| Popis: |
Viscosity studies have been carried out on a series of oil/water solubilized micellar solutions (so-called “microemulsions”) of liquid paraffin, glycerol, water and blends of Tween 60 and Span 80. The variation of relative viscosity, ηrel, with volume fraction, φ, of the micelles conformed to η rel = exp [ao/(1 - ko)] , where a is a constant and k is the hydrodynamic interaction coefficient. The value of k was found to be independent of micellar diameter over the range 13.3 to 48.6 nm. Decrease in the surfactant/glycerol molar ratio of the solution from 0.231 to 0.028 produced a linear decrease in k from 1.10 to 0.62. For φ ⩽ 0.15, an exponential relationship existed between ηre1 and the surfactant concentration. The effect of the surfactant concentration on the viscosity has been discussed in terms of the interaction between the polyoxyethylene chains at the surface of the micelles. Allowance for the hydration of the polyoxyethylene chain, reduced the value of a towards the theoretical value of 2.5 for solid spheres. Increase of the Tween/Span molar ratio from 1.0 to 1.6 had no significant effect on the values of a or k. |
