Light-induced capacitance switching in spiropyran-based capacitors

Photoresponsive components for electric and electronic systems have received considerable attention, mainly due to the low cost of used materials and their manufacturing in mild conditions. Optically responsive materials have been prepared blending polymers with photochromic molecules to obtain systems with tuneable properties. Among photoresponsive systems, some have been developed to provide light-induced capacitance switching. Reported systems have been obtained from polymeric blends with azobenzenes and diarylethenes, while spiropyran copolymers were not yet fully investigated. To form a better view of photochromic materials performances in this field, we report the behaviour of three spiropyran-based dielectric materials in active capacitors. We studied the UV- and temperature-dependent switching of systems by varying test conditions. Materials, selected on their thermomechanical properties, clearly indicate their optical responsiveness, with significant dielectric properties changes in respect to reference materials non containing spiropyran moieties. We also demonstrate that light-induced capacitance switching is mainly related to spiropyran-to-merocyanine isomerization, thus the phenomenon is reversible after the inverse isomerization in the dark. The observed reversible and replicable capacitance switching allows using prepared materials in reusable responsive electronic systems.