CHROMOPHORE LABELING AS A TOOL TO STUDY INTERACTIONS BETWEEN MALEIC-ACID COPOLYMERS AND AMMONIUM SURFACTANTS

The binding of n-dodecyl-, n-hexadecyl- and -cyanoazobenz-4-oxy)decyl) -N,N,N-trimethylammonium bromide to poly(maleic acid-co-alkyl vinyl et her)s with n-butyl, n-dodecyl, n-[(4-cyano-4'-biphenylyl)oxy]hexyl and n-[(4-cyano-4'-biphenylyl)oxy]dodecyl side chains has been investigat ed by UV spectroscopy. Results from dynamic Light scattering studies o f the polyelectrolytes in the absence of surfactants are in agreement with the presence of the extended conformation for the butyl copolymer between pH 7 and 11. For the other polyelectrolytes an increase in hy drodynamic radius is observed upon increasing the pH. By UV spectrosco py the shifts in absorption maxima of the (cyanobiphenylyl)oxy and cya noazobenzoxy chromophores, due to mutual pi-pi stacking interactions, were monitored to provide information on the interaction between polye lectrolytes and surfactants. Changes on both polyelectrolyte and surfa ctant could be studied upon addition of surfactant to polyelectrolyte in aqueous solution. For the butyl polyelectrolyte, cooperative intera ction is observed (pH > 7), whereas for the other copolymers no cooper ativity is observed. A model for the different interactions is propose d.