Abstract
.Inspired by experimental work on colloidal cuboid-polymer dispersions (Rossi et al., Soft Matter, 7, 4139 (2011)) we have theoretically studied the phase behaviour of such mixtures. To that end, free volume theory (FVT) was applied to predict the phase behaviour of mixtures of superballs and non-adsorbing polymer chains in a common solvent. Closed expressions for the thermodynamic properties of a suspension of hard colloidal superballs have been derived, accounting for fluid (F), face-centred cubic (FCC) and simple cubic (SC) phase states. Even though the considered solid phases are approximate, the hard superballs phase diagram semi-quantitatively matches with more evolved methods. The theory developed for the cuboid-polymer mixture reveals a rich phase behaviour, which includes not only isostructural F1-F2 coexistence, but also SC1-SC2 coexistence, several triple coexistences, and even a quadruple-phase coexistence region (F1-F2-SC-FCC). The model proposed offers a tool to asses the stability of cuboid-polymer mixtures in terms of the colloid-to-polymer size ratio.Graphical abstract
Highlights
Ness [12, 13] in lyotropic systems have received increasing attention [14, 16]
The calculated phase diagram for a suspension of pure hard superballs is presented in fig. 6, and compared with more evolved simulation results
A simple model for the thermodynamic properties of superballs was presented, where all thermodynamic functions required for the phase diagram calculation are expressed in closed form
Summary
Ness [12, 13] in lyotropic systems have received increasing attention [14, 16]. analytical treatments for entropic patchiness between non-axisymmetric particles are scarce. A commonly applied model to describe colloidal cuboids is the superball shape. A a a where a is the radius of the superball (the shortest distance from the centre of the superball to its surface) and m is the shape parameter. The phase behaviour of colloidal superballs has been studied both experimentally [18, 27] and via computer simulations [26, 28, 29]. Some experimental studies on the effect of non-adsorbing polymers on the phase behaviour of colloidal superballs have been conducted [22, 30]. We provide a reproducible, closed model whose insights may provide a better understanding of experimentally observed phase behaviour of superball-polymer mixtures [22, 30]
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