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

Abstract

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 ± 0.40 μm⁻¹.

Keywords:

• Lyotropic liquid crystal
• cholesteric phases
• phase transition
• brucine
• helical twisting power
• intrinsically biaxial micelles model

Acknowledgments

We thank The Scientific and Technological Research Council of Turkey (TÜBİTAK), and Abant Izzet Baysal University Directorate of Research Projects Commission (BAP, grant number: 2012.03.03.529) from Turkey; the National Institute of Science and Technology on Complex Fluids (INCT-FCx), CNPq and FAPESP from Brazil for supporting this study.