Abstract
Understanding the phase behaviour of mixtures continues to pose challenges, even for systems that might be considered "simple." Here, we consider a very simple mixture of two colloidal and one non-adsorbing polymer species, which can be simplified even further to a size-asymmetrical binary mixture, in which the effective colloid-colloid interactions depend on the polymer concentration. We show that this basic system exhibits surprisingly rich phase behaviour. In particular, we enquire whether such a system features only a liquid-vapor phase separation (as in one-component colloid-polymer mixtures) or whether, additionally, liquid-liquid demixing of two colloidal phases can occur. Particle-resolved experiments show demixing-like behaviour, but when combined with bespoke Monte Carlo simulations, this proves illusory, and we reveal that only a single liquid-vapor transition occurs. Progressive migration of the small particles to the liquid phase as the polymer concentration increases gives rise to composition inversion-a maximum in the large particle concentration in the liquid phase. Close to criticality, the density fluctuations are found to be dominated by the larger colloids.
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Feb 3, 2019·The Journal of Chemical Physics·Huy S NguyenClifford E Woodward
Dec 25, 2019·Physical Review. E·Sophie HermannMatthias Schmidt
Feb 3, 2019·The Journal of Chemical Physics·M BorówkoE Słyk
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May 26, 2021·Journal of Physics. Condensed Matter : an Institute of Physics Journal·C Patrick RoyallJames E Hallett