Polyelectrolyte effects on rates of hydrated electrons

The effect of polyvinylsulfate (PVS) on the rate of the reaction of e-/sub aq/ with several species highly reactive toward e-/sub aq/ was investigated using the pulse-radiolysis technique. The rate of e-/sub aq/ reactions with cations (Cu2+, Cd2+, Ni2+, Zn2+, Ru(bpy)32+, Fe(phen)32+, Cr3+, Eu3+) is greatly inhibited by the presence of the polyelectrolyte. On the other hand, the reaction wth negatively or uncharged species (NO-3 and O2) is hardly affected. It is shown that using this kinetic method the effective number of available sites on te polymer can be titrated. Furthermore, the specificity constants of cations, inert toward e-/sub aq/ (Mg2+, Ca2+, Ba2+, Li+, Na+, K+), could be determined by measuring their effect on the rate of the reaction of e-/sub aq/ with a probe cation (Cu2+) ''condensed'' on the polymer. As expected from measurements of thermodynamic properties of similar polyelectrolytes, and from theoretical models, it was found tha divalent ions are bound to the polymer much stronger than are univalent ions. For ions of similar valence the specificity constant is larger, the smaller is the hydrated ionic radius