Synthesis and characterization of multifunctional hybrid materials: Tuning the mechanical and magnetic properties of hydrogels

铁凝胶结合了凝胶或聚合物基质的特性和铁磁流体的磁性。水凝胶通常被用作基质材料，因为它们可以被水膨胀。由于许多水凝胶对温度、pH值或光线等外部刺激有反应，所以这些凝胶也被称为响应性水凝胶。与磁性纳米粒子结合，混合凝胶可以被交流磁场加热，因此凝胶的机械性能可以调整。在最后一个阶段，重点将放在磁性微凝胶和磁性大凝胶的合成上，并在磁场的影响下对它们进行表征，以及磁场对基质的影响。对于这种多响应水凝胶，选择特定的磁性颗粒种类对于期望的应用至关重要。将合成具有聚n -异丙基丙烯酰胺基质的微凝胶和大凝胶，其磁芯由磁铁矿或钴铁氧体组成。本文将通过动态光散射来研究该基体的温度依赖行为。此外，磁性能将表征重点放在饱和和磁松弛行为。特别是对于硬磁性材料，将在磁芯周围引入空腔，因此磁芯能够自由旋转。通过这种方法，磁芯应该能够通过施加交流磁场来加热矩阵，从而诱导相变进入热响应矩阵的崩溃状态。我们将研究粒子在这些空腔内旋转的自由程度。为了更好地控制基体的热响应性能，将引入不同的基体材料，这些材料将通过受控的自由基聚合直接在颗粒表面合成。通过这种方法可以生产出非常薄且可重复的微凝胶壳。通过将这些微凝胶颗粒交联到大凝胶中，可以在大凝胶中实现更高的磁性含量。通过这种方法，磁芯的磁性（形状、尺寸、材料）和基体可以相互定制，从而实现通过磁场调节机械性能的能力。

Ferrogels combine the properties of a gel- or polymer matrix with the magnetic properties of a ferrofluid. Hydrogels are often used as matrix materials as they can be swollen with water. Since many hydrogels respond to external stimuli like temperature, pH or light these gels are also named responsive hydrogels. In combination with magnetic nanopartilces the hybridgels can be heated up by an AC magnetic field and thus the mechanical properties of the gel can be adjusted. In this last period the focus will be set on the synthesis on magnetic micro- and macrogels and additional their characterization under the influence of a magnetic field and its effect on the matrix. For such multiresponsive hydrogels the choice of the specific magnetic particle species is crucial for the desired application. Micro- and macrogels with a poly-N-isopropyl acrylamide matrix will be synthesized containing a magnetic core consisting of either magnetite or cobalt ferrite. The temperature dependent behavior of the matrix will be investigated via dynamic light scattering. Additional the magnetic properties will be characterized focusing on the saturation and magnetic relaxation behaviour. Especially for hard magnetic materials cavities will be introduced around the core, so the magnetic cores are able to rotate freely. By this the magnetic core should be enabled to heat up the matrix by applying an AC magnetic field that induces a phase transition into the collapsed state of the thermoresponsive matrix. We will investigate how freely the particles are able to rotate within these cavities. To achieve a better control over the thermoresponsive properties of the matrix different matrix materials will be introduced which will be synthesized by a controlled radical polymerization directly on the surface of the particles. By this method very thin and reproducible microgel shells can be produce. By crosslinking these microgel particles to a macrogel, even higher magnetic content within the marogel can be achieved. With this the magnetic properties of the core (shape, size, material) and the matrix can be tailored to each other, to achieve the ability to tune the mechanical properties by magnetic fields.