Surface Forces Apparatus Measurements Between Oppositely Charged Polyelectrolyte Brushes as a Function of Ionic Strength

Interactions between polyanions and polycations result in polyelectrolyte complexation and the formation of polymer dilute (aqueous) and polymer rich (coacervate) phases. Understanding the forces governing the formation and stability of these complexes as well as their dependence on solution conditions is of great interest. We directly measure the interactions between densely grafted, apposing polycationic and polyanionic brushes as a function of ionic strength using the surface forces apparatus (SFA). Additionally, we compare these force profiles with SFA measurements between apposing polyanionic brushes and between apposing polycationic brushes.