Development of quantum chemistry-based polarizable potential to describe intermolecular interactions of nonionic polymers with water

A new quantum chemistry-based, atomic point polarizable dipole potential was developed for molecular dynamic (MD) simulations of poly (ethylene oxide) (PEO) and poly (propylene oxide) (PPO) aqueous solutions employing a modified version of a single water molecule with four interaction sites and Drude polarizability (SWM4-DP). A twoextended charge ether model has been chosen as best describing electrostatic potential of DME. Ether/water interactions were parameterized to reproduce the binding energy of water with 1,2-dimethoxyethane (DME) that was determined from high-level quantum chemistry calculations. The DME/water nonbonded parameters were found to be transferrable to 1,2-dimethoxypropane (DMP). An accuracy of the developed force field was justified by comparing thermodynamics properties obtained from molecular dynamics simulations with experimental data including free energy, enthalpy, and entropy of DME solvation. Free energy of DME solvation in water was obtained employing a new interface transit method (ITM) followed by calculations using perturbation theory. Simulations of DME/water solutions at room temperature using the new polarizable force field yielded enthalpy of solvation in a good agreement with experiment. Simulations of PEO/water and PPO/water solutions improved ability of the new force field to capture, at least qualitatively, low critical solution temperature (LCST) behavior in these solutions. The predicted miscibility of PEO and water as a function of temperature was found to be strongly correlated with the predicted free energy of solvation of DME in water for the various force fields investigated. Intermolecular pair correlations are employed to analyze phase behavior of nonionic polymers in aqueous solution.