Poly(cyclohexylsilsesquioxane)-Based Hydrophilic Thermoset-Resistant Deep-Ultraviolet-Transparent Glasses with Low Melting Temperatures

Silsesquioxane (SQ)-based glasses with low melting temperatures were prepared by the cosolvent-free (solventless) hydrolytic polycondensation of organotrimethoxysilanes with cyclopentyl ( c -Pe) and cyclohexyl ( c -Hx) groups. Copolymers consisting of phenylsilsesquioxane (Ph-SQ) units and c -Pe-SQ units [poly(Ph- co - c -Pe-SQ)] or c -Hx-SQ units [poly(Ph- co - c -Hx-SQ)] were melted at 140 °C and formed clear glasses. The glasses prepared by this method contained many residual SiOH groups and exhibited high adhesive strength to microscope glass plates, metals, and several polymers. The glass-transition temperature of poly( c -Hx-SQ) was lower than that of poly(Ph-SQ) by only a small margin, whereas that of poly( c -Pe-SQ) was much lower. The poly( c -Hx-SQ)-based glasses were stiff at room temperature and transparent in the deep-ultraviolet spectral region (≲300 nm). They formed fragile melts with kinetic fragility parameters as high as ∼0.8. The melts of poly( c -Hx-SQ) and poly( c -Hx- co -Et-SQ) exhibited better resistance to thermal curing than that of poly(Ph-SQ) and maintained thermoplasticity even after heat treatment at 200 °C for 6 h.