Photoinduced switching of ionic conductivity by metal ion complexes of vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain

Abstract

Vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain were synthesized and their photoresponsive ion-conducting behavior was investigated in the presence of sodium perchlorate. Any of the copolymers or the homopolymer of crowned azobenzene can undergo photochemical switching of ionic conductivity in composite films containing an ion-conducting carrier. UV-light-induced isomerization of the azobenzene moiety causes some disorder in the crown ether moiety (an ion-hopping site), in the liquid crystal state of the polymers, thus decreasing ionic conductivity, and this is reversed by subsequent visible-light irradiation. The highest magnitude in the photoinduced ionic-conductivity changes was attained in polymers containing the highest content of crowned azobenzene moiety, owing to the more efficient photoinduced phase transition. The polymers with the highest content of crowned azobenzene moiety also showed the fastest response in photoinduced switching.