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

研究发现，在处理一类流体（如表面活性剂和聚合物）的过程中，施加的剪切会导致溶液中的非均质性，这种现象称为剪切诱导带。这是一项开发准确而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，并有可能为这类材料设计更好的制造技术。对制造业有影响的研究解决了一个被确定为国家需要的领域。高分子软质材料的带状现象目前正在理论上进行研究，但世界上很少有实验室有能力进行实验来确定这种现象背后的基本机制。PI的实验室就是其中之一，她建议开发一种分子水平的实验技术来动态观察剪切带。我们建议提供实验时空速度和微观结构数据，以验证现有理论，并为未来的建模工作提供信息，这些建模工作与时间依赖条件下类暖胶束溶液（WLMs）中剪切带的动力学有关。具体目标包括：(1)利用快速流变核磁共振速度成像检测WLM中的剪切带，以检验先前理论提出的大学标准；(2)利用快速流变核磁共振速度成像和流量补偿脉冲梯度自旋回波（PGSE）核磁共振测量和量化与瞬态应力响应相关的速度波动的时间和长度尺度；(3)通过2H光谱测量与剪切带和速度波动相关的WLM溶液的分子水平有序度。流变核磁共振技术是非侵入性、非破坏性的，可以提供从宏观到微观的信息，可以深入了解启动条件和振荡流动下剪切带的形成，以及流场、微观结构和瞬态应力之间的耦合。这项工作将对聚合物、表面活性剂、化学和食品工业产生影响，在这些工业中，控制材料性能和复杂流体是很重要的。建议研究生和本科生参与，以及向蒙大拿州的URM学生开展外展活动。

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.