Preparation and characterization of hydrophilic methylsilsesquioxane aerogels through adjusting the water/ethanol ratio

Abstract Ever-increasing application domains of Methylsilsesquioxane aerogels place a higher demand on the diverse wettability. This work prepares hydrophilic Methylsilsesquioxane aerogels under ambient pressure (APD) using 25 ml water and ethanol (EtOH) as co-solvents (12–36 vol% ethanol) and CTAB as a surfactant. We also find that the unique Methylsilsesquioxane aerogels with hydrophilic surface and hydrophobic interior are prepared when the volume fraction of EtOH ranges between 0 and 12 vol% and 36–60 vol%. The surface consists of a thin layer derived from the dissolved CTAB, which is responsible for the hydrophilicity of Methylsilsesquioxane aerogels. The hydrophilicity and hydrophobicity of the interior of Methylsilsesquioxane aerogels are related to the aggregation form of CTAB in EtOH-water mixed solvent. Too low or too high volume fraction of ethanol causes CTAB to form micellar aggregates, resulting in hydrophobicity. Further study reveals that the microstructures of Methylsilsesquioxane aerogels including skeletal size and silica particle size are significantly affected by the volume fraction of EtOH in co-solvent, which further influences the content of CTAB. In summary, the work provides a new method for the preparation of Methylsilsesquioxane aerogels with hydrophilicity, which enables the customization of the wettability of Methylsilsesquioxane aerogels and facilitates the expansion of their diverse applications. Graphical Abstract