Properties of magnetic hybrid materials - a microscopic simulational approach

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The goal of this project is to study magnetic soft matter by means of particle-based simulations. In the previous funding period we have focussed mainly on the investigation of static properties of magnetic gels. Amongst other things we have developed simulation models that capture the different mechanisms for a gel's deformation in an external field. Furthermore, we have examined the interplay between the spatial configuration of magnetic nanoparticles in the gel and the sample shape, as well as the influence of the polymer network structure. Many experiments on magnetic soft matter, however, use time-dependent stimuli such as AC magnetic fields and probe the dynamics. We therefore have started to investigate the dynamical properties of magnetic gels. In particular, we investigated the relaxation processes in a gel caused by switching an external field on or off. In the last funding period, we will continue these efforts. On one hand, we investigate the various factors that control the polymer network structure of a magnetic gel, and how they affect its magnetodeformational properties. On the other hand, we will extend our work on time-dependent stimuli. Here, we will focus on the deformational response of magnetic gels in AC magnetic fields. This will support the design of materials for applications which require oscillatory actuation. Furthermore we concentrate on the micro-rheology of spherical and anisotropic particles in a polymer suspension. The objective is, first, to gain a better understanding of the particle-matrix coupling; Second, we aim to elucidate on how the local matrix properties can be changed by the magnetic particles response to an AC magnetic field. This relates to various experiments performed by several groups within the priority program. Moreover, we will devise a simulation model for PNIPAAM gels into which magnetic hematite spindles are embedded and compare the obtained results to experimental measurements performed within the priority program. The first focus will be on the particle-matrix coupling, followed by the gel's rheological properties.Lastly, we will provide numerical data for theories used and developed in other groups, e.g. for DFT calculations on polymer matrix mediated interactions between magnetic particles.