Abstract
A series of silicon-containing polymers, which have the Si (H)-C ≡ C unit in the molecule, were studied. Six kinds of poly (silyleneethynylenephenyleneethynylene)s [-Si(R)H-C≡C-C6H4-C≡C-], wherein the phenylene group was the meta-, para- or ortho-form, and R represents a phenyl, methyl, or hydrogen atom, were prepared by two methods, which are (1) the dehydrogenative polymerization reaction between trihydrosilane (RSiH3) and diethynylbenzene using magnesium oxide as a catalyst and (2) the condensation reactions using dichlorosilane (RSiHCl2) and organic magnesium reagent. The properties of the resulting polymers were investigated. The polymers, especially poly [(phenylsilylene) ethynylene-1, 3-phenyleneethynylene] (R=Ph), which were thermosetting (curing temperature 150~210°C), soluble in solvent, fusible and moldable (100~150°C), showed high heat-resistant (Td5 860°C) and burning-resistant (oxygen index 40~42) properties. Poly (silyleneethynylene-1,3-phenyleneethynylene) (R=H) (Td5>1000°C) and poly [(methylsilylene) ethynylene-1, 3-phenyleneethynylene] (R=CH3) (Td5 850°C) were also showed high thermal stability. A cross-linking reaction mechanism concerning the Si-H and C ≡ C bonds was proposed and the correlation between the molecular structures and the thermal properties was discussed. Fiber reinforced polymers prepared using glass, carbon or SiC fiber showed sufficient mechanical strength even at 400°C under air. A black, hard and glassy material (C-SiC) was obtained when poly [(phenylsilylene) ethynylene-1, 3-phenyleneethynylene] was heated above 1000°C under argon.
