DYNAMICS OF JUMP-WISE TEMPERATURE PITCH VARIATIONS IN PLANAR CHOLESTERIC LAYERS FOR FINITE STRENGTH OF SURFACE ANCHORING
Belyakov V.A.

Received: September 15, 2003

PACS: 61.30.-v, 68.15.+e

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The dynamics of pitch jumps in cholesteric layers with finite surface anchoring strength at temperature variations is investigated theoretically. General expressions are presented that connect the dynamics of the pitch jumps with the parameters that determine the process, such as the viscosity, the specific form of the anchoring potential, and the dimensionless parameter S_d=K₂₂/Wd, where W is the depth of the anchoring potential, K₂₂ is the twist elastic modulus, and d is the layer thickness. It is found that the shape of the anchoring potential essentially influences the temporal behavior of the cholesteric helix in the process of a pitch jump. To illustrate this revealed dependence of the pitch jump dynamics on the shape and strength of the anchoring potential, the problem was investigated for two different models of the surface anchoring potential for a jump mechanism connected with the slipping of the director at the surface over the barrier of the anchoring potential. Calculations for the unwinding (winding) of the helix in the process of the jump were performed to investigate the case of infinitely strong anchoring on one surface and finite anchoring on the other, which is important in applications. The results show that an experimental investigation of the dynamics of the pitch jumps will allow one to distinguish different shapes of the finite strength anchoring potential, and in particular, will provide a means for determining whether the well-known Rapini-Papoular anchoring potential is the best suited potential relevant to the dynamics of pitch jumps in cholesteric layers with finite surface anchoring strength. The optimal conditions for the experimental observation of the phenomena discussed here are briefly considered.