CENTRAL NEUTRON-SCATTERING ANALYSIS OF TH E FORMATION AND STRUCTURE OF CATIONIC SURFACTANT MICELLES IN FORMAMIDE

We report here a study of the micellization of different surfactants t o observe the effects of the chain length, counterions and headgroups in a non-aqueous polar solvent-formamide. Small-angle neutron scatteri ng measurements were performed in a PACE spectrometer in L.L.B. The so lvent used was a 2/3 deuterated formamide. The aggregation number and the spontaneity of the association depend on the chain length ; but, i n formamide, micelles always are smaller and more ionized than in wate r. Their growth is much more low in formamide than in water where ''ro d-like micelles'' form especially with Br-. Cl- in formamide leads pre ferentially to the formation of small micelles as it does in water. Th e micellar ordered phase is observed in the binary C-16 Py Cl/formamid e system at high concentration. With regard to the headgroup N+(CH3)3, the pyridinium ring encouraged the micellization in formamide close t o 20-degrees-C.