Maxwell-displacement current generated by cis-trans photoisomerisation in azobenzene-containing Langmuir-Blodgett films

Cis-trans isomerisation induced by light irradiation in polymer Langmuir-Blodgett (LB) films is investigated using the Maxwell-displacement current method and uv-vis spectroscopy. The materials looked at are statistical copolymers of polymethacrylate with azobenzene groups incorporated in the side chains. Relaxation times for cis-to-trans as well as trans-to-cis isomerisation were determined from the Maxwell-displacement current/time plots at different temperatures. Uv-vis spectroscopy showed that the isomerisation process is almost completed after 3 minutes and that the thermal back relaxation requires less then 24 hours. From the experimental results, the change in the normal component of the dipole moment was calculated.