Sequence- and Microstructure-Controlled Alternating Copolymerization of 1,1-Diphenylethylene with 1-Phenyl-1,3-butadienes via Living Anionic Polymerization

Abstract

Simultaneous control over the alternating sequence and diene microstructure remains a significant challenge in the anionic copolymerization of 1,1-diphenylethylene (DPE) with conjugated dienes. Herein, we report the synthesis of well-defined alternating copolymers of DPE and 1-phenyl-1,3-butadiene derivatives (E-1PBDs). Defect structures containing consecutive E-1PBD units were efficiently suppressed by employing a large excess of DPE ([DPE]/[E-1PBDs] > 13) combined with a bulky tert-butyldimethylsilyl (TBS) substituent on the E-1PBD framework under optimized polymerization conditions (THF, –40 °C). Consequently, highly alternating copolymers containing approximately 81% 1,4-units were obtained. Subsequent hydrogenation using p-toluenesulfonyl hydrazide proceeded quantitatively without any detectable side reactions, affording sequence-controlled alternating ternary copolymers. Hydrogenation caused only a small decrease in the glass transition temperature (from 103 to 92 °C), indicating that the thermal properties of the alternating copolymer were largely preserved after post-polymerization modification.