Suspensions of magnetic nanogels at zero field: equilibrium structural properties

TL;DR

This study uses Langevin dynamics simulations to explore how magnetic nanogel concentration and particle interactions influence their equilibrium self-assembly at zero magnetic field, revealing conditions for cluster formation and structural changes.

Contribution

It provides new insights into the self-assembly mechanisms of magnetic nanogels and quantifies the interaction strength needed for aggregation compared to free nanoparticles.

Findings

Self-assembly occurs at higher interaction ratios for nanogels than free nanoparticles.

Formation of larger clusters involves nanogels with internal ring structures.

Structural properties are significantly affected even at low nanoparticle volume fractions.

Abstract

Magnetic nanogels represent a cutting edge of magnetic soft matter research due to their numerous potential applications. Here, using Langevin dynamics simulations, we analyse the influence of magnetic nanogel concentration and embedded magnetic particle interactions on the self-assembly of magnetic nanogels at zero field. For this, we calculated radial distribution functions and structure factors for nanogels and magnetic particles within them. We found that, in comparison to suspensions of free magnetic nanoparticles, where the self-assembly is already observed if the interparticle interaction strength exceeds the thermal fluctuations by approximately a factor of three, self-assembly of magnetic nanogels only takes place by increasing such ratio above six. This magnetic nanogel self-assembly is realised by means of favourable close contacts between magnetic nanoparticles from different nanogels. It turns out that for high values of interparticle interactions, corresponding to the formation of internal rings in isolated nanogels, in their suspensions larger magnetic particle clusters with lower elastic penalty can be formed by involving different nanogels. Finally, we show that when the self-assembly of these nanogels takes place, it has a drastic effect on the structural properties even if the volume fraction of magnetic nanoparticles is low.