Suspensions of magnetic nanogels at zero field: Equilibrium structural properties

Abstract

A B S T R A C TMagnetic 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.

Theoretical Modeling of Magnetoactive Elastomers on Different Scales: A State-of-the-Art Review

“…The rigidity of the matrix in these cases can be controlled by the value of the elastic constant in the harmonic spring potential. In more detailed approaches, polymer chains are explicitly modeled as beads on springs, forming either a regular network ( Figure 3 c) with magnetic particles occupying all [ 31 , 32 , 33 ] or a certain fraction of crosslinks [ 34 , 38 ], or a non-regular network ( Figure 3 d) with some beads acquiring magnetic moments and thus mimicking magnetic particles [ 39 , 40 , 41 ]. The fraction of magnetic beads can be varied but the total amount of particles in this case increases considerably (due to additional beads representing segments of the chains), making the simulations much more time consuming, however, in a sense more realistic, in particular, in the description of magneto-responsive behavior of magnetic gels capable of a large variation of volume.…”

Nanonutraceuticals: The New Frontier of Supplementary Food

“…These drug delivery systems can be administered through different routes [ 133 , 134 ]. Nanogels can be formulated in order to be responsive to different stimuli, such as temperature [ 135 ], pH [ 136 ], and magnetic field [ 137 ]. For example, nanogels made of ovalbumin and dextran were produced by Maillard reaction and were successfully employed to improve curcumin bioaccessibility in the gastrointestinal tract, as was demonstrated in an in vitro-reproduced model.…”

The influence of an applied magnetic field on the self-assembly of magnetic nanogels

“…In this study we take λ = 6. With this value, in zero external magnetic field, the clusters of MNGs due to magnetic interparticle interactions just begin to form [65]. The dimensionless field strength was chosen to span the range…”

“…In our preliminary studies, we employed the aforementioned model to investigate the equilibrium structural properties of single magnetic nanogels [63] and their suspensions [65] in absence of an applied external field. The latter work allowed us to understand the influence of nanogel concentration and the impact of interparticle magnetic interaction strength on the structural properties of the suspensions.…”