CHARACTERIZATION OF MICELLAR SYSTEMS BY THE CONDUCTIVITY METHOD - SODIUM-SALT OF PERFLUOROPOLYETHER CARBOXYLIC-ACID

A new method for the interpretation of the conductivity of ionic surfactants is proposed. The model considers the contribution of ions and of charged micelles, and is based on the approximation of constant concentration of surfactant chains above the critical micellization concentration (CMC), and on the equilibrium constant of counterion binding to the micelles (K). These two parameters evaluated for aqueous solutions of sodium salt of perfluoropolyether carboxylic acid are as follows: K=35800 dm(3) mol(-1); CMC = 1.19 x 10(-3) mol dm(-3). The third quantity obtained by this procedure is the product of the aggregation number (N) and the size parameter (f = e(2)L/6 pi eta r): Nf = 76.5 S cm(2) mol(-1).