METACHROMATIC BEHAVIOR OF METHYLORANGE IN THE PRESENCE OF IONENES

The addition of different ionenes, polycations with defined structure and charge distances, to methylorange 1 in very dilute solutions of wa ter resulted in an observable shift of the absorption maxima from 464 nm to shorter wavelengths. The extent of this so-called metachromasy e ffect was found to be dependent on the nature of the hydrophobic unit of the polymer backbone. The comparison of UV/VIS spectra's of these s olutions with the absorption of a film of a model substance - a dicati on with methylorange as counteranion - lead to the conclusion that ion enes undergo an exchange of the counteranions when added to a dilute s olution of methylorange. Precipitation is slowed down, but the absorpt ion is equivalent with solid product. The new absorption spectra of me thylorange can be explained by the interaction of the quaternary nitro gen with the dye anion.