Polymer induced phase coexistence in systems of lamellar phases

TL;DR

This paper presents a theoretical study showing that adding nonadsorbing polymer to lamellar surfactant bilayers induces phase coexistence between two lamellar phases with different spacings, driven by depletion effects, matching experimental observations.

Contribution

The study introduces a theoretical model explaining polymer-induced phase coexistence in lamellar phases, highlighting depletion as the driving mechanism.

Findings

Polymer addition causes coexistence of lamellar phases with different spacings.

The coexistence region forms a closed loop, consistent with experiments.

Depletion effects drive the phase separation.

Abstract

The effect of adding nonadsorbing polymer to a lamellar phase of surfactant bilayers is studied theoretically. We find that the polymer produces coexistence between two lamellar phases of different layer spacings. The coexistence region is a closed loop, as in the experiments of Ficheux et al. [J. de Physique II 5 823 (1995)]. Within our model the coexistence is driven by depletion.