Ring-Pattern Dynamics in Smectic-C*and Smectic-CA*

Abstract

Ring patterns of concentric 2pi solitons in molecular orientation form in freely suspended chiral smectic-C films in response to an in-plane rotating electric field. We present measurements of the driven dynamics of ring formation under conditions of synchronous winding and of the zero-field relaxation of ring patterns, and propose a simple model which enables their quantitative description in low polarization DOBAMBC. In smectic-C*A TFMHPOBC we observe an odd-even layer number effect, with odd layer number films exhibiting order of magnitude slower relaxation rates than even layer films. We show that this rate difference is due to a much larger spontaneous polarization in odd layer number films.

Vortex Flow in Freestanding Smectic Films Driven by Elastic Relaxation of thecDirector

“…Regular director distortions are prepared by an electric field and their relaxation is monitored. In an earlier study of a similar experiment [3], Link et al have measured the c-director relaxation and described it by a model derived from the standard nematic equations, involving the rotational viscosity for the c director. They neglected flow and achieved satisfactory qualitative agreement with experimental data.…”

“…The plain geometry, uncomplicated preparation and handling, and easy observability of the dynamic variables make these films very attractive scientific research objects. The dynamics of simple director textures, including targets and spirals, in freestanding smectic films [1][2][3][4][5][6][7][8][9] as well as the observation of flow patterns, driven mechanically [8,9], electrically [10 -13], or thermally [14], have been described. Interestingly, there has been no quantitative analysis of macroscopic flow driven purely by orientational elastic relaxation in such systems so far.…”

2πandπwalls in antiferroelectric smectic-CA*and smectic-Долганов1, Bolotin2, Fukuda3 2004Phys. Rev. E

“…The reason for such behavior of N-odd films, as well as a large displacement of outer bands in electric field, is not understood. It should be noted that earlier unusual behavior of N-odd films has been also pointed out, in particular, an intriguing odd-even dependence of the ring-pattern relaxation and the ratio of viscous and elastic constants / K on layer numbers was reported [8]. In N-odd films this ratio essentially depends on the transverse polarization.…”

“…In N-odd films this ratio essentially depends on the transverse polarization. Link et al [8] explained this phenomena by the influence of a large net transverse polarization in N-odd films. Possibly, the unusual behavior of N-odd films in a magnetic field and nonuniform halfwidths of outer bands in an electric field is also connected with their larger polarization than that of N-even films.…”

“…Pindak et al [4] determined K / P (P is the layer polarization) from measured wall widths in ferroelectric free-standing films. A similar method was used by Link et al [8] for measurement of transverse layer polarization in antiferroelectric SmC A * films. The ratio K / was measured from the collapse rate of circular walls in the SmC * and SmC A * free-standing films [4,8] and from linear wall mobility in SmC films [9].…”