CAREER: Using numerical simulation to investigate the influence of collective behaviors on the sequences of step-grown copolymers

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Polymers are long molecular chains formed by linking together many repeating molecular sub-units called monomers. Copolymers are a special class of polymers. They are made by using two (or more) different monomers and, depending on how the monomers are combined, the copolymers can exhibit unique properties. In biological copolymers, such as DNA and proteins, the sequence of monomers is precisely controlled by the cell. In contrast, controlling the sequence of monomers in the laboratory remains a significant challenge, and this limits the usefulness of synthetic copolymers. With support from the Macromolecular, Supramolecular and Nanochemistry and the Chemical, Structure Dynamics, and Mechanisms A Programs in Division of Chemistry, Professor DuBay at the University of Virginia is using computer simulations to study copolymers that are grown step-by-step. Professor DuBay and her students have developed a computer model to simulate copolymer growth. They are using the model to better understand the factors that determine the monomer sequence. Insights gained from their studies could enable better sequence control, which could impact technologies ranging from energy conversion, to water purification and drug delivery. This research project is conducted by a diverse team of undergraduate and graduate researchers, training them for productive careers in the chemical industry. In addition, the next generation of professional communicators are embedded into the lab, enabling them to better understand the scientific process and recognize and report on breakthrough achievements. Finally, this project focuses on improving the scientific information literacy of current college students to better equip them to carefully assess information from a variety of public sources. Emergent collective behaviors among the polymerizing chains, such chain alignment, self-templating, or phase separations, can significantly influence how often different reactive species encounter one another during a copolymerization and the probability of a reaction when they do. As a result, such behaviors are expected to affect the incorporation frequency and placement of different monomers in the chain. However, the current theoretical framework for understanding what governs copolymer sequences does not account for such complexities. Professor DuBay is utilizing coarse-grained simulations of step-growth copolymerizations to study the influence of such behaviors on copolymer sequence. By combining Langevin dynamics with a reactive cutoff distance approach that allows for the formation of polymer bonds, these simulations enable a comprehensive investigation of the influence of various monomer characteristics and reaction conditions on the resulting copolymer sequences. Copolymers and reaction regimes that are shown to be sensitive to this unconventional mechanism of sequence biasing are being studied through a collaboration with synthetic polymer chemists. In addition, Professor DuBay is developing a program to embed future writers and communicators in polymer-focused research labs as well as a novel polymer case-study based curriculum for introductory chemistry courses. 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.