PHOTORESPONSIVE CONDUCTIVITIES OF COPOLYMERS OF 3-HEXYLTHIOPHENE AND AZOBENZENE-MOIETY MODIFIED 3-HEXYLTHIOPHENE

Photoresponsive conductivities of copolymers of 3-hexylthiophene and azobenzene-modified 3-hexylthiophene prepared by chemical oxidation with FeCl3 were measured by placing a thin film (40 mum thick) in between an ITO glass and a disk-like Cu electrode. Upon irradiation of UV-light (lambda=365 nm) (100 W Hg-lamp), conductivities of the copolymers increase by a factor of 0. 1 to 1.5 depending on the amount of the azobenzene moiety within 5 min to maxima and, upon turning off the light, return to original levels within the same period of time. Reversibility of the photoresponsive conductivity is excellent. It is found that the increase in conductivity upon irradiation is not due to a variation in interchain distance resulting from trans-cis isomerization in the azobenzene-moiety. This phenomenon can be attributed mainly to a generation of photoexcited hopping sites in the azobenzene moiety.