Smectic ordering in nematic and smectic liquid-crystalline films probed by means of surface light scattering.

Abstract

We present the first results of experiments that measure the intensity of light scattered by capillary waves on the surface of free-standing liquid-crystalline thin films. The intensity of the scattered light provides information about the surface tension of the liquid-air interfaces and, more interestingly, about the interactions between the surfaces as a function of the film thickness. Light scattering experiments performed on 4-n-octyl-4’-cyanobiphenyl (8CB) in the nematic phase show the sudden onset of a strong interaction between the interfaces when the film thickness is decreased. The range of this interaction increases with decreasing temperature. The suppression of the out-of-phase capillary waves coincides with the point where the range of surface-induced smectic ordering becomes comparable to the film thickness. We argue that these experiments probe the growth of the interlayer elasticity modulus B. .AE