Diffusion Coefficients in a Lamellar Lyotropic Phase: Evidence for Defects Connecting the Surfactant Structure

TL;DR

This study measures diffusion in a lamellar lyotropic phase and finds a sharp increase near the phase transition, attributed to defects connecting surfactant layers, with estimations of defect density and energy variations.

Contribution

It provides experimental evidence linking defect structures to diffusion behavior near phase transitions in lyotropic surfactant systems.

Findings

Diffusion coefficient sharply increases near the phase transition.

Defect density and energy variation estimated close to transition.

Defects likely facilitate enhanced diffusion across layers.

Abstract

We measure diffusion coefficients in the lamellar phase of the nonionic binary system C$_{12}$EO$_6$/H$_2$O using fluorescence recovery after photobleaching. The diffusion coefficient across the lamellae shows an abrupt increase upon approaching the lamellar-isotropic phase transition. We interpret this feature in terms of defects connecting the surfactant structure. An estimation of the defect density and of the variation in defect energy close to the transition is given in terms of a simple model.