CONDUCTIVITY OF LITHIUM PERFLUORONONANOATE IN WATER-POLY(VINYL PYRROLIDONE) SOLUTIONS

Conductivity measurements, focused on the counterion binding of lithiu m perfluorononanoate (LiPFN) micelles in pure water and in the presenc e of poly(vinyl pyrrolidone) (PVP), have been carried out. An abrupt d ecrease of the conductance of the LiPFN in pure water, due to the self aggregation of anions and to dynamic linkage of cations on the micell ar surface, has been found. Analysis of the conductometric data indica tes that about 50% of the stoichiometric concentration of Li+ interact s with the head groups of the perfluorinated anions involved in micell ar assembly. Conductometric data of LiPFN-water-PVP systems reveals a favorable influence of the PVP on the micellization process modulated by the concentration and by the molecular weight of the polymer. Analy sis of these data shows that in presence of PVP the degree of binding of lithium ion to the micellar assemblies linked to the polymer is sma ller than in pure water. By increasing the amount of surfactant in sol ution up to: the concentration where the polymer becomes saturated by LiPFN micelles, the binding of lithium ion in the system becomes sligh tly greater than that observed in LiPFN-water system. This finding can be interpreted in terms of additional binding of lithium ion to the p olymer chains. Conductivity measurements carried out on LiClO4 and KCl O4 in water + PVP support this interpretation.