Eur. Phys. J. E (2012) 35: 50
https://doi.org/10.1140/epje/i2012-12050-9

Regular Article

Lyotropic mixture made of potassium laurate/1-undecanol/K₂SO₄/water presenting high birefringences and large biaxial nematic phase domain: a laser conoscopy study

¹ Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, 14280, Bolu, Turkey
² Instituto de Física, Universidade de São Paulo, 05314-970, São Paulo, SP, Brasil

^* e-mail: afigueiredo@if.usp.br

Received: 15 February 2012
Revised: 18 April 2012
Accepted: 30 May 2012
Published online: 22 June 2012

Abstract

The lyotropic liquid crystalline quaternary mixture made of potassium laurate (KL), potassium sulphate, 1-undecanol and water was investigated by experimental optical methods (optical microscopy and laser conoscopy). In a particular temperature and relative concentrations range, the three nematic phases (two uniaxial and one biaxial) were identified. The biaxial domain in the temperature/KL concentration surface is larger when compared to other lyotropic mixtures. Moreover, this new mixture gives nematic phases with higher birefringence than similar systems. The behavior of the symmetric tensor order parameter invariants σ ₃ and σ ₂ calculated from the measured optical birefringences supports that the uniaxial-to-biaxial transitions are of second order, described by a mean-field theory.