Teixeira, Paulo2016-12-212016-12-212017-02-05TEIXEIRA, Paulo Ivo Cortez - Very low surface tension liquid–vapour interfaces of patchy colloids. Colloids and Surfaces A: Physicochemical and Engineering Aspects. ISSN 0927-7757. Vol. 514 (2017), pp. 63-680927-7757http://hdl.handle.net/10400.21/6638The liquid–vapour interface of a model of one-component patchy colloids is re-visited. The model consistsof hard spheres decorated with short-ranged attractive sites (‘patches’) of different types on their surfaces.In an earlier paper [A. Oleksy and P.I.C. Teixeira, Phys. Rev. E 91 (2015) 012301], the density-functionaltheory (DFT) form of Wertheim’s first-order perturbation theory (TPT1) was used to study a realisationof this model with two patches of type A and nine patches of type B (2A9B colloids), which exhibit re-entrant liquid–vapour coexistence curves and very low-density liquid phases. Here, it is shown that thenon-monotonic temperature dependence of the surface tension and interface thickness in this modelcan be qualitatively reproduced by a local DFT, where the spatial non-uniformity is introduced throughthe square gradient of the density multiplied by a density-dependent prefactor. This simpler theory isthen applied to colloids decorated with two patches of type A and ten patches of type B (2A10B colloids),and interactions chosen so as to exhibit a closed-loop phase diagram when only AA and AB bonds arepresent [N.G. Almarza et al., J. Chem. Phys. 137 (2012) 244902]. In this case, the surface tension goesto zero at both upper and lower critical points, with a maximum at some intermediate temperature. AsBB attractions are gradually switched on, the lower critical point disappears and the surface tension vstemperature curve acquires a very deep minimum at a temperature lower than that of the maximum. Onfurther increasing the strength of the BB attractions, both the minimum and the maximum disappear andthe surface tension becomes a monotonically decreasing function of the temperature, as in atomic fluids.The very low surface tension at the minimum for weak BB attractions, combined with the ability to formphysical gels, suggests that 2AnB colloids might be exploited as temperature-controlled surfactants andfoam stabilizers.engPatchy colloidsLiquid–vapour transitionInterfacial propertiesjournal articlehttp://dx.doi.org/10.1016/j.colsurfa.2016.11.034