Synthesis of Block Copolymers of Silicon-Containing Norbornene Derivatives via Living Ring-Opening Metathesis Polymerization Catalyzed by a Ruthenium Carbene Complex

Abstract

Block copolymers (5) of silicon-containing norbornene derivatives were prepared using living ring-opening metathesis polymerization (ROMP) with a well-defined ruthenium carbene complex [1, (R 3 P) 2 Cl 2 Ru=CHCH=CPh 2 ; 1a, R = phenyl ; 1b, R = cyclohexyl]. For example, the living polymerization of norbornene 2a (NBE) by 1a was carried out at room temperature in a mixture of methylene chloride and 1,2-dichloroethane. After 3 h, the polymer isolated had a narrow molecular weight distribution (MWD) (M n = 58 000, M w /M n = 1.20). On addition of a silicon-containing norbornene derivative (4), polymerization immediately ensued at 50 °C from the living ends of 3 and afforded a block copolymer 5a. The MWD curve of the resulting block polymer 5a shifted toward the higher molecular weight region, and the polydispersity remained narrow (M n = 129 000, M w /M n = 1.25). The segment ratio (m :n = 1.86) of 5a determined by 1 H NMR was in good agreement with the calculated value (m :n = 1.78). Silicon-containing block copolymers with polar functional groups were also synthesized by ROMP with 1b.