关键词:

三（五氟苯基）硼, 反应机理, 密度泛函理论, 缩聚, 聚亚苯基硅氧烷

Abstract:

The mechanism of B(C₆F₅)₃ catalyzed Si—H/Si—OR polycondensation reaction was studied through the quantum chemistry methods.Poly(silphenylene-siloxane)s were prepared by polycondensation of 1,4-bis(dimethylsilyl)benzene (BDSB) and dimethyldimethoxylsilane, vinylmethyldimethoxylsilane and diphenyldimethoxylsilane respectively.The microstructure of the polymer was characterized by ²⁹Si NMR and the influence of vinyl and phenyl groups of alkoxylsilane on the microstructure of the polymer was also discussed.B(C₆F₅)₃ first activated Si—H to form weak adduct, then Si—OR attacked Si—H/B(C₆F₅)₃ adduct to break Si—H and form oxonium ion complex.The decomposition of the complex occurred by the H- transfer to one of the three electrophilic centers, which explained the competition between condensation and Si—H/Si—OR exchange.Vinyl or phenyl group of alkoxysilane decreased the positive charge of Si atom and increased the positive charge of C which bonded to O, and it also reduced the strength of C—O, resulting in more alternated polymers.

Key words:

三（五氟苯基）硼, 反应机理, 密度泛函理论, 缩聚, 聚亚苯基硅氧烷