Abstract
Abstract The effect of temperature on the viscosities of cetyltrimethylammonium salts (CTA X , X =Br − , NO 3 − , Tosylate) in the presence of added salts is presented. It was found that plots of 1n of relative viscosity vs 1/ T was linear and the activation free energy ( ΔG* ) of the viscous flow was obtained from the slopes of such plots. The activation enthalpies ( ΔH* ) and entropies ( ΔS* ) for the viscous flow were also calculated and the entropic contribution was found to be negligible. The ΔG* are interpreted in terms of the energy required to create a hole or an activated transition micellar structure capable of being transformed into smaller micelles and finally into spherical micelles. The ΔG* and ΔH* values are highly dependent on the nature of the counterions. The more strongly bound counterions produce the greatest effect on the energy of the rod-to-sphere transition.
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