Solvent-Driven Biphasic Architectures in Polymer Gels via Polymerization-Induced Solvent Phase Separation

Polymer gels with biphasic architectures enable diverse functions, such as enhanced mechanical robustness and programmable drug release. Conventional fabrication of biphasic gels typically relies on the copolymerization of monomers with differing solvent affinities, which constrains structural diversity and tunability. In this study, we introduce "polymerization-induced solvent phase separation" (PI-SPS) as a novel and facile solvent-driven strategy for constructing biphasic gels. Polymerization of a homogeneous precursor solution containing two mutually immiscible solvents and a monomer triggers solvent demixing, yielding a hierarchical structure in which a polymer-rich continuous phase composed of the good solvent encapsulates dispersed droplets of the less favorable solvent-rich phase. We demonstrate the generality of PI-SPS across systems comprising water, organic solvents, and ionic liquids. The resulting biphasic architectures confer emergent properties, including self-healing ability, shape-memory behavior, and enhanced crack resistance, with a fracture energy of 4600 J m^-2 derived from the spatial organization of solvent domains and polymer networks. Overall, the PI-SPS strategy provides a versatile platform for engineering multiphase soft materials through controlled tuning of solvent affinities.