CAREER: Molecular Modeling of Ring Polymer Mechanics - Expanding Applicability of Ring Polymer

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NONTECHNICAL SUMMARYThis CAREER award supports an integrated research, education, and outreach project on the mechanics of ring polymers. Common polymeric materials include plastics and elastomers, as used in car bumpers and tires, respectively. Mechanical properties, such as stretchability, softness, and fracture toughness, serve as one critical foundation for the proper functions of polymeric materials. The design of polymer mechanics starts with the synthesis of polymer molecules. While conventional polymers are made by linking monomers to long linear chains with open ends, recent substantial progress in polymer chemistry has enabled the synthesis of ring polymers as closed loops. Ring polymers offer unprecedented building blocks to transform polymer mechanics because various topological structures can be introduced through the unique loopy conformations of ring polymers. In this project, the PI will combine molecular simulations and theory to identify transformative ring-topology-based pathways to tailor polymer mechanics. The team of the PI will address fundamental questions that need to be answered for harnessing the synthetic capability of controlling ring polymer topology to design novel polymeric materials with tailored topological structures and mechanical properties. The combined molecular simulations and theory will elucidate the dependencies of the ring-polymer-based topological structures on experimentally controllable parameters as well as the relations between the topological structures and mechanical properties of ring polymers in the bulk, at polymer interfaces, and in nanoparticle polymer composites. These efforts will be connected to experiments that will guide the choice of the system parameters and test the predictive capability of the computational and theoretical research to carried out. The PI’s teaching and scientific outreach will leverage the rich and novel research portfolio of ring polymer mechanics, especially molecular simulations. Simulations derived from the PI’s research will act as the major components of on-site workshops for high school students, research projects for summer students, and tutorials for learners of molecular simulations. With the vivid rendering of the microscopic world, molecular simulations are well-positioned to disseminate molecular science to the public. The PI’s team will design simulation-based demonstrations for visitors to local museums as well as viewers of online media. The activities will benefit diverse participants including members of economically disadvantaged families and underrepresented minority groups in science, technology, engineering, and mathematics (STEM). TECHNICAL SUMMARYThis CAREER award supports an integrated research, education, and outreach project focusing on the role of ring polymers in transforming polymer mechanics that serve as the foundation for the proper functions of versatile polymeric materials. Novel ring-polymer-based topological structures include the non-concatenation of rings, the threading of a ring by linear polymer chains, and concatenated “Olympic” rings. These topological structures differ qualitatively from the entanglements in conventional linear polymers and their derivatives and are anticipated to enrich the topology-based pathways to tailor the mechanical properties of polymers, such as stretchability, softness, and fracture toughness, for customized applications. In this project, by combining molecular simulations and theories, the PI’s team will delineate the microscopic picture of ring polymers in the formation of topological structures and the mechanical response of various systems in the bulk, at polymer interfaces, and in nanoparticle polymer composites. The quantitative relations necessary for integrating ring polymer chemistry and physics into the molecular engineering of polymer mechanics will be identified. The team of the PI will work closely with experimentalists who synthesize ring-polymer-based systems and characterize their mechanical properties to test the results of the computational and theoretical work. The proposed research will validate the transformative ideas that expand the capabilities of ring polymers in polymer mechanics and advance the frontier of knowledge about ring polymers. Molecular simulations have precise control of polymer topology and direct access to microscopic information. Coupled with a topological analysis, the simulations will provide unparalleled insights into the role of cyclic topology in mechanical deformation and fracture. Traditional theories for the elastic, plastic, and fracture mechanics of polymers will be extended by incorporating more recently established models for the unique conformations and dynamics of ring polymers. The computational and theoretical efforts will motivate the refinement of chemical synthesis techniques, spur experimental studies of ring polymer mechanics, and thus set a new paradigm of integrating molecular simulations and theory with chemistry and mechanical engineering. The PI’s teaching and scientific outreach will leverage the rich and novel research portfolio of ring polymer mechanics, especially molecular simulations. Simulations derived from the PI’s research will act as the major components of on-site workshops for high school students, research projects for summer students, and tutorials for learners of molecular simulations. With the vivid rendering of the microscopic world, molecular simulations are well-positioned to disseminate molecular science to the public. The PI’s team will design simulation-based demonstrations for visitors to local museums as well as viewers of online media. The activities will benefit diverse participants including members of economically disadvantaged families and underrepresented minority groups in science, technology, engineering, and mathematics (STEM).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.