SiO2 aerogels modified by perfluoro acid amides: a precisely controlled hydrophobicity

摘要

Five series of novel fluorinated aerogels based on acylated (3-aminopropyl) trimethoxysilane (APTMS) (MeO)(3)Si(CH2)(3)NHC(O)R-F (R-F = CF3, C2F5, CF3CF(OCH3),C6F13 and C8F17) were prepared by a sol-gel method followed by supercritical drying in four different solvents, including isopropanol, CO2, methyl tert-butyl ether (MTBE) and hexafluoroisopropyl alcohol (HFIP). The hydrophobicity of the aerogels was shown to increase smoothly with the increase in the length of the fluorinated substituent - the water drop contact angle theta changed from 0 degrees and reached 143 degrees for isopropanol dried samples, 133 degrees for CO2 dried samples, 136 degrees for MTBE dried samples, and similar to 140 degrees for HFIP dried samples. The results obtained provide an easy method for the preparation of aerogels with precisely controlled hydrophobicity.