Disentangling the dynamics of shear banding in entangled polymer solutions

解开缠结聚合物溶液中剪切带的动力学

• 批准号: 1700771
• 负责人: Xiang Cheng
• 金额: $ 35.74万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1700771&HistoricalAwards=false
• 关键词: Disentangling; dynamics; shear; banding; entangled

Plastics are ubiquitous to modern society, used in food packing, electronic devices, transportation, sports equipment, and medical devices. The precursor to all formed plastics is a polymer fluid. Polymer fluids are a unique type of fluid, as the chain-like polymer molecules act like springs, and within a collection of fluid molecules, the polymer springs become entangled. Unlike water and many other fluids, this complex fluid does not respond to the forces of stress and shear in a manner that is proportional to the applied force. This non-proportional response is classified as Non-Newtonian. Non-Newtonian fluids have not been adequately described by general engineering models of fluid flow. Without general models, prediction of flow in industrial processing is limited to trial-and-error. Under some circumstances, such as slow flow or low concentration, many of these complexities can be ignored. However, these are not the most industrially relevant conditions, where high concentration and fast flow are prevalent. This project supports a fundamental experimental study on the fast flow of concentrated polymer fluids, and uses state-of-the-art imaging techniques to directly image single polymer molecules to reveal the microscopic dynamics of complex fluid flow. The challenge in understanding the dynamics of concentrated polymer fluids is the nonlinear viscoelasticity of entangled polymer solutions, particularly the formation of shear-banding in concentrated polymer solutions at high shear rates. These phenomenon are difficult to probe experimentally. This research project combines high-speed confocal microscopy with a custom shear cell to investigate the origin of shear-banding flows of a model system, namely, concentrated DNA solutions. The applications of these unique experimental tools to the problem will resolve a controversy regarding on shear-banding in polymer fluids. The phase diagram of the shear-induced dynamics of concentrated DNA solutions is being mapped. The project aims to establish a direct link between the microscopic dynamics of DNA molecules and the macroscopic flow behavior of polymer fluids. The project is elucidating the dynamics of single polymer molecules in concentrated solutions under fast shear and experimentally validating competing theories on shear banding of polymer fluids. These results are uncovering the missing theoretical understanding of concentrated polymer fluids under fast flows and, ultimately, practical engineering models for polymer fluids under the most industrially relevant conditions. Increased control and prediction of polymer flow will increase throughput and efficiency, and therefore greatly impact the U.S. manufacturing sector. This research project also involves K-12 outreach programs with local high school students, especially those underrepresented in science and engineering.

塑料在现代社会中无处不在，用于食品包装，电子设备，运输，运动器材和医疗器械。 所有成型塑料的前体都是聚合物流体。 聚合物流体是一种独特类型的流体，因为链状聚合物分子像弹簧一样起作用，并且在流体分子的集合中，聚合物弹簧变得缠结。 与水和许多其他流体不同，这种复杂的流体不会以与所施加的力成比例的方式对应力和剪切力作出反应。这种非比例响应被归类为非牛顿响应。 非牛顿流体尚未被流体流动的一般工程模型充分描述。 在没有通用模型的情况下，工业过程中的流量预测仅限于试错。在某些情况下，如流速缓慢或浓度低，这些复杂性中的许多可以忽略不计。然而，这些并不是工业上最相关的条件，其中高浓度和快速流动是普遍的。该项目支持对浓缩聚合物流体快速流动的基础实验研究，并使用最先进的成像技术直接对单个聚合物分子进行成像，以揭示复杂流体流动的微观动力学。理解浓缩聚合物流体动力学的挑战是缠结聚合物溶液的非线性粘弹性，特别是在高剪切速率下浓缩聚合物溶液中剪切带的形成。这些现象很难用实验来探测。本研究项目结合了高速共聚焦显微镜与自定义剪切单元，以研究模型系统的剪切带流的起源，即浓缩的DNA溶液。这些独特的实验工具的应用，将解决一个关于剪切带在聚合物流体的争议。浓缩DNA溶液的剪切诱导动力学的相图正在绘制中。该项目旨在建立DNA分子的微观动力学和聚合物流体的宏观流动行为之间的直接联系。该项目阐明了在快速剪切下浓缩溶液中单个聚合物分子的动力学，并通过实验验证了聚合物流体剪切带的竞争理论。这些结果揭示了在快速流动下对浓缩聚合物流体缺乏理论理解，并最终揭示了在最工业相关条件下聚合物流体的实际工程模型。增加对聚合物流动的控制和预测将提高产量和效率，从而极大地影响美国制造业。该研究项目还涉及K-12与当地高中学生的外联计划，特别是那些在科学和工程方面代表性不足的学生。

项目成果

Shear-banding and superdiffusivity in entangled polymer solutions

缠结聚合物溶液中的剪切带和超扩散率

• DOI: 10.1103/physreve.96.062503
• 发表时间: 2017
• 期刊: Physical Review E
• 影响因子: 2.4
• 作者: Shin, Seunghwan;Dorfman, Kevin D.;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Dynamics of DNA-Bridged Dumbbells in Concentrated, Shear-Banding Polymer Solutions

DNA 桥哑铃在浓缩剪切带聚合物溶液中的动力学

• DOI: 10.1021/acs.macromol.0c02890
• 发表时间: 2021
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Shin, Seunghwan;Kou, Yangming;Dorfman, Kevin D.;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Effect of edge disturbance on shear banding in polymeric solutions

边缘扰动对聚合物溶液中剪切带的影响

• DOI: 10.1122/1.5042108
• 发表时间: 2018
• 期刊: Journal of Rheology
• 影响因子: 3.3
• 作者: Shin, Seunghwan;Dorfman, Kevin D.;Cheng, Xiang
• 通讯作者: Cheng, Xiang