Poly(n-alkylsilsesquioxane) liquids prepared by cosolvent-free hydrolytic polycondensation of n-alkyltrialkoxysilanes: effects of liquid-liquid phase separation during aging and alkyl chain length on structure and viscosity.

The effect of the alkyl chain length and alkoxy groups on the viscosity and related properties of polysilsesquioxanes (PSQs) prepared by cosolvent-free hydrolytic polycondensation from n-alkyltrialkoxysilane-water binary systems via aging was investigated. n-Alkyltrialkoxysilanes with ethyl, n-propyl, and n-butyl groups gave PSQ liquids, whereas those with methyl groups yielded gels. The viscosity of the PSQ liquids remained stable over a month at room temperature despite the presence of many SiOH groups, and decreased with an increase in the alkyl chain length.