Frederiks Transition in the Nematic and Smectic A Phases of Polar Thioesters

Chruściel, J.; Czerwiec, J.M.; Jaglarz, Magdalena; Marzec, M.; Wawrzyniak, Adriana; Ossowska‐Chruściel, M. D.; Wróbel, S.

doi:10.1080/15421406.2011.572782

Cited by 1 publication

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“…So far the Frederiks transition has not been established in the TGBA phase and even in the SmA phase it is quite rare. 16 The reason might be ascertained in the complicated reversing process in smectics. While in nematics the field rotates each molecule separately, in smectics the layering prevents such a process.…”

Section: Resultsmentioning

confidence: 99%

Unique effect of an electric field on a new liquid crystalline lactic acid derivative

et al. 2015

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A new chiral lactic acid derivative is presented, exhibiting a frustrated liquid crystalline phase, namely the orthogonal twist grain boundary TGBA phase in a broad temperature interval. A unique effect is observed that the applied electric field reversibly transforms the planar TGBA texture to the homeotropic one, homogeneously dark in crossed polarizers. The transformation is analogous to the Frederiks transition known in nematics, in which switching under electric field is driven by the positive dielectric anisotropy. A similar effect is established also in the SmA phase of the racemic mixture, where the field induced transformation is irreversible. A positive dielectric anisotropy in both the chiral compound and the racemic mixture is detected up to the frequency of about 10 kHz, above this frequency the anisotropy is negative. The unusual behavior of the TGBA phase under the electric field can be explained by the specific packing of molecules within the smectic layers, resulting in a relatively high layer compressibility which lowers the energy of the structural defects and thus facilitates the structure transformation. The perfectly dark state of the studied compounds, induced by the electric field, either stable or reversible, is appealing for specific applications. The change of the sign of the dielectric anisotropy, known in nematics as the dual frequency effect, might be important for photonics such as adaptive or diffractive optics.

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Section: Resultsmentioning

confidence: 99%