C-13-NMR OF MICELLAR SOLUTIONS - MICELLAR AGGREGATION NUMBER FROM THE CONCENTRATION-DEPENDENCE OF THE C-13 CHEMICAL-SHIFTS

13C NMR chemical shifts were determined as a function of concentration for aqueous solutions of sodium hexanoate, sodium octanoate, and nonylammonium bromide. Using the mass action law model for micelle formation, we have estimated the aggregation numbers by fitting calculated chemical shifts as a function of amphiphile concentration to the experimental values. For sodium octanoate and sodium hexanoate the calculations indicate the formation of an appreciable amount of premicellar aggregates with an aggregation number of about 3 or 4. For nonylammonium bromide the results are explained by the formation of large aggregates only. © 1979 American Chemical Society.