Sea-island polyethylene glycol/carboxylated styrene-butadiene rubber phase-change films enabled by ion-triggered inverse nanoencapsulation for flexible thermal management

Flexible organic phase-change films hold great promise for wearable thermal energy management and storage. However, their widespread application is hindered by the inherent liquid leakage of phase-change components and the common trade-off among mechanical flexibility, high latent heat, and shape stability. This study pioneers a novel reverse nano-encapsulation strategy. In this approach, La 3+ ions are directly introduced into a blend of PEG and XSBR latex, triggering the demulsification of the latex into discrete rubber particles. Subsequently, coordination cross-linking between oxalic acid and these La 3+ ions assembles the discrete particles into a continuous rubber phase. This process ultimately achieves the reverse nano-encapsulation of PEG, yielding a flexible phase change composite film characterized by a nanoscale sea-island structure. The prepared flexible film exhibits a remarkable latent heat of 92.65 J/g with high nanoencapsulation efficiency, which maintains 95.5% of its latent heat after 500 thermal cycles, demonstrating exceptional thermal reliability. Crucially, the material retains excellent mechanical flexibility, shape adaptability, and foldability, inherited from the elastomeric matrix. Benefiting from these integrated properties, it's applied in wearable thermal management, where it can be heated to 60 °C using a low voltage (1.5 V). Furthermore, a proof-of-concept device is developed, demonstrating stable and efficient solar-thermal-electric energy conversion. This work provides a groundbreaking pathway for designing high-performance, flexible phase-change materials for advanced energy applications.