Thermomechanical Synergistic Enhancement of Boron Nitride Nanosheet-Reinforced Phase-Change Hydrogels for Highly Efficient Thermal Management

To address the significant heat accumulation in architectural metal curtain walls under sunlight, highly efficient thermal management materials have been developed to enhance building energy efficiency. This study designed and synthesized shape memory phase change hydrogels with synergistic enhancement of thermal conductivity and mechanical properties. The hydrogel (BNNS/Zn2+-PPCH) employs water (H2O) and polyethylene glycol (PEG) to establish a double-solvent system while incorporating Zn2+ coordination enhancement and BNNS enhancing strategies. Low BNNS loading not only increased the thermal conductivity by over 90% but also improved its fracture stress and compressive stress by 96% and 40%, respectively. The presence of PEG endows the hydrogel with excellent heat storage and temperature control capabilities. Within this system, BNNS also functions as a crystallization nucleation site, elevating the phase change enthalpy to 97.69 J·g–1, thereby further enhancing heat storage performance. Additionally, the material exhibits outstanding shape stability and thermal stability. Based on the dynamic hydrogen bonds formed between the hydrogel network and PEG within the BNNS/Zn2+-PPCH system, this material exhibits thermally induced shape memory behavior during heating–cooling cycles. In simulated solar radiation experiments, this hydrogel reduced internal and external temperatures of the building model by 9.6 and 9.8 °C, respectively. This multifunctional BNNS/Zn2+-PPCH, combining energy storage and temperature control capabilities, offers an effective approach to reducing building cooling loads and advancing low-carbon construction.