Interfacial charge transfer and transport in polyacetylene-based heteroionic junctions: Quantum chemistry calculations and molecular dynamics simulations

A theoretical description of the heteroionic junction Au vertical bar P-C vertical bar P-A vertical bar Au (poly(tetramethylammonium 2-cyclooctatetraenylethanesulfonate) (PA), poly[(2-cyclooctatetraenylethyl) trimethylammonium trifluoromethanesulfonate] (PC)) is presented on the basis of the relative energy levels of its components and the characteristics of each interface in the device. Electronic structures of ionically functionalized polyacetylene analogues, PA and PC, are surveyed by both oligomer investigations (using density functional theory with the aid of an effective linear scaling strategy) and polymer calculations (with the periodic boundary condition). The solvent effects on the band edges of PA and PC in the solvent of acetonitrile are also estimated by using both the polarizable continuum model (PCM) and the explicit solvent model. The absence of n-doping wave of the PA observed experimentally is attributed to its high conductance band edge (-2.71V vs SCE in gas phase and about -2.17V vs SCE in solvent of acetonitrile) or the breakdown of effective interfacial electron transfer. The reported unidirectional transport behavior of Au vertical bar P-C vertical bar P-A vertical bar Art junctions is rationalized on the basis of analyses of electron transfer between PA and Au electrode and electron tunneling at the P-C vertical bar P-A interface.