EAGER: Rheo-NMR measurement of spatiotemporal dynamics in shear banding wormlike micelle solutions

已经发现，在一类流体的处理过程中，表面活性剂和聚合物，所施加的剪切可导致溶液中的非均匀性，称为剪切诱导条带的现象。这是一个开发准确和优雅的实验来理解这一过程的建议，影响了几个行业的当前实践，并可能允许为此类材料设计更好的制造技术。对制造业有影响的研究涉及被确定为国家需求领域的一个领域。 目前，高分子软材料的成带正在理论上进行研究，但世界上只有很少的实验室有能力进行实验，以确定这种现象背后的基本机制。PI的实验室就是其中之一，她正在提议开发一种分子水平的实验技术来动态观察剪切带。 建议提供实验时空的速度和微观结构的数据，以测试现有的理论，并告知未来的建模工作有关的动态warmlike胶束溶液（WLM）在时间依赖性条件下的剪切带。具体目标包括：（1）使用快速Rheo-NMR速度成像检测WLM中的剪切带，以测试由现有理论提出的大学标准，（2）使用快速Rheo-NMR速度成像和流动补偿脉冲梯度自旋回波（PGSE）NMR测量和量化与瞬时应力响应相关的速度波动的时间和长度尺度，（3）通过~ 2 H光谱测量WLM溶液的分子水平有序性，并与剪切带和速度涨落相关联。Rheo-NMR技术是非侵入性的、非破坏性的，提供从宏观到微观的信息，提供对启动条件下剪切带的形成和振荡流以及流场、微观结构和瞬态应力之间的耦合的洞察。拟议的工作将对聚合物，表面活性剂，化学和食品工业产生影响，其中材料特性和复杂流体的控制非常重要。研究生和本科生的参与建议，以及推广活动，以URM学生在蒙大拿州。

It has been found that during the processing of a class of fluids, e.g., surfactants and polymers, the applied shear can lead to non-homogeneities in the solution, a phenomenon called shear-induced banding. This is a proposal to develop accurate and elegant experiments to understand this process, impacting current practice in several industries and potentially allowing the design of better manufacturing techniques for such materials. Research with impact in manufacturing addresses an area identified as an area of National need. The banding of macromolecular soft materials is currently under investigation theoretically, but there are very few laboratories in the world that have the capability to conduct the experiments that will determine the fundamental mechanism behind this phenomenon. The PI's laboratory is one of these, and she is proposing to develop a molecular level experimental technique to dynamically observe shear banding. It is proposed to provide experimental spatiotemporal velocity and microstructure data in order to test existing theory and inform future modeling efforts relevant to the dynamics of shear banding in warmlike micelle solutions (WLMs) under time dependent conditions. Specific objectives include: (1) detect shear banding in WLMs using rapid Rheo-NMR velocity imaging to test the university criteria proposed by prior theories, (2) measure and quantify time and lengthscales of velocity fluctuation, as correlated with transient stress responses, using rapid Rheo-NMR velocity imaging and flow compensated pulsed gradient spin echo (PGSE) NMR, and (3) measure molecular level ordering for WLM solutions via 2H spectroscopy as correlated with shear banding and velocity fluctuation. Rheo-NMR techniques are non-invasive, non-destructive and offer information ranging from the macroscopic to the microscopic, providing insight into the formation of shear bands under start-up conditions and oscillatory flow as well as the coupling between the flow field, microstructure and transient stress. The proposed work will have an impact on the polymer, surfactant, chemical and food industry, where control of material properties and of complex fluids is important. Graduate and undergraduate student participation is proposed, as well as outreach activities to URM students across Montana.