Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 23: Complex Fluids and Soft Matter 1 (joint session DY/CPP)

CPP 23.2: Talk

Wednesday, September 7, 2022, 09:45–10:00, H18

Composition Dependent Instabilities in Mixtures With Many Components — •Filipe Thewes, Matthias Krüger, and Peter Sollich — Institut für Theoretische Physik, Georg-August-Universität Göttingen, Göttingen, Germany

Understanding the phase behavior of mixtures with many components is a key step towards a physics-based description of intracellular compartmentalization. We study the instabilities of a model where the interactions as quantified by the second virial coefficients are taken as random Gaussian variables. Using tools from free probability theory we obtain the spinodal curve and the nature of instabilities for an arbitrary distribution of components, thus lifting the drastic simplification of uniform composition that has been made in earlier work. We illustrate our results with examples and show that, by controlling the density of only a few components, one can systematically change the nature of instabilities and achieve demixing for realistic scenarios, which appeared to be ruled out by previous studies. Inspired by these results, we introduce an additive model taking into account also deterministic interactions. We show how this systematic interaction leads to a competition between different forms of instabilities that can be tuned by controlling the model parameters. Since most experimental protocols for complex mixtures rely on tuning either the composition or systematic interactions, we expect our results to significantly extend the range of mixtures that can be treated within the mean-field model.