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, environment, and catalysis due to their highly open porous structures. The freeze-dried aerogels prepared from hydrophilic polymers further bring a booming of aerogels. However, the freeze-dried aerogels usually suffered from relatively lower specific surface area (SSA), lower contact angle, weaker mechanical strength, higher density, and higher thermal conductivities. Herein, an aerogelfunctionalization-aerogel (AFA) strategy is proposed by introducing superhydrophobic silica aerogel powders (SSAPs) into polymer solutions before freeze-drying. As proofs of concept, five types of aerogels based on chitosan, gelatin, polyvinyl alcohol, methyl cellulose, and polyacrylamide are synthesized. Notably, the SSAPs functionalized aerogels demonstrating significance improvement in their overall physical properties, e.g. the gelatin AFA shows an 3248% increment in SSA (from 5.77 m 2 /g of the native gelatin aerogel to 193.50 m 2 /g of the AFA), the compressive stress of PVA-AFA at 65% strain increased by 1228.01%, and the superhydrophilic chitosan aerogel become hydrophobic with a contact angle of 137° after adding SSAPs. This study presents a universal method for enhancing traditional freeze-dried aerogel's properties and provides insights into the modification mechanisms of silica aerogels, which offering a scalable and cost-effective pathway for the fabrication of next-generation aerogels.