Heide-Marie Buchhammer

Interaction of colloidal dispersions of non-stoichiometric polyelectrolyte complexes and silica particles

Abstract Stable non-stoichiometric polyelectrolyte complex dispersions (PEC) with cationic excess charges were used to study the efficiency of charge modification of silica particles. The complex dispersions formed by the interactions of poly(diallyldimethyl-ammonium chloride) (PDADMAC) or polyethylenimine (PEI) with poly(maleic acid-co-α-methylstyrene) are stable but differ in their cationic net charge. It can be seen from the results that the amount of preformed complex dispersion necessary for complete adsorption and for discharging the negative surface of the substrates tested is quite different for the PDADMAC complex and the PEI complex. Depending on the molecular weight and the type of functional groups of PDADMAC and PEI, polyelectrolyte complex particles that differ in their conformation, diameter and charge accessibility are formed. In the case of glass pearls, a substrate with a very high surface charge density, we can demonstrate that the effectiveness of charge modification with the PDADMAC complex is higher than with the PEI complex. Accordingly, the results suggest that the steric differences between the polyelectrolyte complexes tested is less significant for silicic acid, a substrate with a large specific surface.

The interaction between oppositely charged polyelectrolytes in the presence of solid surfaces

Abstract The interaction between the oppositely charged polyelectrolytes poly(dimethyldiallylammonium chloride) (PDMDAAC) and poly(maleic acid-co-α-methylstyrene) (P(MS-α-MeSty)) in the presence of inorganic fine particles such as clay, silicic acid and glass pearls has been investigated. In experiments involving only adsorption of PDMDAAC the driving forces are electrostatic attractions between the anionic particles and the polycation. The amount of adsorbed PDMDAAC necessary for changing the surface charge of the substrates from negative to positive increased with increasing specific surface area. The adsorption of PDMDAAC and P(MS-α-MeSty) from their mixed solutions on to the inorganic fine particles showed a synergistic effect with respect to the amount of cationic surface charge. This effect increased with the surface charge density of the solid particles. The interaction of P(MS-α-MeSty) with preadsorbed PDMDAAC led to a change in the polarity of the modified particles and did not show a synergistic effect. The obvious difference between the adsorption from the mixed solutions and sequential adsorption is discussed in terms of the configuration of adsorbed polyelectrolyte complex particles formed in the solution or at the solid/liquid interface.