| Abstract
| - Micellar solutions of tetramethylammonium dodecyl sulfate have been studied to determine the degree ofcounterion binding. Tetramethylammonium chloride was added over a wide range of surfactant concentrationssuch that the total concentration of tetramethylammonium ions in solution remained constant. Small angleneutron scattering experiments showed a constancy in aggregation number across this series, consistent withthe constant Caq concept of Bales et al. (J. Phys. Chem. B2001, 105, 6798). Pulsed-field gradient andelectrophoretic NMR experiments were used to determine the degree of counterion dissociation, α, whichwas found to be 0.33. This value is in contrast to the value from conductivity measurements (α = 0.2), butsupports the concept of an aggregation number based definition of α.
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