Solid-solid phase change fibers with enhanced energy storage density for temperature management

Solid-solid phase change fibers are advantageous for thermal management and latent heat storage, because they don't have the issue of liquid leakage facing those common ones that have a solid-liquid phase-transition. However, the relatively low heat density hinders such fibers from real applications. Herein, we report a strategy to fabricate solid-solid phase change fibers with much enhanced energy storage density, through coaxial wet spinning using thermoplastic polyurethane solution and polymerizable polyethylene glycol solution as outer spinning solution and inner spinning solution, respectively, followed by light-driven radical polymerization. The resulting fibers exhibited good flexibility and good tensile performances, with elongation at break and breaking strength of approximately 629.1 % and 3.8 MPa, respectively. Moreover, the fibers showed quite high heat density of 122.5 J/g, much higher than that of the previously reported phase change fibers with a solid-solid phase-transition, and high reusability, with heat density of 102.0 J/g preserved after 100 heating-cooling cycles. These attractive features make the fibers to be promising for wearable temperature management, energy harvesting and heat storage applications.