# Controlled self-aggregation of polymer-based nanoparticles employing shear flow and magnetic fields

## TL;DR

This study demonstrates how magnetic fields and shear flow can be used to precisely control the self-aggregation and orientation of magnetically functionalized star polymers, revealing novel behaviors and tunable properties.

## Contribution

It introduces a new polymeric system with controllable morphology and aggregation via combined magnetic and shear stimuli, supported by specialized hydrodynamic simulations.

## Key findings

- Magnetic field strength and direction influence cluster formation.
- Shear rate causes breakup and reorganization of clusters.
- Cluster behavior affects static and dynamic polymer properties.

## Abstract

Star polymers with magnetically functionalized end groups are presented as a novel polymeric system whose morphology, self-aggregation, and orientation can easily be tuned by exposing these macromolecules simultaneously to an external magnetic field and to shear forces. Our investigations are based on a specialized simulation technique which faithfully takes into account the hydrodynamic interactions of the surrounding, Newtonian solvent. We find that the combination of magnetic field (including both strength and direction) and shear rate controls the mean number of magnetic clusters, which in turn is largely responsible for the static and dynamic behavior. While some properties are similar to comparable non-magnetic star polymers, others exhibit novel phenomena; examples of the latter include the breakup and reorganization of the clusters beyond a critical shear rate, and a strong dependence of the efficiency with which shear rate is translated into whole-body rotations on the direction of the magnetic field.