Properties of magnetic hybrid materials - a microscopic simulational approach

这个项目的目标是通过基于粒子的模拟来研究磁性软物质。在之前的资助期间，我们主要关注磁性凝胶的静态性质的研究。在其他方面，我们开发了模拟模型，捕捉凝胶在外场中变形的不同机制。此外，我们还考察了磁性纳米粒子在凝胶中的空间构型与样品形状之间的相互作用，以及聚合物网络结构的影响。然而，许多关于磁性软物质的实验都使用与时间相关的刺激，如交流磁场，并探测动力学。因此，我们开始研究磁性凝胶的动力学性质。特别是，我们研究了由开启或关闭外场引起的凝胶中的弛豫过程。在上一个资助期，我们将继续这些努力。一方面，我们研究了控制磁性凝胶聚合物网络结构的各种因素，以及它们是如何影响其磁变形性能的。另一方面，我们将扩展我们在时间依赖刺激方面的工作。在这里，我们将重点研究磁性凝胶在交流磁场中的变形响应。这将支持需要振荡驱动的应用的材料设计。此外，我们还集中研究了聚合物悬浮液中球形和各向异性粒子的微观流变学。我们的目标是，首先更好地理解颗粒-基质的耦合；其次，我们的目标是阐明磁性颗粒对交流磁场的响应如何改变局部基质的性质。这涉及优先方案内几个小组进行的各种实验。此外，我们将设计一个PNIPAAm凝胶的模拟模型，其中嵌入磁性赤铁矿纺锤，并将获得的结果与在优先计划中进行的实验测量进行比较。首先将重点放在颗粒-基质耦合上，然后是凝胶的流变性。最后，我们将为其他小组使用和发展的理论提供数值数据，例如用于聚合物基质介导的磁性颗粒之间相互作用的密度泛函计算。

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.