Improvement of Solar Thermal Fuels by Anchoring Azobenzene to Polymers of Intrinsic Microporosity AITranslate

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DOI：https://doi.org/10.1021/acsapm.3c00896

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Polymer-based solar thermal fuels (PSTFs) have great potential in flexible thermal management devices; however, it is a challenge to simultaneously realize both high gravimetric energy density (EDg) and good processability. Herein, we report a convenient route to prepare PSTFs with improved EDg and good processability by using 4-bromomethyl-azobenzene (Azo-Br) to quaternize polymers of intrinsic microporosity. The as-prepared Azo-PDAT possesses a high EDg of 180.2 J g–1, and its azo moiety has an energy storage enthalpy (ΔH) of 272.1 kJ mol–1, which are 4.4 and 23.9 times higher than those of parent Azo-Br, respectively. In comparison, Azo-MTLE shows a relatively low EDg of 129.8 J g–1 due to the hindrance of photoisomerization by the relatively flexible polymer backbones and decreased micropores. Furthermore, Azo-DDM was synthesized to represent a repeat unit of the as-prepared PSTFs and exclude micropores and polymer backbones, demonstrating the cation−π interactions for enhancing energy storage. Hence, the improved EDg of Azo-PDAT is attributed to the synergetic effect of cation−π interactions, intrinsic microporosity, and template-enforced steric strain. Both Azo-PDAT and Azo-MTLE show good processability for the success of electrospinning. The robust cyclability and macroscale heat-release with a temperature difference of 6.6 °C were achieved for Azo-PDAT, exhibiting good prospects in intelligent temperature-controlled fabrics.