Synthesis, thermal and mechanical properties of poly(methylphenylsilmethylene)s

The synthesis, thermal and mechanical properties of poly(methylphenylsilylmethylene)s (PMPSMs) were investigated focusing on the effect of polymer microstructure on these properties. Stereoisomers of 1,3-dimethyl-1,3-diphenyl-1,3-disilacyclobutane were used as monomers to provide a series of PMPSMs having different molecular weights and tacticities. The monomers easily underwent bulk polymerization without catalyst as well as catalytic polymerization in the presence of Pt or Rh compounds to give high molecular weight PMPSMs. It is suggested by the C-13 NMR analysis that the stereochemical configuration of the starting material may be retained during polymerization. C-13 NMR spectrometry was also utilized to calculate the meso dyad content (X(m)) which is regarded as a measure of the polymer tacticity. According to the relationship between X(m) and the glass transition temperatures (TgS) of PMPSMs, T(g)s tend to decrease with increasing X(m)s. PMPSM showed the excellent thermostability represented in terms of the 5% weight loss temperature as high as 460 degrees C in the TG-DTA analysis. Pyrolysis of PMPSM both in air and in nitrogen gave a network material with Si-H functionality which can be a precursor for Si-H functional ceramics. Dynamic and static mechanical properties of PMPSMs were also discussed.