ADSORPTION OF CHARGED BLOCK-COPOLYMERS - EFFECT ON COLLOIDAL STABILITY

We study the effect on colloidal stability of the adsorption of dibloc k copolymers with a charged buoy block. Using a scaling as well as an SCF approach, we focus on the high-charge regime and find that adsorbe d amounts are very low. Nevertheless, the adsorbed polymer causes a si gnificant repulsive interaction between two surfaces. For low charges and long anchor blocks (''anchor-dominated regime'') the colloidal sta bility would be expected to rise with increasing charge on the buoy bl ock. In our high-charge regime we find the reverse; i.e., the electros teric repulsive interaction increases with increasing salt concentrati on and decreasing buoy length or buoy charge. This counterintuitive be havior is caused by the effect of the electrostatic interactions on th e adsorbed amount: stronger interactions lead to a lower adsorbed amou nt, which in turn leads to a weaker repulsion. Numerical SCF calculati ons confirm these scaling predictions.