Flow Behavior of Chain and Star Polymers and Their Mixtures.

Deepika Srivastva,Arash Nikoubashman

doi:10.3390/polym10060599

Abstract

Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers as well as of their mixtures under Poiseuille flow. Hydrodynamic interactions are incorporated through the multi-particle collision dynamics (MPCD) technique, while a bead-spring model is used to describe the polymers. For the ultradilute systems at rest, the polymers are distributed uniformly in the slit channel, with a weak dependence on their number of arms. Once flow is applied, however, we find that the stars migrate much more strongly towards the channel center as the number of arms is increased. In the star-chain mixtures, we find a flow-induced separation between stars and chains, with the stars located in the channel center and the chains closer to the walls. In order to identify the origin of this flow-induced partitioning, we conduct additional simulations without hydrodynamic interactions, and find that the observed cross-stream migration originates from a combination of wall-induced hydrodynamic lift forces and viscoelastic effects. The results from our study give valuable insights for designing microfluidic devices for separating polymers based on their architecture.

Highlights

The ability to separate dispersed particles based on their properties, e.g., size, shape, or elasticity, is of immense importance for a large number of industrial and biological applications
In the first part of this work, we studied the flow behavior of single star polymers at infinite dilution for various arm numbers f
Flow-induced partitioning occurred in the star-chain mixtures within the simulation time, which corresponds to a traveled distance of roughly 2 mm at the highest employed flow strength. This distance is smaller than the channel length, and we expect that flow-induced separation of star and chain polymers should in principle be possible in experiments

Summary

Introduction

The ability to separate dispersed particles based on their properties, e.g., size, shape, or elasticity, is of immense importance for a large number of industrial and biological applications. In the past two decades, microfluidic devices have proven themselves as auspicious tools for the efficient separation of particles in solution [3,4,5,6,7,8,9,10,11]. The development of such devices is advantageous, as they can be operated continuously, allowing for high throughput and automation.

Model and Simulation Method

Ultradiulte Conditions

Polymer Mixtures

Conclusions