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RESEARCH PRODUCT

Molecular Mechanisms Controlling the Self-Assembly Process of Polyelectrolyte Multilayers

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The distance dependent interaction between polyelectrolyte-covered mica surfaces in aqueous solution was investigated with the surface forces apparatus. We find the following:  (i) The surface charge changes sign, when an oppositely charged polyelectrolyte from a concentrated polyelectrolyte solution is adsorbed. (ii) Tails and loops of the adsorbed polyions dangle into the bulk phase, inducing a small steric force. If polycations and poyanions are adsorbed on top of each other, a strong short range attractive force is seen due to ion-pair formation after crossing a large repulsive electrostatic/steric barrier. (iii) Obviously, after polyelectrolyte adsorption, there are still nonoccupied binding places (point charges) on the substrate. We show that these adsorption properties regulate the build-up of polyelectrolyte multilayers:  Ion pairs between oppositely charged polyion segments and the substrate are formed, until the surface charge is inversed. The electrostatic barrier limits the adsorbed amount, g...