Effect of Solvents on the Performance and Structure of Polymethylacrylimide Aerogels

Solvent effects play a critical role in solution polymerization, especially in free radical polymerization, where they influence both monomer–solvent interactions and the resulting polymer structure. In this study, polymethacrylimide (PMI) aerogels were synthesized via freeze-drying using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) as solvents. The effects of monomer reactivity ratios, monomer distribution, and solvent–monomer interactions on the shrinkage, bulk density, pore size, and compressive properties of the aerogels were investigated. Results demonstrated that solvent choice significantly impacted the polymerization process, leading to variations in the structure and properties of the final aerogels. Notably, aerogels synthesized in DMSO, the most polar solvent, exhibited the lowest shrinkage (33.98%), highest density (0.1582 g·cm^–3), and highest compressive stress (1695.48 kPa at 70% strain). These findings underscore the importance of solvent selection in controlling the microstructure and enhancing the mechanical performance of PMI aerogels.