Orientational phenomena in magnetic liquid-crystal hybrid materials

磁性液晶杂化材料的取向现象

• 批准号: 492620405
• 负责人: Dr. Joachim Landers
• 金额: --
• 依托单位: Institut für Physikalische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/492620405?language=en
• 关键词: Orientational; phenomena; magnetic; liquid; crystal

Magnetoactive complex systems composed of structured matrices doped with magnetic nanoparticles (MNP) encompass versatile potential for applications in actuators, sensors, and field-controlled switches and valves. We envisage new, otherwise unprecedented functional material properties, in particular by combining well-defined MNP with thermotropic liquid crystalline (LC) molecular and polymer components, based on the active control of their behavior by external stimuli like temperature or magnetic and electric fields.In the scope of this project, we study the internal interactions and dynamic processes in ferronematic fluids and elastomers on the molecular, particulate and macroscopic scale, and plan to analyze and optimize the influence of the local architecture and the interfacial coupling between MNP and matrix to achieve an efficient magneto-mechanical and magneto-nematic coupling in magnetically doped liquid crystalline fluids and polymers, with the ultimate goal to develop ferronematic elastomers with field-dependent properties.Such new phases based on liquid crystalline siloxane-based polymer molecules with mesogenic side groups offer a large variety of synthetically accessible material architectures, opening a wide parameter space by tailored selection of the components and enabling a detailed analysis of underlying physical mechanisms with respect to particle-matrix interaction.To understand the magneto-nematic coupling behavior on a fundamental level, and in order to achieve a systematic variation of the coupling mechanism and strength, we employ superparamagnetic nanoparticles as well as magnetically blocked particles of varying size and shape as dopants in liquid-crystalline fluids, polymers and elastomers of increasingly complex structure. As a general strategy, the embedded magnetic nanoparticles serve as field-controllable actoric components and likewise as nanoscopic probes for the analysis of local structure and dynamics.To understand field-dependent optical and mechanical properties of the new hybrid materials, the ability to analyze the local reciprocal orientation processes of the MNP (magnetic and/or geometric reorientation) and the mesogens relative to the macroscopic directors such us external fields or shear is essential. For that purpose, Mössbauer spectroscopy provides the ability to access information on the translational diffusive particle motion and the magnetic alignment simultaneously under variation of temperature and/or external fields. In combination with AC-susceptometry, the impact of local architecture of the particles’ environment on their orientational dynamics will be studied. In direct correlation to complementary global techniques such as (macro)rheology, thermomagnetometry and small and wide-angle X-ray scattering, we anticipate deep insights into structuring and relaxation phenomena in newly developed functional materials, enabling their future optimization and development.

由掺杂磁性纳米颗粒（MNP）的结构化基质组成的磁活性复合物系统在致动器、传感器以及场控开关和阀中具有广泛的应用潜力。我们设想新的，否则前所未有的功能材料的性质，特别是通过结合定义良好的MNP与热致液晶（LC）分子和聚合物组分，基于他们的行为的主动控制通过外部刺激，如温度或磁场和电场。在这个项目的范围内，我们研究铁磁流体和弹性体的分子上的内部相互作用和动态过程，颗粒和宏观尺度，并计划分析和优化MNP和基质之间的局部结构和界面耦合的影响，以在磁掺杂液晶流体和聚合物中实现有效的磁-机械和磁-磁耦合，最终目标是开发具有场依赖性的铁弹性体。这种基于液晶硅氧烷的新相-具有介晶侧基的基于聚合物的分子提供了多种可合成的材料结构，通过定制选择组分打开了宽的参数空间，并且能够详细分析关于颗粒-基质相互作用的潜在物理机制。为了在基本水平上理解磁致伸缩耦合行为，并且为了实现耦合机制和强度的系统变化，我们在结构日益复杂的液晶流体、聚合物和弹性体中使用不同尺寸和形状的超顺磁性纳米颗粒以及磁性阻挡颗粒作为掺杂剂。作为一般的策略，嵌入的磁性纳米粒子作为场可控的actoric组件，同样作为纳米探针的局部结构和动力学的分析。为了了解场依赖的新的杂化材料的光学和机械性能，分析MNP的局部相互定向过程的能力（磁性和/或几何重取向）和介晶相对于宏观指向矢（例如外部场或剪切）的取向是必要的。为此，穆斯堡尔谱提供了在温度和/或外部场的变化下同时访问平移扩散粒子运动和磁性对准信息的能力。结合交流阻抗法，将研究粒子环境的局部结构对其取向动力学的影响。在与互补的全球技术，如（宏观）流变学，热磁测量和小角度和广角X射线散射直接相关，我们预计深入了解新开发的功能材料中的结构和弛豫现象，使其未来的优化和发展。