Control of porous structure in flexible silicone aerogels produced from methyltrimethoxysilane (MTMS): the effect of precursor concentration in sol-gel solutions

Controllable nanoporous structure in MTMS-based silicone aerogels is required to improve their thermal conductivity. Silicone aerogels were formed in a two-step acid-base catalysed sol-gel process combined with supercritical drying. The influence of MTMS concentration, specifically the molar ratio of methanol:MTMS and water:MTMS in the sol-gel process was studied in relation to the porous structure of resultant silicone aerogels. Samples were characterised to determine the dimensions of micro, meso and macro-pore structure by means of both nitrogen gas adsorption-desorption for detection of pores < 300 nm and by analysis of FEG-SEM images for pores > 300 nm. Porosity, pore volume distribution and Brunau er-Emmitt-Teller surface area in the silicone aerogels were all found to be influenced by adjustment of the molar ratio of methanol:MTMS and the molar ratio of water:MTMS during sol-gel processing.