Salt effects on the interaction between adsorbed cationic polyelectrolyte layers - Theory and experiment

• The effect of inert salt concentration on polyelectrolyte adsorption from aqueous solutions onto oppositely charged surfaces, and the interactions between such surfaces were studied experimentally using a surface force technique and compared to theoretical predictions from Monte Carlo simulations. At a polyelectrolyte concentration of 10 ppm and a low inert salt concentration (10-4 M) the polyelectrolytes adsorb in a flat conformation and the force acting between the surfaces is close to zero down to a separation of 10-15 nm, where the surfaces jump inwards. The attractive force observed at separations below 10 nm is stronger than the expected van der Waals force. The magnitude and range of the attraction agrees with forces obtained from Monte Carlo simulation and we interpret the attraction as being due to bridging polyelectrolytes. When the salt concentration is increased, additional polyelectrolyte adsorption takes place. This gives again rise to a repulsive force, which is significantly larger than what is observed between bare surfaces. The extra repulsion is due to adsorbed polyelectrolytes stretching out from the surfaces and is also predicted from simulations.

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)