Self-aggregation of surfactants in water solution by NMR

Dynamic behavior of surfactant molecules, sodium dodecyl sulfonate （SDSN）, cetyl trimethyl ammoniumbromide （CTAB） and triton X-100, and their micelles in water solution at various concentrations were studied bychemical shift, self diffusion coefficient （D） and nuclear magnetic resonance relaxation （Tand T） measurements.Experimental results show that there exist turning points at surfactant concentration （C） nearby the critical micelleconcentration （cmc） for all of the above-mentioned parameters, which approach the constant values when C equals 5to 10 times cmc. Tand Tmeasurements show that when C < cmc, Triton X-100 molecules exhibit fast isotropicmotion in water solution. After micellization, the motion of hydrophobic chains is far away from the extreme narrow-ing condition, however, the long hydrophilic oxyethylene chains move relatively freely, although their Tand Tbe-come shorter in comparison with those of the molecules in mono-molecular state. The behavior of the hydrophobicchains