One-step fabrication of transparent hydrophobic silica aerogels via in situ surface modification in drying process

Abstract

We developed a novel method to facilely prepare transparent hydrophobic silica aerogels via in situ surface modification in drying process in one-step. The as-prepared silica aerogels were characterized by means of scanning electron microscope, transmittance electron microscope, nitrogen adsorption, and contact angle/interface system. In the process, methyltrimethoxysilane was used as the surface modification agent to modify wet gels simultaneously in the supercritical drying process without any solvent exchange. This was beneficial for the sufficient surface hydrophobic modification and time-effective as well as maintaining transparent pore structure of silica aerogels. We reported to rationally design and facilely fabricate transparent hydrophobic silica aerogels via in situ surface modification in drying process in one-step. In the process, the methyltrimethoxysilane (MTMS) molecule was used as the surface modification agent to modify wet gels simultaneously in the supercritical drying process. Thus, the in situ surface modification in drying process illustrated simplification of the surface hydrophobization for silica aerogels. Meanwhile, due to the inertial property of methyl groups in the MTMS molecule, it had been found that when the MTMS ratio was 3, the silica aerogel had the lowest volume shrinkage. Furthermore, all the modified silica aerogels maintained the typical three-dimensional pore structure and showed highly transparent (~80 % at λ = 550 nm) and hydrophobic property (higher than 140°). In a word, owing to its sufficient surface modification and time-effective, the method via in situ surface modification in drying process in one-step would be widely used to facilely fabricate transparent hydrophobic silica aerogels with stable microstructure in future.