Nonequilibrium patterns in the electric-field-induced splay Fréedericksz transition

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Abstract
Static and dynamic behavior around the electrically driven Fréedericksz transition in a nematic liquid crystal [4-pentyl-4’-cyano-biphenyl, Merck K15 (5CB)] with large dielectric anisotropy has been studied experimentally as well as theoretically. Nematodynamic equations have been solved and numerical results for the homogeneous distortion and its dynamics have been compared with the experiment. The effect of the conductivity, that of the surface anchoring and a pretilt, as well as the influence of the magnitude of the dielectric anisotropy, has been treated and compared with the experiment. The surface anchoring constant has been determined. A two-dimensional fluctuating structure was detected, which becomes visible slightly below the transition and originates presumably from the thermal director fluctuations. In the dynamical regime a transient pattern also arises, consisting of a set of fairly regular stripes with a preferred direction parallel to the initial director alignment. The distribution and the time behavior of the light intensity of the patterns has been measured and growth rates have been determined.