Topologically Frustrated Dynamics and Memory in Polyelectrolyte Systems

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

NON-TECHNICAL SUMMARY Macromolecules made of monomers carrying electrical charges are ubiquitous in all living organisms and continue to catalyze formulations of modern water-based materials. A fundamental understanding of the behavior of such charged macromolecules dispersed in aqueous electrolyte solutions continues to be a challenge. The origin of the challenge lies on the fact that these molecules do not behave on their own as individual molecules, but they are correlated over very large distances spanning the whole collective system. As a result, the properties of charged macromolecules are full of challenges without adequate conceptual framework to understand their rich phenomenology. In fact, formulation of a fundamental understanding of such strongly correlated macromolecules remains one of the most difficult subjects in physical and biological sciences. Yet, such a fundamental understanding is crucial to successfully design new materials for separation science, highly water-absorbent goods, drug delivery, water-based electrical conductors, and memory devices, in addition to rationalizing the rich phenomenology already accumulated over many decades. The PI proposes to formulate a fundamental understanding of how electrically charged macromolecules move around in an electrolyte solution, or inside a gel, or from one region to another through intervening barriers due to crowding, and how to endow macromolecular memory effects in water-based systems. In addition to advancing the field of charged macromolecules, the proposed activities include strong support of diversity and training a new generation of scholars to enable their future participation in the multi-billion dollar industry of water-based materials. TECHNICAL SUMMARY The PI proposes experiments and theoretical developments to investigate polyelectrolyte dynamics, polyelectrolyte gel dynamics, topologically frustrated non-diffusive dynamical state, coacervate gel composites, and macromolecular memory in hydrogels, by combining light scattering, neutron scattering, impedance spectroscopy, rheology, single molecule electrophoresis, statistical mechanics, field theory, and several simulation techniques. Specifically, the proposal addresses (a) topologically frustrated non-diffusive polymer dynamical state and its boundaries with the entropic barrier and reptation regimes, (b) phase diagrams, structure and hierarchical dynamics in coacervate gel composites, (c) electrical conductivity of gel composites, and (d) memory in hydrogels. This proposal is aimed at understanding charged hydrogel composites under severe non-equilibrium conditions, and discovering new conceptual models for polyelectrolyte transport and memory in aqueous charged polymer systems. A fundamental understanding of the behavior of this important class of materials will help to design novel water-based polymeric materials with enhanced benefits to society. Training of graduate students and postdocs in this challenging research area is also an important component of the proposed activity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.