PHOTORESPONSIVE MEMBRANES INCORPORATING 6-SUBSTITUTED 1',3',3'-TRIMETHYLSPIRO-(2H-1-BENZOPYRAN-2,2'-INDOLINES)

Photoresponsive membranes incorporating 6-X-1',3',3'-trimethylspiro-(2H-1-benzopyran-2,2'-indolines) (6-X-BIPS), with X equals H, OH, Br, NO2 and 1',3',3'-trimethylspiro-(2H-1-naphthopyran-2,2'-indoline) (NIPS), supported by cellulose 2,4-diacetate, have been prepared. Membrane potentials, while irradiated by visible and UV light alternatively, in a pH range between 0. 5 and 10, were found to depend not only on the photochemical equilibrium between 'closed' and 'open' forms of 6-X-BIPS, but also on pH. Isoelectric points of membranes, which substantially coincide with zero point charge of 6-X-BIPS, were found to be independent of X substituents.