Coarse-grained Molecular Dynamics Simulation of Polyethylene Terephthalate (PET)

A coarse-grained (CG) model of Polyethylene Terephthalate (PET) was developed and implemented in CG Molecular Dynamics (MD) simulations of PET chains with degree of polymerization up to 50. The CG potential is parameterized to structural distribution functions obtained from atomistic simulations [Wang et al. J. Phys. Chem. B 2010, 114, 786] using an inversion procedure based on the Ornstein-Zernike equation with the Percus Yevick approximation (OZPY) [Wang et al. Phys. Rev. E 2010, 81, 061204]. The CGMD simulation of PET chains satisfactorily reproduces the structural and dynamic properties from atomistic MD simulation of the same systems. We report the average chain end-to-end distance and radius of gyration, relaxation time, self-diffusivity and zero-shear-rate-viscosity’s dependence on degree of polymerization. For the longest chains, we find the scaling exponents of 0.51, 0.50 and -2.00 for average chain end-to-end distance, radius of gyration and self-diffusivity respectively. The exponents are very close to the theoretical values of entangled polymer melt systems (0.50, 0.50 and -2.0). The study of entanglement in the longer chains shows that the tube diameter, number of monomers between entanglement points and interentanglement strand length are in close agreement with the reported values for an entangled PET melt.