Constraint Release Dynamics in Entangled Polymers

缠结聚合物中的约束释放动力学

• 批准号: 1403335
• 负责人: Ronald Larson
• 金额: $ 38万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1403335&HistoricalAwards=false
• 关键词: Constraint; Release; Dynamics; Entangled; Polymers

TECHNICAL SUMMARY:Mixtures of a monodisperse linear polymer with a monodisperse "star"-branched polymer represent the simplest polymers that expose the greatest deficiencies in current understanding of "constraint release" -- the effect that motion of one polymer chain has on its entanglements with other chains. This problem will be attacked by (1) obtaining a series of carefully synthesized star 1,4-polybutadiene polymers, which are then thoroughly characterized by the most advanced method available, namely temperature gradient interaction chromatraphy, or TGIC, (2) formulating and measuring the rheology of a set of some 40 mixtures of "star"-branched and linear polymers covering a range of constraint-release conditions, (3) applying the most advanced "tube" theories to predict the rheology of these mixtures and other such mixtures already available in the literature, and (4) collaborating through an international network, thereby accessing new polymer materials, dielectric relaxation data on cis-polyisoprene star/linear mixtures, and accessing results from "slip-link" and molecular dynamics polymer simulations for the prediction of the rheology and dielectric relaxation of these star/linear blends. NON-TECHNICAL SUMMARY:Polymers are among the most widely used synthetic materials; over 300 million tons are produced annually, for use in automobiles, medical supplies and equipment, wrappings for food preservation, and many other applications. The manufacture of such polymers in the United States is now increasingly attractive, due to cheap and abundant sources of natural gas, from which the starting chemicals for common polymers, such as polyolefins, are obtained. To economize on the quantity needed and to speed and cost-reduce the shaping of polymers into products, the flow properties of polymers must be optimized. This often involves the strategic addition of controlled amounts of long-chain branching to the polymer molecules. However, design of branching strategies depends on a thorough knowledge of polymer dynamics, which is currently inhibited by lack of understanding of a phenomenon called "constraint release" -- the effect that motion of one polymer chain has on its entanglements with other chains. This proposal represents a direct attack on this unsolved problem, using advanced tools of polymer synthesis and newly discovered methods of characterization of branching at unprecedented levels of accuracy. Understanding will be greatly enhanced by collaborating with an international team, which includes the most knowledgeable scientists in the world on various aspects of the problem, including synthesis (in Saudi Arabia, Korea, and the U.S.), characterization (in Korea and Japan), and computational modeling (in the U.S. and United Kingdom). The research will create the most complete body of experimental work on "constraint release" in branched polymers, and the data and theories will be made available to industrial researchers through publication, web-based access, and direct interaction with industrial researchers. Ph.D., Undergraduate, and High School students will be trained in the course of the research.

单分散线性聚合物与单分散“星星”-支化聚合物的混合物代表了最简单的聚合物，其暴露了目前对“约束释放”--一种聚合物链的运动对其与其它链的缠结的影响--的理解中的最大缺陷。该问题将通过以下方式解决：（1）获得一系列精心合成的星星1，4-聚丁二烯聚合物，然后通过最先进的可用方法，即温度梯度相互作用色谱法或TGIC对其进行彻底表征，（2）配制并测量一组约40种“星星”-支化和线性聚合物的混合物的流变学，所述混合物覆盖约束释放条件的范围，（3）应用最先进的“管”理论来预测这些混合物和文献中已经可用的其它这类混合物的流变学，以及（4）通过国际网络合作，从而获得新的聚合物材料，关于顺式聚异戊二烯星星/线性混合物的介电弛豫数据，并访问来自“滑动链接”和分子动力学聚合物模拟的结果，以预测这些星星/线性共混物的流变学和介电弛豫。聚合物是使用最广泛的合成材料之一;每年生产超过3亿吨，用于汽车，医疗用品和设备，食品保鲜包装以及许多其他应用。由于天然气的廉价和丰富来源，在美国制造这种聚合物现在越来越有吸引力，从天然气中可以获得普通聚合物如聚烯烃的起始化学品。 为了节省所需的数量并加快和降低聚合物成型为产品的成本，必须优化聚合物的流动性能。这通常涉及向聚合物分子中战略性地添加受控量的长链支化。然而，支化策略的设计取决于对聚合物动力学的透彻了解，目前由于缺乏对一种称为“约束释放”的现象的理解而受到抑制-一种聚合物链的运动对其与其他链的缠结的影响。该提案代表了对这一未解决问题的直接攻击，使用聚合物合成的先进工具和新发现的表征支化的方法，其准确性达到前所未有的水平。通过与一个国际团队合作，将极大地增强理解，该团队包括世界上最有知识的科学家，他们对该问题的各个方面都很了解，包括合成（沙特阿拉伯，韩国和美国），表征（在韩国和日本）和计算建模（在美国和英国）。这项研究将创造最完整的实验工作的“约束释放”在支化聚合物，数据和理论将提供给工业研究人员通过出版物，基于网络的访问，并与工业研究人员直接互动。哲学博士、本科生和高中生将在研究过程中接受培训。