Orientational transition of P-pentyl-p '-cyano-biphenyls triggered by conformational change of surface azobenzene monolayer

We examined the orientational transition process of p-pentyl-p'-cyano-biphe nyl (5CB) molecules in liquid-crystal (LC) cells triggered by the conformat ional change of the surface azobenzene monolayer on polyimide (PI) Langmuir -Blodgett (LB) films, by measuring the optical transmittance and the electr ical capacitance simultaneously. The experimental results were analyzed usi ng a continuum theory describing the free energy of LC cells. It was shown that the motion of 5CB molecules triggered by the surface azobenzene monola yer on PI LB films was ruled by the continuum theory. The transmittance and the capacitance of the LC cells with 1-layer PI LB films were changed reve rsibly by the alternating irradiation of ultraviolet (UV) and visible light , whereas those of LC cells with 5- and 11-layer PI LB layers were not chan ged reversibly. These results were discussed, taking into account the diffe rence in the anchoring strength of PI LB films.