Closed-Form Coexistence Equation for Phase Separation of Polymeric Mixtures in Dissipative Particle Dynamics

Abstract

To date, no extensive study of the phase diagram for binary fluid mixtures in dissipative particle dynamics (DPD) has been published. This is especially pertinent for newer parameterization schemes where the self–self interaction, or the effective volume, of different particle types is varied. This work presents an exhaustive study of the parameter space concerning DPD particles with soft interaction potentials. Moreover, we propose a closed-form coexistence equation or binodal curve that is inspired by the Flory–Huggins model. This equation describes the phase diagram of all binary mixtures made up out of monomers, homopolymers, and the mixtures thereof when self–self interactions are varied. The mean absolute percentage error (MAPE) of the equation on simulated data, including validation simulations, is 1.02%. The equation can a priori predict the phase separation of mixtures using only DPD interaction parameters. The proposed coexistence equation can therefore be used to directly validate interaction parameters resulting from novel parameterization schemes, including coarse graining and equations of state, without the need for additional simulations. Finally, it is shown that the choice of bond potential markedly influences phase behavior.

Understanding and Modeling Polymers: The Challenge of Multiple Scales

“…Typically, a certain functional form of potentials is assumed, and the parameters are matched such that the CG model reproduces the desired thermodynamic properties. For example, van der Haven et al 349 have recently derived a very accurate approximate closed-form expression for the coexistence phase diagrams of binary polymeric mixtures in DPD models with pair interactions, which allows to directly relate the soft DPD interaction parameters with experimental data on demixing phase behavior.…”

Virtual Issue on Polymers: Recent Advances from a Physical Chemistry Perspective

“…4 A number of studies address interactions and interaction mechanisms in polymer solutions and the resulting structural and dynamical behavior. Van der Haven et al 1 present an exhaustive simulation study of demixing phase diagrams for coarse-grained models of polymer/solvent mixtures which can serve as a reference for future coarse-grained simulations. Mayoral and Goicochea investigate the rheological properties of solutions containing branched polymers by molecular dynamics simulations and find strong shear-thickening effects in good solvent.…”

“…This Virtual Issue on polymers collects 34 selected publications that have appeared in 2020 and 2021 and highlight the breadth of ongoing research in the fascinating and multifaceted area of polymer science. The questions addressed in these studies range from fundamental issues regarding, e.g., polymer–solvent interactions − to highly applied problems such as identifying factors that influence the degradation of cultural heritage objects …”