• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.231-237
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• 2005

The sizes and structure of micelles and vesicles formed in ammonium dodecyl sulfate (ADS)/octadecyl trimethyl ammonium chloride (OTAC) mixed aqueous solutions were analyzed by small-angle neutron scattering. In micellar regions of pure ADS and OTAC aqueous solution, the spherical micelles were formed at given concentrations and their sizes were 40 and $61{\AA}$, respectively. The structure transition of pure micelles occurred above 300 mM due to the constancy of the intermicellar distance above 250 mM. The coexisting region of mixed micelles and vesicles in phase diagram of mixed system was also assured. It was investigated that vesicle formed spontaneously took a bilayer structure. The lamellar thickness of vesicles decreased with increasing concentration of vesicle samples. However, the size could not be determined for mixed micelle and vesicle above 100 nm due to limitation of low q ranges. Finally, The 9 mM solution of ADS mole fraction 0.9 (${\alpha}$=0.9) showed bilayer structure compared to phase diagram classified into mixed micelle.