Swelling and shrinking kinetics of a lamellar gel phase

TL;DR

This study examines the swelling and shrinking behavior of lamellar gel phases upon contact with polymer solutions, revealing diffusion-like kinetics and a model that describes the composition-dependent swelling coefficient.

Contribution

It introduces a generic model that quantitatively describes the swelling coefficient's dependence on composition in lamellar gel phases.

Findings

Swelling follows a diffusion-like square root time dependence.

Increasing polymer concentration leads to slower swelling, no swelling, and eventual shrinking.

The diffusion coefficient aligns with previous measurements.

Abstract

We investigate the swelling and shrinking of L_beta lamellar gel phases composed of surfactant and fatty alcohol after contact with aqueous poly(ethylene-glycol) solutions. The height change $\Delta h(t)$ is diffusion-like with a swelling coefficient, S: $\Delta h = S \sqrt{t}$. On increasing polymer concentration we observe sequentially slower swelling, absence of swelling, and finally shrinking of the lamellar phase. This behavior is summarized in a non-equilibrium diagram and the composition dependence of S quantitatively described by a generic model. We find a diffusion coefficient, the only free parameter, consistent with previous measurements.