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Issue 12, 2011
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Phase diagrams of binary mixtures of patchy colloids with distinct numbers of patches: the network fluid regime

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Abstract

We calculate the network fluid regime and phase diagrams of binary mixtures of patchy colloids, using Wertheim's first order perturbation theory and a generalization of Flory–Stockmayer's theory of polymerization. The colloids are modelled as hard spheres with the same diameter and surface patches of the same type, A. The only difference between species is the number of their patches – or functionality – f(1)A and f(2)A (with f(2)A > f(1)A). We have found that the difference in functionality is the key factor controlling the behaviour of the mixture in the network (percolated) fluid regime. In particular, when f(2)A ≥ 2f(1)A the entropy of bonding drives the phase separation of two network fluids, which is absent in other mixtures. This drastically changes the critical properties of the system and drives a change in the topology of the phase diagram (from type I to type V) when f(1)A > 2. The difference in functionality also determines the miscibility at high (osmotic) pressures. If f(2)Af(1)A = 1, the mixture is completely miscible at high pressures, while closed miscibility gaps at pressures above the highest critical pressure of the pure fluids are present if f(2)Af(1)A > 1. We argue that this phase behaviour is driven by a competition between the entropy of mixing and the entropy of bonding, as the latter dominates in the network fluid regime.

Graphical abstract: Phase diagrams of binary mixtures of patchy colloids with distinct numbers of patches: the network fluid regime

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Publication details

The article was received on 15 Dec 2010, accepted on 04 Apr 2011 and first published on 23 May 2011


Article type: Paper
DOI: 10.1039/C0SM01493A
Citation: Soft Matter, 2011,7, 5615-5626
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    Phase diagrams of binary mixtures of patchy colloids with distinct numbers of patches: the network fluid regime

    D. de las Heras, J. M. Tavares and M. M. Telo da Gama, Soft Matter, 2011, 7, 5615
    DOI: 10.1039/C0SM01493A

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