Dual polyelectrolyte–ionomer behavior of poly(acrylic acid) in methanol: 1. salt-free solutions

The behavior of poly(acrylic acid) (PAA) partly neutralized with tetramethylammonium hydroxide in methanol was studied by the viscometry, 1 H NMR spectroscopy, light scattering, and conductivity methods. It was shown that, when the degree of PAA neutralization increases from 0.1 to 0.2, a transition from a poly-electrolyte to ionomer state occurs. This transition is caused by the formation of ion pairs due to the binding of counterions with the charged groups of the polymer chain and is accompanied by a macromolecule collapse. Collapsed macromolecules aggregate. At degrees of neutralization above 0.4, the restored polyelectrolyte state is accompanied by polymer swelling. The data obtained are qualitatively explained.