Nonlinear orientational interaction of a nematic liquid crystal with a heat flux

We have observed the influence of heat flux on the orientation of a nematic liquid crystal (NLC), which initially occurred in a homogeneously oriented state. The action of a spatially periodic heat flux leads to a change in the NLC director orientation, which is not accompanied by a hydrodynamic flow. The pattern observed in a polarized light resembles the system of bands that arises during the Fr,edericksz transition in a static spatially periodic electric field. It is concluded that the observed behavior is evidence for the existence of orientational thermoelasticity, which is determined by the quadratic dependence of the director deviation on the temperature gradient. The observation of this thermoorientational interaction contradicts the commonly accepted notions, according to which the director of a mirror-symmetric liquid crystal must be immobile.