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Radical copolymerization of N‐methylmaleimide (MeMI) as well as other N‐alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′‐azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the Rp and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher Rp and an alternating tendency compared with those in dioxane (rMeMI = 0.14, r1B = 0 in chloroform and rMeMI = 0.47, r1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (Tg) and excellent thermal stability, e.g., the Tg and the thermal decomposition temperature (Td) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the Tg and Td increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties. © 1996 John Wiley & Sons, Inc.

SYNOPSISAn alternating copolymer of N-methylmaleimide and isobutene was produced by a radical precipitation polymerization method. The copolymer thus produced is a new class of transparent polymeric material that shows a unique balance of optical, thermal, and mechanical properties. The visible light transmittance was more than 90% and the stress optical coefficient was smaller than that of polycarbonate, leading to moldings with lower birefringence. The heat deflection temperature of the copolymer was as high as 157"C, and the thermal expansion coefficient was about 30% smaller than those of poly(methy1 methacrylate) and polycarbonate. The copolymer showed excellent mechanical properties, specifically, the flexural modulus was the highest among the typical amorphous polymers. 0 1996

SYNOPSISPolymerization of methyl acrylate ( M A ) with benzyl N,N-diethyldithiocarbamate (BDC ) was carried out in bulk or in benzene under UV irradiation. The polymerization proceeded to give a high yield of polymer, however it was found that BDC did not function as an iniferter in the MA polymerization. Bimolecular termination leading to deactivation of the iniferter site was observed during the polymerization in preference to chain transfer and primary radical termination which reproduce the iniferter site. The deactivation was successfully prevented by combining BDC and tetraethylthiuram disulfide ( T D ) as a twocomponent iniferter. This two-component iniferter system was also applied to synthesis of a star polymer with 1,2,4,5-tetrakis (N,N-diethyldithocarbamylmethyl) benzene (DDC ) as a tetrafunctional photoiniferter.

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