Interplay between particle microstructure, network topology and sample shape in magnetic gels -- A molecular dynamics simulation study

TL;DR

This study uses molecular dynamics simulations to explore how particle microstructure, network topology, and sample shape influence deformation and particle alignment in magnetic gels under external magnetic fields.

Contribution

It introduces a coarse-grained simulation model that accounts for microstructure, shape, and topology, revealing their combined effects on gel behavior.

Findings

Magnetic fields reduce clustering in isotropic microstructure gels.

Uniaxial microstructure gels do not show reduced clustering under magnetic fields.

Sample shape and network topology significantly influence gel deformation and particle alignment.

Abstract

Ferrogels, i.e., hydrogels loaded with magnetic nanoparticles, have the ability to deform in external magnetic fields. The precise shape of deformation and the alignment of the gel in the field, however, depend on the interplay of several factors. In this paper, we introduce a coarse-grained simulation model, which takes into account the configuration of magnetic particles in the gel, the sample shape, and aspects of the polymer network topology. We use this model to show that in gels with an isotropic microstructure, an external magnetic field reduces clustering, while this is not the case for uniaxial gels, in which the particle configuration is anisotropic due to the presence of a magnetic field during cross-linking. For ellipsoidal gels, we find that a uniaxial microstructure additionally can override the deformation and alignment expected as indicated the demagnetization energy. Finally, we examine to what degree gels with different network topologies maintain the particle microstructure ``frozen in`` during the cross-linking process.