Polyelectrolytes carrying pendant (cyanobiphenylyl)oxy chromophores. Synthesis, behavior in aqueous solution, and interactions with surfactants

Poly(sulfonylethylmaleic acid monoamide-co-alkyl vinyl ether)s carrying both a sulfonic acid and a carboxylic acid moiety are obtained by reacting the corresponding poly(maleic anhydride-co-alkyl vinyl ether)s with 2-aminoethanesulfonic acid. The alkyl vinyl ethers have a n-hexyl or n-dodecyl group or the alkyl groups have a terminal (cyanobiphenylyl)oxy chromophore and spacer lengths of 6-12 methylene units. Dynamic light scattering experiments show that all polymers form large aggregates in water in which the polymer chains are entangled. The formed aggregates are highly ordered as can be deduced from the blue shift of the absorption maxima of the chromophores by UV spectroscopy. When the charge density on the polyelectrolyte backbones is increased by varying the pH or the hydrophobicity of the polyelectrolyte is decreased by variation of the spacer length, the aggregates become more open and less ordered. The interaction between the polyelectrolytes and n-dodecyltrimethylammonium bromide (DTAB) has been investigated by potentiometry using a DTAB-selective electrode and surface tension measurements. The binding already has begun at very low DTAB concentrations and has been shown to be noncooperative, This is caused by the presence of hydrophobic microdomains formed by the polyelectrolytes. With small amounts of DTAB the polyelectrolytes form highly surface active complexes. These complexes are more hydrophobic than the individual components, resulting in an accumulation of the complexes at the air-solution interface. UV spectroscopy was used to investigate the interactions between the polyelectrolytes and DTAB, n-hexadecyltrimethylammonium bromide, poly(oxyethylene(4)lauryl ether), and sodium dodecyl sulfate.