Photo-crosslinked pluronic hydrogels: micelle self-assembly and thermoresponsive behavior

Amphiphilic block copolymers, such as pluronic triblock copolymers, are widely employed to engineer stimuli-responsive hydrogels for applications ranging from biomedicine to energy and food industries. In this study, we investigated how the self-assembly temperature of pluronic P123, P104, and F127 affects the crosslinking behavior and the temperature-dependent volume changes of the resulting hydrogels. Each pluronic bearing hydroxyl end-group was functionalized with methacrylic moieties to enable chemical photo-crosslinking and hydrogel formation. Before crosslinking, the impact of chain-end functionalization on micellar organization was evaluated using rheological measurements to map changes in the phase diagrams of the micellar solutions. The results revealed significant shifts in micellar organization for all three pluronics following methacrylation of the hydroxyl groups. Photorheological experiments further demonstrated that the micellar organization directly influenced the kinetics of chemical crosslinking: organized micellar states facilitated faster and more efficient photocrosslinking reactions. Temperature sweeps on the crosslinked systems showed that F127-MA, P123-MA, and P104-MA hydrogels exhibited significantly reduced thermoresponsiveness when crosslinked in an organized state. Finally, the rheologically observed thermal behavior was correlated with the hydrogels' swelling properties. The thermal responses of the pluronic hydrogels resulted in up to 30% water release when crosslinked in an isotropic state, compared to 20% when crosslinked in an organized state. These findings highlight the critical role of micellar organization in tuning the physicochemical properties of pluronic-based hydrogels.