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

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Polyorganosilsesquioxanes (RSiO3/2) (R: organic group) particles with different organic groups such as alkyl and aryl groups were prepared using a two-step acid–base catalyzed sol–gel process. Spherical particles were formed at room temperature using the two-step acid–base catalyzed sol–gel 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 acid–base catalyzed sol–gel 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.