A general strategy for dramatic enhancement of aerogels via an aerogel-functionalization-aerogel approach

Abstract

Aerogels have garnered significant attention for their unique applications in thermal insulation, the environment, and catalysis, due to their highly open porous structures. Freeze-dried aerogels prepared from hydrophilic polymers have brought about a further boom in aerogels. However, freeze-dried aerogels usually suffer from relatively low specific surface area (SSA), low contact angle, weak mechanical stren 21`gth, high density, and high thermal conductivity. Herein, an aerogel-functionalization-aerogel (AFA) strategy is proposed by introducing superhydrophobic silica aerogel powders (SSAPs) into polymer solutions before freeze-drying. As proof of concept, five types of aerogel based on chitosan, gelatin, polyvinyl alcohol, methyl cellulose, and polyacrylamide are synthesized. Notably, SSAP-functionalized aerogels demonstrate a significant improvement in their overall physical properties, e.g. gelatin AFA showed a 3248% increase in SSA (from 5.77 m² g⁻¹ of native gelatin aerogel to 193.50 m² g⁻¹ of AFA), the compressive stress of PVA–AFA at 65% strain increased by 1228.01%, and the superhydrophilic chitosan aerogel became hydrophobic with a contact angle of 137° after adding SSAPs. This study presents a universal method for enhancing the properties of traditional freeze-dried aerogels and provides insights into modification mechanisms for silica aerogels, offering a scalable and cost-effective pathway for the fabrication of next-generation aerogels.