Acrylonitrile-styrene alternating copolymer

Peak Notation Assignment of Main Peaks Molecular Weight Retention Index Relative Intensity 

---

A variety of trichloroethylene copolymers have been reported, none with apparent commercial significance. The alternating copolymer with vinyl acetate has been patented as an adhesive (11) and as a flame retardant (12,13). Copolymerization with 1,3-butadiene and its homologues has been reported (14—16). Other comonomers include acrylonitrile (17), isobutyl vinyl ether (18), maleic anhydride (19), and styrene (20). 

ABS Three-component copolymer of acrylonitrile, butadiene, and styrene, alloy Rubber-toughened materials in which the matrix can be a mixture of polymer tyrpes. alternation copolymer Ordered copolymer in which every other building is a different mer. azeotropic copolymer Copolymer in which the feet and composition of the copolymer are the same, blends Mixtures of different polymers on a molecular level may exist in one or two phases, block copolymer Copolymer that contains long sequences or runs of one mer or both mers. 

Draw representative structures for (a) homopolymers, (b) alternation copolymers, (c) random copolymers, (d) AB block copolymers, and (e) graft copolymers of styrene and acrylonitrile. 

Other commercial copolymers which are typically random are those of vinyl chloride and vinyl acetate (Vinylite), isobutylene and isoprene (butyl rubber), styrene and butadiene (SBR), and acrylonitrile and butadiene (NBR). The accepted nomenclature is illustrated by EP, which is designated poly-ethylene-co-propylene the co designating that the polymer is a copolymer. When the copolymers are arranged in a regular sequence in the chains, i.e., ABAB, the copolymer is called an alternating copolymer. A copolymer consisting of styrene and maleic anhydride (SMA) is a typical alternating copolymer. 

In later communications (27, 28) Hirooka reported that in addition to acrylonitrile, other conjugated monomers such as methyl acrylate and methyl methacrylate formed active complexes with organoaluminum halides, and the latter yielded high molecular weight 1 1 alternating copolymers with styrene and ethylene. However, an unconjugated monomer such as vinyl acetate failed to copolymerize with olefins by this technique. 

Alkylaluminium chlorides form complexes with methyl acrylate which can react with styrene yielding alternating copolymers [164], The donor-acceptor complex of acrylonitrile (donor) and potassium persulphate (acceptor) makes possible the homopolymerization of acrylonitrile in polar media (in water, dimethylformamide, dimethylsuphoxide, dioxan) at low temperatures [165]. The initiating radicals are formed according to the scheme... 

There exist many alternating copolymerizations ethylene or propene with alkyl acrylates [244], vinyl acetate with maleic anhydride [245], styrene with acrylonitrile [246], styrene with fumaronitrile [247], vinyl carbazol with fumaronitrile, vinyl ferrocenne with diethylfumarate [248], and further pairs or systems of three monomers [238, 249-253]. External conditions can support or hinder alternation. At not too high temperatures, vinyl acetate forms a donor—acceptor complex with maleic anhydride. Under these conditions (and in the presence of a radical initiator), an alternating copolymer is formed. The concentration of the complex decreases with increasing temperature above 363 K the complex cannot exist. Under these conditions, copolymerization yields a statistical copolymer whose composition depends on the composition of the monomer mixture [245]. 

The copolymerization of styrene and acrylonitrile in the presence of AlEt under UV irradiation yields equimolar, alternating copolymers when the initial comonomer charge is equimolar or contains excess acrylonitrile and products with compositions intermediate between that of the equimolar copolymer and that of the radical copolymer when the initial charge is rich in styrene (Table III) (lO). The intermediate compositions may represent mixtures of equimolar and radical copolymers, block copolymers generated as shown in Eq. (6)-(l0) or random copolymers resulting from copolymerization of complexes and monomers. 

The rates of radical-monomer reactions are also dependent on considerations of steric effects. It is observed that most common 1,1-disubstituted monomers — for example, isobutylene, methyl methacrylate and methacrylo-nitrile—react quite readily in both homo- and copolymerizations. On the other hand, 1,2-disubstituted vinyl monomers exhibit a reluctance to ho-mopolymerize, but they do, however, add quite readily to monosubstituted, and perhaps 1,1-disubstituted monomers. A well-known example is styrene (Ml) and maleic anhydride (M2), which copolymerize with r — 0.01 and T2 = 0 at 60°C, forming a 50/50 alternating copolymer over a wide range of monomer feed compositions. This behavior seems to be a consequence of steric hindrance. Calculation of A i2 values for the reactions of various chloroethylenes with radicals of monosubstituted monomers such as styrene, acrylonitrile, and vinyl acetate shows that the effect of a second substituent on monomer reactivity is approximately additive when both substituents are in the 1- or cr-position, but a second substituent when in the 2- or /3-position of the monomer results in a decrease in reactivity due to steric hindrance between it and the polymer radical to which it is adding. 

Chlorine is virtually absent in the copolymer produced in the azobisisobutyronitrile (AIBN) catalyzed copolymerization of styrene and maleic anhydride in the presence of chloroform or carbon tetrachloride (3, 4), or of p-dioxene and maleic anhydride in the presence of acrylonitrile in chloroform (5). This absence indicates that trichloromethyl radicals generated by the reaction of the chlorinated hydrocarbons with the radicals from AIBN are not incorporated into the polymer chain. Similarly, there is little or no cnlorine in the alternating copolymer that is formed in the copolymerization of styrene and methyl methacrylate in the presence of ethylaluminum sesquichloride (EASC) in the presence of chloroform and carbon tetrachloride, and with or without a peroxide initiator (6). 

The rate of polymerization of polar monomers, for example, maleic anhydride, acrylonitrile, or methyl methacrylate, can be enhanced by coraplexing them with a metal halide (zinc or vanadium chloride) or an organoaluminum halide (ethyl aluminum sesqui-chloride). These complexed monomers participate in a one-electron transfer reaction with either an uncomplexed monomer or another electron-donor monomer, for example, olefin, diene, or styrene, and thus form alternating copolymers (11) with free-radical initiators. An alternating styrene/acrylonitrile copolymer (12) has been prepared by free-radical initiation of equimolar mixtures of the monomers in the presence of nitrile-coraplexing agents such as aluminum alkyls. 

Other functionalized monomers that were polymerized by ATRP are shown in Table HI. Using ATRP, N-vinylpyrrolidone and hydroxypropyl methacrylamide were successfully homopolymerized when a cyclam was used as the ligand instead of bipy. Methyl aciylate and vinyl acetate were copolymerized and a random copolymer with narrow molecular weight distribution was obtained. Copolymerization of isobuter and acrylonitrile monomers was also successful to prepare alternating copolymers. M alternating copolymer was also obtained when styrene and N-(cyclohexyl)maleimide... 

For a particular application, it has been established that an alternating copolymer is most suitable. Given the following monomers — butadiene, styrene, acrylonitrile, and vinyl chloride — which monomer pair... 

---