Photoresponsive permeation characteristics of a ternary composite membrane of polymer/artificial lipid/azobenzene derivative

A ternary composite membrane composed of polymer/artificial lipid/azobenzene derivative was prepared by casting from a tetrahydrofuran solution of poly(vinyl chloride) (PVC), dioctadecyldimethylammonium bromide (DOAB) and p-ω-hydroxypropyloxy-p′-dodecyloxy azo-benzene (AZO). AZO dispersed almost molecularly within the multilayer liposome of artificial lipid (DOAB), and even in the ternary composite membrane, AZO exhibited trans-cis photoisomerization in a similar manner to that in solution. The water or ion permeations through the composite membrane apparently increased upon the irradiation of ultraviolet (UV) light when artificial lipids were in a liquid crystalline state. The water permeability coefficient, P depended on the trans-fraction of AZO. This suggests that the conformational change due to the trans-cis photoisomerization of AZO makes compact packing of artificial lipid molecules around AZO loosed, being followed by formation of permeation channel.