Energy Level Gradient Under Electric Field Revealed by Molecular Dynamics Simulation of Polyethylene and Antioxidant

In polyethylene (PE), a non-polar polymer, the lowest unoccupied molecular orbital level decreases and the highest occupied molecular orbital level increases with an increase in the external electric field. Consequently, the energy gap of PE appears to be narrowing. However, the energy gap is not actually narrowed, but inclined by the internal potential distribution. In contrast, antioxidants (AO), which are polar polymers, are characterized by polar groups, and the energy gap does not appear to be affected by the application of an external electric field. This is because the potential distribution of the polar groups has a significant influence and the external electric field has a small influence on the potential. Furthermore, we will discuss molecular dynamics simulations to explain why the combination of PE and AO appears to have a significantly narrower energy gap at lower external electric fields than PE alone.