Micellar cholesteric lyotropic liquid crystals

Abstract

The physico-chemical properties of cholesteric liquid crystals still provide new insights for researchers investigating the structure, local ordering, and phase transitions in condensed matter physics in spite of the fact that they have been known for more than a century. Among cholesterics, the micellar lyotropic cholesteric liquid crystals present outstanding properties which place them in a special category of complex-fluids. One of these key properties is the possibility for changing the micelle shape and shape anisotropy as a function of temperature and/or relative composition of the mixture. Moreover, the existence of polar and nonpolar regions in the lyotropic cholesteric medium, i.e. the loci of the polar heads and hydrocarbon chains of the amphiphilic molecules, respectively, permits a large number of different types of chiral dopants to induce helical structure in the mesophases. Besides this point, the existence of three types of cholesteric phases, originating from the cholesterization of the two uniaxial and one biaxial nematic phases, opens an interesting field of research into fundamental aspects of phase transition and statistical mechanics. In this review, we put together different aspects of the physics of these liquid crystals, from texture observations in a polarized light microscope, to the structure, local ordering, and phase transitions. Some perspectives of new studies are suggested in the concluding remarks.

Keywords:

• lyotropic
• cholesteric
• chiral
• helix
• phase transitions
• micelles
• biaxial

Acknowledgements

Many friends and colleagues participated in some of the researches reviewed here. It is a pleasure to cite them in this review. One of them was Dr Lionel Liébert (in memoriam), from Orsay, France, who left us too early. The others, just in alphabetic order, are E. Akpinar, Y. Galerne, A.M. Levelut, A.G de Oliveira Filho and D. Reis. Mr. Carlos Roberto Marques made the drawings. Prof. Dr Wayne Seale is acknowledged for helpful discussions. FAPESP, CNPq, CAPES, INCT-FCx and NAP-FCx partially supported this work.