Comparative Study of Oxygen Diffusion in Polyethylene Terephthalate and Polyethylene Furanoate Using Molecular Modeling: Computational Insights into the Mechanism for Gas Transport in Bulk Polymer Systems

derived polyethylene furanoate (PEF) has recently gained attention as a sustainable alternative to polyethylene terephthalate (PET), amidst environmental concerns over fossil fuel depletion. Herein, we outline a computational approach to investigate the tenfold difference in barrier properties between the two materials, using a statistically robust methodology to predict diffusion coefficients from molecular dynamics simulation. Oxygen diffusion was predicted to a high level of accuracy, at 3.24 x 10(-8) and 2.88 x 10(-9) cm(2) s(-1) for PET and PEF, respectively (D-experimental = 1.16 x 10(-8) and 1.04 x 10(-9) cm(2) s(-1)). Simulations quantifiably demonstrated the contributions of ring-flipping chain dynamics on oxygen diffusion, and novel Monte Carlo techniques revealed atomistic insights into the mechanism by which this occurs. Areas of accessible volume within the polymer matrix were seen to converge to facilitate lateral oxygen displacement. Infrequent convergences in PEF, due to subdued polymer chain dynamics and higher system density, accounted for the slower oxygen diffusion relative to PET.