We report the observation of a novel isotropic phase of amphiphile bilayers in a mixed system consisting of the ionic surfactant, sodium docecylsulphate (SDS), and the organic salt p-toludine hydrochloride (PTHC). This system forms a collapsed lamellar (Lα) phase over a wide range of water content, which transforms into an isotropic phase on heating. This transition is not observed in samples without excess water, where the Lα phase is stable at higher temperatures. Our observations indicate that the Lα - isotropic transition is driven by the unbinding of edge dislocation loops and that the isotropic phase in the present attraction-dominated system is the analogue of the sponge phase usually seen in amphiphile systems dominated by interbilayer steric repulsion.
@article{arxiv.1111.5902,
title = {A defect mediated lamellar to isotropic transition of amphiphile bilayers},
author = {Antara Pal and Georg Pabst and V. A. Raghunathan},
journal= {arXiv preprint arXiv:1111.5902},
year = {2011}
}