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1988
Conference Paper
Titel
Distorted and homogenous structures of thin ferroelectric liquid crystals layers stabilized by various boundary conditions
Alternative
Verdrillte und homogene Strukturen in randstabilisierten ferro-elektrischen Flüssigkristallschichten
Abstract
Since the discovery of the surface stabilized ferroelectric liquid-crystal layers by Clark and Lagerwall, several other layer structures with suppressed conical pitch have been discussed, as for example splayed, tilted and bent layers as well as chevron structures. In this paper observations about the stability of polar and apolar structures in thin ferroelectric liquid-crystal layers are reported. These observations were carried out at different temperatures and for different treatments and distance of the supporting plates. In order to explain the observed effects, an attempt was made to summarize the know defect-free layer structures and to complete them in a schematic way. Some classes of novel uniformly distorted layer structures are proposed. Some of them show an external polarization, others have a polarization compensated externally with respect to the substrate normal. In addition, calculations of the free elastic energy of the different possible structures were carried out. K eeping the smectic tilt angle Theta constant within the layers, no restrictions on the values of the elastic constants were introduced. In contrast to previous calculations, also the parameters for the spontaneous twist and bend were taken as independent from each other. It was found that for special combinations of material parameters transversally twisted states can have a lower free elastic energy than a homogeneous state. (-y-)
Language
English