Adsorption of poly(tert-butylstyrene)/poly(styrenesulfonate) diblocks on polystyrene latices from water is reported and interpreted with scaling theories to demonstrate the effects of ionic strength and curvature on layer thickness. The adsorbed amount increases with ionic strength from no added salt to 0.1 M, forming a dense polyelectrolyte brush. The influence of particle radius on layer thickness is correlated quantitatively via the Daoud−Cotton model, but the effect on surface coverage is obscured by uncontrolled aspects of surface chemistry. Decreasing the ionic strength dramatically increases the dimensions of polyelectrolyte micelles and adsorbed layers; the sensitivity, while strongly 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.

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We propose a means of accounting for the contribution of counterions to the ionic strength within a polyelectrolyte brush, which is then incorporated into models treating the effects of electrostatic interactions, chain stretching, and curvature on the layer thickness for chains attached to a spherical particle. Combining an electrostatic wormlike chain model originated by Odijk, Fixman, and co-workers with the blob model of Daoud and Cotton predicts without adjustable parameters the layer thickness for a wide range of ionic strengths and particle radii. A simplified scaling version that neglects stiffening due to electrostatic interactions greatly underestimates the layer thickness but captures the dependence on ionic strength reasonably.

Conformations of neutral and charged brushes on spheres have been explored for diblock and triblock copolymers adsorbed on colloidal particles and associated in micelles. The variation of layer thickness L with adsorbed amount for a wide range of core radii R (0.04 < L/R < 20) agrees well with the blob model of Daoud and Cotton for neutral polymers and a new "electrostatic blob model" for semirigid polyelectrolytes. The latter combines the Daoud and Cotton model with the electrostatic wormlike chain theory for polyelectrolytes to account for chain stiffening and excluded volume interactions inside the blobs.