Study of hole mobility in amorphous polyethylene via kinetic Monte Carlo methods

Abstract: This thesis presents a study of hole mobility in amorphous polyethylene using kinetic Monte Carlo (KMC) methods together with a novel chain segmentation model developed by Unge and Nilsson, which determines hole localization sites based on torsion angles along the polymer chain. An extension to the KMC algorithm was developed which improves performance by modelinground-trips between strongly interconnected localization sites. Energy barriers and electron coupling for transitions were approximated by modeling each localization site as an isolated oligomer and calculated using Density Functional Theory, from which the transfer rates were determined via Marcus Theory. A variety of amorphous polyethylene systems were generated using Molecular Dynamics, after which hole trajectories within these polyethylene systems were simulated via the developed KMC model. The results of these simulations were then compared to experimental measurements with regards to hole mobility and activation energy, and a parameter analysis was performed to examine the sensitivity to errors in the included approximations. While the results differ moderately from experimental measurements the model still shows promise, and several possible improvements has been identified whichcould bring the results more in line with experiments.