Polymerization of monomers containing functional silyl groups. 12. Anionic polymerization of styrene derivatives para-substituted with pentamethyldisilyl (Si-Si), heptamethyltrisilyl (Si-Si-Si), and nonamethyltetrasilyl (Si-Si-Si-Si) groups

Three styrene derivatives, para-substituted pentamethyldisilyl (Si-Si), heptamethyltrisilyl (Si-Si-Si), and nonamethyltetrasilyl (Si-Si-Si-Si) groups 1 - 3 were synthesized and polymerized in tetrahydrofuran (THF) at −78°C and in benzene at 40°C. The polymerizations of 1 and 2 in THF were found to proceed without transfer and termination reactions to afford stable living polymers. The Si-Si and Si-Si-Si bonds are found to be completely stable under the conditions. Under the same conditions, novel block copolymers with well-defined structures were synthesized by sequential addition of 1 or 2 and styrene. By contrast, side reactions occurred during the polymerizations of 1 and 2 in benzene at 40°C, although polymer yields were quantitative. More seriously, polymer was not obtained in the polymerization of 3 both in THF and in benzene. Thus, the effect of chain length of the oligosilyl group is found to be critical in the anionic polymerization of 1 - 3 .