Studies on the electrochemical properties of copolymers of maleic acid, II : potentiometric titration at high ionic strength

Abstract

The potentiometric titrations of two copolymers, maleic acid-vinyl acetate and malefic acid-styrene copolymers, were carried out at high ionic strength. The dissociation constants, pK_1^° and pK_2^°, in which the influence of polyion potential was fully eliminated, were evaluated by means of the titration results and compared with the corresponding values of proper α, β-disubstituted succinic acids. The results were examined in detail, assuming that the nearest neighbor interaction was independent of the ionic strength. As a result, the ΔpK' value which represents the difference between pK_2^° and pK_1^° in the vinyl acetate copolymer, was regarded as a rather reasonable value, judging from the localized electrostatic neighbor interaction. On the other hand, the larger ΔpK' value in the styrene copolymer was attributed to the fact that the neighbor interaction was fairly apart from the localized type.