The temperature dependence of liquid-crystal tilt angles

Abstract

The temperature behavior of various liquid crystals has been studied on obliquely evaporated SiOx (α°) layers. The structure of such layers is discussed and the competition between the effects of two inherent anisotropies of these layers is indicated as the possible origin of the observed temperature dependence of the tilt angle. Attention is also paid to the structure of liquid-crystal layers close to the nematic to isotropic transition temperature (clearing point). Experimental results for tilt angles as a function of temperature have been adapted to a two-torque model, which is suggested by the above considerations. This allows comparison between the structural data for SiOx and the parameters from the two-torque model. It is found that indeed one of the directions of preference is connected roughly with the columnar axis of the SiOx.