Thermodynamic defects, instabilities and mobility processes in the lamellar phase of a non-ionic surfactant

Abstract

The lamellar phase Lα of the aqueous solution of the non-ionic surfactants C12E5 and C12E6 shows up many features which do not exist in usual lamellar phases : high mobility of non-thermodynamic defects, structural dislocation loops whose density increases at the approach of the transition towards the high temperature isotropic phase, low temperature curvature instabilities. We discuss these phenomena with regard to the low value of the curvature splay modulus K1 (comparable to that of microemulsions) and molecular models which stress the influence of water linked to the hydrophilic heads