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.
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.
Polymeric materials are widely used in our everyday life and will have even broader use in future advanced technologies. This project is focused on fundamental understanding of molecular motions in polymers that is crucial for their macroscopic properties. This understanding is instrumental in design of new polymeric materials with desired macroscopic properties. During the award period we deepen our knowledge of parameters controlling segmental and chain dynamics in polymers, exposing in particular the role of intermolecular interactions. Our studies also improved the understanding of molecular and ion transport mechanism through polymers. In particular, we demonstrate that the decoupling of ionic motions from structural dynamics in polymers is the only effective way to reach sufficient ionic conductivity required for polymer electrolytes. Based on this ideas and earlier knowledge of polymer dynamics we developed a novel concept for design of solid polymer electrolytes (SPE). SPE with sufficiently high ionic conductivity would significantly improve battery and fuel cells technology vital for our energy storage and conversion. Our studies of polymeric nanocomposite materials reveal significant influence of interfacial polymer layer on macroscopic properties of entire composite. They demonstrate significant intrinsic heterogeneity in dynamics and properties of the composite materials. They should be taken into account explicitly in any model describing nanocomposites. We discovered that quantum effects might play significant role in the glass transition of light molecules, such as water. They significantly broaden the glass transition range and lead to unusual temperature dependence of materials properties. Detailed analysis demonstrated the importance of quantum effects in dynamics of deeply supercooled water. In contrast to traditional view, these results emphasize that quantum effects might be not negligible in structural relaxation of materials with low glass transition temperature. Results of our studies are published in 20 peer-reviewed papers and were presented on many National and International meetings. These results deepen our fundamental understanding of polymer dynamics, Soft Matter dynamics and glass transition in general. This knowledge is crucial for several energy-related technologies and for many bio-technologies. Besides these scientific achievements the NSF funding helped significantly in development of human resources and education. Four graduate students and two undergraduate students were actively involved in this research. One of the PhD students successfully graduated and started his postdoctoral appointment at the University of Pennsylvania. Four postdoctoral researchers were also involved in this project. Two of them received faculty positions and one accepted an industrial position. Students and postdocs in our group were also involved in Science Olympiad and Science Fair events for school kids organized at the University of Tennessee. PI of the project, Dr. Sokolov, presented many tutorial lectures on National and International meetings educating young scientists in use of scattering techniques for studies of Soft Materials.