Syntheses and spectroscopic pH titrations of naphthol-labeled poly(methacrylic acid)s

Poly(methacrylic acid) (PMA) and poly(acrylamide) (PAAm) with a small mole fraction of naphthol (NpOH) residues were prepared by polymerization of methacrylic acid or acrylamide with three position isomers, methacryloylaminonaphthol. The substituent effect on the apparent pK values (pK_obsd), determined by spectroscopic pH titrations in aqueous solution, was observed for the NpOH-labeled PAAm. The electrostatic surface potential (ψ) for PMA was calculated from the difference in the pK_obsd values for the labeled PMA and PAAm. The obtained ψ value decreased as the spacing between the OH moiety and the polymer main chain increased. This clearly indicates that the ψ value is a sensitive function of the distance from the polyion surface.