Metallic-Ion Controlled Dynamic Bonds to Co-Harvest Isomerization Energy and Bond Enthalpy for High-Energy Output of Flexible Self-Heated Textile.

Abstract

Molecular light‐harvesting capabilities and the production of low‐temperature heat output are essential for flexible self‐heated textiles. An effective strategy to achieve these characteristics is to introduce photoresponsive molecular interactions (photodynamic bonds) to increase the energy storage capacity and optimize the low‐temperature photochromic kinetics. In this study, a series of sulfonic‐grafted azobenzene‐based polymers interacted with different metal ions (PAzo‐M, M = Mg, Ca, Ni, Zn, Cu, and Fe) to optimize the energy level and isomerization kinetics of these polymers is designed and prepared. Photoinduced formation and dissociation of M—O dynamic bonds enlarge the energy gap (∆E) between trans and cis isomers for high‐energy storage and favor a high rate of isomerization for low‐temperature heat release. The suitable binding energy and high ∆E enable PAzo‐M to store and release isomerization energy and bond enthalpy even in a low‐temperature (−5 °C) environment. PAzo‐Mg possesses the highest energy storage density of 408.6 J g−1 (113.5 Wh kg−1). A flexible textile coated with PAzo‐Mg can provide a high rise in temperature of 7.7–12.5 °C in a low‐temperature (−5.0 to 5.0 °C) environment by selectively self‐releasing heat indoors and outdoors. The flexible textile provides a new pathway for wearable thermal management devices.