Hydrophobic silica composite aerogels using poly(methyl methacrylate) by rapid supercritical extraction process

Abstract

A poly(methyl methacrylate) solution was mixed in an optimized tetraethoxysilane-based silica sol and a silica aerogel was obtained by a rapid supercritical extraction process. The hydrophobicity was enhanced by an addition of poly(methyl methacrylate), the silica aerogel prepared with 6 wt% poly(methyl methacrylate) has the contact angle of 156° with low density (0.067 g/cm3), high surface area (829 m2/g), and low thermal conductivity (0.072 W/m·K). The thermogravimetric-differential thermal analysis also showed that the aerogels were hydrophobic up to a temperature of 393 °C. An extra hydrophobicity could be expected for silica aerogel using poly(methyl methacrylate) through the surface modification of silica aerogel with generated –OCH3 and –CH3 radicals by the thermal decomposition of poly(methyl methacrylate) excluding poly(methyl methacrylate) itself. This study provided a simple and cost effective method that used an inexpensive polymer additive without using an expensive surface modification agent nor hydrophobic silica precursor.