Polyurethane-polysiloxane interpenetrating polymer networks: 2. Morphological and dynamic mechanical studies

Abstract

The reaction between an α,ω-hydroxy-terminated poly(ethylene oxide)-poly(dimethylsiloxane)-poly(ethylene oxide) triblock copolymer and toluene diisocyanate was investigated. Network formation was shown to occur through allophanate linkages. Interpenetrating polymer networks based on this triblock copolymer network and on a poly(dimethylsiloxane) network were shown to be substantially phase separated, although 13C n.m.r. linewidth studies suggested some mixing at domain boundaries. A prepolymer containing silylurethane linkages was synthesized from a low molecular weight α,ω-hydroxy terminated poly(dimethylsiloxane) and toluene diisocyanate. A blend of this silyl-urethane prepolymer crosslinked with trimethylol propane and a polyurethane based on Adiprene L-100 and trimethylol propane was also incompatible. The silyurethane linkage was rapidly hydrolysed on exposure to atmospheric moisture.