PHOTOCHEMICAL SWITCHING OF IONIC-CONDUCTIVITY IN COMPOSITE FILMS CONTAINING A CROWNED SPIROBENZOPYRAN

Spirobenzopyran derivatives incorporating a monoazacrown ether moiety at thc 8-position, i.e., crowned spirobenzopyrans, have been applied to composite films that undergo Photoinduced switching of ionic conductivity, taking advantage of the Photochemical cation-binding ability changes of the crowned spirobenzopyrans. In plasticized poly(vinyl chloride) films containing LiClO4 arid a crowned spirobenzopyran, which show bi-ionic conducting behavior, isomerization Of the crowned spirobenzopyran to its corresponding merocyanine form Proceeded under UV-irradiated or dark conditions. This depressed the Li+ conduction in the film, thus decreasing its ionic conductivity by about a half. Subsequent visible-light irradiation allowed isomerization back to the spiropyran form, restoring the ionic conductivity to the initial value. Much more significant ionic-conductivity switching with about 20-fold changes was realized in composite films of lithium poly(perfluorosulfonate)/oligooxyethylene diacetate/crowned spirobenzopyran, which are single-ionic conductors, by alternatively turning on and off the visible light.