Thermodynamics of droplets undergoing liquid-liquid phase separation

Abstract

We study the thermodynamics of binary mixtures wherein the volume fraction of the minority component is less than the amount required to form a flat interface. Based on an explicit microscopic mean field theory, we show that the surface tension dominated equilibrium phase of a polymer mixture forms a single macroscopic droplet. A combination of elastic interactions that renormalize the surface tension, and arrests phase separation for a gel-polymer mixture, stabilize a micro-droplet phase. We compute the droplet size as a function of the interfacial tension, Flory parameter, and elastic moduli of the gel. Our results illustrate the importance of the rheological properties of the solvent in dictating the thermodynamic phase behavior of biopolymers undergoing liquid-liquid phase separation.

Protein conformation and biomolecular condensates

“…Although minimalist Flory–Huggins models are adequate for a preliminary analysis, more elaborate treatment is needed to explain accurately the experimental data in protein systems with significant conformational fluctuations and sequence effects. In these cases, additional terms accounting for effective macromolecular volumes and inter- and intra-chain interactions need to be included ( Overbeek and Voorn, 1957 ; Wei et al., 2017 ; Berry et al., 2018 ; Zhou et al., 2018 ; Shapiro et al., 2021 ; Biswas et al., 2021 ). Likewise, multicomponent and in vivo systems demand specific treatments ( Saha et al., 2016 ; Fritsch et al., 2021 ).…”