Eur. Phys. J. E (2007) 24: 247-250
https://doi.org/10.1140/epje/i2007-10234-0

Regular Article

Reentrant isotropic-calamitic nematic phase transition in potassium laurate-decanol- D₂O mixtures

Departamento de Fısica, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900, Maringá, Brazil

^* e-mail: palanga@dfi.uem.br

Received: 2 August 2007
Accepted: 25 October 2007
Published online: 23 November 2007

Abstract

The phase diagram is an interesting field of research, particulary in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic --N_C and discotic --N_D) and one biaxial nematic (N_B) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I_RE) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I_RE-N_C-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N_C phase, where the absolute value of the optical birefringence (Δn is maximum.