SYNTHESIS OF BLOCK-COPOLYMERS OF SILICON-CONTAINING NORBORNENE DERIVATIVES VIA LIVING RING-OPENING METATHESIS POLYMERIZATION CATALYZED BY A RUTHENIUM CARBENE COMPLEX

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)Cl2Ru = CHCH=CPh(2): 1a, R = phenyl; 1b, R = cyclohexyl]. For example, the living polymerization of norbornene 2a (NBE) by la 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) over bar(n) = 58 000, (M) over bar(W)/(M) over bar(n) = 1.20). On addition of a silicon-containing norbornene derivative (4), polymerization immediately ensued at 50 degrees 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) over bar(n) = 129 000, (M) over bar(W)/(M) over bar(n) = 1.25). The segment ratio (m:n = 1.86) of 5a determined by H-1 NMR was in good agreement with the calculated value (min = 1.78). Silicon-containing block copolymers with polar functional groups were also synthesized by ROMP with 1b.