Orientation Behavior of Polyelectrolyte in Solution under an External Electric Field. A Coarse Grain Molecular Dynamics Simulation Study

Abstract

Abstract A coarse grain molecular dynamics simulation method was applied to polystyrenesulfonate in aqueous solution to investigate the conformational and orientational behavior of flexible polyion under an external electric field. When the electric field was applied, the deviation of the counter-ion distribution and the rotational orientation of the polyion toward the direction of the electric field were observed. The orientation behavior of flexible polyelectrolytes depended on the field strength, and two typical orientational motions were detected. That is, at low electric field strength, elongation of the whole polyion chain conformation occurs at first stage and subsequently rotationally orients toward the field direction. On the other hand, segment orientation occurs at the high field because of the fast displacement of the counter ions on each polymer segment. The ionic polarization of the flexible polyion was evaluated by the component analysis of the counter-ion deviation. Results showed that the loosely-bound counter ions contribute largely to the ionic polarization.