The nematic liquid crystal free surface

We now turn our attention very briefly to the nematic liquid crystal surface. A variety of experimental studies have established conclusively that orientationally ordered states, and in certain materials even density modulations, develop in the vicinity of the free surface. We describe below the salient features of these observations. 

Open circles represent measurements using the pendant drop method. Filled circles in (c) are values determined independently by Gannon and Faber using the 

It is a well known result that the gradient of the surface tension (y) versus temperature is directly related to the surface excess entropy per unit area as 

Light scattering and optical reflectivity studies again reveal the existence of orientational ordering at the surface. For MBBA it is found 

Smectic and cybotactic nematic systems may be expected to show an oscillatory density profile near the surface. That this is the case has been strikingly demonstrated by the very fine X-ray reflectivity measurements of Pershan et (figs. 2.7.3 and 2.7.4). Surface-induced smectic 

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