POLAR ORIENTATIONAL PHASE-TRANSITION IN SMECTIC MONOLAYERS INDUCED BYMONOLAYER

Taking into consideration the mean electric field produced by a molecu lar configuration, a self-consistent-field state equation is derived t o describe the behavior of polar smectic phase for monolayers. A gener al equation of orientational phase transition between a normal-directo r phase and a tilted-director phase induced by monolayer compression f or monolayers is obtained. It was revealed that smectic monolayers sho w a possible second-order orientational phase transition under a neces sary condition 4-16/g(y)<g(z)<g(y)/4, Here g(y) and g(z) are two param eters proportional to the internal electric fields in the directions p arallel and perpendicular to the monolayer surface, respectively. The two-dimensional orientational phase transition theory developed here m ay reveal such a transition in smectic monolayers by some techniques, for example, the Maxwell-displacement-current measuring technique.