Field-Theoretic Simulations: Polarization Phenomena and Coherent States

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

NONTECHNICAL SUMMARY This award supports theoretical research, software development, and education aimed at understanding two broad classes of emerging soft materials: ion-containing polymers and supramolecular polymers. These are materials that have great promise in emerging technology areas such as batteries, fuel cells, and lightweight vehicles and aircraft. Polymers are large, linear molecules that are ubiquitous in daily life in the form of plastics, rubbers, and textiles. However, their properties and processing behavior can be significantly changed by the incorporation of ions (electrical charges) along their backbones, or by the introduction of small chemical units that can participate in reversible chemical bonds, such as hydrogen bonds. This project aims to develop the theoretical and computer simulation tools necessary to understand the physical properties of these systems and to tailor them for applications. Both types of polymer systems have defied conventional theoretical and computational approaches either because of the large size and high concentration of the polymers, or the complexity of the electrostatic charge interactions and reversible bonds. This project will tackle these difficulties by modeling the polymers using "field theory" frameworks adapted from the theoretical physics literature. The PIs will further develop numerical algorithms that enable efficient computer simulations of the polymer field theory models. The fundamental understanding and the software tools emerging from the project will accelerate the rational design of this fascinating class of soft materials. Broader impacts of the proposed research include a continuance of the PIs' involvement in graduate, undergraduate, and post-doctoral training in theoretical and computational polymer science. Theoretically-oriented students will be exposed to broader soft materials disciplines through a close coupling with experimental groups at UCSB in chemical engineering, materials, and chemistry. The knowledge gained under the proposed project will be leveraged through the Complex Fluids Design Consortium at UCSB, an industry-national lab-academic partnership that is addressing the computational design of commercially relevant polymer formulations. The participants will further contribute to the vibrant education and outreach programs of UCSB's Materials Research Science and Engineering Center. TECHNICAL SUMMARY This award supports theoretical research, software development, and education aimed at understanding two broad classes of emerging soft materials: ion-containing polymers and supramolecular polymers This project will build on recent developments by the PIs of the "field-theoretic simulation" method, enabling direct numerical investigations of field theory models of polymers and soft materials without resorting to the mean-field approximation. The proposed research aims to make fundamental, transformative advances in understanding and methodology by providing a computationally efficient framework in which charge correlation and polarization phenomena can be explored without approximation in field-theoretic models. This will enable breakthrough studies of broad classes of ion- containing, inhomogeneous soft matter. A second thrust involves the development of "coherent states" field theory representations of supramolecular polymer models and robust numerical methods for simulating them. Such simulations will provide comprehensive guidelines for understanding the interplay of self-assembly and supramolecular bonding equilibria in this complex and emerging class of materials. In the context of polarizable field theory, models and efficient algorithms will be developed for simulating polymeric systems containing ions, permanent dipoles, and polarizable segments. These will be used to investigate the structure and phase behavior of ion-containing block copolymers, ionomers and polymeric ionic liquids, and inhomogeneous polyelectrolyte complexes. Electric field-induced phenomena in these important classes of systems will be further elucidated. The second thrust relates to coherent-states polymer field theory, a long neglected representation of interacting polymers inspired by second-quantized field theory. The proposed work aims to develop and optimize algorithms for simulations of coherent states models and apply those algorithms to fundamental studies of reversibly bonding, supramolecular polymers. The work will explore relationships between variables such as bonding equilibrium constants, stoichiometry and polymer architecture, and self-assembly behavior and thermodynamic properties. A focus will be on multi-component, inhomogeneous supramolecular systems, for which little understanding and few material design guidelines exist. Broader impacts of the proposed research include a continuance of the PIs' involvement in graduate, undergraduate, and post-doctoral training in theoretical and computational polymer science. Theoretically-oriented students will be exposed to broader soft materials disciplines through a close coupling with experimental groups at UCSB in chemical engineering, materials, and chemistry. The knowledge gained under the proposed project will be leveraged through the Complex Fluids Design Consortium at UCSB, an industry-national lab-academic partnership that is addressing the computational design of commercially relevant polymer formulations. The participants will further contribute to the vibrant education and outreach programs of UCSB's Materials Research Science and Engineering Center. 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.