Electric Linear Dichroism Study of Sodium Poly(p-styrenesulfonate) and Its 9-Aminoacridinium Complex in Aqueous Solutions

Abstract

Abstract Electric linear dichroism (ELD) of sodium poly(p-styrenesulfonate) (NaPSS) and its 9-aminoacridinium (AA) complex at a mixing ratio of polymer residue-to-dye of 6.14 was studied in aqueous solutions at 20 °C. ELD signals were measured in the electric field strength range 0—ca. 19 kV/cm at the absorption peak wavelengths; they showed a saturating trend at extremely high fields. The average angles between the orientation axis of NaPSS and the transition moments of chromophores were estimated to be 60° at 224.5 nm and 57° at 262 nm for the side chain phenyl group and 50° at 404 nm for the bound AA by using theoretical orientation functions derived for mono- and polydisperse systems. The ELD spectra were measured at fixed field strengths; 275–215 nm for NaPSS and 440–282 nm for NaPSS–AA. The reduced dichroism of NaPSS remained nearly constant throughout the 262 nm band but steadily changed below 224 nm in the 224.5 nm band, indicating that another band exists in the far UV region. The ELD spectrum of the NaPSS–AA complex revealed that the two electronic 1La and 1Lb transition moments of the bound AA are tilted at different angles to the orientation axis of the NaPSS backbone.