Effects of Phenyltriethoxysilane Concentration in Starting Solutions on Thermal Properties of Polyphenylsilsesquioxane Particles Prepared by a Two-Step Acid-Base Catalyzed Sol-Gel Process

Abstract

Spherical polyphenylsilsesquioxane particles were prepared by a two-step acid-base catalyzed sol-gel process, in which various amounts of ethanol were used as a solvent to vary the concentration of phenyltriethoxysilane PhSi OEt 3 used as a starting alkoxide. The decrease in the PhSi OEt 3 concentration led to the decrease in the average molecular weight and glass transition temperature of the polyphenylsilsesquioxanes. Thus, the change of the PhSi OEt 3 concentration in the preparation of polyphenylsilsesquioxane particles by the two-step acid-base catalyzed sol-gel process is an effective means to control the glass transition temperature of the particles.

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.…”

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

“…On the other hand, we had regarded the PhSiO 3/2 particles as a homogeneous substance and reported that T g increased with the increased average molecular weight of the particles [16]. However, the relationship described above only represented the results for PhSiO 3/2 species with low molecular weight, which were soluble in EtOH.…”

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

“…As described above, a similar tendency was observed in the formation of solid particles. Our previous work 23) showed that T g of the PhSiO 3/2 particles prepared from PhSi(OEt) 3 was increased with increased molecular weight: T g is dependent primarily on the degree of polymerization. The difference in T g shown in Table 1 must be brought about by the difference in the polymerization degree.…”

“…95°C). The glass transition temperature is primarily dependent on the degree of polymerization; 23) T g is increased with the increased degree of polymerization. i-BuSi(OEt) 3 has a larger organic substituent (R) and a larger alkoxy group (OR¤) than n-Bu(OMe) 3 ; consequently, the development of three-dimensional siloxane networks of the sample prepared from i-BuSi(OEt) 3 should be prevented.…”