight of sample pyrolyzed :

~L3~4~7~

Sub;ecting these co = onolysis products to the DHCD
reaction, using KH as a base resul~ed in white solids in virtually quantitative yield. The solids are easier to handle and store than the oils. Pyrolysis of the white solids obtained in these KH-catalyzed DHCD reactions (under argon from 50-950C) produced black ceramic residues, with the exception of the 1:1 THF ammonolysis-deri~ed solid which left a brown residue. The ceramic yields were excellent (all greater than or equal to 82~, with the highest being 88~).
Analysis of bulk samples of the ceramic materials produced ln the pyrolysis of the various XH-catalyzed DHCD products shows that a hlgher Si3N4/SiC ratio has been achieved (Table 3):
for the 1:1 coammonolysis products-derived polymers, 86 Si3N4, ~ SlC and 5% C (TH~ coammonolysis) and ~3~
Si3N4, 11% SiC and 6~ C (Et20 coammonolysis); for the 3:1 and 6:1 coammonolysis products-derived polymers: 77~ Si3N4, 18-19~ SiC and 4-5~ C (Et20 co { onolysis) and 74% Si3N4, 20~ SiC and 5-6% C (THF coam~onolysis).
However, the KH-catalyzed DHCD reactions with the 1:3 coammonolysis-derived polymer were slow, producing soluble products in poor yields. Pyrolysis of this material produced a black ceramic.
There are situations where one desires a ceramic material and/or preceramic polymer that contains differing amounts of silicon carbide and silicon nitride. The present process can ba used to result in a preceramic polymer that will typically produce a ceramic material that is enriched in silicon nitride when compared to reactions in which the precursor dihalosilane is used alone a~ the initial starting material.
For example, when Rl was CH3, X was Cl, and R was CH3, CH2~CH or C2H5, the Eollowing results were obtained.
As control experi~ents, the ammonolysis of CH3SiC13 alone was studied. Ammonolysis of this precursor in Et20 gave ~L3~ '7S

a 46~ yield of soluble solid product, molecular weight 70Z
g/mol, ceramic yield (by TGA to 950C) 56~. A similar CH3SiCl3/NH3 reaction in THF gave soluble solid produat in 82~ yield, molecular weight 672 g/mol, ceramic yield (by TGA) 69%. By proton NMR (C_3Si/N_ integration), the Et20 product may be for~ulated as [CH3Si(NH)1 3]x~ the THF product as [CH3Si(NH)1 6]x (This is only a rough approximation because integration of the broad N~ signals is rather : inaccurate~. The results o-f the coammonolyses of CH3SiHC12 : -17-`` ~L341~ 7S

CH3SiHC12/
HSiC13 Molar Ratio _ Product C.~ H.~ _ N.% _ S~
of a~monolysis 17.75 7.53 25.80 in Et2O
6 of DHCD 20.05 6.73 25.82 ceramica 10.36 30.94 58.92 --of } onolysis in Et2O 16.19 7.31 27.04 3 of DHCD 17.61 6.46 25.85 ceramicb 9,35 30.79 59,99 1 of DHCD 14.10 6.12 27.60 ceramicC 9.10 0.70 32.56 56.52 __ of am~onolysiS
; in THF 18.22 7.89 25.21 6 of DHCD 19.89 6.85 25.08 cerAmicd 11.72 29.71 59.03 of ammonolysis in THF 16.10 7.45 25.51 3 of DHCD 18.00 6.71 27.32 - ceramice 11.21 29.77 59.09 1 of DHCD 12.42 5.97 ceramicf 7.74 0.54 34.29 57.17 aCalc. 77% (by weight) Si3N4, 18% SiC, 5% C
bCalc. 77% Si3N4, 19% SiC, 4% C
Calc. 83~ Si3N4, 11% SiC, 5.7~ C
dCalc. 74~ Si3N4, 20% SiC, 6% C
eCalc. 74% Si3N4, 20% SiC, 5~ C
fCalc. 87~ Si3N4, 8% SiC, 5.4% C

~304B'75 and CH3SiCl3 are gi~en in Tables 4 and 5. In all cases, whether the solvent was Et20 or THF, oils ware obtained in high yield. These were of low (300-500) molecular weight and their pyrolysis gave only low ceramic yields. The KH-catalyzed DHCD reaction of these coammonolysis products gave white solid products of higher (ca. two-to-threefold) molecular weight.
Based upon the lH NMR analysis, th~ following formulations of the products were generated:
cH3siHcl2/
CH3SiC13 Reaction L_~3~lQ Solv_nt Formula 6 Et20 [CH3SiHNH]1 o[CH3Si(NH)1.5]0.26 THF [CH3SiHNH]1 o[CH3Si(NH)2.1]0.27 3 Et20 [CH3SiHNH]1 o[CH3Si(N~l)l.1]0.29 THF [CH3SiHNH]1 o[CH3Si(NH)1.1]0.29 Et20 [CH3SiHNH]1 o[CH3Si(NH)1.5]0.63 THF [CH3SiHNH]1 o[CH3Si(NH)1.8]0.80 These are only approximate constltutions, but agreement of combustion analysas (C, H, ~) was fairly good for the for~ulations given. The ceramic yields obtained on pyrolysis of these polymers were high:
78-82% for the products generated by initial coammonolysis in THF. In all cases, a black ceramic residue resulted when the pyrolysis to 950C was carried out in a strPam of argon. As expected, the carbon content (in the for~ of SiC and free C) was hi~her than that of the CH3SiHC12/HSiC13-derived ceramics (Table 6): 12-18~ SiC, up to 9.5% carbon. Nonetheless, higher S13N4 contents than those obtained when CH3SiHCl2 is used alone ( 67~) were obtained.
DHCD products of polysilazanes from a~onolysis in Et20:
75-76% Si3N4; 15-18% SiC; 7-9~ C.

~3~8~75 ~ .

w~a~
METH~LTRICH~OROSILANE IN DIE~ ET~ER AND
DEHYDROCYCLODTMERIZATION OF THE PRODUCTS

Ceramic CH3SiHC12/CH3SiC13 - Yield Reaction _ Molar Ratio _ Product _ Yield(~) MW bv TGA.
Coammonolysis in Et20 6 oil 75 376 21 3 oil 80 373 40 1 oil 81 526 44 1/3wax 89 627 --1/6white solid 65 642 --DHCD Reaction, 1% KH in THF 6solid 97 1260 82 3solid 100 795 78 1solid 98 786 78 1/3white solid 95 850 58 1/6white solid 90 1012 56 ~3(~ 7S

TABLE_5 QND METHyLTRICHLOROSILANE IN THF~
DEHYDROCYCLODIMERIZATION OF THE PRODUCTS

Ceramic CH3siHC12/C~3siC13 Yield Reaction __ Molar Ratio Product Yield(~) MW _bv TGA.%

6 o~l 81 311 26 Coam~onolysis in THF 3 oil 91 363 31 1 oil 89 484 44 1/3white solid 88 --- --1~6white solid 98 --- --6solid 72 1171 86 DHCD Reaction, 1~ KH in THF 3 solid 84 1170 83 1solid 100 838 82 .

1/3white solid 92 1180 76 1/6white solid 95 925 71 .

~;3g~48~5 PRODUCTS OF THE REACTIONS OF TABLES 4 AND 5.

CH3siHcl2/
CH3SiC13 Analysis Molar Ratio _ . _ Product C.% H.% N.% Si,~
of ammonolysis in Et2O 20.248.02 6 of DHCD 21.85 7.09 ceramica 12.16 0.51 30.4457.23 _ _ of ammonolysis in Et2O 20.01 7.90 3 of DHCD 21.67 7.26 ceramicb 13.04 0.72 31.0555.30 . _ . _ of ammonolysis in Et2O 19.66 7.49 1 of DHCD 21.04 7.29 22.20 ceramicC 11.36 0.61 31.9056.35 of ammonolysls in THF 20.26 8.06 23.79 6 of DHCD 21.85 7.02 ceramicd 12.87 0.60 29.3553.94 of ammonolysis in THF 20.13 7.93 3 of DHCD 22.05 7.03 ceramice 12.36 0.63 29.5756.77 9..~ 8'75i of ammonolysis in THF 19.53 7.42 1 of DHCD 22.35 7.24 ceramicf 11.19 0.63 31.01 56.36 aCalcd. 76~ (by weight) Si3N4, 16~ SiC, i~ C
bCalcd. 78~ Si3N4, 12~ SiC, 9~ C
CCalcd. 80~ Si3N4, 12~ SiC, 8~ C
dCalcd. 76~ Si3N4, 154 SiC, 9~ C
eCalcd. 75~ Si3N4, 18~ SiC, 7% C
fCalcd. 79% Si3N4, 14~ SiC, 7~ C

gL3~17~

Changing the "monomer" ratio from 6 to 3 to 1 does not vary the compositions of the final ceramic materials very much: the Si3N4 content varies by only 5~, while the SiC content shows a 6~ range and the carbon content is within 2~ for all the materials.
To produce a ceramic material containing only Si3N4, the white solid polysilazane derived from the DHCD of the oil obtained by ammonolysis of 6:1 CH3SiHC12/CH3SiC13 in Et20 medium was pyrolyzed in a stream of ammonia (to 1000C). A white ceramic residue containing only 0.36~ by weight C resulted.
Essentially the same reactions were carried out using vinyltrichlorosilane in place of methyltrichlorosilane tCH3SiHC12/CH2-CHSiC13 molar ratios of 6, 3 and 1; ammonolysis in Et20 and THF medium; subsequent KH-cataly~ed DHCD in THF: see Tables 7, 8, and 9). Control experiments involving the ammonolysis of CH2-CHSiC13 alone, in Et20 and in THF medium, were also perfor~ed. In both solvents, glassy white solids were obtained. The yield of soluble products in Et20 was low (61%); in THF it was quantitative. The molecular weights were relatively high (1165 and 1185, respectively) and the ceramic yields obtained on pyrolysis to 950C were high (76% and 82~, respectively). This is a result, at least in part, of a greater incorporation of carbon. Analysis of the ceramic obtained in the pyrolysis of the CH2-CHSiC13 ammonolysis (in THF) product showed a composition 71% Si3N4, 29% C.
The coammonolysis of CH3SiHC12 and CH2~CHSiC13 in ~t20 i i 3~D~!37~i ~ '.

COA~ONOLYSIS QF METHYLDICHLOROSILANE AND
VIN L~RICHLOROSIL4NE I~ DIETHYL ET~
PEHYDROCYCLODIMERIZATIQN OF THE PRODUCTS

CH3SiHC12/ Ceramic CH2;CHSiC13 ~ Yield Reaction Molar Ratio Product Yield~? . MW_ by TGA.
Coammonolysis in Et20 6 oil 86 305 43 3 oil 87 333 53 1 oil 90 605 74 DHCD Reaction, 1~ KH in T~F 6 solid 99 880 83 : 3 sol$d 98 999 84 1 solid 98 970 78 _ _ .

~3~8~7~

C AMMONOLYSIS OF METHYI.~ICHLOROSILANE AND
VINyLTRTcHLoRos L~E__N_~E
D~HYDROCyCLODIMERIZA~ION OF THE PROD~

CH3SiHCl2/ Ceramic CH2-CHSiC13 Yield Reaction Molar Ratio _ Product _ Yield(~) MW _ bv TGA,~
Coammonolysis in THF 6 oil 89 350 47 3 oil 92 361 57 1 oil 94 536 74 - DHCD Reaction, 1~ KH in THF 6solid 88 773 84 3 solid 100 716 78 - 1solid 99 777 85 .

, `` ~3~'48~S

CH3SiHCl2/
CH2-CHSiC13 Analysis olar Ratlo _ _~roduet C% _ _H~ _ N% Si~ _ of ammonolysis in Et20 22.80 7.86 23.91 6 of DHCD reaction 24.486.86 23.51 eeramiea 17.06 28.33 54.62 of ammonolysis in Et20 24.39 7.65 24.59 3 of DHCD reaction 26.216.89 23.31 eeramieb 17.21 28.43 54.91 of ammonolysis in Et20 26.83 7.08 24.73 1 of DHCD reaetion 27.666.48 25.14 eeramieC 20.87 29.09 49.85 _ aCaled. 71% (by weight) Si3~4, 17% SiC, 12% C
bCaled. 71% Si3N4, 17~ SiC, 12% C
CCaled. 73% Si3N4, 9% SiC, 18% C
dCaled. 69~ Si3N4, 19~ SiC, 12% C
eCalcd. 70~ Si3N4, 16~ SiC, 13% C
fCalcd. 71~ Si3~4, 11% SiC, 18~ C

~304~7S

and in THF medi~n gavs polysilazane oils in high yield, molecular weights 300-600 g/mol. Pyrolysis of the coammonolysis products gave higher ceramic yields, the higher the C~2-CHSiC13 content in the chlorosilane mixture. Application of the K~-catalyzed DHCD reaction to the ammonolysis products in all cases gave white solids of higher molecular weight whose pyrolysis to 950C gave high (78-85~) ceramic yields. However, their Si3N4 content was lower and their carbon content (as SiC + free C) was higher than observed in the ceramics from the CH3SiHC12/HSiC13 and CH3SiHCl~/
CH3SiC13 systems: For the CH3SiHC12/CH2-C~SiC13 ratio ~
6 and 3 products: 69-71% Si3N4; 16-19~ SiC; 12-13% C. For the 1:1 products: 71-73% Si3N4; 9-11~ SiC; 18~ C.
A mixture oE CH3SiHC12 and C2H5SiC13 (3:1 molar ratlo) was treated wlth ammonia in Et20 and in THF at 0C. In both cases, silazane oils, MW 360-370, were obtained in high yield.
Their cerc~nic yields on pyrolysis to 950C were low (15% and 23~, respectively). Application of the DHCD reaction (1% KH in THF) to these oils in both cases gave white solids with increased MW (972 and 860, respectively) and increased cer~nic yield on pyrolysis to 950C (81% and 78%, respectively). 'Fhe pyrolysis product in each case was a black foam when the pyrolysis gas stream was argon.
Analysis of the ceramic products gave ~ C, N and Si values from which compositions of about 71-73~ Si3N4, 14-17~ SiC and 11-12% C could be calculated. Thus, there is essentially no difference between thsse results and the calculated composition of the ceramic product of the corresponding 3:1 CH3SiHC12/CH2-CHSiC13 system ~70-71 Si3N4, 16-17% SiC, 12-13~ C).
In the case of the present polymers, as is seen in Table 10, some were self-curing and on pyrolysis gave ceramic fibers (those noted "yes"). Others melted when heated, so that the fibers were destroyed (those noted "no"). Conversion of the meltable fiber to an infusible iiber by a cure step prior to pyrolysis will enable one to melt spin these materials into fibers.

~3~ 75 CERAMIC FIBERS AND_SiC POWDER COMPOSITES
Molar Ammonolysis Fiber on Chlorosilanes_ _ Ratio _ Solvent ~3~ _PYroly~__a_ CH3SiHCl2/
CH2-SiC13 6/1 Et20 xb Yes '~ 3/1 Et2O x No " 1/1 Et2O x No " 6/1 THF x Yes n 3/1 THF x No " 1/1 THF x Yes CH3SiHC12/
HSiC13 6/1 Et20 x Yes .. 3/1 Et2O x Yes n1/1 Et2O x Yes n6/1 THF x No n3/1 I~F x No "1/1 I'HF x Yes -CH3SiHC12/
CH3SiC136/1 E:t2O x Yes n 3/1 Et2 x No ~ t2o x No -" 6/1 THF x Yes 3/1 THF x No " 1/1 THF x Yes a Yes - Fibers remained after heating to 1000C under Ar.
No - Fibers did not remain after pyrolysis to 1000C.
b x means a bar was made and pyrolyzed to obtain a ceramic bar.

~L39~4B7~

The "cure" step prior to pyrolysis can be accomplished when either R or Rl is alkenyl by curing the fiber through hydrosilylation. This reaction can be induced by ultraviolet and other hlgh energy radiation, as well as by chemical free radical sources and transition metal catalysts. These compounds can readily be selected by the person of ordinary skill in the art and include H2PtC16 6H20, peroxide and azo compounds, preferably organic peroxides, such as benzoyl peroxide, more preferably azo compounds such as azobisisobutyronitrile and the like. Preferably, a radiation source is used.
W irradiation, irradiation with an electron beam or an X-ray source, etc. will cure the alkenyl containing polymer. Subjecting the preceramic fiber to W irradiation (Rayonet Reactor) for 2 hours results in an infusible fiber that does not melt upon subsequent pyrolysis under argon, producing ceramic fibers. By incorporating C C
into the coammonolysis product, this strategy can be broadly applied to the present invention. The addition of a third compound containing an unsaturated functionality to the ammonolysis mixture results in a mixture of ollgomers. The particular amount to be added to the coammonolysis mixture will depend upon the desired US2 and compounds being used.
Fibers were prepared in the following manner: In the dry box, a few drops of toluene was added to a polymer sample and the resulting mixture stirred with a glass rod until a sticky residue resulted from which fibers could be drawn. These fibers (1/4" to 2" in length) were placed in a boat, taken out of the dry box and placed in a tube furnace flushed with Argon. The fibers were heated to 1000C at 10C~minute. The poly~ers listed in Table 10 were used in preparing fibers.
The present polymers can be used as binders for SlC powder processing.
Ceramic composite bars were prepared in the following manner:
In the dry box, a 100 ml, one-necked, round-bottomed flask was charged with 0.6 g polymer and 2.4 g of commercial Fujima SiC powder.

~3~ 75 The flask was removed from the dry bo~ and charged with 25 ml of toluene. me flask was placed in an ultrasonic bath for at least 15 minutes. The toluene was then removed on a rotary evaporator and the residue then dried under vacuum at 0.03 mm Hg for at least 1/2 hour.
The SiC/polymer residue was ground with a mortar and pestle to produce a fine powder. This powder was pressed in a 1.5" x 0.5" x 0 ln dle at 6000 lbs. for 5 minutes. The bar was then isostatically pressed at 40,000 lbs. Finally, the bar was pyrolyzed under Ar in a tube furnace to 1000C.
The polymers shown in Table 10 were used to form composite bars.
All bars retained their rectangular shape upon pyrolysis.
In a different embodiment, the polymeric silylamide which is the intermedlate formed from the DHCD reaction of [RlSiHX2] and [R2SiX3] (wherein Rl, R2 and X are as defined above) can be used to form another preceramic polymer. This poly~eric silylamide is the intermediate formed aEter the DHCD reaction and prior to treatment with an electrophile, such as Ch3I. This intermediate species (sometimes also reierred to as a ~reactive 'living' polymer", si].ylamide, poly(silylamide) or alkali metal sllylamide)n) can react with electrophiles other than CH3I. We have discovered that the reaction o this silyamide with an organosilicon polymer containing Si-H repeat units (referred to as an Si-H containing organosilicon polymer) results in novel preceramic polymers.
The Si-H containing organosilicon polymer is preferably 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 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, or a tri(lower)alkyl- or di(lower)alkylsilyl group) (See U.S. Paten~
Application Serial No. 756,353 filed July 18, 1985), a polycarbosilane polymer containing repeat units of the ormula [RaSi(H)-(CH2)q],i.e., ~a -~i-(CH2)q~ (II) (where q is an integer 1 or greater, Ra is H, a lower alkyl group , .

~304~375 having from 1 to about 6 carbon atoms, a 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 or a substituted or un~ubstituted lower aryl group having from 6 to about 10 carbon atoms) (See the aforementioned U.S. patent No.

4,650,837), or an organohydrogensiloxane polymer containing repeat units of the formula C RbSi ( ~ ) ] b~,i.e., -~i-0- (III) (where n is an integer 1 or greater, Rb is 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 alkenyl group having from 2 to about 6 carbon atoms or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms) (See U.S. Patent Application Serial No.
849,390 filed April 8, 1986).
In accord with the present invention, treatment of, for example, organopolysilanes with the silylamide will provide higher molecular weight preceramic materials and improve the ceramic yield.
We have now found that organopolysilanes such as methylpolysilanes ([(CH3SiH)X(CH3Si)y]n) obtained in the above reactions, upon treatment with catalytic quantities of silylamides 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 solvent.
Polycarbosilane polymers that are used in the prsent invention preferably contain a multiplicity of repeat units of the formula [R~Si(H)~(CH2q~ (where q and R~ are as defined above( (hereinafter polymers containing such repeat units are referred to as "polycarbosilanes"). The reaction of these -~` i3(~4~

polycarbosilanes with an alkali metal silylamide results in novel preceramic polymers. Typically, the prolysis of this new polymer gives a black ceramic ................................

~i , : ~:

., 1 `

,. .
.~

- 3~ -... :~ ' , ' '"~ ~ ' `' "

.. '. :': . .
"' .
.

l3~al~s solid in a yield that is greater than that obtained on pyrolysis of the parent polycarbosilane.
The polycarbosilane polymer should contain at least 25 mol~ % of repeat units of the formula II, i.e. [RaSi(H)-(CH2)q], in addition to other repeat units, such as [Ra2Si(CH2~q] (e.g. the Yajima 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 dif~erent than Ra and q'may be different than q). Ra is pr~ferably a lower alkyl group, more preferably Ra is CH3. Preferably q is equal to 1 - 3, more preferably it i5 equal to one.
The polycarbosilane and silylamide are typically added in a weight ratio o polycarbosilane: silylamide o~ 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.
Additionally, the reaction of organohydrogensiloxane polymers containing a plurality of repeat units of the formula [RbSi(H)O]n ~where n and Rb are as defined above) (hereinafter polymers containing such repeat units are referred to as "polysiloxanes"), with a poly(silylamide) also results in a novel preceramic polymer.
- The pyrolysis of this new preceramic polymer under a stream oi`
ammonia typically results in a hi~h yield of a white ceramic material.
By choos.ing the correct stoichiometry one is readily able to obtain a ceramic material that is virtually only silicon oxynitride. This process provides silicon oxynitrides at high yield and at low costs.
The pyrolysis of the preceramlc polymer of the present invention under an inert atmosphere such as nitrogen or argon typically results in a black ceramic solid in high yield. This black ceramic material generally contains SiC, Si3N4 and SiO2 and can be used as a binder or coating.

~30~L8~5 The polysiloxane polymer used in the present invention can be readily obtained by the hydrolysis of the appropriate RbSiHC12 (where Rb is as defined abo~e). The hydrolysis may be steered to give a high yield of cyclic [RbSi(H)O]n oligomer or to produce higher molecular weight linear [RbSi(H)O] polymers. They yield o cyclic oli~omers (n - 4, 5, 6,...) may be maximized by using the method taught by Seyferth, D., Prud'homme, C; and Wiseman, G.H., Inor~. Chem , 22: 2163 2167 (1983). Additionally, ona can use commercially available [RbSi(H)O]n polymers.
The polysiloxane polymers useful in the present invention encompass polymers having a wide range of [RbSi(H)O] repeat units. The number of repeat units contained in the polymer will vary depending upon the desired end product.
Preferably, the polysiloxane polymer should contain at least 25 mole g of repeat units of the formula III, i.e. [RbSi(H)O]n, in addition to other repeat units, for example, [RbRb SiO], [Rb Rb SiO], Rb and Rb are defined the same as Rb;
and Rb, Rb , and Rb may be the same as or different from each other. More preferably the polysiloxane polymer contains at least 35 mole ~ of repeat units of formula III. Even more preferably, the polymer contains at least 50 mole ~ repeat units of formula III. Most preferably, the polymer contains at least 75~ mole repeat units of formula III.
~ ith respect to the silylamide used, Rl is preferably a lower alkyl group, more preferably CH3, while R2 is preferably H or a lower alkyl group, more preferably H or CH3. X is pre~erably chlorine, fluorine, bromine or iodine. The dihalosilane can be added to the trihalosilane over a wide range, but preferably the mole ratio of RlSiHX2:RSiX3 is about 20:1 to 1:20, more preferably it is from about 8:1 to about 1:6, still more preferably about 8:1 ~o about 1:2, and even more preferably from about 6:1 to about 1:1.
This silylamide when pyrolyzed will typically produce a ceramic material that is richer in silicon nitride than that obtained on pyrolysis of the polysilazane DHCD product obtained from the -34- .~

. .

~ 8~

corresponding dihalosilane alone.
The use of the above polymeric silylamide in one embodiment of the present invention upgrades the Si-H containing organosllicon polymer, for example, the organopolysilanes, the polycarbosilanes and the polysiloxanes to new polymers which give a high ceramic yiel.d on pyrolysis. When this silylamide 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 pyroly7ed, the ceramic yield is significantly greater than that of the "parent" organosilicon polymer. Additlonally, the silicon nitride/silicon carbide ratio of the resulting material can be varied depending upon the particular dihalosilane and trihalosilane, ratio of dihalosilane to trihalosilane and Si-H organosilicon polymer used. The ratios to use to obtain a particular result can be determined empirically by the skilled artisan based upon the ~resent disclosure.
The weight ratio of Si-H containing polymer to polymeric silylamide can ~ary widely. For example, mole ratios of organopolysilane:
polymeric silylamide from 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 silylamide from about 10 to about 1; and preferably from 5:1 to 1:1 typically provide useful results. Ueight ratios of polysiloxane: polymeric silylamide of 1:1 and 1:5 typically provided useful results. Ueight ratios of polysiloxane: polymeric silylamide from about 15 to about 1 to about 1 to about 15, should also provide useful results. Preferably the weight ratio of polysiloxane:
polymeric silylamide ranges from abo~t 5:1 to 1:5, and more preferably, from 5:1 to 1:1. Howe~er, in all three 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 organosilicon polymer containing Si-H repeat units with the preformed silylamide "living intermediate" followed by treatment with an electrophile, henceforth will be referred to as "graft" polymers.

~L3~ 37S

Polysilanes of type (RSiH)n (i.e., the general case where y 0, x - 1) also react with the polymeric silylamides that are the DHCD
reaction product of ths coammonolysis of a dihalosilane and trihalosilane. Thus, a reaction of (C6H5SiH~n with the silylamide "living intermediate" (l:l molar ratio) in THF at room temperature gives a new organosilicon polymer which is 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 polym~ric 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.
In this system, R or Ra is preferably a lower alkyl, more preferably, R or Ra is CH3. However, R or Ra need not be the same and, as aforesaid, mixtures of Si-H con~aining organosilicon compounds and~or repeat units, e.g., [(RSiH)X(RSi)y~n and [ (R SiH)X, ~R Si)yl ]n'~ [RaSi(H)~(CH2)q] Rnd [Ra Sl(H)-(CH2)q'], and [~RSiH)x(RSi)y]n and [RaSi(H)-(CH2)q] can be used to obtain further flex~bility in tailorlng the properties of the aforesaid product. Similarly, mixed polymers of the type [(RSiH)a(RSi)b(~R Si)c]m (where a, b, m and R are as defined above, and R is defined as is R above and R may be the same or diferent than R) can be used as well.
Preferably, at least one of the grouping R, R', Ra, and Ra for each mixture is CH3.
The polysiloxane polymer may also contain a mixture of repeat units of the above described formula, e.g., both [RbSi(H)O] and [Rb Si(H)O] (Rb is defined the same as Rb but Rb' may ba different than Rb). Rb is preferably a lower alkyl group, more preferably Rb is CH3.
Further, these aforesaid mixtures of compounds can be used to obtain . .. .

~IL3~ S

additional flexibility in tailoring the properties of the aforesaid product.
Mixtures of polysilazanes, for example where R2 i9 H and R2 is CH3 also may be used.
As indicated above, this invention also includes the case of (RSiH)x(RSi)y~n~ where x~l, y O, with R as defined abo~s. Thus, [(RSiH)]n ma~ be a linear or a mixture o~ cyclic species, or a hybrid of both types. For example, [PhSiH]n (Ph is a phenyl group), cf, Aitken, C. et al., J. Org~nomet. Chem., ~ Cll-C13 (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. Similarly, aryl-substituted repeat units of either IRaSi(H)-(CH2)q] or [RbSi(H)O], for example, where Ra or Rb is a phenyl or substituted phenyl group, and Ra and * can be a lower aryl group is also included.
The preceramic product one obtains by using these silylamides, even in only catalytic amounts, differs from the starting organosilicon compound. Thls difference in products apparently arises because both Si-H and Si-Si bonds are reactive towards nucleophilic reagents.
The ~'graft" polymer is for~ed by combining the already formed polymeric silylamide with the Si-H containing organosilicon polymer, for example, the organopolysilane i~ varying proportions in an organlc solvent. Thereafter, the mixture is stirred at room temperature for sufficient time for the two compounds to react. In one embodiment, the polysilo~ane, ~or example, [C~3Si(~)O]n oligomers with a high cyclic content, is added slowly to an organlc solution such as THF
containing the preformed silylamide. An immediate reaction with some gas evolution occurs. Thereafter, the mixture is stirred at room temperature for sufficient time for the two compounds to more completely react.
Any organic solvent in which both polymer systems are soluble without reaction can be used. Such organic solvents include, for example, THF, diethyl ether, glycol ethers, alkanes, arenes and !

., ' .' '`;'.'' , ~, ''` ` '`' , ' ~3~7S

combinations thereof. The mixture may be heated above room temperaeure, and can be refluxed to sp0ed up the completion oE the reaction. After refluxing, the mixture is quenched with an electrophile, E-21, to form the organosilicon "graft" polymer. The electrophila can be an alkyl halide, sulfate, or sulfonate; a halosilanc; or the like. Typically, CH3I or a chlorosllane is used, although oth0r equivalent electrophiles well-known to those skilled in the art can also be usQd. E is preferably a lower alkyl group or silyl group; Xl is preferably a halide, sulfate or sulfonate.
The organosilicon polymer formed by the present ("graftn) 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 1600-2200 g/mol range. This preceramic organosilicon polymer can then by pyrolyzed under inert atmosphere conditions (As used herein, nitrogen will be considered an inert gas, argon is another example) to result in a ceramic material in high yield. Pyrolysis under nitrogen gave ceramic products in a yield 75-85~.
~ he organosilicon preceramic polymers formed by the present (ngraft") process when polycarbosilane is used were produced in high yields (as high as 95%). Pyrolysis of this preceramic polymer gave ceramic products in a yield of 75-85% (based on weight of the starting materials).
The resultant preceramic polymer when polysiloxane was used were produced in good yields, typically better than 70%. The polysiloxane-derived preceramic organosilicon polymers can then by pyrolyzed under nitrogen or other Inert atmosphere to result in ceramlc materials in high yield. Typically, pyrolysis under nitrogen gave black ceramic products in a high yield (as high as 88%). More significantly, pyrolysis under ammonia will give a white ceramic solid ln high yield. The white ceramics contain little, if any, carbon.
What is referred to herein as an "~ situ" polymer can be obtained by carrying out the DHCD reaction of the dihalosilane and trihalosilane coammolysis product in solution in the presence of the Si-H containing -3~-. . ~ . . ~ . . , , ~ . .
.

, , ~3~ 7S

organosilicon polymer. In this method, the organopolysilane or polycarbosilane is added to an organic solvent. Afterwaxds, the mixture (generated b~ reacting in solution anhydrous = onia with the dlhalosilane and trihalosilane) is added. The polysiloxane i8 added to the coammonolysis mixture which is in an organic solvent.
One then adds to the solution a basic catalyst capable of daprotonating the hydroge~ from a nitrogen atom ad~acent to a silicon atom. See U.S. ~atent No. 4,482,669. The reaction mixture gradually changes color and hydrogen is evolved. The resultin~ solution ls then stirred at room temperature for sufficient time for the silylamide intermediates and the Si-H 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. Afterwards, the reaction mixture is allowed to cool to room temperature, if required, and quenched with an electrophile such as CH3I or a halosilane, such as a chlorosi~ane, to produce the organosilicon "in situ" polymer. The molecular welght of the "~ sitU" polymer is variable. 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 greater than that obtained on pyrolysis of the polycarbosilane alone.
On pyrolysis under nitrogen or argon tbe polysiloxane-derived material provides a yield of a black ceramic material, that is typically greater tha~ that obtained on pyrolysis of the polysiloxane alone. Pyrolysis under ammonia typically rPsults in silicon oxynitrides in high yields.
The organosilicon polymer formed by either of the above "graft" or "ia 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, typically 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.

`` 13~1~87S

The "in situ" preceramic polymer differs physically rom the "gra~t" preceramic polymer. ~a;or differences will be observed in their proton NMR spectra and in the form of their thermogravimetric analysis ~TGA) curves. both types of polymers are useful as preceramic materials.
The use of coammonolysis-derived, DHCD-catalyzed silylamide described herein not only improves the ceramic yield of the organopolysilanes, but, more significantly, when this silylamide is reacted with organopolysilane of the formula [(RSiH)X(RSi)y]n in ths appropriate stoichiometry, the reaction product of [tRSiH)X(RSi)y]n and the "living intermediate" silylamide after treatment with a suitable electrophile such as an organic or a silyl halide, incorporates both starting materials. When this reactlon 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 silylamide alone combine so that there is no substantial excess of either element in the ceramic product. Consequently, one can obtain a ceramic material preferably with less than about 1~ free silicon or free carbon, more preferably less than about 0.5~ free carbon and less than 0.5~ free silicon, and most preferably with less than about ~.1% of free sillcon and less than about 0.1~ of free ~arbon, i.e., a ceramic material containing substantially no free carbon a~d no free silicon. The exact combination o the two compounds necessa~y to result in the desired stoichiometry can readily be calculated by a person of ordinaxy skill ln 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: metal silyla~ide from about 4:1 to about 1:4, and preferably from 2.5:1 to 1:2 should 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 polymeric silylamide, , .. -~ ~'"'` `

~L3~ 375 either preformed or generatad n situ) and (3) a polysilane whose pyrolysis alone gives a ceramic product which contains an excess of silicon. ~xamples of such polysilanes are organopolysilane~ as described`above, for example, those which ara produced by the sodium condensation of methyldichlorosilaDe. 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 praferably R is CH3. Using an appropriate mixture of the three polymers (which can be calcul~ted from the results of the analyses of the ceramic products of the pyrolysis of each individual polymer, e.g., the CH3I- quenched polymer in the ca~e of the polymeric silylamids), one can obtain a ceramic product which contains a minimal excess of either element, carbon or silicon. Such hybrid ternary preceramic polymers are soluble in organic solvents and, depending on component ratios used, are of variable molecular weight. Their yyrolysis gives black ceramic products in high (generally > 80%) yield.
In the preceramic polymer which results from a combination of a polysiloxane polymer (A) and an alkali metal (poly)silylamide (B), the ratio of Si/O/N of the resultant ceramic material can be broadly varied by ad~usting the stoichiometry of the preceramic polymer, i.e. the A:B
ratio. For example, at one extreme, the pyrolysis of a CH3I-quenched silylamide derived from the coammonolysis o~
CH3SiHC12 and HSiC13 and subsequent DHCD reaction under a NH3 atmosphere produced white silicon nitride. By appropriate selection of reactant stoichiometry it should be possi~le to obtain a ceramic product that is virtually pure silicon oxynitride.
For example, it should be possible to obtain distinct crystalline phase Si20N2 after pyrolysis under a stream of ammonia from a preceramic polymer one obtains by the in situ process. In this instance the weight ratio of polysiloxane:alkali metal poly(silylamide) is about 1:1 and R and Rl are CH3 and R2 is H or CH3. In the above-described system, deviating from a 1:1 ratio results in a ceramic polymer having some Si3N4 when you usa more poly(silyamide) or some SiO2 when you use more polysiloxane. It is simple to empirically ' ~3~41 3~7S
determine the appropriate weight ratio for a desired ceramic product with the use of any of the claimed starting materials.
The polysiloxane and silylam:ide are typically added in a weight ratio of polysiloxane: silylamide from 15:1 to 1:15.
Preferably this ratio is about 5:1 to 1:5. More preferably the ratio is about 3:1 to 1:3. Most preferably the ratio is about 1 : 1 .
Physical blends of Si-H containing organosilicon polymers, for example the organopolysilane, the polycarbosilane polymers containing repeat units of [R~Si(H)~(CH2)q]~ for example, the Yajima polycarbosilane or the polysiloxane containing repeat uni~s of [RbSi(H)o]n, with the "quenched"
organosilazane polymer of U.S. patent No. 4,720,532 (issued January 19, 1988) can be used since these will react when they are heated together. When approximately equal molar quantities of the polymers where R, R~ or Rb = CH3, Rl = CH3, R = H or CH3, are mixed and finely ground together and then subjected to pyrolysis to 1000 C, ceramic yields are obtained which are approximately the average of the ceramic yields when the organopolysilane and the organosilazane polymers are pyrolyzed separately, are significantly higher than that which results when the polycarbosilane is pyrolyzed separately and is still higher than that which results when the polysiloxane is pyrolyzed separately.
When polycarbosilane/organosilazane mixtures are heated, in the absence of a solvent at 200 C under nitrogen, white foamy solids are obtained which are insoluble in nonpolar organic solvents. When organosilane/organosilazane mixtures are heated, either in the absence of a solvent at 100 C under nitrogen or in a toluene solution at reflux, white powders are obtained which are insoluble in nonpolar organic solvents.
Ternary blends of the polycarbosilane, the polysilazane and the [(CH3SiH)y(CH3Si)y]n polysilane behave similarly.
The combined polymers obtained by the "graft," "in situl' and physical blend methods can be converted to black ceramic fibers. Pyrolysis of pressed bars of the combined polymers to ~000 C provides................................

~3 ~3~7~

a black solid product. In other experimants, silicon carbide powder is dispersed in a toluene solution containing 25% by weight of the combined organosilane/organosilazane polymers. The solvent i5 eYaporated and the residue, a fine powder of silicon car~lde with combined polymer binder is pressed into bars and pyrolyzed at 1000C.
A ceramic bar is obtained showing a low weight loss and slightly shrunken size.
Similarly, when silicon carblde powder is dispersed in toluene solutions of the combined polycarbosilane/organosilazane polymers, the solvent evaporated and the residue, a fine powder of silicon carbide with combined polymer binder, is pressed into bars and pyrolyzed at 1000C, a ceramlc bar is obtained showing a low weight loss and slightly shrunken size.
Pyrolysis of bars of the combined polysiloxane-organosilazane polymers under am~onia results in a white rectangular body. Pyrolysis under either pyrolysis condition results in ceramic bars showing low to moderate weight loss and slightly shrunken size.
The invention will be further illustrated by the examples that follow:

I. General All reactions and manipulations were carried out under a dry nitrogen atmosphere using standard Schlenk techniques or a Vacuum Atmospheres dry box. All solvents were distilled under nitrogen:
diethyl ether and tetrahydrofuran from sodium ben2ophenone ketyl, and he~ane from lithium aluminum hydride. Chlorosilanes were obtained from Petrarch Systems, Inc. or Silar Labs., Inc. and were distilled from magnesium filings prior to use. Anhydrous ammonia (Matheson) was dried by passing through a KOH-filled drying tube. Methyl iodide was distilled under nitrogen from P205. Potassium hydride (Alfa) was obtained as a 40% slurry in mineral oil which was filtered, washed with hexane and dried prior to use.
Proton ~MR spectra were obtained on either a Jeol FX-9OQ (90 MHz) or a Bruker WM-250 (250 MH7) using a CDCl3 reference (7.24 ppm . .

. .~

.

~L3~

shit). Infrared spactra were obtained on a Perkin-Elmer Model 1430 infrared spectrophotometer.
Nolecular weights were determined by cryoscopy ln benzene.
Thermogravimetric analysis (TGA) yields were obtained using a Perkin-Elmer TGS-2 system. Samples were heated from 50C to 950C
under an argon atmosphare at 10C/min. Large-scale tube furnace pyrolyses to produce gram quantities of ceramics were performed in a Lindberg Model 59344 tube furnace with controller. Samples were heated from 200C to 1000C at 10C/minute in an argon atmosphere.
Analyses of all oils and polymers were performed by Scandinavian Microanalytical Labs, Herlev, Denmark. Ceramic analyses were performed by Galbraith Labs, Knox~ille, Tennessee.

II. Ammono~ysis Reactions ~ typical reaction is described. All other ammonolyses of the RSiC13 alone or of mixtures of CH3SiHC12 with RSiC13 (R D H, CH3, CH2 CH) were carried out using the same general procedure.
For each CH3SiHC12/RSiC13 molar ratio used, separate reactions were carried out in Et20 and in THF medium. The yields of soluble products (soluble in the reaction medium), the molecular weights, the ceramic yields (by TGA under argon) obtained on their pyrolysis and their analyses are given in the appropriate Tables (1-9).
A 1000 ml three-neGked, round-bottomed flask equipped with a Dry Ice condenser, an overhead mechanical stirrer and a rubber septum was flame-dried while a stream of dry nitrogen was passed through. Dry diethyl ether (600 ml) was added and then 33.6 ~ (0.'292 mol) of CH3SiHC12 and 6.B g (0.05 mol) of HSiC13. The solution was cooled to 0C (ica bath). The ori~inal septum was replaced with another septum through which a one~foot gas inlet tube passed.
Gaseous a~monia then was bubbled into the solution at a moderate rate for 4.5 hours until ammonia was obser~ed condensing on tha -7BOC
condenser. The a~monia inle~ tube was replaced with a rubber septum after the addition of ammonia had been stopped.

.
. , ,~ ~
, ' .

.~, . , j, . ..

` ~L3()4a75 The reaction mixture was allowed to warm to room temperatura and stirred under nitrogen overnight. Filtration (in the dry box) removed NH4Cl and any other insoluble products of the resction.
The solids were washed with three 50 ml portions of ether.
Trap-to-trap distillation of the solvent (25C, Q.l mm Hg) from the combined ether phases left a clear, mobile oil (15.0 g, 74~ based on the (CH3SiHNH) and [HSi(NH)l 5] components). The oil was characterized by analysis (Table 3), by IR and lH NMR
spectroscopy. The molecular weight was measured (cryoscopy in benzene) and a thermogravimetric trace was obtained (50-950C, 10C per minute).
H NMR (250 MHz, in CDC13): ~ 0.17 (broad m, 2.6 H, CH3Si), 0.85 (broad m, 1.3, NH), 4.37 (broad s, 0.25 H, SiH), 4.63 (broad s, 0.41 H, SiH) and 4.81 (broad s, 0.33 H, SiH).
IR (thin film, cm 1): 3380 (s), 2960(s), 2900(w), 2140-2120 (broad,s), 1545(w), 1405(m), 1255(s), 1200-1150 (broad, vs), 980-750 (broad, vs).
MW: 390 g/mol TGA: 33% by weight ceramic residue, black solid Anal.(Based on NMR-derived formula [CH3SiHNH][HSi(NH)1 4]0 li) alcd for CH5.41Nl.24Sil.l7, C, 17.7; H, 8.05; N, 25.7 Found: C, 17.75; H, 7.53; N, 25.80.

III. -Catal~zed Dehydrocyclod~merizstion Reactions One such experiment is described in order to pro~ide details of the procedure used. All reactions were carried out in THF using 1 moL % of the KH catalyst. In all cases, the white solid polymer obtained after the CH3I quench was characterized by analysis and IR
and lH NMR spectroscopy. The molecular weight was measured by cryoscopy in benzene and a thermal analysis trace (TGA, 50-950 at 10C/minute, under argon) was obtained. The results of these experiments are gi~en in the Tables.
A 250 ml, three-necked, round-bottomed flask was equipped with a . ' ' .. . ~ ~; -,.

-` ~30413~5 magnetic stir-bar, a gas inle~ tube and two rubber sspta and charged with KH (0.04 g, 1.0 mmol). The flask then was connected to the nitrogen line. Dry THF (100 ml) was added by syringe and then 6.355 g (0.1 mol, based on CH3Si~ + [HSi(NH)l 5] units) oE the polysilazane oil (obtained by ammonolysis of a l:l molar ratio mixture of CH3SiHC12 and HSiC13 in diethyl ether) dissolved in 20 ml of THP. The latter solution was added dropwise over a period of 20 minutes. Gas evolution (H2) was observed. The requlting clear solution was stirred at room temperature under nitrogen for 1 hour. Subsequently, methyl iodide (0.46 g, 3.2 m~ol) was added by syringe. An immediate white precipitate of KI formed. The mi~ture was stirred for 30 minutes at room temperature and then the solvent was removed by trap-to-trap distillation. To the residue was added 70 ml of benzene and the mixture was centrifuged to remove insolubleq. The solution phase was trap-to-trap distilled (25C, 0.03 mm Hg) to remove the benzene, leaving a white or~anic-soluble solid (5.41 g, 93~ yield). (Generally, in all other such reactions, the reaction mixture was stirred for 1-18 hours at room temperature after the initial gas evolution was observed. In the present case, such longer reaction times led to formation of insolubles.) lH N~R (250 NHz, in CDC13): ~ 0.17 (broad m, 2.5 H, CH3Si), 0.94 (broad, 1.2 H, NH), 4.82 (broad s, 1.0 H, SiH).

IR(CC14, cm 1): 3480 (w), 3400(s), 2960(s), 2900(w), 2120(s), 1540(w), 1410(m), 1250(s), 1180-1130(broad,s), 1030(s), 970-850(broad,vs).

MW: 1630 g/mol TGA (50-950C, 10C per minute, under argon): 87~ ceramic yield (black solid).
Anal. Found: C, 14.10; H, 6.12; N, 27.60.

A 3 g sample of this product was pyrolyzed in a tube furnace under 130~87S

argon, leaving a residue of 2.4 g (80%) in the form of a chunk of black solid.
Anal. Found: C, 9.10; H, 0.70; N, 32.56; Si, 56.52.
Assuming that all nitrogen is present as Si3N4, that the rest of the silicon is present as SiC and that the remaining carbon is present as free carbon, one can calculate from this analysis the composition 1.0 Si3N4 + 0.46 SiC + 0.81 C or, by weight, 83 Si3N4, 11% SiC and 6~ C.
Pyrolysis of the white solid obtained from another such preparation (1:1 CH3SiHC12/HSiC13 ammonolysis in THF
followed by KH-catalyzed DHCD and CH3I quench; a 3.53 g sample) in a fused silica boat in a tube furnace in a stream of ammonia (25-1000C within 3 hours~ gave a white powder residue in 84~ by weight yield (100~ yield based on the silicon content of the polysilazane). Analysis indicated a carbon content of only 0.29~.

IV. Preparation of Organosilicon Compounds 1. Preparation of ~(CH3SiH~x(CH3Si~
~all operations under nitrogen) ~
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.
Hexane (60 ml) was added. The mixture was transferred by cannula to a heavy-walled centrifuge bottle and centrifuged.

~L3~4a'7S

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 residual solid and the resulting suspension WA9 centrifuged. The supernatant layers were combined and solvents were removed by trap-to-trap distillation ln vacuum until the residual liquid volume was about 100 ml. This liquid was cannulatcd into a 250 ml single-necked Elask 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 sotened around 40C and "m~lted"
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 W8S poorly soluble in hexane, only somewhat soluble in benzene (precluding measurement o~ 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, lH). 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 ccnstitution [(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), 1019(s), 931(s), 865(vs, Si-CH3), 770(vs), 685(vs~, cm 1.
TGA(25-1000C, 10C/min.): 60~ yield o 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.
Anal. of the Ceramic Po~der. Found: C, 22.56; Si, 78.42; H, 0.01; N, 0.009%. (SiC requires C, 29.94; Si, 70.06~; actual ~30~1L8~75 composition: SiC + 0.49 Si). X-ray powder diffractlon (do~
A): 1.315(s) (~ -sic), 1.542(s) (~ -sic), l.91(m) (si), 2.181(m), (~ -sic), 2.52(vs) (~ -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 wcll with the reported fragmentation of CH3SiH3. At 445C, CH3SiH3 was still observed and a peak at ~ m/~ - 16 (CH4) began to grow in. By 580c, when weight loss was about over, only the methane peak was observable.

b. In Hexane/THF 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 st 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 bottle. The mixture was centrifuged and the clear, colorless supernatant layer transferred by cannula into a 1 liter round-bottomed flask equipped with a 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.

' ~oa~ 75 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 whit~ oil.
H NMR (90 MHz, C6D6~:~ 0.37 (broad, SiCH3, 3.74H) 3.92 (broad, SiH, 1 H).
NMR integration of the product gave a constitution oi [(CH3SiH)o 8(CH3Si)0,2]n.
IR (thin film, cm 1): 2967(s), 2900(s), 2800(w), 2099(vs), 1410(s), 1385(w), 1249(s), 1055(br), 933(s), 865(vs), 770tvs), 685(br), 650(sh), 585(w).
Molecular weight (cryoscopic in benzene): 600 g/mol.
Anal. (material from another similar preparation3. 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 ig high, as when in contact with a fritted funnel or a paper or cloth towel (in which cases spontaneous inflammation may occur).
Other, similar reactions have given 62-75% yields of (CH3SiH)x(CH3Si)y~ Nolecular we~ght determinations of several preparations ranged from 520-740 g/mol. All products had ~ery similar lH NMR spectra, but with different SiCH3:SiH ratios. Physical data of these products are listed in Table 11.

~3~

P~SICAL DATA FOR ~(CH3SiH)~(CH3Si~y~ _~Y~

Sample ~ Polymer M.W.a SiCH3:SiHb CeramicC x y Yield (%~ i91~_L3~ _ 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 ~Cryoscopic in ben~ene.

b lH ~MR integration ratio.

CUnder nitrogen gas, 25-1000C, 10C/min (TGA) ~3~375;

For the purpose of slmplifying calculation, an average formula weight value 44 was assigned for the unit (CH3SiH)X(CH3Si)y.
Therefore, in each of the following experiments, tha numb&r of moles of the reaction unit (CH3SiH) was calculated from the weight of the polymer used divided by 44.
The product formed in the THF solution glves a 60% ceramic yield, but it is of limited 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/THF
mixture of approximately 6 to 7:1 resulted in satisfactory yields of a soluble product. However, pyrolysis of this material resulted in very low ceramic yields, ranging from 16 to 27%.

2. Characteri~ation of the Polycarbosilane, The polycarbosilane, a white solid, was purchased from Dow Corning Corporation. The following data were collected on it:
H NMR (90 MHz, C6D6): 6 4.52 (broad, Si_, lH) 0.26 (broad, SiCH3 and SiCH2SI, 8.6H) IR (KBr, NU3O1, cm 1~ 2104(s~, 1253(s), 1014(s, broad), 845(s, broad), 734(s).
Molecular Weight (cryoscopic in benzene): 1210 g/mol TGA (25-1000C, 10C/min): 58% yield of a black ceramic solid.
Tl/2 ~ 510C

3 Preparation of Slloxanes a. Pre~_ration of ~CH3~ Qln~
A 500 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser, and a serum cap was charged with 90 ml (0.87 mol) of CH3SiHC12 and 250 ml of CH2C12. To the solution was added slowly (syringe pump) 20 ml (1.11 mol) of H20 over a two hour period. The reaction mixture was stirred at room temperature for 24 hours. Eight 100 ml portions of H2O were added to the reaction ~l3~ 75 mixture. The CH2C12 layer was washed with two 100 ml portions of H20 and dried over MgS04. The solvent was removed by rotary evaporation to give 44.5 g (85% yi~ld based on (CH3Si~H)0) unit) of a clear oil.
H ~ (90 MHz, C6D6):6 4.71, 4.69 (broad, SiH, 1 H) 0.23, 0.21 (broad, SiÇH3, 3 H) (neat, cm~l): 2976(s), 2918(w), 2162(s), 1410(w), 1260(s), 1030-1140 (broad,s), 830-920 (broad,s), 769(s), 715(w).
This is the procedure described by D. Seyferth, C. Prud'hom~e and G.H. Wiseman (Inor~. Chem., 22 (1983) 2163) in the hydrolysis of CH3SiHC12. A good yield of cyclic [CH3Si(H)O]n oligomers was reported, mostly n~4, 5 and 6, but some higher n (up to n 22) was also obtained in lower yield. The cera~ic yield of these oligomers is low and wlll vary from 0 to 5 ~ depending upon the W rolysis conditions and the particular oligomer used.

b . Preparatlon of Mixed Siloxane r (cH3~ Q~ 3)2sio)s ~

A 500 ml three-necked, round-bottomed flask equipped with a stir-bar, a reflux condenser, and a serum cap was charged with 100 ml (0.96 mol) o~ CH3SiHC12, 50 ml (0.41 ~ol) of (CH3)2SiC12, and 250 ml of CH2C12. To the solution t:here was added 60 ml (3.33 mol) of H20 (slowly by syringe pump) over a 4 hour period. Reaction occurred immedia~ely. The réaction mixture was stirred at room temperature for 24 hours and then was washed with fifteen 200 ml portions of H20 until the h20 washings were neutral pH. The CH2C12 layer was dried over MgS04 and the solvent was removed by rotary evaporation to give 64.7 g (87~ yield by weight) of a clear oil.
H NMR (90 MHz, C6D6):~ 4.99 (broad, SiH, 1 H) 0.22, 0.16 (broad, SiCH3, 6H) IR (neat, c~ 2972(s~, 2168(s), 1410(w), 1260(s), 1030-1120 (broad,s), 880(s), 836(s), 804(s), 769(s), 708(w) ~ ' :

13~4B75 C. Characterization of Commercial ~CH3Si(H)Ol~(Petrarch_ PS-122~
IR (neat): 2982(m), 2171(s), 1413(w), 1262(s), 1030-1140 (s,broad), 860;905 (s,broad), 765(s), 718(w) cm H NMR (C6D6):~ 0.25 (broad s, SiCH3, 3.4H), 5.04 (broad s, SiH, lH) Y9~ L~ LL~L~y~h~: 4500-5000 (vendor data) Ceramic Yield: (TGA, 25-1000C., 10C./minute): 13~ (black solid) V. Graft Reactions A. Graft Reaction of the Coammonolvsis Product of Methyldichlorosilane and Vin~ltrichlorosilane (3:1 Ratio. THF) and Polvmethvlhvdridosiloxane (PS 122) with Potassium Hydride in THF.
A 100 ml, three-necked, round-bottomed flask was~equipped with a reflux condenser with gas inlet tube on top, a stir-bar and two septa and oven-dried for 1 hour. (This wilI be termed the ~standard reaction apparatus".) The apparatus W8S taken into the dry box and charged with potassium hydride (0.02 g, 0.50 mmol) and was then connected to a nitrogen line, and charged with 50 ml of THF. The oil (1.64 g, 26.0 mmol) from the coa~monolysis of CH3';i~C12 and CH2-CHSiCl3 (3:1 ratio) in THF was added dropwise by syringe over 15 minutes. Gas evolution was observedO The reaction mixture was stirred for an additional hour at room temperature. By syringe, polymethylhydridosiloxane tPetrarch Systems, Inc. PS 122) (1.59 g, 26.5 mmol) was added to the reaction mixture. After stirring 35 minutes, methyl iodide (0.46 g, 3.2 mmol) was added and an immediate white precipitate formed. The solvent was removed by trap-to-trap distillation (25C, 0.03 mm Hg) and the residue extracted wlth 40 ml of hexane. The reaction mixture was centrifuged and the supernatant liquid cannulated into a 100 ml flask. Removal of the hexane by trap-to-trap distillation left a white solid (2.44 g, 75%).

`~ ~.. 3~ 7S

H NMR (CDC13, 250 MHz): 6 0.17 (broad, 9.7 H, SiCH3), 0.99 (broad, 3.0 H, NH), 4.38 (broad, 0.07 H, SiH), 4.74 (broad, 0.93 H, SiH), 5.91 (broad, 2.1 H, SiCH~CH2).
IR (CC14, cm 1): 3400(s), 3050(m), 3010(sh), 2960(s), 2900(sh), 2140-2120 (broad, s), 1595(m), 1405(s), 1270-1250 (broad, vs), 1200-1020 (broad, vs), 990-840 (broad, vs).
MW (cryoscopy in benzene): 1340 g/mol.
TGA (10C/min, Ar, 50-950C): 86~ ceramic yield, black residue.

B. Graft Reaction of the Coa~monolysis_Product of Methy~dichl_rosilane and Vin~ltrichlorosilane (3 1 Ratio. THF) and PolymethylhYdridosilane with Potassium Hydride in THF.

The standard reaction apparatus was charged with potassium hydride (0.02 g, 0.50 mmol) and 50 ml THF as previously described. The oil (1.70 g, 27.1 mmol) from the coammonolysis of CH3SiHC12 and CH2~CHSiC13 (3:1 ratio) in THF was added dropwise over 15 minutes.
Gas evolution was observed. The reaction mixture was stirred an additional hour at room temperature. Polymethylhydridosilane (1.24 g, 28.2 mmol) from the reaction of CH3SiHC12 and excess sodium in a 6:1 hexane/THF solvent mixture was added by syrlngs. The reaction mixture became orange and then afte:r 10 minutes turned yellow. The reaction mixture was stirred an addltional 35 minutes at room temperature and then methyl iodide (0.46 g, 3.2 mmol) was added by syringe. An immediate white precipitate formed and the yellow color of the reaction mixture was discharged. The solvent was removed by trap-to-trap distillation and the residue extracted w~th 40 ml hexane.
The reaction mixture was centri~uged and the supernatant liquid cannulated into a 100 ml flask. Removal of the hexane by trap-to-trap distillation left a white solid (2.74 g, 93~).
H NMR (CDC13, 250 MHz): 6 0.28 (broad, 3.1 H, SiCH3), 1.25 (broad, 0.55 H, ~H), 3.65 (broad, 0.21 H, SiH), 4.38 (broad, 0.35 H, SiH), 4.76 (broad, 0.44 H, SiH), 5.95 (broad, 0.53 H, SiCH-CH2).
IR (CC14, cm 1): 3390(w), 3150(w), 3050(m), 2960~s), 2900(m), ~L304a7S

2160-2140 (broad, vs), 1410(s), 1260~s), 1190-1140 (broad, s), 1040-840 (broad, vs), 710 (vs), 590(w).

MW (cryoscopy in benzene): 1612 g/mol.
TGA (10C/min., Ar, 50-950C): 86~ csramic yield, black solid residue.

C. ~aft Reacton o the Coam~onolYsis Product of MethYldichlQxs~__ne and Vinyltrichlorosilane (3:1 Ratio. THF~ and Polycarbosilane (Dow Cornin~_~9-6348) with Potassiwn HYdride l~ THF.

The apparatus was charged with potassium hydride (0.02 g, 0.50 mmol) and 50 ml of THF. The oil (1.65 g, 26.0 ~mol) from the coammonolysis of CH3SiHC12 and CH2-CHSiC13 (3:1 ratio) in THF
was added dropwise by syringe over 15 minutes. Gas evolution was observed. The reaction mixture was stirred for an additional hour at room temperature. Polycarbosilane (1.64 g, 28.0 m~ol, Dow Corning X9-6348) was ground to a fine powder with a mortar and pestle and placed in a 25 ml, one-necked flask. The flask was degassed and then 10 ml of THF was added. The resulting solution was cannulated into the reaction mixture. After stirring for 35 minutes., methyl iodide (0.46 g, 3.2 mmol) was added and an immediate white precipitate formed. The solvent was removed by trap-to-trap distillation (25C, 0.03 mm Hg) and the residue extracted with 40 ml of hexane. The reaction mixture was centrifu~ed and the supernatant liquid cannulated into a 100 m~
flas~. Removal of the hexane by trap-to-trap distillation le~t a white solid (3.04 g, 92~).
~' H NMR (CDC13, 250 MHz): ~ 0.16 (broad, 5.6 H, SiCH3), 0,95 (broad, 1.25 H, ~H), 4.16 (broad, 0.3 H, SiH), 4.71 (broad, 0.7 H, SiH), 5.91 (broad, 0.8 H, SiCH~CH2).
IR (CC14, cm~l): 3400(s), 3050(m), 3010(sh),. 2960(s), 2900(m), 2120-2100 (broad, s), 1600(w), 1410(s), 1360(m), 1270-1250 (broad, vs), 1190-1130 (broad, vs), 1050-840 ~broad, vs).
MU (cryoscopy in benzene): 862 g/mol.

~ 3~ il7S

TGA (10C/min., Ar, 50-950C): 85~ ceramic yleld, black solid residue.

D. Graft Reacti~ of the Coammonolysi~ duct of ~ethYldichlorosilane and Trichlorosilane_(3:1 Rat~o. THF~ and P~olvmethylhvdridosiloxane (PS
122) with Potassiu~ Hydride in THF

A three-necked round-bottomed flask was equipped with a gas inlet tube, a stir-bar and two septa, oven-dried for 1 hour and then was charged with potassium hydride (0.02 g, 0.50 ~mol). The apparatus was then connected to a nitrogen line and 50 ml of THF was added. The oil (1.64 g, 0.029 mol) from the coammonolysis of CH3SiHCl2 and HSiC13 (3:1 ratio) in THF, was added over 5 minutes. Gas evolution was observed. The reaction mixture was stirred for an additional 45 minutes at room temperature. By syringe, polymethylhydridosiloxane (1.58 g, 0.026 mol., Petrarch Systems, Inc., PS 122) was added to the reaction mixture. Aiter stirring 30 minuteq, methyl iodide (0.46 g, 3.2 mmol) was added and an immediate white precipitate formed. The solvent was removed by trap-to-trap distillation (25C, 0.1 m~ Hg) and the residue extracted with 40 ml of hexane. The reaction mixture was centrifuged and the supernatant liquid cannulated into a lO0 ml flask. Removal of ths hexane by trap-to-trap distillation left a white solid (2.30 g, 71%).

H NMR (CDC13, 250 MH~): 6 0.10 (broad, 4.5 H, SiCH3), 0.93 (broad, 2.0 H, NH), 4.84 (broad, 1.0 H, SiH).

IR (CC14, cm 1): 3490(w), 3400(s), 2960(s), 2900(w), 2870(sh), 2820(w), 2130(s), 1580(w), 1425(m), 1265 (broad, s), 1200-1020 (broad, vs), 980-850 (broad, vs).
MW (cryoscopy in benzene); 1855 g/mol TGA (10C/min, Ar, 50-950C): 88~ ceramic yield, black solid residue.

~3~ S

E. Graft Reaction of the Coammmono~ysis Product of ~ichlorosilane and Trichlorosilane f3:1 Ratio ~THF)_and Polymethvlhydridosilane with Potassium Hvdride in T~E~

The apparatus wa~ charged with KH (0.02 g, 0.50 mmol) and 50 ml of THF. The oil (1.77 g, 0.031 mol) from tha coammonolysis of CH3SiHCl2 and HSiCl3 (3:1 ratio) in THF was ~dded o~er 5 minutes. Gas evolution was obQerved. The reaction mlxture was stirred an additional 45 minutes at room temperature. Polymethylhydridosilane (1.30 g, 0.030 mol) fxom the reaction of CH3SiHC12 and excess sodium in 6:1 hexane/THF was addcd. The reaction mixture became orange and then after 10 minutes turned yellow. The reaction mixture was stirred an additional 30 minutes at room temperature and then methyl iodide (0.46 g, 3.2 mmol) was added. An immediate white precipitate formed and the yellow color of the mi~ture was discharged. The solvent was remov~d by trap-to-trap distillation and the residue extracted wtin 40 ml of hexane. The reaction mixture was centrifuged and the supernatant liquid cannulated into a lO0 ml flask. Removal of the hexane by trap-to-trap distillation left a white solid (2.70 g, 88%).

H NMR (CDC13, 250 NHz): ~ 0.30 (broad, 2.6 H, SiCH3), 1.23 (broad, 0.58 H, MH), 3.65 (broad, 0.19 H, SiH), 4.4 (broad, 0.28 H, SiH), 4.8 (broad, 0.53 H, SiH).

IR (CC14, cm~l: 3670 (broad, w), 3490 (m), 3150 (s), 3060 (s), 2960(s), 2900(w), 2280(s), 2150 (broad, vs), 1815(s), 1670(w), 1415(s), 1265(s), 1190 (broad, w), 1050-1020 (broad, vs~, 980-350 (broad, vs), 700(w).
MW (cryoscopy in benzene): 2200 g/mol TGA (10C/min., Ar, 50-950C): 75% ceramic yield, black solid residue.

` ``" ~3t~ 7~i F. Graft Reaction of the Coammonol~sis Product of MethYldichlorosllane and Trichlorosila~e t3:1 Ratio, THF) and Polycarbosilane (Do~ Cornin~
X9-6348) with Potassium Hydride in THF~

The apparatus was charged with KH (0.02 g, 0.50 mmol) and 50 ml oE
THF. Th~ oil (1.61 g, 0.028 mol) from the coammonolysis of CH3SiHC12 and HSiC13 (3:1 ratio) in THF was added over 5 minutes. Gas evolution was observed. The reaction mixture was stirred an additional 30 minutes at room temperature. Polycarbosilane (1.45 g, 0.025 mol, DGW Corning X9-6348) was ground to a fine powder and placed in a 25 ml one-necked flask. The flask was degassed and then 10 ml of THF was added. This solution was then cannulated lnto the reaction mixture. After stirring for 30 minutes, methyl iodide (0.46 g, 3.2 mmol) was added and an immediate white precipitate formed. The solvent was removed by trap-to-trap distillation (25C, 0.1 mm Hg) and the residue extracted with 40 ml of hexane. The reaction mixture was centrifuged and the supernatant liquid cannulated into a 100 ml flask.
Removal of ~he hexane by trap-to-trap distillation left a whlte solid (2.97 ~, 95~)-H NMR (CDC13, 250 MHz): ~ 0.16 (broad, 5.0 H, SiCH3), 0.95(broad, 0.8 H, NH), 1.24 (0.7 H, ~H), 4.4 (broad, 0.3 H, Si~), 4.8 (broad, 0.7 H, SiH).
IR (CC14, cm 1): 3490(w), 3400~s), 2960(s), 2900(m), 2875(sh), 2120 (broad, s), 1460(w), 1415(m), 1365(m), 1260(s), 1175 (broad, vs), 1030 (broad, s~, 1080-850 (broad, vs).
MW (cryoscopy in benzene): 845 g/mol TGA (10C/min., Ar, 50-950C): 76~ ceramic yield, black solid residue.

c ~L3q~487~i ~L~

Ceramlc _ Yield Reaction Product Yield.~ _ MW _ _bY TGA.
3:1 CH3SiHC12/
ViSiCl3 (THF) with KH/PS 122 solid 75 1340 86 3~1 CH3SiHCl2/
ViSiC13 (THF) solid 92 862 85 with KH/D.C. Polycarbosilane 3:1 CH3SiHC12/
ViSiC13 (THF) solid 93 1612 86 with KH/(CH3SiH)0.7g (CH3si)0~22 3:1 CH3SiHC12/
HSiC13 (THF) with KH/PS 122 solid 71 1855 88 3 1 CH3SiHCl2/
HSiC13 (THF) solid 95 845 76 with KH/D.C. Polycarbosilane 3-1 CH3SiHCl2/
HSiC13 (THF) solid 88 2200 75 with KH/(CH3siH)0.78 C~13Si) o . 22 * V~ vinyl -6~-:: . .. ; . . .: . . .

~L3~ S

VI . n In-Situ Procedure"
A. Reaction of a Coammonolysis Mixture of_CH~SiHC~2~ 3 and ~CH3SiH~ 3~ n with KH_5~aly~5_ 1. Usin~ Coammonolysis Product PrePared in Dieth~l Ether In a dry box, a 250 ml round-bottomed flaqk equipped with a stir-bar, reflux condenser and a serum cap is charged with 0.10 g of KH
(0.0025 mol). THF (50 ml) is added to suspend the KH. A separate 250 ml Schlenk flask is charged with 2.0 g of a CH3SiHC12/HSiC13 coammonolysis mixture that is prepared as described in section II.
Thls mixture is prepared by ammonolysis of CH3SiHC12 and HSiC13 in ether solution, and then combined with 2.2 g of [(CH3SiH)X(CH3Si)y]n (0.05 mol, x ~ 0.74, y ~ 0.26), and 100 ml of THF. The mixed polymer solution is transferred by cannula into the KH suspension. The reaction mixture gradually changes color to light orange and hydrogen gas is slowly evolved. The resulting solution is stirred at room temperature for 14 hours and is then heated at reflux for 1 hour. The light orange color of the solution persists. The reaction mixture is allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I is added to form a white precipitate.
The solvent i5 removed by trap-to-trap distillation. The product is extracted with 200 ml of hexane and the insoluble residue is removed by centrifugatlon.
The clear, colorless supernatant layer is transferred via cannula into a weighed 250 ml round-bottomed flask The hexane is removed by trap-to-trap distillation leaving 3.8 g (91~ by weight) of a white - powder. The latter is soluble in THF, benzene, and hexane.

2. Usin~ a Coammonolysis mixture of CH3SIHC12/HSiC13 Prepared in THF
- According to the procedure described above, the reaction between O.1 g of KH (0.0025 mol), 2.0 g of the coammonolysis product of CH3SiHC12/HSiC13 (prepared in THF solution), and 2.2 g of .~ ...

~75 [(CH3SiH)~(CH3Si)y]n (x ~ 0.74, y - 0.26) is carried out under nitrogen. The resulting reaction mixture also gradually changes color to light orange with 910w evolution of hydrogen gas. The ~olution is stirred at room temperature for 14 hours and then 0.5 ml (7.9 mmol) of CH3I is added. Work-up as described in the previous experiment leaves a white, soluble solid.
B. Reactio~s of a Mixture of a Coammonolys~ i3~ and Polycarbosilane with KH Catalyst.
1. Usin~ a Coammo~ol~sis Mixture o~ 3SiHC12/HSiC13_ Pre~ared fro~ Diethyl Ether, c. Polycarbosilane~Coa~monolysis Mixture in l:l weieht ratiQ
In a dry box, a 250 ml round-bottomed flask equipped with a stir-bar, reflux condenser and a serum cap is charged with 0.15 g of KH
(3.75 mmol). THF (50 ml) is added to suspend the KH. A separate 250 ml Schlenk flask is charged wtih 5.0 g of the coammonolysis product of CH3SiHC12 and HSiC13 prepared in ether solution, and 5.0 g of polycarbosilane, and 150 ml of THF. The mixed polymer solution is transferred by cannula into the KH suspension in THF. The reaction mixture gradually turns clear and hydrogen gas slowly evolves. The resulting solution is stlrred at room temperature for 2 hours and is then heated at reflux for 24 hours. The reaction mixture ls allowed to cool to room temperature and 0.5 ml (7.9 mmol) of CH3I is added and the mixture is heated for several hours. The solvent is removed by trap-to^trap distillation. The product is extracted with 200 ml of hexane and the insoluble residue is removed by centrifugation. The clear, colcrless supernatant layer is transferred via a cannula into a weighed 250 ml round-bottomed flask. The hexane is removed by trap-to-trap distillation le~ving a white powder. The white powder is soluble in THF, benzene, and hexane.

C. Reacti ns of a Mixture of a Coa~monolYsis Mixtu~e and cy~_ic L~_3Si(H~O1n with KH catalyst ~04~7S

1. L~3Si~H)Oln/Coa~onolYsi.s Mixture oE
_3~iHC12~H__~_3 in 1:1 wei~ht ratlo In a dry box, a 250 ml round-bottomed flask equipped with a stir-har, reflux condenser, and a serum cap is charged with 0.1 g of KH
(2.50 mmol). THF (100 ml) is added to suspend the KH. A separate 250 ml flask is charged with 4.0 g of the product, prepared by coammonolysis of CH3SiHCl2 and HSiC13 in THF solution, and 3.6 g of [CH3Si(H)O]n, and 50 ml of THF. This solution i3 transferred by cannula into the KH suspension in THF. The reaction mi~ture gradually turns clear and hydrogen gas is slowly evolved. The resulting solution is stirred at room temperature for 4 hours and then 0.5 ml (7.9 mmol) of CH3I is added. The solvent is removed by trap-to-trap distillation. The residual solid is treated with 80 ml of hexane and the insoluble residue is removed by centrifugation. The clear, colorless supernatant layer is transferred via cannula into a weighed 100 ml round-bottomed flask. The hexane is removed by trap-to-trap distillation leaving of a white powder. The latter is soluble in THF, benzene, and hexane.

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 of this disclosure, may ~ake modificatlons and improvements within the spirit and scope of the invention.

-63- ;

, . .

Claims (23)

1. A method for preparing preceramic organosilicon polymers, wherein the method comprises:
(a) mixing an organosilicon polymer containing Si-H
repeat units with at least a catalytic amount of a polymeric silylamide in an organic solvent, wherein the silylamide is a polymeric silylamide formed by reacting in solution anhydrous ammonia with a mixture of R1SiHX2, wherein R1 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, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and X is a halogen, and R2SiX3, wherein R2 is H, 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, or a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, thereby forming a polysilazane; and reacting said polysilazane in the presence of a basic catalyst capable of deprotonating the NH functions in said polysilazane to form said polymeric silylamide;
(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 preceramic organosilicon polymer.

2. The method of claim 1, wherein the Si-H containing organosilicon polymer is selected from the group consisting of an organopolysilane of the formula [(RSiH)x(RSi)y]n, wherein x + y = 1, R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having 6 to about 10 carbon atoms, and n is an integer greater than 1; a 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; and a polysiloxane having a plurality of repeat units of the formula [RbSi(H)O]n where Rb is 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 n is an integer greater than 1.

3. The method of claim 2, wherein the polycarbosilane contains at least about 25 mole % of repeat units of the formula [RaSi(H)-(CH2)q] and the polysiloxane contains at least about 25 mole % of repeat units of the formula [Rbsi(H)O]n.

4. The method of claim 2, wherein R, Ra and Rb are a lower alkyl group.

5. The method of claim 2, wherein R, Ra and Rb are CH3.

6. The method of claim 2, wherein the Si-H containing the organosilicon polymer is an organopolysilane and x =
1, y = O.

7. The method of claim 2, wherein the reaction mixture is quenched with an electrophile, E-X1, 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 sulfonate.

8. The method of claim 2, wherein the Si-H containing organosilicon polymer is organopolysilane, and the polymeric silylamide is added in a sufficient quantity so that the excess carbon obtained on pyrolysis of the silylamide can react with excess silicon from the pyrolysis of the organopolysilane compound, thus producing a ceramic product which contains substantially no free silicon or free carbon.

9. The method of claim 2, wherein R1 is a lower alkyl group, R2 is H or a lower alkyl group.

10. The method of claim 9, wherein the preceramic polymer is pyrolyzed under an inert gas stream to form a ceramic material.

11. The method of claim 8, wherein the mole ratio of organopolysilane to polymeric silylamide ranges from about 4:1 to about 1:4.

12. The method of claim 2, wherein the preceramic product is pyrolyzed in an inert atmosphere for a sufficient time and at a sufficient temperature to form a ceramic material.

13. The method of claim 2, wherein the Si-H containing organosilicon polymer is a polysiloxane and the preceramic product is pyrolyzed under an ammonia atmosphere for a sufficient time and at a sufficient temperature to form a ceramic material.

14. A method for preparing a preceramic organosilicon polymer, wherein the method comprises:
(a) generating a polymeric silylamide in the presence of an Si-H containing organosilicon polymer wherein the polysilylamide is generated by reacting the coammonolysis product of a mixture of R1SiHX2, where R1 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, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms; and X
is a halogen; with R2SiX3 wherein R2 is H, a lower alkyl group having 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms 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 polymeric silylamide and the Si-H containing organosilicon polymer 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.

15. The method of claim 14, wherein the Si-H containing organosilicon polymer is selected from the group consisting of an organopolysilane of the formula [(RSiH)x(RSi)y]n, where x + y = 1, R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and n is an integer greater than l; a 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; and a polysiloxane having a plurality of repeat units of the formula [RbSi(H)O]n where Rb is 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 n is an integer 1 or greater.

16. The method of claim 15, wherein the polycarbosilane contains at least about 25 mole % of repeat units of the formula [RaSi(H)-(CH2)q] and the polysiloxane contains at least about 25 mole % of repeat units of the formula [RbSi(H)O]n.

17. The method of claim 15, wherein R, Ra and Rb are a lower alkyl group.

18. The method of claim 15, wherein R1 is a lower alkyl group and R2 is H or a lower alkyl group.

19. The method of claim 15, wherein the Si-H containing organosilicon polymer is organopolysilane, and the organopolysilane is added in a sufficient quantity so that the excess carbon obtained on pyrolysis of the silylamide can react with excess silicon from the pyrolysis of the organopolysilane compound, thus producing a ceramic product which contains substantially no free silicon or free carbon.

20. The method of claim 15, wherein the preceramic polymer is pyrolyzed under an inert gas stream for a sufficient time and at a sufficient temperature to form a ceramic product.

21. The method of claim 15, wherein the mole ratio of organopolysilane to in situ generated silylamide ranges from about 4:1 to about 1:4.

22. The method of claim 15, wherein the Si-H containing organosilicon polymer is a polysiloxane and the preceramic product is pyrolyzed under an ammonia atmosphere for a sufficient time and at a sufficient temperature to from a ceramic material.

23. The method of claim 15, wherein the Si-H containing organosilicon polymer is a mixture of the polycarbosilane and the organopolysilane, with a sufficient quantity of the organopolysilane added so that the excess silicon obtained on pyrolysis of the organopolysilane can react with excess carbon from the pyrolysis of the polycarbosilane and the in situ generated polymeric silylamide, thereby reducing the amount of free carbon.