A coarse-grained model capturing partitioning and magnetic response in polymeric aqueous two-phase systems

Aqueous two-phase systems (ATPS) are phase-separating water solutions commonly consisting of a binary mixture of incompatible polymers and/or salts. They provide an accessible tool for partitioning, with paramount applications in, e.g., biopharmaceuticals, biotechnology, and environmentally benign extraction techniques. Advanced control by chemical gradients and external fields has been demonstrated. However, molecular level connection to the macroscopic response of these systems is currently lacking, both from experimental and modeling point of view. Here we present a general Brownian dynamics-based coarse-grained simulation approach capturing the phase separation response both at general, qualitative level, but also matching partitioning and interfacial tension for specific experimental system and conditions [1]. By considering a magnetically responsive partitioned component, we study the system response under external magnetic field. Modelling results, combined with our experimental work, reveal interesting patterns at the interface between the two polymer phases, at a scale experimentally overlooked, potentially motivating scrutiny at the nanometric scale. We discuss the generalization of the observations to other ATPS systems besides the direct experimental comparison ferrofluid, and demonstrate the modelling framework as an accessible tool to address the effects of system variations in an easily up-scaled way.