Rod~haped mlcelles were produced by mixing 0.1 M cetyltrimethylammonium bromide (CTAB) and 0.1 M KBr in aqueous solution. The effects of the addition of aliphatic n-amines (C4, C6, C7 and Cst and temperature on the shape of micelles were studied by viscosity measurements. The viscosity data show that transition of rod~haped micelles to larger aggregates is induced by addition of higher amines (>~Ce) up to a certain concentration; a further increase in concentration produced the opposite effect. Addition of C4-amine induces only a rod-to-sphere transition. The data were interpreted in terms of solubilization/inco~ poration (decrease of micellar surface charge density) of amines inside the micelles and the nature of the effective solvent (water + amine}. The latter effect dominated the change from larger aggregates to smaller micelles at higher concentrations of the added amine. Increasing the tempeP ature produced effects similar to C4-amine addition, namely, rod-to~phere transition. Activation free energy (AG*) and enthalpy (AH*) were also computed from the temperature dependence of the viscosity. AG* and AH* values were higher for larger aggregates (long rods) than for smaller ones (spherical micelles) and AH* covered almost the total contribution to AG*

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We have measured the viscosity of solutions of 0.3 M sodium dodecy[ sulfate (SDS) + 0.3 M NaBr + n-alkanols as a function of [alkanol] and temperature. When propanol was added, the viscosity of micellar solutions remained almost constant and then decreased, whereas it continuously increased with hexanol. However, with butanol or pentanol, depending upon the added concentration, increases followed by decreases in viscosity were observed. This behavior has been discussed in light of solubility of alkanols in various soluble phases of the micellar system with a resultant change in the Mitchell-Ninham parameter of the "effective surfactant" (i.e., SDS + n-alkanol). An increase in temperature caused a decrease in viscosity, which is related to micellar breakdown. Activation parameters (AG* and AH*) were computed from the temperature dependence data. AH* Covered almost the total contribution to AG*.

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