Solar Thermal Storage and Room-Temperature Fast Release Using a Uniform Flexible Azobenzene-Grafted Polynorborene Film Enhanced by Stretching

Deformation-controlled solar thermal storage and release are important for thermal management of dynamic systems. However, few researchers have examined cyclic solid-state solar thermal utilization with different deformations. A uniform flexible stretchable solar thermal fuel film is presented using polynorbornene-templated azobenzene (PNB-Azo) with ring-opening metathesis polymerization and covalent grafting. This film has a high degree of isomerization and good storage room-temperature stretching stability compared to push-pull electronic interaction. At 20% strain rate, the film combines high-degree photocharging (85%), high energy density (49.0 Wh kg(-1)), and high rate of heat release induced by blue light (475 nm) at room temperature. Greater free volume improves isomerization and the first-order kinetic constant is increased by 1 order of magnitude. Reversible electric-driven dynamic stretching during charging and discharging enables PNB-Azofingers to release heat more rapidly than static stretched film, resulting in a temperature increase of 1.5 degrees C. The result indicates that PNB-Azofilm can be used as a high-power dynamic solar heat source by controlling the deformation.