Photo-induced electrical switching through a mainchain polymer

A copolymer of diarylethene and trimethylsilyl-substituted p-phenylene vinylene (TPV) was synthesized to achieve photo-induced electrical change in a solid medium. The photo-isomerization of the polymer was induced by incorporating a 2,3-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene (BTF) unit, while TPV units directly connected to BTF allowed the extension of π-electron delocalization. The conductivity of the polymer was significantly increased when the BTF unit was converted to a closed form (colored) using UV light. The conductivity switching was reversible by using UV and visible-light sources. The neat polymer film showed higher conductivity, while the doped polymer film with a BTF-TPV content of 10 wt% showed conductivity that was 10 times smaller than that of the neat polymer film, as estimated by the I-V plot on a photocell structured as Au/polymer/ITO. This shows the importance of π-electron connectivity through a mainchain polymer.