Dynamic Photothermal Control of Ion Transport in Azobenzene-Based Polymer Networks

Controlling ion mobility in polymers is crucial for applications in batteries, sensors, and soft electronics. Photo-ionics, where light is used as a noninvasive stimulus to direct ion transport, provides a unique opportunity for unprecedented material versatility and spatiotemporal control. Here, we present a method to modulate ionic conductivity in polymer networks using light by incorporating light-responsive azobenzene chromophores as pendant groups within poly(ethylene glycol) networks. These materials exhibit rapid and reversible ionic conductivity enhancement of ≈ 40~110% upon exposure to both UV and visible light, with rapid response times (τ ≈ 30 seconds) and excellent cyclability over multiple cycles without degradation. While previous reports demonstrate that photoisomerization of azobenzene affects ion transport via changes in specific intermolecular interactions, we reveal that photothermal heating dominates ionic conductivity modulation. By using detailed spectroscopy and thermal imaging, we attribute the observed response to localized heating generated within the polymer matrix due to azobenzene moieties that effectively convert light into heat via nonradiative decay. We anticipate that this work could find interesting applications in next-generation electronics, such as flexible batteries, sensors, and actuators, where light-driven control of ion transport could offer advantages in performance and adaptability.