Programmable phase transition enables tunable microstructures and micromechanics in thermoresponsive polysaccharide hydrogels.

Understanding polymer-surfactant interactions is essential for regulating phase transition and polymer aggregation, enabling the design of functional materials with tailored properties. Here, we introduce programmable dextran-based thermoresponsive polysaccharide condensates that exhibit reversible phase transitions with tunable lower critical solution temperatures. Photo-initiated radical polymerization permits hydrogel crosslinking, harnessing phase separation to generate hydrogels with distinct microstructures and mechanical heterogeneity. We systematically investigate the impact of anionic sodium dodecyl sulfate (SDS), cationic hexadecyltrimethylammonium bromide (CTAB), nonionic Pluronic F-127, and zwitterionic 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS) surfactants on phase transition dynamics. Surfactant charge density, hydrophilic-lipophilic balance (HLB), and critical micelle concentrations (CMC) collectively govern temperature-triggered phase separation. The resulting photo-crosslinked gels demonstrate surfactant-specific microstructures, including core-shell domains, interconnected elongated micelles, and dual emulsions. Micromechanical characterization exhibits structurally coordinated stiffness and adhesion, where Pluronic forms core-shell structures with reduced adhesion, while CTAB presents elongated structures and lowered modulus. These findings provide a framework for tailoring surfactant-polysaccharide interactions to direct microstructure-property-performance relationships in biocomposite materials design.