Mechanical properties of multifunctional magnetic microgel particles

该项目研究多功能杂化聚合物微凝胶颗粒的磁机械性能。聚合物微凝胶颗粒的直径可以在300纳米- 2微米的范围内调节。它们含有磁性纳米颗粒（MNP），直径高达20纳米，从SPP的其他基团中获得（Schmitt, Behrens）。凝胶是基于热负性聚合物聚（n -异丙基丙烯酰胺）（PNIPAM）。进一步增加的平民允许调整pH值敏感性。其中一个挑战是控制MNP和聚合物基体之间的耦合，以适应磁场引起的整个微凝胶的变形和力学变化。为了优化磁性颗粒的吸收和控制其迁移率，将根据磁性颗粒的大小通过交联剂的量来调整网格尺寸。MNP的直接耦合将通过静电相互作用和氢键来定制，通过添加带电单体，然后通过共价结合。MNP的吸收将通过不同的策略实现，部分也直接在均匀磁场中实现。凝胶颗粒的变形将通过小角中子散射（SANS）测量来研究（Prevost, Gradzielski）。项目的另一部分将解决约束对微凝胶颗粒磁灵敏度的影响。因此，颗粒将被吸附在一个平面（晶片）上。此外，这种结构也适用于机械和执行器性能的研究。在该项目中，将开发用于原子力显微镜测量的磁环境。最后得到垂直于平面的梯度非均匀磁场和平行于平面的均匀磁场。研究了取向对粘弹性和变形的影响。我们想要了解凝胶的性质，以便于后期开发新材料，例如执行器。因此，一个全球性的目标是弥合从分子水平到介观到微观长度的不同长度尺度之间的差距，并将结果与来自其他基团的宏观凝胶的结果进行比较（Schmidt）。实验结果将与各自的模拟结果（Holm）和DDFT计算结果（Löwen）进行比较。水凝胶微粒将作为软pH值和温度敏感基质提供给SPP的几个项目（Richter, Odenbach, Auernhammer, h<s:1> tten）。凝胶的性质，如电荷密度、标记和染料标记，可以根据每个单独的任务进行调整。在第一节课中，我们将把磁场当作外场来讨论。长期目标是利用聚合物基体的响应特性（温度和pH值）来改变MNP和聚合物基体之间的耦合。

The project addresses the magneto-mechanical properties of multifunctional hybrid polymer microgel particles. The diameter of the polymer microgel particles can be adjusted in a range between 300 nm - 2 micrometer. They contain magnetic nanoparticles (MNP) with a diameter up to 20 nm, obtained from other groups in the SPP (Schmitt, Behrens). The gel is based on the thermoreponsive polymer Poly(N-isopropyl-acrylamide) (PNIPAM). The further addition of commoners allows tuning the pH sensitivity. One challenge is the control of the coupling between the MNP and polymer matrix in order to tailor the deformation and mechanical changes of the whole microgel induced by a magnetic field. For the optimization of the uptake of magnetic particles and for the control of their mobility the meshsize will be adjusted with respect to the size of the magnetic particles by the amount of crosslinker. The direct coupling of the MNP will be tailored by electrostatic interaction and hydrogen bonding via the addition of charged comonomers and later by colvalent binding. The uptake of MNP will be realized with different strategies, partially also directly in a homogeneous magnetic field. The deformation of the gel particles will be studied by small angle neutron scattering (SANS) measurements (Prevost, Gradzielski)Another part of the project addresses the effect of confinement on the magnetic sensitivity of the microgel particles. Therefore the particles will be adsorbed at a planar surface (wafer). In addition this configuration serves also for studies of mechanical and actuator properties. Within the project a magnetic environment for AFM measurements will be developed. Finally a gradient non-uniform magnetic field perpendicular and a homogeneous field parallel to the planar surface will be available. The influence of the orientation on the viscoelastic behavior and the deformation will be studied. We want to understand the gel properties for the later development of novel materials for e.g. actuatoric. Therefore, a global goal is to bridge the gap between different length scales from the molecular level over the mesoscopic to microscopic lengths and to compare the results with the ones for macroscopic gels from other groups (Schmidt). The experimental results will be compared with the outcome of respective simulations (Holm) and DDFT calculations (Löwen). The hydrogel microparticles will be offered as soft pH and temperature sensitive matrix to several projects within the SPP (Richter, Odenbach, Auernhammer, Hütten). The gel properties like charge density and sign and dye-labeling can be adjusted for each individual task. In the first period we will address the magnetic field as an external field. A long-term goal is to profit from the responsive character (temperature and pH) of the polymer matrix to switch the coupling between the MNP and the polymer matrix.