Thermoresponsive Hydrogel with Thermal Memory

Thermal plasticity-the capacity to dynamically reconfigure material properties in response to thermal history-is a hallmark of biological systems that remains elusive in synthetic hydrogels. Inspired by coral symbiont acclimatization, thermally plastic hydrogels (TP-gels) based on polyvinyl butyral are reported, which emulate biological thermal memory through a bioinspired feedback loop: thermoresponsive equilibrium swelling encodes thermal history, while elastic network constraints translate this memory into programmable phase transition thresholds (T_c). By exploiting temperature-dependent polymer-water miscibility, TP-gels achieve multi-stable states through adaptive swelling, enabling reversible opacity transitions with T_c shifts of 3-7 °C per thermal training cycle. Crucially, elasticity-mediated suppression of spinodal decomposition stabilizes metastable states during thermal encoding, preventing premature phase separation. This plasticity is leveraged for cryptographic applications, demonstrating sequential information decryption via thermal trajectory programming-where spatially resolved T_c gradients serve as thermodynamic keys. This work establishes a paradigm for materials with embodied environmental intelligence, bridging the divide between biological adaptability and synthetic systems through thermodynamic metastability engineering.