Optical signals of uniaxial and biaxial cholesteric lyotropic phases

Lyotropic cholesteric liquid crystalline phases were prepared by doping the ternary mixture of potassium laurate eth KL/decanol (DeOH)/ deuterium oxide (D2O) with brucine sulphate, in two different concentrations. Using the variation of the average color in a heating cycle, with and without the insertion of compensator a gypsum plate (1 lambda), in the light path, the optical signal of the cholesteric phases Ch(D)(-)& nbsp;(Ch(C)(+) ) was confirmed as being negative(positive). When the biaxial cholesteric phase (Ch(B)) is between two uniaxial phases (Ch(D) -Ch(B)-Ch(D)) or (Ch(D) -Ch(B) -Ch(C)), the sign of the ChB phase depends on the uniaxial phase in its vicinity. In the case (Ch(D)(-)-Ch(B)-Ch(D)(-), the phase Ch(B) has a negative optical signal (Ch(B)(-)) across the domain. However, if the ChB phase is between uniaxial cholesteric phases of opposite optical signals, it cannot have just one signal, but must have a change at some point in the biaxial domain showing (Ch(D)(-)-Ch(B)-Ch(B)(+)-Ch(C)(+)) phase sequence.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

By studying the optical signals of lyotropic cholesteric liquid crystalline phases under different conditions, it was found that the optical signal of the biaxial cholesteric phase depends on the phases surrounding it when situated between uniaxial cholesteric phases, and must undergo a change if located between uniaxial phases with opposite optical signals.