Charge-Transfer Complexation in Aqueous Polyelectrolyte Solution. II. Interaction between Polycations and CT Complexes

Abstract

Abstract The CT complexation between 9,10-dimethoxyanthracene-2-sulfonate ion (DMACS−; donor) and 9,10-anthraquinone-2-sulfonate ion (AQS−; acceptor) has been studied in aqueous solution of poly(1,1-dimethyl-3,5-dimethylenepiperidinium chloride) (PDDP+Cl−). In aqueous PDDP+Cl− solution, both DMACS− and AQS− are electrostatically bound to the polyion and the CT complex between them is formed around the polyion due to the close proximity of DMACS−–AQS− pairs. By comparing the CT complexation in aqueous PDDP+Cl− solution with that in aqueous poly(allylammonium chloride) (PAAH+Cl−) solution studied previously, the effects of the charge density of the polyion, the structure of charged groups on the polyion and the local conformation of the polyion upon the CT complexation have been clarified. A plausible structure of the CT complex has been determined so as to satisfy the symmetry-allowed interaction between the HOMO of DMACS− and the LUMO of AQS−. The CT complex interacts more strongly with the polyion than Cl− and the decrease in the viscosity of the polymer (the contraction of the polymer chain) is more effectively caused by the CT complexation. Moreover, the strength of the association (stacking interaction) of aromatic counterions (DMACS−, AQS−) including the CT complexation affects the binding of these counterions to the polyion.