CA1037635A - Polymers and process of producing - Google Patents

Abstract

ABSTRACT

Graft copolymers having sidechains of uniform size. The points of attachment of the sidechains to the backbone are separated by uninterrupted polymer segments of the backbone having at least about 20 recurring monomeric units. The graft copolymers are useful as self-supporting films.

Description

.~

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Thi3 invention relates to polymers ~nd, more par tlcularlyJ to copolymers. In a 9till more partlcular ~en~e, it relates to certain gra~t copolymer~ which have a wide var-lety o~ propertie~0 More particularly there i~ de~cribed a gra~t co~
polymer having a linear copolymeric backbone and polymeric 3idechaln~ o~ relatively uni~orm molecular welghtJ each said sldechain being an integral part of ~aid backbone/ the polnt~
of attachment o~ ad~acent pair~ o~ ~aid sidechalns to said backbone ~eing separated by unlnterrupted segment~ o~ said backbone, o~ at least about 20 recurring monomerlc units.
There 1~ also provided a proce~s compriylng pre-parlng a living polymer, terminatlng 3aid livlng polymer by reactlon with a halogen-containing epoxide or halogen-con-taining vinyl compound to ~orm a polymeriæable monomer, and polymerizln~ said monomer.
Still ~urther, there i disclosed a proces3 ~or the preparation o~ polymerizable Palymeric monomers comprising terminatlng a monorunctlonal llvlng polymer by reactlon with a halogen-contalnlng compound havlng a polymerizable molety.
Mbst polymer~, both natural and synthetic, are in-compatible wlth one anotber~ Thl~ has become increaslngly apparent as more and more polymers having particularly good propertie~ ~or ~peclal u~es have become available, and as e~-~orts have been made to combine palrs of these polymer~ ~or the purpose of incorporating the di~rerent~ good properties o~ each polymer into one product. More o~ten than not? these e~ort~ have been unsuccess~ul becau3e the reeultlng blend~
have exhiblted an in3tabllity, and in many cases~ the de3ir-able properties o~ the two polymer~ were completely 108t, Polyethylene i~ incompatlble with polyisobutylene~ ~or ex-37~ii35ample, and a blend o~ the two ha3 poorer physical propertie~
than either o~ the homopolymer~. ~hese ~ailu~e~ were at first attributed to inadequQte mixln~ ~locedures, bu~ even-tually it was concluded that the failure~ were due 8i~ply to inherent incompatibilit1esO Alkhou~h it; i~ now believed that this is a correct explanation~ the genex-al nature of such in-co~patibility hag remained somewhat unclear, even to the present. Pol~rlty see~s to be a ~actor, i.e. J two polar polymer3 are more apt to be compatible than a polar polymer and a non-polar polymer. Also, the two polymers must be structurally and composit1onally somewhat similar if they are to be compatible. Stlll ~urther, a partlcular pair o~ poly-mers may be compatible only within a qertain range o~ rela~
tive proport1ons o~ the two polymers; outside that range they are lncompatible.
Desplte the general acceptance o~ the ~act o~ in-~ compatibility of polymer pairs, there i8 much interest in de-; vising means whereby the advantageous properties of combina-tions o~ polymers may be combined lnto o~e product.
One way in which this obJective has been sou~ht in-volves the preparation o~ block or grart copolymers. In this way, two d1r~erent polymeric segments, normally incompa~ible with one another, are Jolned together chemically to give a sort o~ ~orced compatibility. Thus, the block or gra~t co-polymer in many instances possesses a combinatlon o~ prop-erties not normally found in a homopolymer or a random co-polymer.
Resort to block copolymers or gra~t copolymers, however, has lts limitations in the case o~ block copolymers inasmuch as only those monomers can be used which are 8U~-ceptlble to anionic polymerlzation and this elimInate~ a lot :1~37~35 of potential polymeric segments. In the case of those graft copolymers previously available, they invariably are characterized by the presence of substantial amount of homopolymer, either of the original homopolymer backbone or of the grafting monomer. To the extent that such homopolymer is present, it serves not only as a diluent, but detracts materially from the ef~ectiveness of the desired properties which are sought to be built into the graft copolymer.
It is the purpose of the present invention to provlde graft co-polymers having sidechains of predetermined molecular weights, relatively free of homopolymers and which have novel combinations of physical pro-perties.
It is a further purpose of the present invention to provide a process for the preparation of such graft copolymers.
The present invention provides a graft copolymer comprising a copolymeric backbone and polymeric sidechains, wherein the sidechains are comprised of a residue of an anionic initiator, polymerized units of at least one anionically polymerizable monomer and a copolymerizable end group which is copolymerized into the backbone of the graft copolymer, said sidechains having a molecular weight in the range of from 5,000 to 50,000 and a narrow molecular weight distribution; and wherein the backbone is comprised of polymerized units of a backbone-forming compound and the copolymerized end group of the sidechains, the points of attachment of the adjacent sidechains being separated by at least about 20 uninterrupted recurring units of the backbone-forming compound.
The present invention also provides a process for preparing a graft copolymer, comprising preparing a living polymer by polymerizing at least one anionically polymerizable monomer in the presence of an anionic polymerization initiator to thereby form monofunctional living polymers having a molecular weight in the range of ~rom 5,000 to 50,000 and a narrow molecular weight distribution, reacting the monofunctional living polymer ~ ~ _ 3 -1~3~ 5 with a halogen-containing epoxide or halogen-containing vinyl compound to form a macromolecular monomer having a copolymerizable end group, and thereafter copolymerizing said copolymerizable end group with a backbone-forming compound.
These purposes of the invention are accomplished by a graft co-polymer having a linear copolymeric backbone and polymeric sidechains of relativ~ly uniform molecular weight, the points of attachment of adjacent pairs of said sidechains to said backbone being separated by uninterrupted segments of said backbone of at least about 20 recurring monomeric units.
The graft copolymers herein differ from those previously available in that the polymeric sidechains are prepared first, by the method of - anionic polymerization. Such method produces a living polymer which may be terminated by reaction with a halogen-containing compound, and by selection - 3a -7~3~

of the appropriate terminating agen~, a polymer having a te~minal polymerizable group may be obtained. This polymer may itself be further polymerized to form graft copolymers of the kind described above. Alternatively, copolymerization of this high molecular weight polymerizable compound with a sec-ond compound, usually of relatively low molecular weigh~, also yields a graft copolymer of this type.
Particularly useful graft copolymers of this type are those in which the copolymeric backbone and polymeric sidechains are thermodynamically incompatible. Such graft copolymers are obtained when the uninterrupted polymeric seg-men~s of the copolymeric backbone and of the polymeric side-chains are large enough to impart to the graft copolymer the physical properties characteristic of the polymers which cor-respond to these polymeric segments. In general, for this purpose, the polymeric segment, whether it be a part of the backbone or of the sidechain, should consist essentially of at least 20 uninterrupted recurring monomeric units, and preferably at least about 30 recurring monomeric units.
The graft copolymers of the present invention assume a "T" type structure when only one sidechain is copoly-merized into the copolymeric backbone. ~lowever, when more than one side chain is copolymerized into the backbone poly-mer, the graft copolymer may be charac~erized as having a comb-type structure illustrated in the following manner:
c-c-c-b-c-c-c-b-c~c-c-b-c-c-c 1' a a a a a a a a a r ~ ~376~35 wherein "a" represents a substantially linear, uniform mole-cular weight polymer or copoly~er having a sufficient mole-cular weigh~ such that the physical properties of a~ leas~ one o~ the substantially linear polymers are manifest; "b"
represen~s a reacted and polymerized end group chemically bonded to the sidechain, "a", which is integrally polymerized ~nto the backbone polymer, and "c" is the backbone polymer having uninterrupted segments of sufficient molecular weight such that the physical properties of the polymer are mani-1~ fest.
The preparation of these graft copolymers begins, as noted above, with anionic polymerization o~ a polymeriz-able monomer. In most instances, such monomer is one having an olefinic group although it may be an epoxy or thioepoxy gro~p.
Those monomers susceptible to anionic poly~eriz-ation are well known and the present invention contemplates the use of all anionically polymerizable monomers. Illus-trative species include styrene, alpha-methyl styrene, acryl-amide, N,N-lower alkyl acrylamides, N,N-dilower alkyl acryl-amides, acenaphthalene, 9-acrylcarbazole, acrylonitrile, methacrylonitrile, organic isocyanates including lower alkyl, 37~3S
phenyl, lower alkyl phenyl and halophenyl i~Ocya~ate3, or-ganic diloscyanates includlng lower alk~lene, phenylene and tolylene diisocyanatesJ lower alkyl and allyl aorylate~ and methacrylates, lower ole~lns, vinyl estler~ o~ aliphatic car-boxyllc acids such a~ vinyl acetate, vinyl propionate, vinyl octoate, vin~l oleate and vinyl stearat~J vlnyl benzoate, vlnyl lower alkyl ethers, vinyl pyridines, isoprene, buta-dlene and lower alkylene o~idesO The term "lower" is used above to denote organic groUPg containing eight or ~ewer lQ carbon atOm3.
The catalyst rOr these anionic ~olymerizations is an alkall metal alkyl, the alkyl being a lower al~yl, i.e , having eight or ~ewer carbon atom~. The butyl lithiums are pre~erred particularly ~ec-butyl lithium, Lower alkyl lithiums and lower alkyl sodiumes are especially use~ul, Other suitable catalysts include i~opropyl lithlum, ethyl sodlum, n-propyl sodium, n-butyl potassium, n-~cty~ potas~ium, n-butyl lithiumJ ethyl llthlum, t~butyl lithium and 2-ethyl-hexyl lithium. The alkali metal alkyls are either available commercially or may be prepared by known methods Phenyl lithium, phenyl sodium, etc. may also be u~ed a~ a catalyst and they are llkewise conveniently availableJ by the reactlon o~ bromo benzene and the approprlate alkall metal The amount of catalyst iB an important ~actor in anlonlc poly~erlzatlon because it determlne~ the molecular weight of the living polymer. I~ a small ~roportlon o~ cat-alyst 18 u~ed, with respect to the amount o~ monomer, the molecular weight of the llving polymer will be larger than i~
a large proportion o~ catalyst is used Generally, it i9 ad-vi~able to add cataly~t dropwi~e to the monomer ~when that isthe selected order o~ addition) untll the persl~tence o~ the 763~iicharacterlst1c color o~ the orKanic an~on, then add the cal-culated amount o~ catalyst. The prellm1nary dropwi~e addi-tion serves to destroy contaminant~ and thu~ permits better control o~ the polymerization.
The anionic polymerization must be carried out under care~ully controlled condltion~, so as to exclude moiR-ture and other contaminants. The monomer and catalyst should be ~reshly purl~ied and the apparatus in which the polymeriz-ation ls to be carried out should be care~ully cleaned Techniques for purl~ying the reactants and cleaning the re-action equipment are well knRwn and need not be set ~orth here, The alkali metal cataly~t ~ay be added to the monomerJ
or the monomer may be added to the catalyst, A solvent ~en-erally i9 u~ed to ~acilitate heat tran~er and adequate mix-ing of cataly~t and monomer, The ~olvent should be lnert, Hydrocarbons and ethers are pre~erred, lncluding benzene, toluene, dimethyl ether, diglyme, glyme~ diethgl ether, tetrahydro~uran, N-hexane, cyclohexane and N-heptane. The temperature of the polymerization will depend on the monomer.
The polymerization of styrene i8 generally carrled out at ~lightly above room temperature; the polymerization of alpha-methyl ~tyrene preferably i9 carried out at -80C. The tem-perature Or the anionic polymerizatipn i8 not a critical fea-ture of th1s invention.
The polymeric product is a so-called "llving poly-mer", i.e., it is not terminated in the usual sense of that word as it is used in polymer chemigtry, but iR ~usceptible of further reaction including further polymeriæationO The anionic polymerizatlon 1~ lllustrated by the ~ollowin~ equa-tion, where styrene ls polymerized by ~ec-butyl lithium:

Bec-BuLi + n C~ = CH _~ sec-Bu- ~C~ CH - -C~ CH Li L~ ~
; . n-l I~ styrene 18 added to the above living polymer, the poly-merizatlon i9 renewed and the chain gro~ until no more monomeric styrene remains. A~ternatively, lf another dif-rerent anionically polymerlzable monomer 18 added, ~uch as butadiene, the above living polymer initlate~ the polymeriza~
tion of the butadiene and the ul~imate llvlng polymer which re~ults Consl~ts o~ a poly~tyrene segment and a polybutadlene segment, The llving polymer may be termlnated bg reaction wlth a halogen_conta~nlng compound, Termination o~ thq above living polystyrene wlth methyl iodide is lllust~ated by the ~ollowin~ equatlon:
sec-Bu-C~ C~- C~ CM- ~ + CH3I-~sec-Bu - ~C~ C~- -C~ CXC~ + LiI
~ L ~
n-l n-l ~ ivlng polymers are characterized b~ relatively uni-Porm molecular weight, i.e.l the di~tributlon o~ molecular weights in an average l~vlng polymer i~ quite narrow. Thi8 i&-in marked contrast to the typical polyme~, where the molecular weight distributlon 1~ quite wide.
An ~mportant ~eature o~ this lnvention 18 the uni-~ormlty of molecular welght o~ the ~idechaln~ o~ the ~raPt copol~mer and this uni~ormity of mQlecular wei~ht lnhere3 in the livlng polymer whlch i8 prepared as the flr~t step in the overall synthe~is o~ these gra~t copolymer~. A p~rtlcularly ~37~35 Rreferred embodiment of this înventîon resides in graft co-polymers containîng sîdechains havîng an average molecular weight of from about 5,000 to about 50,000.
The lîving polymers herein are terminated by reac-tion with a halogen-containing compound which also contains either a polymerizable olefinic group or an epoxy or thio-epoxy group. Suitable halogen-containing terminatîng agents include vinyl halo alkyl ethers wherein the alkyl groups contains six or fewer carbon atoms, vinyl esters of halo-alkanoic acids wherein the alkanoic acîd contains six or fewer carbon atoms, allyl halides, epihalohydrîns, acrylyl halides, methacrylyl halides, halomaleîc anhydrîdes, halo-maleate esters, vinyl halides and halovinyl silanes. The halo group may be chloro, fluoro, bromo or îodo; preferably, lt is chloro.
Termination of the living polymer by any of the above types of teminating agents is accomplished sîmply by adding the terminating agent to the solution of living poly-mer at the temperature at which the living polymer is pre-pared. Reactîon is immediate and the yield is theoretical.
A sllght molar excess of the terminating agent, with respect to the amount of catalyst, is used although the reactîon proceeds on a mole-for-mole basis.

~1~37~3S
The following equations illustrate typical reactions in accordance with the prac~ice of ~he presen~ invention:
Living Polymer:
--Rl - Rl R - CH2 - R n R2 Terminating Agents:

(a) X R3 - o _ C = CH2 R

(b) X - R3 _ C - O C = CH2 . R4 ~c) X ~3 - f = C~2 ~d) X - R3 - ~

(e) X - CC = CH2 (f) X~ ----CO ~
R4{;--co /
(g) X--C~CoOR4 R4{---COOR

(h) X - R3 - CH - \ CH2 ~0 ~i} X - C - C
Il \O
R4- C - C ~

1 ~37~;i3S
Rl R
(a) R----Cl{ - C------CH2 C----R3--- OC = C~

Rl I Rl o (b) R--_CH2- R2~--Cl-l _ C--R3 C OC = CH

Rr ~Rl (c) R--- CH - C ---CH--- C--R3--C = CH

Rl Rl .
(d) R--~ C.H2 , --CH2----C-- R3-- C----CE12 R2 n R2 R4 Rl Rl o (el R--CH2~ C R2 R4 Rl R
(f) R - CH2 C ---CH2--C C--CO

R2 n R R4--C _ CO

Rl Rl (g) R--- CH -- C - CH2--C--C - CoOR4 R nR R--C COOR

( ) iH2 C2,~ C112 - C - R - CH - CH2 1~2o Rl Rl OH Oll C112 ~ c----CH2 - C - R CH C 2 ~.~

1~3~63~

(i) R C~lz - C 2 C - R - C - C ~ ~12o n ~ O

R ~ C~ - C ~ C~l - C - R~ C COOH

In the above equations, R, R1, R2 and R4 are selected from the group consisting of hydrogen and lower alkyl and aryl radicals; X is halogen and R3 is a valence bond or a lower alkylene radical. Preferably, R will be lower alkyl, such as sec-butyl; Rl will be either hydrogen or methyl; R2 will be phenyl; and R4 will be either hydrogen or lower alkyl radical.
In some instances, because of the nature of the living polymer and the monomer from which it is prepared, or because of the nature of the terminating agent, it is advisable to "cap" the living polymer with a re-actant such as a lower alkylene oxide, i. e., one having eight or fewer carbon atoms, or diphenyl ethylene. This "capping" reaction yields a product which still is a living polymer, but which is less susceptible to reaction with functional groups or any ~ - 12 1~37~35 active hydrogeng Or a terminating agent. Thus, ~or example, acrylyl chloride while it act~ ~8 a terminating agent because of the pre~ence o~ the chlo~ine ato~ in its s~ructure, al~o provide a carbonyl group in the termlnated polymer chain and this carbonyl ~0up may provide a center rOr attack by a second living polymer. The u~e o~ acrylyl chloride as a ter-minatlng agent is much ~acilitated 1~ the living polymer ls ~irst capped, then reacted with the acrylyl chloride. The resulting living polymer i8 a substantlally pure vinyl ester, i.e., a living pQlymer which has been terminated by a mole-cule Q~ acrylyl chloride. If no capping agent i8 used in this intermedlate step, tbe resultlng polymer either has ; twice the expected molecular welght or contaln~ some chlorine, lndicatlng that ~ome Q~ the living polymer has been terminated by reaction with a second living polymer or with one Or the actlve hydrogens o~ the acrylyl chloride.
A particularly prererreq termlnating sgent is ethylene oxide. It reacts with the llving polymer, with the destruction Or its oxirane range as rOllow8:

seo-Bu ~ H ~ ~ G ~

L1 + C~ /CH2 --~ sec-Bu ~ ~ ¦ B ~ CB2CB20 Ll The above equatlon hows the reactlon o~ ethylene oxide a~ a capping reagent with a living polymer prepared by th~ poly-merization Or ~tyrene with ~ec-but~l lithiu~.

~ ~ 3~ S
m e cappin~ reaction is carried out quit~e simPly, as in the case of the terminating reaction~ by adding the capping reactant to the living polymer at ~olymerization temperature. ~he reaction occuræ immediately. As in the case o~ ~he termination reactant, a ~ ht molar excess o~
the capping reactant with respect to the amount o~ catalyst, is used. m e reactlon bccurs on a mole-~or-mole basi~.
When an epihalohydrin i8 uæed as the term1nat1ng reagent, the resulting polymer contains a termlnal epoxy group. Thi~ terminal epoxy group nay be converted to the corresponding glycol by warming with a~ueoua sodium hydrox-lde The resulti~g glycol may be converted to a copolymer by reaction with a high molecular welght dicarbo~ylic acid wh~ch may be prepared, e g " by the polymeriza~lon o~ a gly-aol or diamine with a molar excess of phthalic anhydride~
maleic anhydride, succinic anhydride~ or the like. It may also be reacted with a dilsocyanate to ~orm a polyurethane, The diisocyanate may be e.g., the reaction product o~ a poly-ethylene glycol havin~ an average molecular weight o~ 400 with a molar excess o~ phenglene diisocya~ate.
In another embodiment Or the invention, an organ1c epoxide is copolymerized with a term~nated living polymer containing an epoxy or thioepoxy end group. The graft co-polymer which results is characterized by a backbone having uninterrupted segments of at least about 20 and Pre~erably at least about 30 recurring units Or the organic epoxide, Pre-rerred organic epoxides include ethylene oxlde, propylene oxide, butylene oxide, hexylene oxide, cyclohexene epoxide, and styrene oxlde, i eO, tho~e havln~ 8 or fewer carbon atom~.
When a halomaleic anhydride or halomaleate ester is lQ~317~3~i used as the terminating agent, the resulting polymer conta1ns ester groups which may be converted by hydroly~1s to carboxyl group~0 The result1ng dicarboxylic polymer may be copolymer-ized w1th glycols or diamines to form polyegters and poly-amides hav~ng a grart copolymer structureO
It will bç noted that the reaction o~ the living polymers herein with the above term1nat1ng reagents yields products whichJ while they are not living poly~er~, are them-selves ~urther polymerizableO Such ~urther polymerization may proceed either through the double bond or the glycol por-tion or epoxy portion of the terminating reagent, so that the terminatlng reagent thus acts as a ~ ln the ~ormation o~ a gra~t copolymer It will be noted ~urther that t~e~e gra~t copolymergJ while their ~tructure conforms generally to that o~ the gra~t copolymer3 o~ the prior art, are prepared in a notably different manner than the method of preparatlon of the gra~t copolymers o~ the prior art. Furthermore, they are significantly dir~erent, structurally~ Prior to the inYen-tion herein, gra~t copolymers were prepared by synthe~iz1ng a linear "backbone"~ then grafting onto this backbone, growing polymeric chains, and the ultimate result wa~ a backbone hav-ing several pendant polymeric chains. The graft copolymers o~ this invention, on the other hand, are prepared by ~irst synthesizing these pendant polymeric chain~ (the liv1ng polymers) then polymerizing the terminal pQrtions of the~e polymeric chain~ into a backbone That is, the pendant chains, 1.e.) sidechains, are synthesi~ed ~irst, then the backbone. ~he sidechains are thus 1ntegral partg o~ the backbone. Obviously, although the two type~ o~ gra~t copoly-mers resemble each other eenerally, they are di~erent compo-sitlonsg not only because they are prepared hy s1gni~icantly -~037~35 dif~erent processes, but because the pendant pol~merlc chains o~ the gra~t copolymers o~ thi~ lnvention are Or relatlvely uni~orm, mlnimum length, and are each an integral part Or the backbone, and becau~e the backbone contains polymerlc ~eg-ments o~ certain minlmum length. The~e characteristics ~on-tribute materially to the advantageous properties which in-here in these novel grart copolymers A~ noted earller, the gra~t copolymers o~ this in-ventlon have unique properties and unique combinations of propertie~ These unique properties and combination~ o~
properties arç made possible by the novel process hçrein whlch ~oroes the compatibil~ty o~ otherwise lncompatible polymer segments. ~hus, the advantageous propert~es of a polystyrene may be combined with thq ad~antageous propertie~
o~ a polymethyl acrylate, al~hough these two p~lymers nor-mally are incompatible w1th one another and mere phy~ical mixtures of them have very little ~trength and are not use-ful, To combine these advantageou~ proper~ies in one prod-uct, it is neceqsary that the dlfferent polymeric ~egments be Present as relatively large sçgment~. The properties Or poly~tyrene do not beoome apparent until the polymer con-3ists essentially o~ at least about 20 recurring monomeric unit~, Thls same relationship appl1eR to ~he polymeric seg_ ments present in the gra~t copolymers herein~ i,e., i~ a gra~t copolymer comprisin~ p~lystyrene ~egments i~ to be characterlzed by the advantageous propertie~ o~ poly~tyrene, then those polystyrene segments must, lndlvidually, con~1s~
essentially Or at leaRt about 20 recurring monom~ric units.
Thi~ rela~ionship between the physical properties a~ a poly-meric ~egment and its minlmum size 1~ applic~ble to thepolymeric segments o~ all gra~t copolymers herein. In gen-1~3~35 eral, the minimum q1ze of a polymeric segment whlch 1~ a~so-ciated with the appearance o~ the phys1cal properties Or th~t pol~mer in the gra~t copolymer~ herein :i9 that which con-sists o~ about 20 recurrlng ~onomeric ull1ts. Pre~erably~ as noted earlier herein, the polymeric segments, both o~ the co-polymeric backbone and of the sidechain~, will cons1~t essen~
tially of more than about 30 recurring monomer units. These polymeric segment~ may themselve~ be homopolymerlc or they may be copolymeric. Thus, a graft copolymer o~ thi~ inven-tion may be prepared by the copolymerization o~ methyl metha-crylate, lauryl methacrylate and a terminated polyqtyrene containing a polymerlzable olerinic group, The u~interrupted polymeric segment~ o~ the backbone o~ such a gra~t copolymer w1ll be copolymeric segments o~ methyl methacrylate and lauryl methacrylate, The grart copolymers comprising polyme~ic segments having rewer than about 20 recurring monomeric units areJ
nevertheless, use~ul for many applications, but the pre~erred graft copolymers are those in which the various polymeric ~egments have at least about 20 recurrln~ monomeric units.
Although, as indicated, the grart copolymera herein are characterized by a wide variety o~ physical properties, depending on the particular monomers used ln their prepara-tion, and also on the molecular weights o~ the various poly-mer segment within a particular ~raft copolymer, all o~ these gra~t copolymers are use~ul, as a minimum, as tough flexlble, sel~-supporting ~ilms. These ~ilm~ may be used as ~ood-wrapping mate~ial, painters' droP-Cloth~, protective wrapping ~or merchandise disp1ayed ~or sale and the like~
The invention i8 illu6trated further by the follow-ing examples, In each case, all material~ should be pure and 1~3~3~ii care should be taken to keep the reactant mlxture~ dry and rree of contamina~ts. All parts and percentages, u~less ex-pre~sly stated to be otherwise, are by weight.
EXAMPIE
A solutlon o~ one drop of diphenyl ethylene at 40Co is treated portionwise with a 12~ ~301ution D~ t-butyl lithium in pentane until the persistence Or a light red colorg at which point an addi~ional 30 ml~ (0.04 mole) o~ the t-butyl lithium solution is added, followed by 312 g, (3.0 moles) o~ styrene. The temperature of the polymerizatlon mixture is maintaineq at 40C. ~or 30 minutes whereupon the living polgstyrene is terminated by treatment with ~ mlO
~o.o8 mole) o~ vinyl-2-chloroethyl ether. The re3ulting polymer i8 preclpitated by addition Or the benzene solution to methanol and the polymer is separated by ~iltration, Its number average molecular wei~ht, as determined by vapor phase osmometry, ls 7,200 (theory: 7870) and the moleculare weight dlstributlon is very narrow, i.e " the Mhi~h 1~ less than 1 oO6 ~

Preparation o~ Polystyrene Terminated With Vinyl Chloroacetate A solution o~ one drop o~ diphe~yl ethylene in 2500 mlO o~ cyclohexane at 40C. is treated portionwise with a 12 solution o~ ~ec-butyl lithium in cyclohexane until the per-sistence o~ a light red color, at which point an additional 18 ml. (0.024 mole) o~ the sec-butyl lithium is added, ~ol-lowed by 312 gO (3,0 moles) o~ styrene. The temperature of the polymerization mixture is malntained at 40C. ~or 30 min-utes whereupon the living polyBtyrene i8 capped by treatment with 8 ml. (0 040 mole) o~ diphenyl ethylene, then terminated by treatment with 6 mlO (0.05 mole) of v1nyl chloroacetate 1~3~7~;35;
The resulting polymer is precipitated by addition o~ the cyclohexane solution to methanol and the polymer is separat-ed by filtratlonO It~ number average molecular weight, a~
determlned by vapor phase osmometry i5 12,000 (theory:
139265), and the molecular weight dlstr~bution 1s very nar-row, iOe.9 the M~/Mn is less than 1006.
EXAMPLE 3~
Preparation of Polystyrene Terminated with ~pichlorohydrin A benzene solution o~ living polystyrene 18 pre-~; 10 pared ln Example 1 and terminated by treatment w1th 10 g.
(OolO mole) o~ eplchlorohydrin. The resulting terminated polystyrene 1s precipitated with methanol and separated by ~iltration. Its molecular weightJ as shown by vapor phase osmometry is 8,660 (theory: 7,757) and its number average molecular weight distribution is very narrow.

Preparation of Poly(~lpha-methyl styrene~ Terminated With Vinyl Chloroacetate~
A ~olution of 357 ~. (3.0 moles) Or alpha-methyl styrene in 2500 ml. o~ tetrahydro~uran is tre~ted dropwise with a 12% solution Or t-butyl lithium in pentane until the persistence o~ a light red color. Thereupon, an additional 15.0 ml (0 03 mole) of the t-butyl solution is added, re-sùlting in the development o~ a bright red color. The tem-perature o~ the mixture i8 then lowered to -80C., and a~ter 30 minutes at that temperature 5.6 ml~ of diphenyl ethylene is added~ The resulting mlxture is poured into 5~0 ml.
(0.04 mole) o~ vinyl chloroacetate and the thus terminated poly(alpha-methyl styrene) is precipitated with methanol and separated by ~iltration. Its ~umber average molecular weight, as determined by vaPor pha~e osmometry, 1R 14,280 (theory;

~ Q37~3S
129065) and the molecular we1ght distr1bution 1s very narrow.

Preparation of Poly(alpha-methyl styrene ~

A solutlon Or 472 g. (4.0 moles) Or alpha-methyl styrene in 2,500 mlO o~ tetrahydro~uran i~ treated dropwise with a 12% solution of n-butyl lithium in hexane until the perslstence Or a light red color. An additional 30 ml, of this n-butyl lithium ~olution is added resulting in the de-velopment o~ a bright red colorl The temperature o~ the mix-ture is then lowered to _80C.9 and a~ter 30 minutes at this temperature 4.5 g. (o.o6 mole) Or allyl chloride is added, The red color disappears almost immediately indicatin~ ter-mination of the living polymer. The resulting colorles~
solution ~ poured into methanol to preclpltate the terminat-ed poly(alpha-methyl styrene) WhiCh is shown by vapor phase osmometry to have a number average molecular weight of 11JOOO
(theory: 12J 300).

.
Preparation of Polystyrene Terminated With Methacrylyl _ A solution o~ 0.2 ml. o~ diphenyl ethylene in 2,500 ml. o~ benzene there 18 added dropwise a 12% solution o~ n-butyl lithium ln hexane until the persistence o~ a light red-diæh brown colorO An additional 24 ml. (0.031 mole) o~ thi~
n-butyl lithium solution is added, and then, 416 g. (4.0 mole) of styrene, resulting in the development of an orange color. A temperature of 40C. i9 maintalned throughout by external cooling and by controlllng the rate at which the styrene is added. mis temperature is mainta1ned for an ad-ditional 30 minutes a~ter all of the styrene has been added, and then is lowered to 20Co whereupon 4.4 g. (0.1 mole) o~

~ 3~3Sethylene oxide 1s added, cau~ing the ~olution to become colorle~sO T~e living poly~tyrene i8 terminated by reactlon w1th 10 mlO ~Ool mole) o~ me~hacrylyl chloride~ The result-ing polymer has a number average molecular weight~ as ~hown by vaPor phase 03mometry, of 103 OOOo Acrylyl chloride can be ~ubstituted ~or methacrylyl chloride in the above procedure to'glve an acrylic acid e~ter end group on the polystyrene chain.
Examples 1-6 show the preparation o~ termlnated li~ing polymers. The~e are used as starting ma~erials in the procedures of Examples 7-14 to prepare the graft copolymer~
herein The terminated living ~olymer~ appear as sidecha1ns in the gra~t copolymers, wi~h the polymerlzable end group o~
the terminated living polymer end1ng up a~ an integral part o~ the backbone of the graft copolymer.

Preparation o~ Gra~t Copolymer ~rom Polystyrene Terminated Wlth Vlnyl-z-~hloroet~yl ~ther~'and ~thyl ~cr~y-late ; ' ' To a solution of 18 gO o~ octylphenoxy polyethoxy ethanol (emulsif1er) in 300 g o~ deionized water there ls added, with v1gorous agitation in a Waring Blender, a 801U~
tion o~ 30 g o~ the polystyrene product o~ Example 1 and 70 g. of ethyl acrylate. The resulting dispersion 1s purged with nitrogen, then heated with stirr1ng at 65C. whereupon o l g~ of amm~nlum persul~ate i3 added to initiate polymer-izatlon. Thereupon, 200 g Or ethyl acrylate and 0 5 g of

2~ aqueous ammonium per~ulfate solutlon are added portionwise over a period of three hours, the temperature being maintained throughout at 65C. The reRulting grart copolymer emulsion 1s cast on a glass plate and allowed to dry in air at room temperature to a ~Iexible sel~-suPPortlng ~llm The ~llm is 15;~37~3~
shown to continue polystyrene segments by extraction with cycl~hexane which dlssolves polystyrene; the cyclohexane extract on evaporation yields no res~dueD

Preparation o~ Graft Copolymer Or Poly(alpha-methyl styrene~
~erminaté~'WI~h~VI-vl Chlo'roac'èta~e''~
A ~olutlon o~ 50 g~ o~ poly(alpha~methyl ~tyrene) macromer terminated with vinyl chLoroacetate and having an average molecular weight of 129600 and 450 g. o~ butyl acry-late in 1,000 g~ o~ toluene is purged with nitrogen at 70G, then treated with 1 g. o~ azobisisobutgronitrile. The tem-perature is maintained at 70C. ~or 24 hours to yield a solution o~ gra~t copolymer which 19 cast a~ a ~ilm on a gla~ plate, The dried ~ilm ls slightly tack~ and i~ sho~n to contaln polystyrene segments by extraction w1th cgclo-hexane and evaporatlon ~f the cyclohexane extract, as above.

~ .
Preparation o~ Graft Copolymer o~ Pol~styrene Termlnated With ~pichlbrohy~rin and I'sobutyIPne ~~ ~' '`
--To a solution o~ 20 g, o~ polystyrene macromer ter-minated w1th epichlorohydrin and having an average molecular weight o~ 10,000 in 1,000 ml. of toluene at -70C" there i8, added 80 g. of isobutylene. 45 Ml. o~ boron tr1chloride ethyl ether complex is added slowly, the temperature being maintained at -70C. throughout. Polymerizatlon occurs as the catalyst is added and i8 complete almost immed$ately a~ter all of the catalyst has been added~ The resulting graft copolymer is obtained by evaporating away the toluene and washing the resi~ual sol1d with methanol.

~ 1~37635 EXAMPL~ 10 Preparation o~ Gra~t Copolymer of Polystyrene Termlnated ~ith ~5p~:chlorohy~rln and Isobutylene .
To 13000 ml. o~ methyl chloride at -70Ct there is added 10 g, Or poly3tyrene macromer terminated with eplehloro-hydrin, having an average molecular weight of 10~000. To this resulting solution maintained at -70C.~ there i8 added concurrently and dropwlse, a solut1on of 2 g. of aluminum ¢hloride in 400 mlt of methyl chloride and 90 g. o~ i~obutyl-ene. The time required for these additions is one hour andat the end of this time polymerization is subQtantial.~ com-plete. The resulting insoluble gra~t copolymer is isolated by evaporatlon of the methylene chloride, AMPL~ 11 Preparatlon o~ Gra~t Copolymer o~ Polytetramethylene Ether Di~s'ocyanate-an~ ~olystyrene Macromer ~ermln~e~ w~n~
plchlorohydr1n Polytetramethylene ether dlisocyanate ls prepared by disæolving 290 g. of polytetramethylene ether glycol hav-ing an average mo~ecular weight of 2,900 in 600 ml. o~ tetra-hydrofuran purging thls solution with nitrogen and then add-ing 14,4 g. (0.05 mole) of a liquid diisocyanate similar in structure to diphenylmethane diisocyanate and available as Isonate 143L from the UpJohn Company, The bottle containing these reactantR is capped and placed in a water bath at 50C. in which lt is tumbled at about 30 rpm. A~ter 8 hours, an additional 7.2 gO (0.025 mole) of the above liquld dilso-cyanate is added and the reaction is continued for another 8 hours~ At this point, 4.35 g. (0.05 mole) o~ 2,4~tolylene ~diisocyanate is added and the polymerl~ation i~ continued under the same conditions ~or another 8 hours.
To a solution of 200 g. of polystyrene ~acromer ~ 37635 terminated with epichlorohydrln and having an average molecu~
lar weight o~ 12,000 in 100 ml. o~ tetrahydro~uran and 100 ml. of water there i~ added dropwise a ~uf~icient quantity o~
dllute sulruric acid to ad~ust the pH to 2~0. The resu1ting solution i8 stirred at 65C. ~or 8 hours rçRulting ln com~
plete hydrolysis of the epoxide group~ to glycol groups.
A mixture Or a solutlon o~ 60 g~ Or the above poly-tetramethylene ether diisocyanate in 60 ml. of tetrahydro-~uran, 60 g. o~ tbe abave polystyrene glycol and 100 ml. o~
tetrahydro~uran i8 placed in a polymeriæation bottle together with oO6 g. of stannous octoateO The bottle is oappecl, purged w1th nitrogen and placed ln a water bath at 65C. rOr 8 hours to produce a graft copolymer~ A portlon 1s cast on a glass plate and allowed to air dry to a ~lexible, elast1c ~ilm. It 18 cut into ~mall p1eRes and molded at 15~C. and 20-30 psig. to a fllm the tensile strength o~ which is found to be 1500 psig.

, Preparation of Graft Copolymer of Polytetramethylene Ether ~IIsocyanate an~ -Pol~styrene ~-lycol - -A reactor bottle containing a mixture of 87 g, o~
polytetrameth~lene ether glycol having an average molecular weight o~ 2,900 and 4,3 g, (0,015 mole) o~ the liquid diiso-cyanate re~erred to in Example 11 i8 capped, purged with ni-trogen, and placed in a water hath at 65C. for 8 hours, The resulting hlgh molecular welght polyurethane glycol is cooled to room temperature and 43 g. of polystyrene glycol (prepared as in Example 11) having an average molecular weight o~ 8,600 and 350 ml, o~ tetrahydro~uran are added and the bottle cap-ped A~ter purging with nitrogen, 5.8 ~. (0.023 mole) o~ theabOve 11quid diisocyanate is added and the bottle i8 rotated at 65C. for 8 hours. The resulting gra~t copolymer i~ iS4-lated as a fl`exible, elastic ~ilm by depoRiting it on a glass plate and alr dxying It~ tensile ~tre~th i~ 1,000 p~ig.

Preparation o~ Graft Copolymer o~ Poly~tyrene M~cromer ~3~r~~Fy~re A mixture o~ 21 g. of polystyrene macromer termin ated with methacrylyl chloride and having an average molecu-lar welght o~ 10,000 prepared a~ in Example 6. 28 g. o~
ethyl acrylate and 0.035 g, o~ azobl~isobutyronltrile i~
prepared at room temperature and kept ~or 18 hours, under nitrogen9 at 67C. The re~ultlng product i~ a tou~h, opalescent material which can be molded at 160C. to give a clear, tough, transparent sheet, Preparatlon o~ Gra~t Copolymer ~om Poly~alpha-methyl 8~ rene~

A solution Or 20 g. of ~oly(alpha-methyl styrene) macromer terminated wlth allyl chloride and havlng an average molecular weight o~ ~,000 prepared as in Example 5 ln 100 ml. Or cyclohexane i8 prepared and t~eated wlth 5!5 ml. Or o,645 M diethyl aluminum chloride in hexane and ~ ml. o~
vanadium oxytrichloride~ then pressured with ethylene to 30 Psig. This sy~tem i8 agitated gently ~or about one hour at

3~C. whereupon a polymerlc material precipitates ~rom the solution. It i8 reqovered by ~iltration and pressed i~to a thln transparent rilm which i~ tought and ~lexible.

Claims (50)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A graft copolymer comprising a copolymeric backbone and polymeric sidechains, wherein the sidechains are comprised of a residue of an anionic initiator, polymerized units of at least one anionically polymerizable monomer and a copolymerizable end group which is copolymerized into the backbone of the graft copolymer, said sidechains having a molecular weight in the range of from 5,000 to 50,000 and a narrow molecular weight distribution; and wherein the backbone is comprised of polymerized units of a backbone-forming compound and the copolymerized end group of the sidechains, the points of attachment of the adjacent sidechains being separated by at least about 20 uninterrupted recurring units of the backbone-forming compound.

2. The graft copolymer of claim 1, wherein the polymeric sidechains are separated by at least 30 recurring monomeric units of the backbone forming compound.

3. The graft copolymer of claim 1, wherein the sidechains are spaced at substantially regular intervals along the copolymeric backbone.

4. The graft copolymer of claim 1, wherein the residue of the anionic initiator is selected from the group consisting of an alkyl or phenyl group.

5. The graft copolymer of claim 1, wherein the residue of the anionic initiator is a secondary butyl group.

6. The graft copolymer of claim 1, wherein the anionically polymerizable monomer is selected from the group consisting of styrene, .alpha.-methylstyrene, acrylamide, methacryl-amide, N-lower alkyl acrylamides, N,N-dilower alkyl acrylamides, acenaphthalene, 9-acrylcarbazole, acrylonitrile, methacrylonitrile, lower alkyl isocyanates, phenyl isocyanates, lower alkyl phenyl isocyanates, halophenyl isocyanates, lower alkylene diisocyanates, phenylene diisocyanates, tolylene diisocyanates, lower alkyl acrylates, lower allyl acrylates, lower alkyl methacrylates, lower allyl methacrylates, lower olefins, vinyl esters of aliphatic carboxylic acids, vinyl benzoate, vinyl lower alkyl ethers, vinyl pyridines, isoprene, butadiene, and lower alkylene oxides.

7. The graft copolymer of claim 1, wherein the copolymerizable end group is selected from the group consisting of wherein R3 is a valence bond or a lower alkylene radical and R4 is either hydrogen or a lower alkyl radical.

8. The graft copolymer of claim 1, wherein the backbone-forming compound is selected from the group consisting of a vinyl compound, an alkylene oxide and a diene.

9. The graft copolymer of claim 1, wherein the anionically poly-merizable monomer is styrene, the copolymerizable end group is a -CH2-CH2-O-CH=CH2 group and the backbone-forming compound is ethyl acrylate.

10. The graft copolymer of claim 1, wherein the anionically poly-merizable monomer is alpha methylstyrene, the copolymerizable end group is -CH2-C-?-CH=CH2 group and the backbone-forming compound is butyl acrylate.

11. The graft copolymer of claim 19 wherein the anionically poly-merizable monomer is styrene, the copolymerizable end group is a group and the backbone-forming compound is isobutylene.

12. The graft copolymer of claim 1, wherein the anionically poly-merizable monomer is alpha-methylstyrene the copolymerizable end group is a -CH2-CH=CH2 group and the backbone-forming compound is ethylene.

13. The graft copolymer of claim 1, wherein the sidechains contain a capping agent selected from the group consisting of an alkylene oxide of 1,1-dephenyl-ethylene between the polymerized units of the anionically polymerizable monomer and the copolymerizable end group.

14. The graft copolymer of claim 13, wherein the alkylene oxide is ethylene oxide.

15. The graft copolymer of claim 13, wherein the anionically polymerizable monomer is styrene, the capping agent is ethylene oxide, the copolymerizable end group is a group, and the backbone-forming compound is ethyl acrylate.

16. The graft copolymer of claim 1, wherein the backbone-forming compound is a copolymerizable prepolymer comprised of at least about 20 recurring polymerized units of at least one copolymerized comonomer and the side chains are a macromolecular monomer comprised of a residue of an anionic initiator, polymerized units of at least one anionically poly-merized monomer and a copolymerizable end group, and said copolymerization reaction is a condensation copolymerization reaction.

17. The graft copolymer of claim 16, wherein the backbone-forming prepolymer is selected from the group consisting of a diisocyanate, a glycol, a diamine and a dicarboxylic acid.

18. The great copolymer according to claim 16 wherein said polymerizable moiety of said macromolecular monomer is an epoxy or glycol group and said copolymerizable backbone-forming prepolymer is a dicarboxylic acid.

19. The graft copolymer according to claim 18 wherein said dicarboxylic acid is prepared by the polymerization of a glycol or diamine with a molar excess of maleic anhydride or succinic anhydride.

20. The graft copolymer according to claim 16 wherein said polymerizable moiety on said macromolecular monomer is a glycol group and said copolymerizable backbone-forming prepolymer is a diisocyanate.

21. The graft copolymer according to claim 20 wherein said diisocyanate is the reaction product of a polyethylene glycol with a phenylene diisocyanate.

22. The graft copolymer according to claim 20 wherein said diisocyanate is polytetramethylene oxide diisocyanate and said macromolecular monomer is a polystyrene terminated with epichlorohydrin.

23. The graft copolymer according to claim 16 wherein said polymerizable moiety on said macromolecular monomer is a dicarboxylic acid or carboxylic acid anhydride and said backbone-forming prepolymer is a glycol.

24. The graft copolymer according to claim 16, wherein said polymerizable moiety on said macromolecular monomer is a dicarboxylic acid or carboxylic acid anhydride, and said backbone-forming prepolymer is a diamine.

25. The graft copolymer according to claim 16 wherein said polymerizable moiety of said macromolecular monomer is a maleic anhydride or maleic ester terminal group, and said back-bone-forming copolymerizable prepolymer is a glycol or diamine.

26. The graft copolymer according to claim 16 wherein said polymerizable moiety of said macromolecular monomer is a vicinal hydroxy or vicinal carboxy terminating group and said backbone-forming prepolymer is an epoxy compound.

27. The graft copolymer according to claim 16, wherein the copolymerized units of said backbone are ethylene oxide units.

28. The graft copolymer according to claim 16, wherein the copolymerized units of said backbone are propylene oxide units.

29. The graft copolymer according to claim 16, wherein the copolymerized units of said backbone are butylene oxide units.

30. The graft copolymer according to claim 16, wherein said polymerizable macromolecular monomer has the structural formula:

wherein R is lower alkyl and R' is either hydrogen or methyl.

31. The graft copolymer according to claim 30 wherein, in the said macromolecular monomer R' is hydrogen.

32. A graft copolymer according to claim 16 wherein said polymerizable macromolecular monomer has the structural formula wherein R is lower alkyl and R' is either hydrogen or methyl.

33. A graft copolymer according to claim 32, wherein in said macromolecular monomer R' is hydrogen.

34. A process for preparing a graft copolymer, comprising preparing a living polymer by polymerizing at least one anionically polymerizable monomer in the presence of an anionic polymerization initiator to thereby form monofunctional living polymers having a molecular weight in the range of from 5,000 to 50,000 and a narrow molecular weight distribution, reacting the monofunctional living polymer with a halogen-containing epoxide or halogen-containing vinyl compound to form a macromolecular monomer having a copolymerizable end group, and thereafter copoly-merizing said copolymerizable end group with a backbone-forming compound.

35. The process of claim 34, wherein an anionic polymerization initiator is selected from the group consisting of alkali metal alkyl and alkali metal phenyl compounds.

36. The process of claim 35, wherein the anionic polymerization initiator is secondary butyl lithium.

37. The process of claim 34, wherein the anionically polymerizable monomer is selected from the group consisting of styrene, .alpha.-methylstyrene, acrylamide, methacrylamide, N-lower alkyl acrylamides, N,N-dilower alkyl acrylamides, acenaphthalene, 9-acrylcarbazole, acrylonitrile, methacrylonitrile, lower alkyl isocyanates, phenyl isocyanates, lower alkyl phenyl isocyanates, halophenyl isocyanates, lower alkylene diisocyanates, lower alkyl acrylates, lower allyl acrylates, lower alkyl methacrylates, lower allyl methacrylates, lower olefins, vinyl esters of aliphatic carboxylic acids, vinyl benzoate, vinyl lower alkyl ethers, vinyl pyridines, isoprene, butadiene, and lower alkylene oxides.

38. The process of claim 34, wherein the halogen-containing epoxide or halogen-containing vinyl compound is selected from the group consisting of acrylyl chloride, methacrylyl chloride, vinyl haloalkyl ethers, vinyl esters of haloalkanoic acids, allyl halides, vinyl halides, halomaleic anhydrides, halomaleate esters, and epihalohydrins.

39. The process of claim 34, wherein the backbone-forming compound is selected from the group consisting of a vinyl compound, an alkylene oxide and a diene.

40. The process of claim 34, wherein the anionically polymerizable monomer is styrene, the halogen-containing vinyl compound is vinyl-2-chloroethyl ether and the backbone-forming compound is ethyl acrylate.

41. The process of claim 34, wherein the anionically polymerizable monomer is alpha-methylstyrene, the halogen-containing vinyl compound is vinyl chloroacetate and the backbone-forming compound is butyl acrylate.

42. The process of claim 34, wherein the anionically polymerizable monomer is styrene, the halogen-containing epoxide is epichlorohydrin and the backbone-forming compound is isobutylene.

43. The process of claim 34, wherein the anionically polymerizable monomeris alpha-methylstyrene, the halogen-containing vinyl compound is allyl chloride and the backbone-forming compound is ethylene.

44. The process of claim 38, wherein the halomaleic anhydrides or halomaleate esters are hydrolyzed after they are reacted with the monofunctional living polymer.

45. The process of claim 34, wherein the epoxy group of the halogen-containing epoxide is hydrolyzed after they are reacted with the monofunctional living polymer.

46. The process of claim 34, wherein the monofunc-tional living polymer is capped by reaction with a capping agent selected from the group consisting of an alkylene oxide or 1,1-diphenylethylene prior to being terminated with the halogen-containing epoxide or halogen-containing vinyl compound.

47. The process of claim 46, wherein the alkylene oxide is ethylene oxide.

48. The process of claim 46, wherein the anionically polymerizable monomer is styrene, the capping agent is ethylene oxide, the halogen-containing vinyl compound is methacrylyl chloride and the backbone-forming compound is ethyl acrylate.

49. The process of claim 34, wherein the backbone-forming compound is a copolymerizable prepolymer comprised of at least 20 recurring polymerized units of at least one copolymerized comonomer and said copolymerization reaction is a condensation copolymerization reaction.

50. The process of claim 49, wherein the backbone-forming prepolymer is selected from the group consisting of a diisocyanate, a glycol, a diamine and a dicarboxylic acid.