Molecular dynamic simulation of polyethylene chain at different temperatures and pressures

Polyethylene plays important roles in human lives all over the world due to its good properties and wide applications. In this study, polyethylene chains under different temperatures (400, 450, 500, 550 and 600 K) and pressures (0, 1, 10, 50 and 100 atm) were simulated by using molecular dynamic simulation method, and the properties such as micro-structure, coordination number, stable conformation, density, and self-diffusion coefficient were detailed. The results show that when the temperature increases from 400 K to 600 K at 1 atm, the average bond distance increases from 1.5299 Å to1.5313 Å, and the coordination number declines from 17.4 to 13.9, making the density decrease from 0.82 g/cm³ to 0.72 g/cm³. The self-diffusion coefficient increases from 0.13 nm²/ns to 0.34 nm²/ns. When the pressure increases from 0 atm to 100 atm at the temperature of 500 K, the non-bonded interaction energy decreases from −1.171 kcal/mol to −1.186 kcal/mol, and the coordination number rises from 15.5 to 15.8, making the density increase from 0.772 g/cm³ to 0.782 g/cm³. The self-diffusion coefficient decreases from 0.39 nm²/ns to 0.36 nm²/ns. The knowledge of polyethylene chain at different temperatures and pressures will boost better understand the industrial solution polymerization process and solid waste pyrolysis engineering of plastics.