Bulk reorientation driven by orientational transition in a liquid crystal monolayr

建立了Nd: YAG激光表面光学二次谐波产生实验装置。通过对门控积分器的改进，研制了一种新型的信号检测系统，为光学SHG实验提供了广泛的检测能力。我们研究了在云母表面与液晶膜界面处，共吸附的挥发性小分子对液晶单分子取向顺序的影响。随着挥发性分子化学势的增加，在单分子膜中观察到一级取向转变。这种表面转变被证明驱动了先前在这些系统中观察到的大块液晶的重定向。

Experimental set-up for surface optical second harmonic generation (optical SHG) was constructed with Nd : YAG laser. Signal detection system was newly developed with a modification of gated-integrators, which provides a wide range of detection capability for optical SHG experiment.We have studied the effect of coadsorbed small volatile molecules on the orientaional order of liquid crystal monolayr at the interface between a mica surface and a liquid crystal film. As the chemical potential of the volatile molecules was increased, a first order orientational transition was observed in the monolayr. This surface transition is shown to drive the reorientation of bulk liquid crystal previously observed in these systems.