Synthesis and Characterization of Poly(3,4-Benzo-1-Phenyl-l-Silapentene) andPoly(3,4-Benzo-l-Silapentene)

摘要

Low molecular weight poly(3,4-benzo-1-phenyl-1-silapentene) (I) has been preparedby the anionic ring opening polymerization of 3,4-benzo-1-phenyl-1-silaclopentene (II), co-catalyzed by methyllithium and Hexamethylphosphoramide in tetrahydrofuran at low temperature. Poly(3,4-benzo-1-silapentene) (III) has been prepared similarly by polymerization of 3,4-benzo-1-silacyclopentene (IV) except that HMPA NOT been utilized in this latter case. I and III have been characterized by 1H, 13C, and 29Si NMR as well as by IR and UV spectroscopy. The low molecular weight of I and III permits end group analysis by 29Si NMR. The molecular weight distributions of I and III have been determined by gel permeation chromatography (GPC) and their thermal stability by thermogravimetric analysis (TGA). The intermediacy of poly(methylsilylene)methylene in the conversion of poly(dimethylsilane) fibers into silicon carbide fibers has increased interest is such carbosilane polymer system. We have been interested in the anionic ring opening polymerization of both silacyclopene-3-enes and 3,4-benzo-1-silacyclopentenes since these reactions provide a convenient route to poly(1-silapent-3-enes) and poly(3,4-benzo-1-silapentenes). These unsaturated polycarbosilanes have a number of interesting properties. In particular, such polymers which possess both reactive silicon-hydrogen and carbon-carbon double bonds undergo thermal decomposition to form high ceramic char yields.