Structural Dynamics of Polymer and Surfactant Solutions in Planar Extensional Flow Using In Situ X-ray Scattering

使用原位 X 射线散射研究平面拉伸流中聚合物和表面活性剂溶液的结构动力学

• 批准号: 1336269
• 负责人: Wesley Burghardt
• 金额: $ 26.32万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1336269&HistoricalAwards=false
• 关键词: Structural; Dynamics; Polymer; Surfactant; Solutions

Burghardt, Wesley 1336269The non-Newtonian properties of polymers and other complex fluids stem from molecular- and meso-scale structural changes induced by flow. This proposal describes a research program centered on creation and application of novel x-ray scattering capabilities for studying mobile fluids in a planar extensional flow produced at the stagnation point of a cross-slot flow device. Prior efforts to apply x-ray and neutron scattering in this vein have been limited by design compromises in flow cell construction that result in kinematic inhomogeneity and spurious effects of parasitic shear gradients. Exploiting capabilities of the Advanced Photon Source (APS), the design concept proposed here provides a marked improvement in the definition of the applied flow field. While the methods to be developed here will have broad applicability to many classes of complex fluids, two targets are proposed for initial study: structural dynamics of viscoelastic wormlike micelle solutions, and the deformation of flexible polymers in dilute solution.Intellectual Merit :Viscoelastic solutions of wormlike surfactant micelles are often viewed as models of both dilute and entangled polymers, but also show a propensity for a variety of flow transitions and instabilities driven by microscopic structural changes. The ability to quantify micellar orientation induced by a well-defined extensional flow will contribute valuable insights into many phenomena in these fluids, including structure formation associated with turbulent drag reduction, differences between shear-banding and non-banding micelle formulations, the origins of strain hardening in certain micellar systems, and the nature of flow-induced nematic phase transitions in concentrated micelle solutions. Measurement of dilute polymer solutions in extensional flow is a very challenging application for x-ray scattering, but has the potential to address a long-standing discrepancy between theoretical prediction (and more recent direct visualization in DNA) of large coil deformations, and prior measurements of coil size using light scattering.Broader Impacts :Viscoelastic phenomena in polymer and surfactant solutions have profound consequences in many complex flows of practical significance, including drag reduction in turbulent pipeline flow and enhanced oil recovery processes that utilize polymer and/or surfactant solutions. Understanding complex fluid rheology in both shear and, especially, extensional flows is a prerequisite to understand the more complex flows that arise in these and other technologies. As a result, the direct measurements of microscopic fluid structure in planar extensional flow proposed here have tremendous potential to positively impact technologies important to society. In addition, this project will have broad impact in scientific infrastructure and human resource development. The PI has extensive experience in the development of novel instrumentation for x-ray scattering studies of polymers under flow, drawing upon his active participation in the DND-CAT research facility at APS. More importantly, he also has a track record of making this instrumentation available to scientific collaborators, as well as to the community of synchrotron users who access APS facilities through "general user" proposals. In a similar way, the instrument developed in this project will be made available to the broader research community, expanding the benefit of this project in both the research to be performed, as well as the training of graduate students and postdoctoral researchers.

Burghardt, Wesley 1336269聚合物和其他复杂流体的非牛顿特性源于流动引起的分子和介观结构变化。该提案描述了一项以新型 X 射线散射能力的创建和应用为中心的研究计划，用于研究跨槽流装置驻点产生的平面拉伸流中的移动流体。先前在该静脉中应用 X 射线和中子散射的努力受到流动池构造中设计妥协的限制，导致运动学不均匀性和寄生剪切梯度的寄生效应。利用先进光子源（APS）的功能，这里提出的设计概念在应用流场的定义方面提供了显着的改进。虽然这里要开发的方法对许多类别的复杂流体具有广泛的适用性，但初步研究提出了两个目标：粘弹性蠕虫状胶束溶液的结构动力学，以及稀溶液中柔性聚合物的变形。 智力优点：蠕虫状表面活性剂胶束的粘弹性溶液通常被视为稀聚合物和缠结聚合物的模型，但也显示出一种倾向 由微观结构变化驱动的各种流动转变和不稳定性。量化由明确的拉伸流引起的胶束取向的能力将为了解这些流体中的许多现象提供有价值的见解，包括与湍流减阻相关的结构形成、剪切带和非带状胶束配方之间的差异、某些胶束系统中应变硬化的起源，以及浓胶束溶液中流动引起的向列相变的性质。拉伸流中稀聚合物溶液的测量对于 X 射线散射来说是一个非常具有挑战性的应用，但有可能解决大线圈变形的理论预测（以及最近在 DNA 中的直接可视化）与之前使用光散射测量线圈尺寸之间长期存在的差异。 更广泛的影响：聚合物和表面活性剂溶液中的粘弹性现象对许多复杂的实际流动产生深远的影响。 重要性，包括减少湍流管道流的阻力以及利用聚合物和/或表面活性剂溶液提高石油采收率。了解剪切流（尤其是拉伸流）中的复杂流体流变学是了解这些技术和其他技术中出现的更复杂流动的先决条件。因此，这里提出的平面拉伸流中微观流体结构的直接测量具有对社会重要技术产生积极影响的巨大潜力。此外，该项目还将对科学基础设施和人力资源开发产生广泛影响。 PI 在开发用于流动下聚合物 X 射线散射研究的新型仪器方面拥有丰富的经验，这得益于他积极参与 APS 的 DND-CAT 研究设施。更重要的是，他还拥有向科学合作者以及通过“一般用户”提案访问 APS 设施的同步加速器用户社区提供该仪器的记录。以类似的方式，该项目开发的仪器将提供给更广泛的研究界，扩大该项目在要进行的研究以及研究生和博士后研究人员的培训方面的效益。