ИСТИНА

Interactions between oppositely charged macromolecules lead to the formation of interpolyelectrolyte complexes that seem to be promising and available polymeric reagents and materials for industry, biotechnology, and medicine. In this work, an influence of low-molecular-weight salt (NaCl) on properties of products formed due to interactions between poly(diallyldimethylammonium chloride) (<Mw> = 2.9E+05 g/mol) and sodium salt of poly(maleic acid-co-propylene) (<Mw> = 7.2E+04 g/mol) in their non-stoichiometric mixtures ([-]/[+] = 0.3) has been studied by means of turbidimetry, quasi-elastic light scattering, and microelectrophoresis. Depending on the salt concentration, salt containing non-stoichiometric mixtures of oppositely charged macromolecules ca be: (I) stable dispersions whose turbidity is nearly independent of time and increases with increasing salt concentration (low salt concentrations), (II) unstable dispersions whose turbidity decreases with time due to a partial (or complete) precipitation of the product formed as a result of interpolyelectrolyte complexation (moderate salt concentrations), and (III) transparent solutions (high salt concentrations). Stable dispersions obtained at low salt concentrations contain relatively large positively charged particles whose z-average hydrodynamic radius increases whereas zeta-potential decreases with increasing salt concentration. These macromolecular aggregates are considered to be particles of non-stoichiometric polyelectrolyte complex (nPEC) that incorporates charged groups of the polycationic component in an excess compared to charged groups of the polyanionic component. A progressive increase in the size and a concomitant decrease in the charge of nPEC particles are supposed to promote their precipitation observed at moderate salt concentrations. A formation of transparent solutions at high salt concentrations (when a salt concentration exceeds a certain "critical" value, no precipitation is detected) is related to a partial (or complete) dissociation of macromolecular salt bonds in the product of interpolyelectrolyte complexation.