Conductivity of lithium perfluorononanoate in water-poly(vinyl pyrrolidone) solutions |
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Authors: | Alessandro D’Aprano Bianca Sesta Noemi Proietti Vincenzo Mauro |
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Institution: | (1) Department of Chemistry, La Sapienza University, P.le Aldo Moro 5, 00185 Roma |
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Abstract: | Conductivity measurements, focused on the counterion binding of lithium perfluorononanoate (LiPFN) micelles in pure water
and in the presence of poly(vinyl pyrrolidone) (PVP), have been carried out. An abrupt decrease of the conductance of the
LiPFN in pure water, due to the self aggregation of anions and to dynamic linkage of cations on the micellar surface, has
been found. Analysis of the conductometric data indicates that about 50% of the stoichiometric concentration of Li+ interacts with the head groups of the perfluorinated anions involved in micellar 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. Analysis 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 smaller than in pure water. By increasing the amount of surfactant in solution up to the
concentration where the polymer becomes saturated by LiPFN micelles, the binding of lithium ion in the system becomes slightly
greater than that observed in LiPFN-water system. This finding can be interpreted in terms of additional binding of lithium
ion to the polymer chains. Conductivity measurements carried out on LiClO4 and KClO4 in water + PVP support this interpretation. |
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Keywords: | Conductance surface tension electrostatic and hydrophobic interactions lithium heptadecafluorononanoate poly(vinylpyrrolidone) lithium perchlorate potassium perchlorate |
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