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

• Published in: The European physical journal. E, Soft matter and biological physics Soft matter and biological physics, 2007-11, Vol.24 (3), p.247-250
• Main Authors: BRAGA, W. S, KIMURA, N. M, LUDERS, D. D, SAMPAIO, A. R, SANTORO, P. A, PALANGANA, A. J
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General and physical chemistry; Physics; Solution properties; Solutions; Specific phase transitions; Transitions in liquid crystals
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2007-10234-0

The phase diagram is an interesting field of research, particularly 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 (Deltan is maximum.