Polymerization of monomers containing functional silyl groups, 12.† Free-radical polymerization of 2-silyl-substituted 1,3-butadienes

Free-radical polymerizations of five 2-silyl-substituted 1,3-butadienes, 2-trimethoxysilyl-1,3-butadiene (1), 2-triisopropoxysilyl-1,3-butadiene (2a), 2-[diisopropoxy(methyl)silyl]-1,3-buta-diene (2b), 2-[isopropoxy(dimethyl)silyl]-1,3-butadiene (2c), and 2-trimethylsilyl-1,3-butadiene (3), were carried out in bulk. Considerable amounts of Diels-Alder dimers as well as polymers were obtained at 80°C with AIBN as an initiator. Formation of the dimer was suppressed completely at 15°C with a redox type initiator, a combination of benzoyl peroxide and N,N-dimethylaniline. In these cases, the polymerization rates were extremely low, resulting in low polymer yield, at most 50%. The microstructures of the resulting polymers were predominantly E-1,4, regardless of the polymerization conditions and the substituents at the silicon atom. The results of copolymerizations of silyl-butadienes (M1) and styrene (M2) show that the former monomers have higher reactivity than the latter (r1 = 4,1 − 2,2;r2 = 0,4 − 0,5). The r1 values decrease with an increase in the number of methyl groups at the silicon atom.