Polar orientational phase transition in smectic monolayers induced by monolayer compression

Abstract

Taking into consideration the mean electric field produced by a molecular configuration, a self-consistentfield state equation is derived to describe the behavior of polar smectic phase for monolayers. A general equation of orientational phase transition between a normal-director phase and a tilted-director phase induced by monolayer compression for monolayers is obtained. It was revealed that smectic monolayers show a possible second-order orientational phase transition under a necessary condition 4216/gy,gz,gy/4. Here gy and gz are two parameters proportional to the internal electric fields in the directions parallel and perpendicular to the monolayer surface, respectively. The two-dimensional orientational phase transition theory developed here may reveal such a transition in smectic monolayers by some techniques, for example, the Maxwelldisplacement-current measuring technique. @S1063-651X~98!03605-8#