Amido-thioether polymers containing pendant carboxylato groups: thermodynamics of protonation and copper(II) complex formation in dilute aqueous solution

Calorimetric data are reported for the enthalpy of protonation of pendant carboxylato groups in new polymers 1a - d containing amido and thioether moieties in their main chain. These data, together with potentiometric and viscometric data, afford a complete thermodynamic description of the protonation process of the new polyacids, which are water-soluble in a narrow range of alpha (degree of protonation) values. Comparison with the non-macromolecular model 2 revealed that the thermodynamic features are attributable to polyelectrolyte effects. In contrast with model 2, all polymers studied form stable hydroxocomplex species with copper(II) ion. The hypothesized [Cu(OH)2L2]2- (where L is the monomeric unit of the polymer) stoichiometry fits the potentiometric data well when processed with the SUPERFIT program. The trend of the corresponding stability constant (log beta) values is to decrease with increasing pH over a wide range.