Reducing the Solvent Quality Gives Rise to the Outward Migration of a Star Polymer in Poiseuille Flow

A hybrid simulation technique combining molecular dynamics with multiparticle collision dynamics was used to investigate the conformation and migration of star polymers in Poiseuille flow under various solvent conditions. The results revealed that the solvent quality could regulate the migration behavior of the star polymer in flow field. At sufficiently high flow strengths, the enrichment of polymers around the tube center is alleviated by decreasing the solvent quality; the polymer center-of-mass distribution even shows depletion when the solvent quality is extremely poor. This phenomenon is consistent with the Segré–Silberberg effect of colloidal particle transport. The flow field analysis indicated a hydrodynamic force balance between shear gradient induced lift force and the polymer-boundary repulsion that stabilizes a collapsed star polymer in a position between the tube centerline and boundary. These results offer a universal understanding of polymer transport at different solvent conditions, providing a possible solution to control polymer separation by fine-tuning the solvent quality.