Electro-Optical Behavior of a Novel Strong-Weak and Weak-Weak Anchored Large-Pitch Cholesteric

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Abstract
The electro-optical behavior of strong-strong, strong-weak and weak-weak anchored tilted and reversely-tilted large-pitch cholesterics has been investigated. The weak anchoring has been achieved after rubbing with soap the previously mechanically-rubbed glass plates. Under a voltage excitation, the most important reversely-tilted weak-weak anchored cholesteric layers giving rise to a nearly-planar Grandjean-like texture showed the appearance of a Helfrich's instability, followed by a π/2 rotation of the helix and finally, a scroll texture which compactly disappeared into a completely unwinded cholesteric. When voltage was switched off, the unwinded cholesteric was returned to the initial Grandjean-like texture for the case of a low voltage (U < 3Uth, where Uth is the threshold voltage for the Helfrich's instability) or has been transformed into a finger-print texture for higher voltages. This novel boundary-induced bi-stability is related to the weakness of the surface anchoring. In addition, attention has been paid on the important electro-optical behavior of the well-known, however insufficiently investigated, finger-print texture embedded into a homeo-tropic matrix.