The influence of ionic strength, electrolyte type and preparation procedure on formation of weak polyelectrolyte complexes

The influence of ionic strength, electrolyte type and preparation procedure on formation of weak polyelectrolyte complexes formed by mixing aqueous solutions of poly(dimethylaminoethyl methacrylate) (PAMA) and poly(acrylic acid) (PAA) was investigated. For that purpose, nephelometric, electrokinetic and microcalorimetric measurements were performed. The influence of preparation procedure on formation of polyelectrolyte complexes was much more pronounced at lower ionic strength (50 mmol dm−3) than at higher ionic strength (200 mmol dm−3). The effect of KCl, NaNO3 and phosphate buffer on weak polyelectrolyte complex formation is discussed. The obtained results are compared with earlier studies of effects of electrolyte type and ionic strength on multilayers formed by alternate adsorption of PAMA and PAA at silica surface. It has been shown that the formation of polyelectrolyte multilayers on metal oxide surface is largely governed by the phase behaviour of polyelectrolyte complexes in solutions and that the presence of different salts influences in similar manner both polyelectrolyte complex formation and polyelectrolyte multilayer formation process.