A Thermoreversible Gelation Pathway to Mesoporous Aerogel Monoliths Based on Poly(methyl methacrylate) Stereocomplex Crystals

In pursuit of lightweight, functional thermoplastic materials, novel monolithic aerogels composed entirely of poly(methyl methacrylate) (PMMA) and its stereocomplex crystals are reported. Herein, PMMA aerogels are fabricated using a one-pot thermoreversible gelation procedure, coupled with supercritical CO₂ (scCO₂) drying. These aerogels exhibit either mixed macro- and mesoporous, or exclusively mesoporous character, with low densities (0.03-0.4 g cm^-3) and high porosities (97.3-66.6%), depending on the concentration of PMMA used in sol-gel processing. These aerogels also exhibit among the highest melting temperature and enthalpy reported for PMMA stereocomplex crystals, a consequence of scCO₂ drying that promotes chain reorganization processes. Despite the characteristically brittle nature of PMMA and aerogels with similar densities, these aerogels exhibit an unusually remarkable balance between stiffness, strength, and toughness that arises from their nanometric-crystalline-ligament-containing structure. These monoliths are also superoleophilic (sorption capacity: 2.9-29.8 g g^-1), are well-suited for oil-water separation, and are effective thermal insulators (k: 24-65 mW m^-1 K^-1). Importantly, these aerogels can be easily recycled via chemical recycling and melt-processing. These findings provide the foundation for future fabrication of recyclable thermogel derivatives, and reveal process-structure-property relationships for stereocomplex crystal-based monoliths.