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

Abstract

Polyorganosilsesquioxanes (RSiO 3/2 ) (R: organic group) particles with different organic groups such as alkyl and aryl groups were prepared using a two-step acidbase catalyzed solgel process. Spherical particles were formed at room temperature using the two-step acidbase catalyzed solgel process in which trifunctional organoalkoxysilanes with R = methyl, n-propyl, n-butyl, phenyl, and benzyl were used as starting materials. Polyorganosilsesquioxanes with longer alkyl groups or phenethyl group prepared by the two-step acidbase catalyzed solgel process were oily material at room temperature. Polyorganosilsesquioxanes with shorter alkyl or aryl groups exhibited the glass transition. In contrast, polyorganosilsesquioxanes with longer alkyl groups showed no glass transition behavior. The occurrence of glass transition phenomena of polyorganosilsesquioxanes was concluded to be strongly dependent on the chain length of organic substituents.

Void Formation/Elimination and Viscoelastic Response of Polyphenylsilsesquioxane Monolith

“…The molar ratio of PhTES:EtOH:H 2 O (in HCl solution):H 2 O (in NH 4 OH solution) was 1:10:40:120. The resultant PhSiO 3/2 particles were washed by repeated dispersion in H 2 O and centrifugation and then dried at 60 °C [ 14 , 15 , 16 ]. Monolithic (pelletized) bulk sample was prepared by pressing the PhSiO 3/2 particles at 120 MPa for 15 min using a metal mold (10 mm in diameter) at 25 °C, followed by increasing temperature to 120~280 °C and further pressed at 120 MPa for 15 min.…”

“…Various applications for a passivation layer for the InGaZnO transistor [ 6 , 7 ], hybridization with epoxy resin [ 8 ], beauty care [ 9 ], a rhodamine 6G-doped laser [ 10 ], framework of cage crystals [ 11 , 12 ] and gemini surfactant [ 13 ], have also been reported so far. PhSiO 3/2 particle with monodispersed size was successfully prepared using a two-step acid-base catalyzed sol-gel process, and its size, molecular weight and glass transition temperature vary by controlling the sol-gel conditions such as the amount of added ethanol solvent and concentration/amount of acid-base catalysis [ 14 , 15 ]. One big advantage of PhSiO 3/2 particle is that a monolithic bulk can be obtained by pressing the particles.…”