Spectroscopic investigation on poly[bis(carboxylatophenoxy)]-phosphazene polyelectrolyte interactions with cationic dyes in dilute aqueous solution

The results of spectroscopic investigations on poly[bis (carboxylatophenoxy )]phosphazene, (NaPCPP), interactions with a cationic dye (methylene blue, MB) and with a cationic fluorescent probe ((1-dimethylaminonaphthalene-5-su lfonamidoethyl)trimethylammonium perchlorate, DA) in dilute aqueous solutio n are reported. The metachromatic behaviour and the DA fluorescence spectra l perturbations induced by NaPCPP was measured as a function of polymer con centration and univalent added salt concentration and compared with that fo und using different, highly charged polyelectrolytes. NaPCPP is shown to st rongly bind both dye molecules, with hydrophobic dye/polymer side chain int eractions playing a significant role in the aggregation (at low polyelectro lyte/dye molar ratios, P/D) and redistribution (at high P/D values) of the dye molecules along the chains. The findings of this work are discussed als o in the light of the results obtained in previous studies on other feature s of NaPCPP polyelectrolytic behaviour in dilute aqueous solution.