Synthesis, structures and properties of hydrophobic Alkyltrimethoxysilane-Polyvinyltrimethoxysilane hybrid aerogels with different alkyl chain lengths

Hypothesis: Alkyltrimethoxysilane (ATMS) is among most widely used silane coupling agents. These commercially available, reasonably priced chemicals are often utilized to improve the compatibility of inorganic surfaces with organic coatings. With three hydrolysable moieties, ATMS is an outstanding candidate for solving the hydrophilicity, moisture sensitivity and high cost of silica aerogels. However, ATMS has a non-hydrolysable alkyl chain that undergoes cyclization reactions. The alkyl chain prevents ATMS from being incorporated in aerogel structures. Polyvinyltrimethoxysilane (PVTMS) is a silica precursor that offers two types of crosslinking to the final aerogel product. This strong doubly-crosslinked network can potentially suppress the cyclization reactions of ATMS and include it in aerogel structure. Experiments: PVTMS was used with ATMS having different alkyl lengths (3-16 carbons) and loadings (25 or 50 wt%) as the silica precursors. Acid and base catalysts were used to perform hydrolysis and conden-sation reactions on the mixture and ATMS:PVTMS aerogels were obtained via supercritical drying. Findings: The incorporation of ATMS in the aerogels was approved by different characterization methods. Results showed that ATMS:PVTMS aerogels possess hydrophobicity (theta similar to 130 degrees), moisture resistance, vary-ing surface area (44-916 m(2)g(1)), meso/microporous structure and thermal insulation properties (lambda similar to 0. 03 Wm(-1)K(1)). These samples also showed excellent performance in oil and organic solvent adsorption. (c) 2021 Elsevier Inc. All rights reserved.