Reentrant isotropic – discotic nematic phase transition: a critical exponent study

Abstract

In this work the critical exponents associated with the behavior of the macroscopic orientational order parameter are determined near the reentrant isotropic (I_RE)–discotic nematic (N_D) and N_D–isotropic (I) phase transitions in a lyotropic mixture of potassium laurate, decanol and D₂O by measurement of optical birefringence. The critical exponents found indicate that the low temperature N_D–I_RE phase transition is quasi‐continuous, having a critical exponent, β₁∼0.17, which is markedly different from that found at the classical N_D–I phase transition, β₂∼0.38. The results are discussed and compared with others obtained with different lyotropic mixtures.

Acknowledgments

We are thankful to the Brazilian Agencies CAPES, Fundação Araucária (PR) and CNPq (PADCT) for financial support of this work.