Molecular Dynamics Simulations of Polytetrafluoroethylene at Glassy Transition Temperature

R. Al-Nsour
Virginia Commonwealth University, US

Keywords: molecular dynamics simulations, polytetrafluoroethylene, force fields, glassy transition temperature


This research is concerned with studying and understanding the thermal and mechanical behavior of PTFE. Such understanding is critical to predicting PTFE behavior and allowing bottom up design of improved polymers for specific applications. While a plethora of experiments have investigated the mechanical properties of PTFE, examining these properties using molecular dynamics simulations (MD) remains in its infancy. The present study is the first MD simulations to research PTFE behavior around the glassy transition temperature. Specifically, the current research utilizes MD simulations to achieve the following objectives: (a) model PTFE glassy transition temperature; (b) examine the impact of glassy transition temperature on the mechanical properties; and (c) determine the governing forces at the molecular level. Achieving the aforementioned objectives involved performing three major tasks. First, generating and testing PTFE force-field parameters. The parameters were produced based on the OPLS-AA model. Second, building PTFE amorphous structure using Cerius2 amorphous builder. Third, performing MD simulations using NAMD®. This task involves a polymer relaxation process to predict PTFE mechanical behavior around glassy transition temperature. Properties that are affected by this transition such as volumetric thermal expansion, specific volume, and bulk modulus were examined and our simulations were in good agreement with experimental findings.