Polyelectrolyte brushes: Counterion distribution and complexation properties

The structure of dense grafted polyelectrolyte layers has been studied with a combination of neutron reflectivity and infrared spectroscopy techniques . The polyelectrolyte brushes were made of poly(styrene sulfonate) neutrali zed by different counterions. Small counterions are distributed throughout the brush in order to ensure a highly local electroneutrality. In addition, they can be readily exchanged with other small ions. On the other hand, ma cromolecular counterions (as well as some proteins) are irreversibly trappe d by the brush, but are located outside the grafted layer and cannot reach the surface. [S1063-651X(99)14311-3].