Structure of polyphenylsilsesquioxane particles prepared by two-step acid-base catalyzed sol-gel process and formation of hollow particles.

Spherical polyphenylsilsesquioxane (PhSiO(3/2)) particles, one of the inorganic-organic hybrid materials, were synthesized by a two-step acid-base catalyzed sol-gel process, and hollow particles were successfully prepared by washing the as-prepared particles with organic solvents. It was found that the inside and outside parts of the as-prepared particles were composed of PhSi03/2 species with relatively low and high molecular weight, respectively, i.e., the PhSiO(3/2) particles had a kind of "core-shell" structure. Because the core portion in the as-prepared particles was soluble in ethanol and tetrahydrofuran, hollow particles were obtained through washing the as-prepared PhSiO(3/2) particles with ethanol or tetrahydrofuran. Furthermore, the molecular weight of the as-prepared particles was varied by the concentration of phenyltriethoxysilane used as a starting alkoxide. As a result of the variation of the molecular weight, the hollow PhSiO(3/2) particles with different stabilities against organic solvents were formed.