Dynamics of Associating Polymers: From Association to Segmental and Chain Relaxations

NON-TECHNICAL SUMMARY:

Associating polymers are a class of polymeric materials that are promising candidates for a large number of applications ranging from energy-related fields to biomedical technologies. This research focuses on fundamental understanding of how the specially designed interactions control molecular motions and macroscopic properties of associating polymers. A broad range of experimental techniques will be employed to analyze molecular motions on different time and length scales, and their dependence on chemical structure and rigidity/flexibility of the individual polymer molecules. A description of structure-properties relationship in this relatively new class of materials will also be developed. This knowledge is important for rational design and synthesis of novel 'smart' materials with self-healing and stimuli-responsive properties for many future technological applications. It will have an impact on various fields of science and engineering, including materials science, physics, chemistry and biophysics. A significant part of this project is the education of specialists through development of graduate courses and active involvement of graduate and undergraduate students in research. Attention will also be paid to working with underrepresented groups and to outreach to K-12 students. This research promotes collaborations with international colleagues and with the Spallation Neutron Source and Center for Nanophase Materials Sciences at the Oak Ridge National Laboratory.

TECHNICAL SUMMARY:

Associating polymers, formed by reversible non-covalent intermolecular interactions, include a wide spectrum of fundamentally and technologically important materials. Rational design, synthesis, and fabrication of novel associating polymers require a deep fundamental understanding of how the local reversible interactions and backbone flexibility affect the macroscopic properties of associating polymers. Despite intense attention and effort in the past, the chain and structural dynamics in associating polymers remain poorly understood, especially in the case of the melt state. In this project, the chain and structural dynamics in model associating polymers will be studied by a combination of rheology, dielectric spectroscopy, light scattering, and neutron scattering. New experimental methods and protocols will be developed by borrowing existing concepts and techniques from the fields of conventional polymers, hydrogen-bonded glass-forming liquids, and ionic solutions. In addition, the current theoretical models for associating polymers will be critically examined. This project aims to establish the phenomenological foundation for understanding the dynamics of associating polymers.