Thermal Softening Behavior of Poly(phenylsilsesquioxane) and Poly(benzylsilsesquioxane) Particles.

Abstract

The thermal softening behavior of poly (phezylsilsesquioxane) (PhSiO3/2) and poly (benzylsilsesquioxane) (BnSiO3/2) particles during heat treatment has been investigated from the results of gel permeation chro matography, thermal and structural analyses of the particles. Both PhSiO3/2 and BnSiO3/2 particles thermal ly softened, and the onset temperature of thermal sintering was about 140 and 50 for PhSiO3/2 and BnSiO3/2, respectively. The thermal sintering of the PhSiO3/2 and BnSiO3/2 particles was caused by the decrease of viscosity at temperatures higher than the glass transition temperatures. Glass transition was ob served for BnSiO3/2 in the repeated heating runs, while for PhSiO3/2 glass transition was appreciable only in the first heating run. From 29Si nuclear magnetic resonance spectra, the development of siloxane network during heat treatment was found to be more significant in PhSiO3/2 than in BnSiO3/2. The difference in the structural evolution during heat treatment makes PhSiO3/2 particles thermosetting and BnSiO3/2 ones ther moplastic.

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

“…Among the several kinds of poly(organosilsesquioxane)s, many studies of the preparation of poly(phenylsilsesquioxane) (PhSiO 3/2 ) particles, which have a siloxane structure with phenyl groups, have been conducted so far [6][7][8][9][10][11][12]. We have reported the preparation of spherical PhSiO 3/2 particles using a two-step acid-base catalyzed sol-gel process, in addition to our finding that the PhSiO 3/2 particles show glass transition behavior [13]. The PhSiO 3/2 particles became a supercooled liquid by heating above the glass transition temperature (T g ) of the particles.…”

Substituent effects on the glass transition phenomena of polyorganosilsesquioxane particles prepared by two-step acid-base catalyzed sol-gel process

“…13) Using the thermal softening behavior of these particles, PhSiO 3/2 and BnSiO 3/2 thick films with high transparency or microlens arrays were formed by electrophoretic deposition of the particles and subsequent heat treatment. 18)20) In this study, we have prepared polyorganosilsesquioxanes with different organic groups from RSi(OR¤) 3 using the twostep acidbase catalyzed solgel process.…”

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

“…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]. Ladder-like polysilsesquioxanes structurally differ from polyhedral oligomeric silsesquioxanes (POSS) and random silsesquioxane networks ( Figure 2).…”