Surface and capillary transitions in an associating binary mixture model

TL;DR

This study explores how surfaces and confinement influence phase separation in an associating binary mixture, revealing that surface and capillary transitions can occur within the one-phase region, with implications for experimental systems.

Contribution

The paper introduces a detailed analysis of surface and capillary transitions in an associating binary mixture under various confinement geometries, highlighting their stabilization in the one-phase region.

Findings

Surface and capillary transitions are stabilized in the one-phase region.

Confinement geometry affects the phase behavior of the mixture.

Results are relevant for interpreting experimental observations.

Abstract

We investigate the phase diagram of a two-component associating fluid mixture in the presence of selectively adsorbing substrates. The mixture is characterized by a bulk phase diagram which displays peculiar features such as closed loops of immiscibility. The presence of the substrates may interfere the physical mechanism involved in the appearance of these phase diagrams, leading to an enhanced tendency to phase separate below the lower critical solution point. Three different cases are considered: a planar solid surface in contact with a bulk fluid, while the other two represent two models of porous systems, namely a slit and an array on infinitely long parallel cylinders. We confirm that surface transitions, as well as capillary transitions for a large area/volume ratio, are stabilized in the one-phase region. Applicability of our results to experiments reported in the literature is discussed.