Photo-excitable membranes. Photoinduced membrane potential changes across poly(vinyl chloride) membranes doped with azobenzene-modified crown ethers

The membrane potentials across a plasticized poly (vinyl chloride) (PVC) membrane entrapping azobenzene-modified 15-crown-5 (1) or 18-crown-6 (2) were measured under conditions of u.v. and visible light irradiation. Irradiation induced significant potential changes across the membranes, of a magnitude depending on the cation species, on the ionic concentration in the solution, and on the crown ether content in the membrane. The sign of the potential shift was dependent upon the direction from which the membrane was irradiated. The results are explained in terms of surface potential changes at both surfaces of the membrane, associated with the release of cations from the membrane phase into the solution upon irradiation.