The Viscosities of Aqueous Sodium Alkylsulfate and Alkyltrimethylammonium Bromide Solutions

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The viscosities of aqueous solutions of sodium alkylsulfate and alkyltrimethylammonium bromide have been measured at various temperatures from 5 to 55°C. The viscosity data have been interpreted in terms of the Jones-Dole equation, and the viscosity B coefficients for the alkylsulfate and alkyltrimethylammonium ions at various temperatures have been calculated. The B values for these ions are all positive; they decrease with an increase in the temperature and increase linearly with an increase in the alkyl-chain length. The increment of B is found to be 0.076/–CH2– at 25°C. The energy and the entropy of activation for the viscous flow at 25°C have been calculated for these ions; they increase with an increase in the alkyl-chain length. This behavior of the B coefficient, and the energy and the entropy of activation for the viscous flow may be interpreted by saying that the longer-chain ions promote the hydrogen-bond structure of water around the hydrocarbon chain of these ions, while shorter-chain ions, e.g., ethylsulfate and ethyltrimethylammonium ions, behave instead as structure breakers because of the predominance of the disordering effect on the water around the ionic head. The viscosities of micellar solutions have also been measured. The volume of micelles as a hydrodynamic moving unit in solution has been estimated.
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