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

建议没有。首席研究员：H. Winter，马萨诸塞大学阿默斯特。这笔拨款用于开发两种新型仪器。设计一种光学微流变仪和一种纤维拉伸流变仪，以同时测量剪切和单轴拉伸中应力和材料结构随时间和累积应变的演变。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。纤维拉伸流变仪能够测量复杂流体对从施加的初始微结构变形、排列和形态开始的瞬态拉伸流的响应。这两种仪器都是为研究非常小的样品而设计的，需要与聚合物化学家合作，他们通常只准备小样品的最先进的材料。使用所提出的仪器进行的实验将对复杂材料的行为产生更深入的理解，如液晶聚合物在剪切作用下的行为、聚合物在分子拓扑结构下的结晶、剪切作用下的相分离聚合物共混物、剪切和拉伸作用下的自组装胶束系统以及颗粒凝胶中的颗粒拓扑结构。除了分子组成外，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，将这种复杂材料的局部应力状态与局部变化率、经过的时间和累积的应变联系起来。特别是在新的实验中，同时测量应力和结构有望得到关于流动诱导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，这取决于是否有合适的材料。因此，有必要开发新的工具，以提高我们创造和理解新材料的能力。此外，拟议的仪器作为多用户设施的可用性将对所有有关研究人员的教育产生重大影响。一旦这些文书完成，将能够进行更广泛的相互作用和思想的交流。定期的跨学科研究会议将包括研究生和本科生。当新的仪器允许研究生进行他们的高级研究时，本科生将特别受益于学习提议的光学方法，这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的主题进行非常先进的材料研究。这将使处于早期教育阶段的学生体会到发现的兴奋。

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.