Spectrophotometric study of the interaction of toluidine blue with poly (ammonium acrylate)

The aim of this work is to study the interaction between Toluidine Blue (TB), a cationic dye, and an anionic polyelectrolyte, poly (ammonium acrylate) (PANH4). The UV-Visible spectroscopy study shows that addition of increasing amounts of poly (ammonium acrylate) induces the formation of a metachromatic complex. The stoichiometry of TB-PANH4 complex evaluated by the molar ratio method is 1:1 and the large hypsochromic absorption shift (73 nm) obtained is attributed to dye H-aggregates. The effects of sodium chloride concentration, pH and Cetyl pyridinium chloride (CPC) concentration, on metachromasy have also been studied. Thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures have been evaluated to determine the stability constant of the complex.