New polyelectrolyte complex particles as colloidal dispersions based on weak synthetic and/or natural polyelectrolytes

This study aims to evidence the formation of stable polyelectrolyte complex particles as colloidal dispersions using some weak polyelectrolytes: chitosan and poly(allylamine hydrochloride) as polycations and poly(acrylic acid) (PAA) and poly(2-acrylamido-2-methylpropanesulfonic acid – co – acrylic acid) (PAMPSAA) as polyanions. Polyelectrolyte complex particles as colloidal dispersion were prepared by controlled mixing of the oppositely charged polymers, with a constant addition rate. The influences of the polyelectrolytes structure and the molar ratio between ionic charges on the morphology, size, and colloidal stability of the complex particles have been deeply investigated by turbidimetry, dynamic light scattering and atomic force microscopy. A strong influence of polyanion structure on the values of molar ratio n–/n+ when neutral complex particles were obtained has been noticed, which shifts from the theoretical value of 1.0, observed when PAA was used, to 0.7 for PAMPSAA based complexes. The polyions chain characteristics influenced the size and shape of the complexes, larger particles being obtained when chitosan was used, for the same polyanion, and when PAMPSAA was used, for the same polycation.