Poly(ethylene oxide) and Water: Simulations and Modeling of Solution Properties, Phase Behavior, Partitioning and Particle Interactions

University Of Utah, Salt Lake City UT

Investigators

Abstract

0076306 Smith This grant is funded jointly by the Theoretical Chemistry and Materials Theory Programs in the Divisions of Chemistry and Materials Research respectively. Poly(ethylene oxide) (PEO), also referred to as poly(ethylene glycol), is used in a multitude of aqueous solution applications ranging from drag reduction to drug delivery. In addition, PEO solutions have been widely studied, being themselves of fundamental interest as well as serving as model systems in efforts to better understand aqueous polymer solutions. Experimental and modeling studies have resulted in valuable insight into the behavior of PEO solutions. However, many of the most interesting characteristics of these solutions responsible for their broad scope of applications, such as conformations, hydrophobic interactions, phase behavior, the influence of salts, and the interactions of the polymer with particles and proteins, remain at best poorly understood. The principal goals of the research are to gain improved understanding of the behavior of aqueous polymer solutions through coordinated simulation and modeling studies of PEO solutions, to develop and disseminate the computational algorithms and tools required to carry out these studies, and to familiarize undergraduate students students with the power and utility of molecular modeling. Atomistic molecular dynamics simulation studies will be carried out in order to investigate the conformational, structural, thermodynamics and dynamic properties of aqueous PEO solutions. Additional simulations aimed specifically at understanding the phase behavior of PEO solutions, including the influence of molecular weight and pressure as well as the role of polymer conformations, water structure, and ether-water hydrogen bonding, will be performed. Finally, simulation studies of the interactions of PEO solutions with model nanoparticles and proteins will be carried out, aimed at gaining a better understanding of polymer mediated depletion attraction between particles as well as the roles of competitive hydration and hydrophobic polymer-particle interactions. Acheiving these scientific goals requires the capability of addressing solution properties over a wide range of length scales. A force field development toolkit will be created to link the electronic structure level to the atomistic level through parametrization of accurate classical atomistic potential functions. In turn, the detailed results of atomistic molecular dynamics simulations of PEO solutions will serve as input into liquid state theory models for polymer solutions and interactions of polymers with particles, potentially extending the length scale of the atomistic studies as well as allowing investigation of parameter space well beyond that directly accessible by molecular dynamics simulations. These studies have important ramifications beyond the benefits provided by an improved understanding of PEO solutions. These efforts will add significantly to the overall understanding of the behavior of aqueous solutions, both synthetic and biological, as well as that of polymer solutions in general, particularly in crossover concentration regimes and at higher concentrations where there is a paucity of simulation studies. The computational tools and algorithms developed for the proposed simulations, such as the force field development toolkit and methods for determining free energies and phase equilibrium in polymer solutions, will be widely beneficial to the simulation community. Molecular dynamics simulations tools, currently used for graduate teaching as well as graduate and undergraduate level research, will be developed into tools for undergraduate coursework and will include materials simulation and property prediction modules designed to give undergraduate students hands-on experience with computational materials science. %%% This grant is funded jointly by the Theoretical Chemistry and Materials Theory Programs in the Divisions of Chemistry and Materials Research respectively. Poly(ethylene oxide) (PEO), also referred to as poly(ethylene glycol), is used in a multitude of aqueous solution applications ranging from drag reduction to drug delivery. In addition, PEO solutions have been widely studied, being themselves of fundamental interest as well as serving as model systems in efforts to better understand aqueous polymer solutions. Experimental and modeling studies have resulted in valuable insight into the behavior of PEO solutions. However, many of the most interesting characteristics of these solutions responsible for their broad scope of applications, such as conformations, hydrophobic interactions, phase behavior, the influence of salts, and the interactions of the polymer with particles and proteins, remain at best poorly understood. The principal goals of the research are to gain improved understanding of the behavior of aqueous polymer solutions through coordinated simulation and modeling studies of PEO solutions, to develop and disseminate the computational algorithms and tools required to carry out these studies, and to familiarize undergraduate students students with the power and utility of molecular modeling. ***