Influence of polymer structure on heterogeneity and cooperativity in segmental and fast dynamics

聚合物的许多独特性质及其加工过程都是由分子运动控制的。因此，理解聚合物动力学的基本原理对于合理设计具有所需性能的新型材料至关重要。本研究主要是对聚合物的动态非均匀性和协同性进行实验研究。拟议的研究的主要目标是发展链连接性，刚性和分子间相互作用的作用，在链段和快速动态聚合物的更深入的理解。几个实验技术（中子和光散射和介电弛豫光谱）将在这个程序中提供详细的微观信息集体动力学，异质性和协同分段和快速动态。对具有不同刚性、分子量和各种分子间相互作用的大分子的研究将揭示它们的化学结构对聚合物的松弛现象和粘弹性的影响。该项目还针对描述聚合物动力学中的异质性和协同性的唯象模型的发展。了解聚合物中的分子运动对于它们的大量应用至关重要-从能源相关领域（例如电池，碳封存）到生物医学技术。这个项目的重点是对控制这些聚合物分子动态运动的微观机制的基本理解。 它将影响材料科学、物理学和生物物理学的各个领域，并可能对当前和未来技术应用的新型材料的合理设计和合成产生影响。 该计划的一个重要组成部分是通过研究生和本科生积极参与这项研究和国际合作，以及通过开发研究生课程，为未来技术培训专家。 还注意与代表性不足的群体合作，并与K-12学生进行外联。拟议的计划促进积极的国际合作，也与橡树岭国家实验室和国家标准与技术研究所的国家多用户设施的合作。

TECHNICAL SUMMARY:Many unique properties of polymers and their processing are controlled by molecular motions. Thus, understanding fundamentals of polymer dynamics is crucial for rational design of novel materials with desired properties. This research is focused on experimental studies of dynamic heterogeneity and cooperativity in polymers. The main goal of the proposed research is to develop deeper understanding of the role of chain connectivity, rigidity and inter-molecular interactions in segmental and fast dynamics of polymers. Several experimental techniques (neutron and light scattering and dielectric relaxation spectroscopy) will be employed in this program to provide detailed microscopic information on collective dynamics, heterogeneity, and cooperativity in segmental and fast dynamics. Studies of macromolecules with different rigidity, molecular weights, and various inter-molecular interactions will reveal the influence of their chemical structure on relaxation phenomena and viscoelastic properties of polymers. The project also targets the development of phenomenological models describing heterogeneity and cooperativity in polymer dynamics. NON-TECHNICAL SUMMARY:Understanding molecular motion in polymers is crucial for their large number of applications -- from energy related fields (e.g. batteries, carbon sequestration) to biomedical technologies. This project focuses on fundamental understanding of microscopic mechanisms controlling the dynamical motions of these polymer molecules. It will impact various fields of materials science, physics, and biophysics, and might have implications for rational design and synthesis of novel materials for current and future technological applications. A significant part of the proposed program is training of specialists for future technologies through active involvement of graduate and undergraduate students in this research and in international collaborations, as well as through development of graduate courses. Attention is also paid to work with underrepresented groups and outreach to K-12 students. The proposed program promotes active international collaborations; also collaborations with national multi-user facilities at Oak Ridge National Laboratory and National Institute of Standards and Technology.