Simulating PEO melts using connectivity-altering Monte Carlo

Collin Wick, Pacific Northwest National Laboratory

Connectivity-altering Monte Carlo simulations have been used to study both structure-property relationships of polyethylene glycol (PEG) and polyethylene oxide dimethyl ether (PEODME) melts. Connectivity-altering methods take advantage of the flexibility of Monte Carlo by reconnecting polymer chains with each other, and circumventing the very long relaxation time required for the equilibrating of high molecular weight polymer melts. In addition, the TraPPE-UA force field, which was fit to reproduce the thermodynamic properties of small molecules over a wide range of temperatures and pressures, was tested on its ability to model the thermodynamic and structural properties of moderate to high molecular weight polymers. The connectivity-altering Monte Carlo simulation techniques were shown to do a very good job of equilibrating moderate to high molecular weight polymer melts. Also, using the TraPPE-UA force field, excellent agreement between experiment and simulation techniques for melt densities at a variety of temperatures, pressures, and molecular weights was obtained. Comparisons made with experimental structural properties, including the structure factor, chain mean squared end-to-end distance, and radius of gyration, showed good agreement between simulation and experiment. Moreover, a thorough analysis performed on the different end-group effects of PEG and PEODME showed the microscopic origins for the differences in their molecular weight dependence on volumetric properties.

Abstract Author(s): Collin Wick