Hydrolytic polycondensation of vinyltrimethoxysilane and formation of vinylpolysiloxane films

Abstract

Hydrolytic polycondensation of vinyltrimethoxysilane (VTM) was investigated in detail to prepare vinylpolysiloxanes (VPS) having spinnability and tough gel films. VTM was hydrolyzed in various molar ratios r₁ (H₂O/VTM) = 0.5–1.6 (HCl/VTM = 0.105, EtOH/VTM = 1.44) at 70°C under a N₂ stream with stirring at 150 rpm to give vinylpolysiloxanes with $\overline {{\text{Mn}}}$=510–2100 ($\overline {{\text{Mw}}} /\overline {{\text{Mn}}}$=1.1–10.4). The controlled hydrolysis in r₁ = 1.40–1.64 formed VPSs having the various degrees of spinnability at N₂ flow rates of 100–500 ml/min. Transparent films of thickness 0.1–0.05 mm and tensile strength 5–16 MPa were prepared when a 20 wt% acetonemethanol (1:1, V/V) solution of VPS (r₁=1.64) was cast at 80°C for several ten days. The reaction was followed by ²⁹Si-NMR spectroscopy to investigate the distribution of unit structures T¹, T² and T³ in VPS depending on r₁.