Abstract
Hydrosilylation of acetylene with a chiral silane, R-(+)-methyl-1-naphthyl-phenylsilane [R-(+)-Me-NpPhSi^*H], in the presence of H_2PtCl_6xH_2O proceeds with retention of configuration of the stereogenic silicon center and produces a chiral vinylsilane or sllylethylene [S-(+)-MeNpPhSi^*Vi] of high optical purity under mild condition (50℃) in high chemical yield (85%). Anionic polymerizations of the chiral silylethylene monomer by an achiral initiator n-BuLi yield optically active polymers with [α]_D^<20> up to -28.1°, while polymerizations of the racemic monomer by a chiral initiator n-BuLi/(-)-sparteine produce polymers with [α]_D^<20> up to +275°. Thus the sign of optical rotation of the polymers can be controlled by different combination of monomer and catalyst. Magnitude of the optical rotation can be "tuned"by changing polymerization temperature with high temperature generally favoring random propagation. All the polymers have low polydispersity indexes (M_w/M_n down to 1.02) or possess narrow molecular weight distributions. Spectroscopic characterization confirms the molecular structure of polymers to be poly (silylethylene), that is, a polyethylene main chain with a bulky methyl-1-naphthyl-phenylsilyl side chain. The polymers are thermally stable (onset temperature for weight loss in air : 380℃), possess high glass transition temperature (T_g > 380℃), and may find a wide range of applications in the optical display systems.
