EFFECTS OF IONIZATION ON MICELLE SIZE OF DIMETHYLDODECYLAMINE OXIDE

Light scattering from aqueous NaCl solutions of dimethyldodecylamine oxide has been measured at different degrees of neutralization adjusted by addition of HCl, and molecular weights of differently charged micelles are determined from the Debye plot. In the absence of added salt, the micelle molecular weight decreases with increasing ionization, indicating the electrostatic effect in micelle formation. In the presence of NaCI above 0.01 M, however, the largest micelle is formed at half-ionization, and its size steeply increases with increasing NaCI concentration. In 0.20 M NaCl the large micelle is composed of about 300 ionized and 300 nonionic molecules, and it grows further with increasing surfactant concentration. © 1979.