MRI: Development of a Filament Stretching Rheometer and Shear Micro-Rheometer with Optical Access for Measurements of Complex Fluids

提案编号 CTS-0421043 首席研究员：H. Winter，马萨诸塞大学阿默斯特分校这笔赠款用于开发两种新颖的仪器。 将设计光学微流变仪和长丝拉伸流变仪，以同时测量应力和材料结构随时间的演变以及剪切​​和单轴拉伸中的累积应变。 光学微流变仪将应力测量与同时观察样品的光散射、显微镜、荧光和双折射相结合。长丝拉伸流变仪能够测量复杂流体对从施加的初始微观结构变形、排列和形态开始的瞬态拉伸流的响应。 这两种仪器均专为研究非常小的样品而设计，这些样品需要与聚合物化学家合作，而高分子化学家通常仅将最先进的材料制备为小样品。 使用所提出的仪器进行的实验将更深入地了解复杂材料的行为，例如剪切下的液晶聚合物、作为分子拓扑函数的结晶聚合物、剪切中的相分离聚合物共混物、剪切和延伸中的自组装胶束系统以及颗粒凝胶中的颗粒拓扑。除了分子组成之外，这些复杂材料的性能还受到其微观结构的变形和排列的强烈影响。 流变学研究试图通过一系列精心设计的实验将此类复杂材料的局部应力状态与局部变形率、经过的时间和累积应变联系起来。特别是对于新实验，应力和结构的同时测量预计将得出有关流动引起的过渡状态的结论性信息。 这项工作的更广泛影响之一是促进新产品的开发，这取决于合适材料的可用性。 因此，开发新仪器来提高我们创造和理解新材料的能力至关重要。 此外，拟议仪器作为多用户设施的可用性将对所有相关研究人员的教育产生巨大影响。 一旦这些工具完成，更广泛的互动和思想的交叉融合将成为可能。 定期的跨学科研究会议将有研究生和本科生参加。 虽然新仪器允许研究生进行高级研究，但本科生将特别受益于学习所提出的光学方法，这些方法将使他们能够在分析技能发展到相当水平之前，通过视觉观察对复杂主题进行非常先进的材料研究。这将使处于教育早期阶段的学生感受到发现的兴奋。

Proposal No. CTS-0421043Principal Investigator: H. Winter, University of Massachusetts AmherstThis grant is for the development of two novel instruments. An optical micro-rheometer and a filament stretching rheometer will be designed to simultaneously measure the evolution of stress and material structure as a function of time and accumulated strain in shear and in uniaxial extension. The optical micro-rheometer combines stress measurement with simultaneous observation of light scattering, microscopy, fluorescence, and birefringence from the sample. The filament stretching rheometer is capable of measuring the response of complex fluids to a transient extensional flow starting from an imposed initial microstructural deformation, alignment and morphology. Both instruments are designed for studies on very small samples that are required for collaboration with polymer chemists who typically prepare their most advanced materials as small samples only. Experiments with the proposed instruments will generate a deeper understanding of the behavior of complex materials such as liquid crystalline polymers under shear, crystallizing polymers as a function of molecular topology, phase separating polymer blends in shear, self assembling micellar systems in shear and extension, and particle topology in particle gels. The properties of these complex materials are strongly affected by the deformation and alignment of their microstructure in addition to their molecular composition. The study of rheology attempts to relate the local state of stress in such complex materials to the local deformation rate, elapsed time, and accumulated strain through a series of carefully designed experiments. Specifically for the new experiments, simultaneous measurement of stress and structure are expected to lead to conclusive information about flow-induced transitional states. Among the broader impacts of this work is to facilitate the development of new products, which depends on the availability of suitable materials. Therefore it is essential to develop new instruments that further our ability to create and understand new materials. In addition, the availability of the proposed instruments as a multi-user facility will have great impact on the education of all researchers involved. Once the instruments are completed, broader interaction and cross-fertilization of ideas will be enabled. Regular interdisciplinary research meetings will involve both graduate and undergraduate students. While the new instruments allow graduate students to perform their advanced research, undergraduate students will particularly profit from learning the proposed optical methods that will allow them to perform very advanced materials research on complicated topics through visual observation before their analytical skills have been developed to a comparable level. This will introduce students at an early state of their education to the excitement of discovery.