The bulk, solution, and emulsion free radical polymerizations of 2-cyanomethyl-1,3-butadiene were studied. Traditional bulk free radical polymerization kinetics were observed, giving polymers with 〈M n〉 values of 20 × 10 3 -60 × 10 3 g/mol and polydispersities near 1.5. In solution polymerization, the highest molecular weight (82 × 10 3 g/mol at 53% conversion) was obtained in tetrahydrofuran, with a broader polydispersity attributed to chain transfer to the solvent. In these two types of polymerizations, the Diels-Alder side product yield was affected by initiator concentration, solvent concentration, and polymerization time. Emulsion polymerization gave the highest molecular weight of poly(2-cyanomethyl-1,3-butadiene) to date of 128 × 10 3 g/mol in significantly shorter reaction time than bulk or solution reactions. Finally, the polymer microstructure of approximately 95% 1,4 and 5% 4,3 structure was determined, with the percent cis-1,4 (36-45%) varying with the polymerization temperatures. The glass transition temperature of poly(2-cyanomethyl-1,3-butadiene) is near -18°C, based on the molecular weight and the microstructure.

The solution free radical copolymerizations of 2-cyanomethyl-1,3-butadiene (CMBD) with styrene and acrylonitrile were studied. Traditional free radical polymerization kinetics were observed, giving copolymers with 〈M n〉 values of 20 × 103−60 × 103 g/mol and polydispersities typically near 1.5. The reactivity ratios of CMBD and styrene of 3.0 and 0.23 and CMBD and acrylonitrile of 1.5 and 0.4 indicated that the cyano monomer was more reactive than styrene or acrylonitrile. The copolymerization behavior was consistent with the reactivity ratios measured, giving nonideal, nonazeotropic copolymerizations, where the copolymers were always richer in cyano monomer than in styrene or acrylonitrile. All of the copolymers showed only one glass transition temperature that agreed well with the theoretical values calculated by the Gordon−Taylor equation. Finally, the cyano diene units incorporated into the copolymers maintained a similar microstructure seen in the homopolymers of approximately 95% 1,4 and 5% 4,3 structure.

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