Cooperative Dynamics in Polymer Fluids and their Mixtures

这是由材料理论计划和理论与计算化学计划共同资助的理论资助。 本研究的目的是发展一个统一的微观描述的聚合物动力学系统在不同的热力学和动力学条件。这里的主要重点是聚合物液体及其混合物。 在过去已经发展了几种严格的理论方法来描述聚合物动力学。然而，每一个都具体描述了一个定义明确的现象。 有时，对同一现象的两种方法都基于物理上不相容的假设（例如，可压缩或不可压缩流体）。我们的方法是微观和系统特定的。它根据局部化学结构、特定的分子内和分子间相互作用以及物理参数来预测动力学性质。到目前为止，我们的方法已经成功地解释了实验观察到的质心异常扩散和正常模式的异常松弛的聚合物熔体的基础上，分子间的时间相关的聚合物链由于动态异质性的性质，我们将优化我们的微观理论方法在几个方向上工作。首先，我们的方法将扩展到聚合物混合物。一个新的分析形式的聚合物熔体和共混物的分子间的潜力将实施：预测ofdynamic量将测试对微观模拟。其次，我们将研究局部和全球聚合物动力学的合作效应（内和分子间起源）。 最后，我们将开发一个粗粒化程序，以优化聚合物液体模拟的计算时间。更广泛的影响开发一个理论工具，正式相关的物理和化学参数的影响（例如，聚合物分子量、密度浓度和温度）和局部分子结构与整体动力学性质（例如，粘度、玻璃化转变温度）将为设计新聚合物材料的定制合成提供重要信息。聚合物动力学的统一方法将有助于发展对聚合物运动的全面理解。后者一直是聚合物物理学中的实际和基本兴趣的长期目标，因为所有聚合物材料（纤维、塑料、涂层材料等）都可以在聚合物物理学中应用。都是在液态下加工的 五名妇女（本科生、研究生和博士后）和一名西班牙裔学生参与了该项目。与俄勒冈州大学实验小组的合作为项目中的学生产生了重要的互动。 学生们参与了宣传我们的研究和俄勒冈州的本科院校和西班牙裔高中生的推广活动。 高分子流体热力学和统计力学教学模块的引入丰富了P.I.教授的本科课程。在初级和高级级别。

This is a theoretical grant funded jointly by the Materials Theory Program and the Theoretical and Computational Chemistry Program. The research is aimed to develop a unified microscopic description of polymer dynamics for systems in different thermodynamic and dynamical conditions. The main focus here is on polymer liquids and their mixtures. Several rigorous theoretical approaches have been developed in the past to describepolymer dynamics. However, each one specifically describes a well-defined phenomenon. Sometimes two approaches to the same phenomenon stand on physically incompatible hypotheses (e.g., compressible or incompressible fluids). Our approach is microscopic and system-specific. It predicts dynamical properties on the basis of local chemical structure, specific intra- and intermolecular interactions, and physical parameters. So far, our approach has successfully explained the experimentally observed center-of-mass anomalous diffusion and the anomalous relaxation of normal modes in polymer melts, on the basis of intermolecular time dependent correlation of polymer chains due to the dynamically heterogeneous nature of polymer liquids.We will optimize our microscopic theoretical approach working in several directions. First, our approach will be extended to polymer mixtures. A new analytical form of the intermolecular potential for polymer melts and blends will be implemented: predictions ofdynamical quantities will be tested against microscopic simulations. Second, we will investigate cooperative effects (of intra- and intermolecular origin) on local and global polymer dynamics. Finally, we will develop a coarse-graining procedure to optimize the computational time in simulations of polymer liquids.Broader ImpactThe development of a theoretical tool that formally correlates the effect of physical andchemical parameters (e.g., polymer molecular weight, density concentration, and temperature) and local molecular structure to the global dynamical properties (e.g., viscosity, glass transition temperature) will provide essential information in designing custom-tailored syntheses of new polymeric materials. A unified approach to polymer dynamics will help developing a comprehensive understanding of polymer motion. The latter has been a long-standing goal of both practical and fundamental interest in polymer physics, since all polymeric materials (fibers, plastics, coating materials, etc.) are processed in their liquid state. Five women (undergraduate, graduate students and postdoctoral associates) and one Hispanic student have been involved in this project. Collaborations with experimental groups at the University of Oregon have produced important interactions for the students in the project. Students have been involved in outreach activities to publicize our research and the University of Oregon to undergraduate institutions and high-school students of Hispanic descent. The introduction of educational modules on thermodynamics and statistical mechanics ofpolymer fluids has enriched undergraduate courses taught by the P.I. at the junior and senior levels.