CAREER: Coarse-grained Theory and Simulation of Ion-containing Liquids: Study of Ion Solvation by Polymers and Ionic Liquids and between Nanoparticles

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NONTECHNICAL SUMMARYThis CAREER project supports research and education to study properties of liquids containing charged molecules. This project is focused on advancing understanding of how charged molecules, also known as ions, are surrounded by liquid molecules. This solvation process is a crucial step in making novel materials for emerging technologies; the lithium-ion polymer battery is one example. Existing computer simulations are unable to access the scales of length and time required for an adequate understanding of ion solvation.In this project, the PI will develop simplified computational models, called coarse-grained models, which represent units containing multiple atoms as effective particles with effective interactions. This procedure reduces the computational intensity of simulations making them tractable, but at the expense of some accuracy. This method will enable more straightforward identification of the key parameters and general mechanisms of ion solvation in polymers, which are long chain-like molecules. The project is aimed to advance the current state-of-the-art of molecular simulations. The knowledge acquired in this study will also help to refine existing theory at the level of atoms and associated simulation methods. Using the developed methods, the PI will also study the role of various nanoparticles in ion solvation. The education component involves framing a pedagogy for both college and high school students, in which students can develop scientific problem-solving skills and cultivate interdisciplinary approaches to problems using computer simulations and visualization. Education objectives will be achieved through utilizing a combination of programming languages and open-source software with an aim to help students visualize mathematical expressions and bridge the gap between practice and theory while enriching their programming skills. The PI also aims to use education innovations developed in this CAREER project to bridge the gap in education between soft- and hard-condensed matter physics. To extend the reach of the project, the PI and his group will collaborate with a K-12 educator to develop and hold short summer programs on topics related to this research. These programs are designed to provide a taste of soft-matter physics to local secondary school students using open-source software, such as PhET and Physlets, and simulation techniques, along with introductory programming. Ultimately, the aim is to develop, evaluate, and disseminate these outreach program resources. TECHNICAL SUMMARYThis CAREER project supports research and education to study the thermodynamic and electrochemical properties of ion-containing liquids. When liquid mixtures, polymers, different time and length scales, and significant spatial inhomogeneity of dielectric responses appear together, electrostatic interactions become amazingly intricate making understanding ion-containing liquids challenging.This study is aimed to provide a deeper understanding of ion solvation at molecular and atomistic scales to enable the design of novel electrochemical materials for next-generation technologies. The PI will focus mainly on the solvation energy of ions and the solvation mechanism in polymers and ionic liquids. The solvation mechanism of nanometer-sized solid bodies, such as metal oxide nanoparticles and quantum dots, will also be investigated with an aim to evaluate the effect of Lifshitz forces. The PI will investigate the hypothesis that the key factors in determining physical properties of ion-containing liquids are: (1) the strong fluctuation of electrostatic potentials, (2) the spatial inhomogeneity of the dielectric response, (3) the synergy among specific interactions such as hydrogen bonding and aromatic interactions, and (4) van der Waals forces from solid bodies. The complexity of polymers, such as chain architecture and chain connectivity, often makes understanding the physical properties that arise from these factors challenging. To address this issue, the PI will develop coarse-grained molecular simulations by connecting dipolar and quadrupolar monomeric units. The PI will also develop effective force fields between uncharged nanoparticles, which account for the molecular interactions of polyelectrolytes and ionic liquids.The proposed education plan seeks to frame a pedagogy for soft-matter sciences in physics. The plan will use open-source software such as PhET, Physlets, and LAMMPS that can be executed on standard computers to ensure wide accessibility. The PI’s main aim is to minimize a gradually surging concern in physics education, specifically, ‘‘the gap in education between hard- and soft-condensed matter physics.’’ To further the impact of the CAREER project, the PI and his group will hold short summer programs based on the PI’s expertise to provide a taste of soft-matter physics to local secondary schools. Developed and delivered in coordination with a K-12 education specialist, these outreach sessions will use open-source software, such as PhET and Physlets, and associated simulation techniques along with introductory programming. The aim of the outreach component is to develop, evaluate, and disseminate resources for use in similar programs nationwide.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.