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.