Magneto-optically switchable anisotropic suspensions and gels

在这个项目中，我们结合了软物质物理中两个成功的概念，磁流体和液晶。目标是开发一种新型多功能材料，这种材料对磁场敏感，可用于磁光开关和磁机械效应。我们将铁磁流体和功能化磁性纳米颗粒与溶向列悬浮和热致液晶结合起来。铁磁纳米颗粒提供了对磁场的敏感性。不等长晶体或液晶介质有助于双折射光学特性。这种组合为多种应用打开了可能性。在本课题前期的应用中制备了稳定的混悬液并对其进行了表征，此外我们还成功地尝试制备了各向异性铁凝胶。本项目计划活动的目的是研究磁性纳米颗粒与不同体系中局部复杂各向异性基质的相互作用。重点研究了基体结构对复合材料磁光和粘弹性性能的影响：外加磁场使磁性纳米颗粒自组织，从而重新组织各向异性环境（基体）。基体的反馈决定了磁性亚相的结构形成动力学以及光学和力学性能。我们将研究三种不同的基质体系，分散在各向同性液体介质中的板状和棒状非磁性颗粒（色素晶体），具有线状内部结构的有机凝胶和有机液晶。一个特殊的方面是从各向同性矩阵到各向异性矩阵的过渡。最相关的实验表征技术是磁光开关，磁诱导双折射和二色性的测量，以及磁诱导机械扭矩。这些技术伴随着流变学研究，磁松弛测量（MRX）和电纳测量（ACS），以及与专题项目中其他小组合作的其他方法。

In this project we combine two successful concepts of Soft Matter physics, magnetic fluids and liquid crystals. The goal is the development of a new class of multifunctional materials that are sensitive to magnetic fields and can be used for magneto-optical switching and magneto-mechanical effects. We combine ferrofluids and functionalized magnetic nanoparticles with lyotropic nematic suspensions and thermotropic liquid crystals. Ferromagnetic nanoparticles provide the sensitivity against magnetic fields. Anisometric crystallites or liquid-crystalline mesogens contribute birefringent optical properties. This combination opens the potential for multiple applications. Stabile suspensions were prepared and characterized in the previous application periods of this topical program, in addition we made successful attempts to prepare anisotropic ferrogels. The aim of the planned activities in this project is the investigation of the interactions of magnetic nanoparticles with the localen complex anisotropic matrix in different systems. The focus is laid on the influence of the matrix structure on the magneto-optical and viscoelastic properties of the composites: External magnetic fields cause a self-organization of the magnetic nanoparticles, which in turn reorganize the anisotropci environment (the matrix). The feedback of the matrix determines the structure forming dynamics of the magnetic subphase as well as the optical and mechanical properties. We will investigate three different matrix systems, plate-like and rod-like nonmagnetic particles (pigment crystallites) dispersed in an isotrop liquid medium, organo-gels with thread-like internal structure and organic liquid crystals. A special aspect is the transition from isotropic to anisotropic matrices. The most relevant experimental characterization techniques are magneto-optical switching, measurements of magnetically induced birefringence and dichroism, as well as magnetically induced mechanical torques. These techniques are accompanied by rheological studies, magnetorelaxometry (MRX) and susceptometry (ACS), and other methods in cooperation with other groups within the topical program.