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

Burghardt，Wesley 1336269聚合物和其他复杂流体的非牛顿性质源于流动引起的分子和介观尺度结构变化。该提案描述了一个研究计划集中在创建和应用的新的X射线散射能力，研究移动的流体在平面延伸流产生的停滞点的交叉槽流装置。在此静脉中应用X射线和中子散射的先前努力受到流动池构造中的设计折衷的限制，这导致寄生剪切梯度的运动学不均匀性和虚假效应。利用先进的光子源（APS）的能力，这里提出的设计概念提供了一个显着的改进，在所应用的流场的定义。虽然这里要开发的方法将具有广泛的适用性，许多类的复杂流体，提出了两个目标的初步研究：粘弹性蠕虫状胶束溶液的结构动力学，和柔性聚合物在稀solution.Intellectual Merit的变形：粘弹性蠕虫状表面活性剂胶束的解决方案通常被视为模型的稀释和纠缠的聚合物，但也表现出一种倾向，为各种流动过渡和不稳定性驱动的微观结构变化。定量胶束取向诱导的一个定义明确的拉伸流的能力将有助于有价值的见解，在这些流体中的许多现象，包括结构形成与湍流减阻，剪切带和非带胶束配方之间的差异，在某些胶束系统中的应变硬化的起源，和流动诱导的浓胶束溶液的相变的性质。拉伸流中聚合物稀溶液的测量是X射线散射的一个非常具有挑战性的应用，但有可能解决理论预测之间长期存在的矛盾。（以及最近的DNA直接可视化），以及先前使用光散射测量线圈尺寸。更广泛的影响：聚合物和表面活性剂溶液中的粘弹性现象在许多具有实际意义的复杂流动中具有深远的影响，包括在湍流管道流中的减阻和利用聚合物和/或表面活性剂溶液的强化采油工艺。理解剪切流和特别是拉伸流中的复杂流体流变学是理解这些和其他技术中出现的更复杂流动的先决条件。因此，本文提出的平面拉伸流中微观流体结构的直接测量具有巨大的潜力，对社会重要的技术产生积极影响。此外，该项目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的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，他也有一个跟踪记录，使这种仪器提供给科学合作者，以及社区的同步加速器用户谁访问APS设施通过“一般用户”的建议。同样，该项目开发的仪器将提供给更广泛的研究界，扩大该项目在研究以及研究生和博士后研究人员培训方面的益处。

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.