Dual-role lignin interfacial engineering for Pickering-stabilized phase change microcapsules toward high-performance thermoregulating polyurethane foams.

Phase change microcapsules are attractive thermal regulation fillers; however, their integration into polymer matrices remains limited by weak interfacial compatibility and structural deterioration during processing. Herein, a sustainable dual-role lignin interfacial engineering strategy is proposed to address these challenges. Poly(ethylene-alt-maleic anhydride)-modified lignin hybrid particles (ELs), prepared via acid-triggered self-assembly, served as both Pickering stabilizers and reactive interfacial modifiers. Lignin-hybrid PCM microcapsules (ELMCs) containing tetradecanol were fabricated by two-step in situ polymerization, yielding a lignin-rich reactive shell. The ELMCs exhibited high encapsulation efficiency and thermal reliability while preserving latent heat storage capacity. Moreover, the lignin-rich reactive shell provided abundant hydroxyl groups that reacted with isocyanate groups during foaming, synergistically refining foam cellular structure and strengthening matrix-filler interfacial integration. The composite foams achieved a compressive strength of 182.19 kPa and low thermal conductivity of 0.0255 W/(m·K), with outstanding thermal buffering capacity regulation. Building model tests further verified effective heat suppression and stabilized indoor temperature under solar irradiation. This work presents a sustainable lignin-based microcapsule platform for designing high-performance thermoregulating polyurethane foams for energy-efficient building applications.