Comprehensive study on the formation of polyelectrolyte complexes from (quaternized) poly[2-(dimethylamino)ethyl methacrylate] and poly(2-acrylamido-2- methylpropane sodium sulfonate)

Polyelectrolyte complexes (PECs) have been prepared from well-defined (quaternized) poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and high molecular weight poly(2-acrylamido-2-methylpropane sodium sulfonate) (PAMPSNa) after a thorough study of their viscometric properties. The effect of pH and quaternization degree of PDMAEMA on PECs stoichiometry has been examined. PEC-based materials have been characterized in terms of thermal stability, equilibrium swelling degree, and free/bound water composition. The stoichiometry and swellability of the physically crosslinked hydrogels obtained from fully quaternized PDMAEMA/PAMPSNa complexes do not depend on pH. In contrast, PECs made of non quaternized PDMAEMA and PAMPSNa are highly affected by pH, and could reversibly disintegrate at pH ≥ 9. Partially quaternized PDMAEMA/PAMPSNa PECs exhibit intermediate properties and form stable loose structures in the whole investigated pH range. Finally, stable dispersions of PECs nanoparticles have been successfully produced from dilute solutions of the complementary polyelectrolytes. The nanoparticle average diameter as determined by dynamic light scattering proved to depend on the molar fraction of DMAEMA-based subunits and on the initial polyelectrolyte concentration.