RUI: Phase transitions of a single polymer chain: Effects of solvent, confinement, and tethering

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TECHNICAL SUMMARYThis award made on an RUI proposal supports computational and theoretical research and education that addresses conformational phase transitions of single polymer molecules in response to variations in environmental variables such as temperature, pressure, or solution pH. This topic is of broad importance since both the bulk properties of polymer containing materials and the functionality of biopolymers and many polymer-based "smart" materials are directly determined by the underlying microscopic conformation of individual polymer molecules. Many smart or biologically active materials utilize polymer chains tethered to surfaces or nanoparticles. The effects of tethering and, more generally, confinement on single-chain phase transitions will also be investigated. This research continues and extends the recent work by the PI with significant contributions from undergraduate collaborators in the areas of solvent effects on polymer conformation and phase transitions of isolated homopolymer chains.The research objectives of this project are: (i) to elucidate the effects of local environment on the conformational phase transitions of a single polymer chain as relevant, for example, to the design and function of polymer based environmentally responsive smart materials; (ii) to study single-polymer phase transitions, in particular, the recently discovered homopolymer all-or-none "folding" transition, in simple models in order to establish the underlying physics of the universal aspects of protein folding; and (iii) to develop conformation and free energy landscapes using a rigorous microcanonical approach to study transition order, pathways, and kinetics of single-chain phase transitions. This work will make use of both the solvation potential approach, recently developed by the PI to reduce computational complexity in modeling polymer-solvent systems, and advanced simulation techniques that allow for direct computation of the density of states of classical many-body systems. The latter methods provide complete thermodynamic information and can be used to carry out subsequent multi-canonical simulations to determine structural information. This research contributes to the understanding of single-macromolecule behavior through the development of rigorous solvation potentials, density of states simulation methods, and microcanonical analysis techniques. It will contribute to efforts to develop rational design principles for functional polymer-based and biomimetic. This research program has been designed to allow for maximum student participation by dovetailing into the physics curriculum at Hiram College. Computation and simulation methods taught in the core courses establish a direct link between classroom learning and this research program and provide students with the tools needed to make meaningful contributions to this work. The undergraduate students who participate in this research will benefit by learning state of the art computer simulation techniques and will have opportunities to present at scientific meetings. Of the fourteen students who have worked with the PI at Hiram, twelve are now, or will be pursuing advanced study in physics, materials science, or engineering. This research proposal intends to continue such student successes and the PI hopes that these successes will help recruit more under-represented students into the sciences.NON-TECHNICAL SUMMARYThis award made on an RUI proposal supports computational and theoretical research and education to study transformations in the size and shape assumed by long chain-like molecules, polymers, as they respond to changes in their environment, such as changes in temperature and pressure. The PI will use advanced computer simulation techniques and models to advance understanding of this important problem. Changes in the size and shape of the polymers in living systems are often necessary to carry out functions at the biomolecular level to sustain life. A better understanding of this process contributes to developing design principles for smart materials that change their properties in response to changes in their environment in way that is reversible. Smart materials have many applications, including actuators, sensors, and a wide range of medical devices. This research program has been designed to allow for maximum student participation by dovetailing into the physics curriculum at Hiram College. Computation and simulation methods taught in the core courses establish a direct link between classroom learning and this research program and provide students with the tools needed to make meaningful contributions to this work. The undergraduate students who participate in this research will benefit by learning state of the art computer simulation techniques and will have opportunities to present at scientific meetings. Of the fourteen students who have worked with the PI at Hiram, twelve are now, or will be pursuing advanced study in physics, materials science, or engineering. This research proposal intends to continue such student successes and the PI hopes that these successes will help a recruit more under-represented students into the sciences.