Synthesis of poly(methylsilsesquioxane-co-dimethylsiloxane) liquids and deep-ultraviolet transparent elastic resins through co-solvent-free water-rich hydrolytic polycondensation of organoalkoxysilanes

Abstract

Liquids of poly(methylsilsesquioxane-co-dimethylsiloxane), called “DT-type methyl silicone”, with a high methylsilsesquioxane unit mole fraction of 80% (methyl/Si ratio of 1.2) were obtained by a cosolvent-free hydrolytic polycondensation of mixtures of methyltrimethoxysilane and dimethylsiloxane at high water to alkoxysilane ratios (≳10). The thermal curing of the liquids yielded dense, stiff, and tough resins that exhibited excellent deep-ultraviolet transparency and complete elastic recovery.