engleski

Polyelectrolyte complexes and multilayers: ion- specific effects and overcharging

The similarities between processes of polyelectrolyte complex (PEC) and multilayer (PEM) formation have been recognized for quite some time. On the other hand, the most important question regarding the apparently different outcomes of interpolylelectrolyte neutralization in solution and at the surface (i.e. overcharging) has not been fully answered yet. In order to investigate the correlation between interpolyelectrolyte neutralization in solution and at the surface, we explored systems containing two oppositely charged synthetic polyelectrolytes by means of dynamic light scattering, electrophoretic light scattering, isothermal microcalorimetry and quartz-crystal microbalance with dissipation monitoring. As cationic polyelectrolytes we used poly(diallyldimethylammonium chloride), poly(allylamine hydrochloride) and poly(N- ethyl-4-vinylpiridinium bromide) and as anionic we used poly(sodium 4-styrene sulfonate). We have managed to observe the overcharging phenomenon in solution directly, by changing the experimental procedure. Apart from the phenomenon of overcharging, the counterion- specific effects, especially counteranion- specific, are of great interest in the field of polyelectrolyte chemistry, however the detailed investigations of related phenomena were mostly performed in the case of multilayers. Even though multilayers offer more promissing application possibilities, the studies of interpolyelectrolyte neutralization in solution are often much simpler and faster to perform. One of our goals was to explore in which measure the results of investigation regarding the influence of counterion type and concentration on the polyelectrolyte complexation in solution could be used for predicting the outcome of interpolylelctrolyte neutralization at the surface, as well as to provide information about long-term stabilty of these systems.

polyelectrolyte complexes, multilayers, ion-specific effects, overcharging

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