Potentiometric titration of a suspension of crosslinked polymethacrylic acid

Abstract

An aqueous suspension of a macro-mesh carboxylic cationite with particles of size ∼ 0·5 μ has been prepared from methacrylic acid and ethylene dimethacrylamide (2·5 mole %). The degree of dispersity was such that methods of polarized luminescence and potentiometric titration could be used for the investigation. Ionization of the polymethacrylic acid (PMAA) chain of the ionite network is accompanied by transition from the form with crosslinking due to hydrophobic interaction to a disordered form. This transition takes place as a cooperative process, and occurrs within a narrow interval of ionization degrees (α), as in the case of soluble PMAA. Three regions corresponding to the crosslinked and disordered forms, and to the transition, are readily distinguishable on the potentiometric titration curves plotted with the coordinates p K− α and pH-log (1−α)/α. The extent to which the ionic strength of solutions influences ionization of the suspention was investigated. The experimental results apply equally to coarse particle suspensions of the studied cationite.