Structure and characterization of aerogel materials and oxidation products from the reaction of (CH3O)4Si and RSi(OCH3)3

Abstract

Reactions of (CH3O)4Si and RSi(OCH3)3 (R=CH3, C2H5, C3H7, C4H9, C16H33) at a mole ratio of 1 to 1 were performed in methanol using base catalysis. Subsequent supercritical drying produced materials that have a wide range of surface areas and porosities. Spectroscopic characterization, revealed normal Si–O substitution as well as incorporation of the carbon chain into the Si framework. Heating of the stable forms of the materials in air at different temperatures yielded, depending upon oxidation conditions, several materials with much higher surface areas, typical of aerogels. Pore-size distribution measurements revealed mesopore features that differed from the non-oxidized materials for some R groups. Spectroscopic characterization revealed the disappearance of the R–Si substitution for all R groups and the appearance of an oxidized intermediate for R=C16H33.