Salt Concentration Dependence of Counterion Condensation

Polyelectrolyte brush is gathering considerable interests from both scientific and engineering viewpoints: protein immobilization on the brushes with their secondary structure nearly undisturbed has been found in recent years ， for example l1 J• Experimental researches for this system ， however ， are scarce other than theoretical and simulation ones because of substantial difficulty in the sample preparation. Counterion condensation is one of the most primitive and important topics about the system ， which is also involved in adsorption of charged molecules like proteins. Proteins adsorb and desorb on polyelectrolyte brushes in low and high ionic strength conditions， respectively. Though the distribution profile of counterions has been investigated using X-ray or neutron ， its detailed dependency on parameters and their condensed or immobilized amount stil remain unexploredl2J • Then we investigated the counterion condensation in a planar strong polyelectrolyte ， sodium polystyrene sulfonate (NaPSS) ， brush under a variety of salt， sodium chloride (NaCl) ， concentration conditions. Zeta potential measurements wer