Molecular Details of the Fast Dynamics and Fragility in Polymers

技术概述：分子运动定义了聚合物的许多独特的宏观特性，了解聚合物动力学的基本原理对于设计具有理想性能的高级聚合物或复合材料至关重要。在聚合物动力学的各个方面中，快速动力学，即在GHz-THz频率范围内的动力学，由于其在先进信息和通信技术、微电子和光子学中的重要应用而值得特别关注。了解聚合物体系中快速动力学的微观机制和片段弛豫（脆性）的温度变化是提出的研究计划的主要目标。在这个程序中使用的许多实验技术（光，中子和x射线散射和介电光谱）提供了聚合物中快速和片段动力学的详细微观信息，以及它们对链分子结构的依赖。所提出的高压测量方法提供了一种分离分子填充、温度和单体结构在聚合物动力学和玻璃化转变中的作用的方法。与理论的紧密合作带来了对实验结果的更深入的理解和解释以及新思想的形成。研究结果将对聚合物科学产生重大影响，并在更广泛的方面对复杂系统的动力学，材料科学和物理学，以及通过对生物大分子动力学的更好理解而对生物物理学产生重大影响。非技术总结：信息和通信技术正在向更高的频率发展，其进步很大程度上取决于我们对该频率范围内材料行为的理解。提出的研究重点是快速分子运动及其在高分子材料宏观性能中的作用。这些方向的进展将影响材料科学、物理学和生物物理学的各个领域。此外，了解快速动力学对当前和未来通信、信息和计算技术材料的设计和合成、光子和微电子应用材料的发展以及一些生物技术的进步具有重大影响。拟议的计划促进积极的国际合作以及与NIST和ANL的国家多用户设施的合作。该计划还通过研究生和本科生积极参与这项研究和研究生课程的开发，对未来专家的教育产生重大影响。此外，还关注弱势群体和K-12学生的外展工作。

Technical Summary:Molecular motions define many unique macroscopic properties of polymers, and understanding fundamentals of polymer dynamics is crucial for design of advanced polymeric or composite materials with desired properties. Among various aspects of polymer dynamics, the fast dynamics, i.e. the dynamics in the GHz-THz frequency range, deserves particular attention due to its importance for applications in advanced information and communication technologies, in microelectronics and photonics. Understanding the microscopic mechanisms of the fast dynamics and the temperature variation of segmental relaxation (fragility) in polymeric systems are the main objectives of the proposed research program. A number of experimental techniques (light, neutron and X-ray scattering and dielectric spectroscopy) employed in this program provide detailed microscopic information on the fast and segmental dynamics in polymers, their dependence on molecular structure of the chain. The proposed high-pressure measurements provide a means to separate the role of molecular packing, temperature and monomer structure in the polymer dynamics and the glass transition. Tight collaboration with theory brings deeper understanding and interpretation of experimental results as well as formulation of new ideas. The results will have significant impact on polymer science, and in broader aspect on dynamics of complex systems, materials science and physics in general, and also on biophysics through a better understanding of dynamics of biological macromolecules.Non-Technical Summary:Information and communication technologies are moving to higher frequency and their progress depends strongly on our understanding of materials behavior at this frequency range. The proposed research focuses on fast molecular motions and their role in macroscopic properties of polymeric materials. Advances in the proposed directions will impact various fields of materials science, physics and biophysics. Moreover, understanding the fast dynamics has significant impact on design and synthesis of materials for current and future communication, information and computation technologies, on developments of materials for photonic and microelectronic applications, and on progress in some bio-technologies. The proposed program promotes active international collaboration and collaboration with national multi-user facilities at NIST and ANL. The proposed program also significantly impacts education of future specialists through active involvement of graduate and undergraduate students in this research, developments of graduate courses. Attention is also paid to work with underrepresented groups and K-12 students outreach.