Dual mechanism for metal-polymer contact electrification

Abstract

Contact charging and triboelectrification are considered a non-equilibrium two-step process consisting of instantaneous bond-forming and bond-breaking. Our proposed concept of a dual mechanism for metal-polymer contact electrification is based on a coexistence model with electrons (or holes) as charge carriers in the formation of a donor-acceptor complex which involves two terms: Coulombic or electrostatic and frontier orbital or charge transfer. The former is long-range and ionic, while the latter is short range ( ⩽ 4 A ̊ ) and electronic. Therefore, for the bond-forming step, both ionic and electronic transfer mechanisms are involved as in a continuum. For the bond-breaking step, air breakdown and bond fracture have been found by Dickinson to be accompanied by the electron emission (EE) and positive ion emission (PIE). Recently, a similar dual mechanism of bond-breaking for frictional electrification has been shown by Sakaguchi and Kashiwabara to involve both mechanoradicals and mechanoions. Thus, our concept of a dual mechanism for contact electrification between metal and polymer is consistent with the two-step non-equilibrium process, and this concept may be applied to help understand some unanswered questions about contact charging and charge accumulation.