Polar, functionalized diene-based materials. 2. Free radical copolymerization studies of 2-cyanomethyl-1,3-butadiene with styrene and acrylonitrile

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 x 10(3)-60 x 10(3) 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.