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

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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.