Strongly Charged Polymer Brushes

Abstract

Charged polymer brushes are layers of surface-tethered chains. Experimental systems are frequently strongly charged. Here we calculate phase diagrams for such brushes in terms of salt concentration n_s, grafting density and polymer backbone charge density. Electrostatic stiffening and counterion condensation effects arise which are absent from weakly charged brushes. In various phases chains are locally or globally fully stretched and brush height H has unique scaling forms; at higher salt concentrations we find H ~ n_s^(-1/3), in good agreement with experiment.