Study of the Cholesteric-to-Cholesteric Phase Transitions on the Lyotropic Mixture of KL/K2SO4/1-Undecanol/Water/Brucine Presenting the Cholesteric Biaxial Phase

Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of potassium laurate (KL)/potassium sulfate (K2SO4)/1-undecanol (UndeOH)/water with brucine. The phase diagram was constructed as a function of the brucine concentration. Three cholesteric phases were identified: cholesteric biaxial, calamitic uniaxial, and discotic uniaxial. It was observed that there is a critical brucine concentration (X*(b)) to cholesterize the nematic host phase when the mixture is confined in a thin sample holder, below which the cholesteric helical arrangement is not achieved. The helical twisting power of brucine was calculated as 12.12 +/- 0.40m(-1).