(545b) Coarse-Grained Molecular Dynamics Simulation of PET

Coarse-grained Molecular Dynamics (MD) simulations of polyethylene terephthalate (PET) with degree of polymerization (DP) from 10 to 50 have been performed. The coarse-grained (CG) model of PET chain we proposed in this work include bonding stretching, bond bending, bond torsion, intra-molecular (for beads over four bonds) and inter-molecular interactions. Then bonded CG potentials (for stretching, bending and torsion) are based on the pair correlation functions obtained from atomistic MD simulations of short (less than 10 monomers) PET oligomers. The non-bonded CG potentials are obtained by solving the Ornstein-Zernike equation with the Percus Yevick approximation (OZPY) with the atomistic pair correlation functions (PCF) as input. CG PET simulations are reported for DP from 10 to 50. Comparison of the atomistic and CG PCFs shows good agreement of with the polymer structure. The relaxation times and diffusion coefficients are also compared between the atomistic and CG simulations. The equipartition theorem has been studied by calculating the temperatures from velocity distribution functions from both atomistic and CG simulations and provide good agreement for the distribution of kinetic energy among the polymer fragments in both simulations. A speed up of at least two orders of magnitude has been observed in the CG simulation, which allows us to do perform long time simulations of long polymer chains. The structural and dynamic results as a function of DP are discussed. cussed.