Characterization of methacrylate copolymers with strong-acid or base groups using 1H NMR spectra

Abstract

The chemical shift and intensity of ¹H NMR bands of the hydroxylic group of a solvent (ethylene glycol, methyl alcohol) were investigated in the presence of methacrylate copolymers containing strong-acid sulfonic acid groups or strong-base tributyl ammonium groups. In addition to the OH band of the so-called “external” solvent, another OH band was detected which was due to the solvent present in the polymer bulk and bound by coordination with the functional groups just mentioned. The difference between the chemical shifts of OH protons of the “external” and “internal” solvent and the relative intensity of the “internal” OH band increase linearly with the concentration of acid functional groups; they also depend on the grain size, and to some extent on the morphology of the polymer. By using NMR spectra, it is also possible to characterize the swelling of polymers containing acid or base groups.