Transport properties for aqueous solution of sodium sulfonate surfactants - 1. Mutual diffusion measurements: Evaluation of the equilibrium parameters for the micellization process

Isothermal mutual diffusion coefficients (D) have been measured for binary aqueous solutions of sodium alkylsulfonates at 25 degrees C. The diffusion coefficient values drop as the concentration of micelles in the system incr eases. As the length of the hydrocarbon chain increases, the observed drop in D becomes increasingly sharp and shifts to lower concentrations. When th e micellization process is treated as a chemical equilibrium, diffusion coe fficients lead to the calculation of the thermodynamic parameters associati on number, n, and the equilibrium constant, K. These parameters are briefly discussed in connection with the alkyl chain length of the surfactants. (C ) 1999 Academic Press.