Charging of weak polyelectrolytes

Michal Borkovec, Ger J. M. Koper Email. [email protected], [email protected] September 15, 2013 Direct link www.colloid.ch/polyelectrolytes In aqueous solutions, bases bind protons, while acids dissociate them. For weak acids and bases, these protonation reactions occur in the intermediate pH range. Dealing with monoprotic or diprotic acids and bases, the corresponding binding isotherm is referred to as the titration curve, and the corresponding chemical equilibria are discussed in all introductory chemistry courses. When one is interested in the binding of protons to weak polyelectrolytes, the situation is more complicated. The principal reason is that in polyelectrolytes many ionizable sites interact and the binding isotherm is the result of the many-body interactions among all of them. For a monoprotic acid or base, there is only one site, and interactions play no role. For a diprotic system, interactions start to play a role, but can be within the classical chemical equilibrium framework. Here we explain how to describe and to understand the titration curves of weak polyelectrolytes [1,2].