Phase behavior of the cetyltrimethylammonium tosylate (CTAT)-water system

Abstract

A partial phase diagram of the cetyltrimethylammonium tosylate (CTAT)-water system has been constructed from polarizing optical microscopy and small-angle x-ray scattering studies. This system is found to exhibit a nematic phase over a wide range of CTAT concentration, from about 32 to 45 wt.%, which is very unusual for aqueous solutions of pure surfactants. At higher CTAT concentrations a hexagonal phase occurs which is stable up to at least 90 degrees C. Detailed analysis of the diffraction data confirms that the hexagonal phase consists of long cylindrical micelles arranged on a two-dimensional hexagonal lattice. (C) 2012 Elsevier B.V. All rights reserved.