Photo‐Switching Thermal and Lithium‐Ion Conductivity in Azobenzene Polymers

Developing materials with dynamic control over multiple transport properties is crucial for developing responsive energy management. Utilizing in situ time‐domain thermoreflectance (TDTR), synchrotron X‐ray scattering, and electrical impedance spectroscopy (EIS), a light‐responsive azobenzene polymer (pPPHM) is demonstrated, featuring simultaneously photo‐switchable thermal and ionic transport properties. Through UV and visible light illumination, pPPHM undergoes a reversible phase transition from a crystalline solid trans state to an amorphous liquid cis state driven by the conformational change of azobenzene moieties. The ordered crystalline structure in the trans state creates pathways for efficient thermal transport while restricting ion mobility, whereas the disordered amorphous state in the cis configuration disrupts thermal conductivity pathways but enables facile ion diffusion. This structural reorganization causes thermal conductivity to switch between solid trans (0.45 W·m −1 ·K −1 ) and liquid cis (0.15 W·m −1 ·K −1 ) states, while ionic conductivity shows 100 fold enhancement compared to liquid trans (≈10 −7 cm 2 ·s −1 ) and liquid cis (≈10 −5 cm 2 ·s −1 ) states. This dual transport offers functional energy materials that can adapt to changing conditions. For example, smart batteries that prevent overheating and regulate ion flow, thermal interfaces that switch between insulating and conducting modes on demand, and solid electrolytes that activate only when needed. These materials will replace multiple separate components with a single responsive system.