Structure of Polyphenylsilsesquioxane Particles Prepared by Two-Step Acid-Base Catalyzed Sol–Gel Process and Formation of Hollow Particles

Abstract

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.

Glass transition and thermal softening of poly(phenylsilsesquioxane) particles prepared using two-step acid–base catalyzed sol–gel process

“…Consequently, hollow particles were obtained by washing the as-prepared particles with EtOH because the low molecular weight species were soluble in EtOH. We also confirmed that hollow particles were formed by washing the as-prepared particles in the composition of 50 5 x 5 100 (x = [EtOH]/[PhSi(OEt) 3 ]) with EtOH, from TEM observations [15]. Fig.…”

“…In a previous report [15], we described that the inside and outside parts of the PhSiO 3/2 particles prepared by the two-step acid-base catalyzed sol-gel process respectively comprised low and high molecular weight species. Consequently, hollow particles were obtained by washing the as-prepared particles with EtOH because the low molecular weight species were soluble in EtOH.…”

“…Furthermore, very recently, we found that the PhSiO 3/2 particles prepared using the two-step acid-base catalyzed sol-gel process have a 'core-shell' structure: the inside and outside parts of the PhSiO 3/2 particles, respectively comprised PhSiO 3/2 species with low and high molecular weights [15]. The PhSiO 3/2 species with low molecular weight were soluble in ethanol (EtOH).…”

Macroporous materials by self-assembly of linear oligo(phenylsilsesquioxanes).

“…However, less branched oligomers of low molecular mass (M w < 3000) exhibit a glass transition at 360 K (Figure 8). An endothermic change in a similar temperature range was observed for cross-linked poly(phenysilsesquioxane) particles obtained by a two-step acidbase catalysed sol-gel process [21,22,54]. T g transition was not sensitive to the thermal treatment during DSC analysis.…”

“…However, the literature reports concern poly(phenylsilsesquioxane) microparticles obtained in a modified Stöber route [18,19] emulsion polymerization [20], a template-free two-step acid-base catalyzed sol-gel process [21,22] and base catalyzed oil-in-water emulsion polycondensation [19]. Phenylsilsesquioxane particles of 'core-shell' structure show both thermoplastic and thermosetting properties [23,24].…”