Photoinduced Potential Changes across Poly(vinyl chloride) Membrane Entrapping a Photoresponsive Crown Ether Effects of Light Intensity on the Membrane Potential

Abstract

Effects of light intensity on the photoinduced potential changes across poly(vinyl chloride)(PVC) membrane entrapping a photoresponsive crown ether 4, 4'-bis[3, 4-(1, 4, 7, 10, 13-pentaoxatridecane1, 13-diyl)benzyloxycarbonyl]azobenzene [1] have been discussed. The photochemical isomerization reaction of [1] in the membrane proceeded rapidly when the membrane was exposed to higher intensity ultraviolet (UV) light, while longer time was required for attaining the photostationary state under weaker intensity light (Fig.3). The intensity of UV light as well as the membrane thickness affected the cis-[1] content in the photostationarystate mixture of the irradiated [1] in the membranes (Table.1).
The magnitude of the potential change was appreciably influenced by t he light intensity. The irradiation with higher intensity light resulted in the large potential shift, but the potential shift was small when the light intensity was low (Tables.2 and 3, Figs.5, 6 and 7). This trend of light-intensity dependence was significantly observed for thicker membranes, presumably because of the enhanced difference in cis-[1] content between the opposite surfaces of the thick membranes. These observations support that the photoinduced potential changes stem from the surface potential changes originating from the perturbation in charge density of the membrane surfaces.