Can Thermodynamics Explain Contact Charging between Insulating Polymer Surfaces?

Contact charging is a well-known phenomenon wherein material surfaces become asymmetrically charged following their contact and separation. Despite its ubiquity in natural processes and importance in engineering technology, the underlying mechanisms and driving forces remain unknown. For insulating materials, water is thought to play a central role, perhaps through the transport of water ions, but there is yet no molecular basis to understand observed behavior. In this talk, I will describe our efforts in using molecular dynamics simulations to characterize possible thermodynamic driving forces for water ions to transfer from one surface to another. By comparing results across a variety of polymer surfaces, we assess to what extent our calculations are consistent with experimental observations derived from contact charging series and what molecular phenomena dictate these thermodynamics. In the end, this work should provide a firmer molecular basis to understand the behavior of water ions on polymer surfaces and the extent to which they may contribute to observed contact charging phenomena.