Computational study on acetophenone in amorphous polyethylene.

Polyethylene (PE) is widely used as an electrical insulating material. Acetophenone (AP) is a major residue in PE and is considered one of the causes of insulation deterioration. However, the physicochemical explanation of the influence of AP is still unknown. Therefore, in the present study, the behavior of AP molecules in amorphous PE was investigated using molecular dynamics (MD) simulations and quantum chemical calculation. First, the basic properties of the AP molecule were evaluated from the viewpoint of molecular electrostatic potential (MEP), molecular orbitals, and energy levels. Subsequently, an amorphous PE system containing AP molecules was studied using MD simulations. The results clearly indicate that AP does not greatly change the density and radius of gyration of amorphous PE. Quantum computations were performed using a part of the structure obtained from the MD simulations, suggesting that AP acts as a trap site in amorphous PE. It was also revealed that under the external electric field, the total density of state (DOS) changes with a dependence on the applied direction. Results of these calculations help in explaining previous experimental results.