The stability of polyelectrolyte complex systems of poly(diallydimethyl-ammonium chloride) with different polyanions

Polyelectrolyte complex (PEC) dispersions formed by fast ionic exchange reaction between polyelectrolytes (PELs) bearing oppositely charged groups have been characterized by turbidity and dynamic light scattering. The stability of the formed PEC dispersions, the average hydrodynamic particle size d(h) and the also determined polydispersity index PI of the PEC particles were of special interest. In this study poly(diallyldimethylammonium chloride) (PD) of different molar mass is used in combination with copolymers of maleic acid and alpha-methylstyrene (P(MS-alphaMeSty)) as well as propene (P(MS-P)), with a copolymer of acrylamide and sodium acrylate (PR2540(UD)) and poly(styrene-p-sodium sulfonate) (NaPSS). A strong dependence of the PEC stability on the molar charge ratio n(-)/n(+), the mixing conditions and especially on the chemical structures of the used polyanions was found. If the employed polyanion (PA) have a pi-system (phenyl-) in the polymer chain a higher tendency to instability results. The average hydrodynamic particle sizes dh and the polydispersity indices PIs of the formed stable PEC dispersions determined by dynamic light scattering were strongly influenced by the mixing conditions of the PECs. If we are able to prepare stable complexes where the isoelectric point is exceeded during complex formation which is possible for PD/P(MS-P) and PD/PR2540(UD) systems a distinct increase of d(h) and decrease of PI is observed. The polymer concentration C-P and the chain length L of the used PELs have a minor effect on d(h) and PI.