Field-Theoretic Simulations: Coherent States and Particle-Field Linkages

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

NONTECHNICAL SUMMARY This award supports theory and computation, and education to advance computer simulation of polymeric materials which are based on polymers, long-chain-like molecules. Polymers are versatile materials that have remarkably broad applications in textiles, plastics and rubbers, paints and coatings, and consumer products including haircare products, cleansers, detergents, etc. They are also increasingly important in new energy harvesting technologies such as organic solar cells, as solid electrolytes in energy storage devices such as batteries, and in advanced drug delivery and medical devices. Perhaps surprisingly, the design of new polymers for such applications proceeds by trial-and-error experimentation until the molecular design yields the targeted properties and function. This project aims to advance in-silico computational design of polymeric materials. One component of the project will develop a new theoretical representation of polymers into a computational platform that will enable the design of materials with thermally reversible bonds. Such materials have unique properties such as self-repair when damaged, or responsiveness to thermal or chemical stimuli, both important in a variety of emerging applications. A second effort aims to link molecular simulations at the atomic scale with simulations that employ a different theoretical formulation and can reach scales of hundreds of micrometers. This capability will enable chemical details to be embedded in the theoretical models; the latter providing the link to polymer material properties. If successful, this multiple length scale modeling platform could dramatically accelerate the design of polymers for existing and new applications. Broader impacts of the proposed research include engagement by the project personnel 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 the University of California, Santa Barbara (UCSB) in chemical engineering, materials, and chemistry. 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. All participants will contribute to the vibrant education and outreach programs of UCSB's Materials Research Science and Engineering Center. TECHNICAL SUMMARY This award supports theory and computation, and education to advance theory and modeling of polymeric materials. This project will enhance the capabilities of the field-theoretic simulation (FTS) method, permitting numerical investigations of field theory models of polymers and soft materials without resorting to a mean-field approximation. One project component builds a new platform for FTS based on coherent-states polymer field theory, a long-neglected representation of interacting polymers inspired by quantum 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. Relationships will be explored between variables such as bonding equilibrium constants, stoichiometry and polymer architecture, and self-assembly behavior and thermodynamic properties. The unique structure of the coherent-states framework will enable a new force-matching scheme for systematic coarse-graining within FTS, applicable to both supramolecular and non-reactive polymer systems. Another component of the proposed research is to develop a workflow in which all-atom particle models are mapped to coarse-grained particle models using relative entropy minimization; the latter models of a form to allow analytical conversion to a fully-parameterized field theory. FTS can then be used to access mesoscale structure and thermodynamic properties directly connected to the underlying chemistry of the polymers. Broader impacts of the proposed research include engagement by the project personnel 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 the University of California, Santa Barbara (UCSB) in chemical engineering, materials, and chemistry. 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 all-atom to FTS workflow targeted by the project has the potential to revolutionize in silico design of such formulations. All participants will 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.