Influence of copolymerization with alkyltrialkoxysilanes on condensation and thermal behaviour of poly(phenylsilsesquioxane) particles

Abstract

Alkyl-modified phenylsilsesquioxane (PhSSQ) particles were prepared from phenyltriethoxysilane by two-step acid-base catalysed sol-gel process, using alkyltriethoxysilanes of varying chain length (methyl, ethyl, pentyl and octyl), in order to control the softening temperature and thermal stability of the resulting particles. Resulting particles were characterized by scanning electron microscopy, X-ray diffraction analysis, gel permeation chromatography and Fourier-transform infrared spectroscopy, while the thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. Increased chain length presents steric hindrance to condensation of phenyltriethoxysilane, leading to decreased softening temperature and thermal stability, while copolymerization with methyltrialkoxysilane leads to increase of softening temperature without influencing the thermal stability. Copolymerization with alkyltrialkoxysilanes is therefore a feasible method to control the softening temperature of PhSSQ particles. By their properties the modified PhSSQ could be grouped in short-chain modified (methyl and ethyl) and long-chain modified (pentyl and octyl) ones.