IONIC-STRENGTH AND CURVATURE EFFECTS IN FLAT AND HIGHLY CURVED POLYELECTROLYTE BRUSHES

Adsorption of poly(tert-butylstyrene)/poly(styrenesulfonate) diblocks on polystyrene latices from water is reported and interpreted with sca ling theories to demonstrate the effects of ionic strength and curvatu re on layer thickness. The adsorbed amount increases with ionic streng th from no added salt to 0.1 M, forming a dense polyelectrolyte brush. The influence of particle radius on layer thickness is correlated qua ntitatively via the Daoud-Cotton model, but the effect on surface cove rage is obscured by uncontrolled aspects of surface chemistry. Decreas ing the ionic strength dramatically increases the dimensions of polyel ectrolyte micelles and adsorbed layers; the sensitivity, while strongl y coupled with curvature, is overestimated by all existing theories. A simple scaling theory that accounts for electrostatic excluded volume more appropriately captures the trends qualitatively.