CHARGED POLYMER BRUSHES - COUNTERION INCORPORATION AND SCALING RELATIONS

Amphiphilic block copolymers consisting of a fluid hydrophobic and a p olyelectrolyte part form monolayers at the air/water interface. With x -ray reflectivity it is shown that the hydrophobic block is a nm-thick melt, while the polyelectrolyte forms an osmotically swollen brush of constant thickness, independent of grafting density and with stochiom etric counter ion incorporation. Only at high salt conditions (above 0 .1 M), the brush shrinks and the thickness scales with the molecular a rea and the salt concentration (corrected for excluded volume interact ions) with an exponent -1/3.