Rheological behaviour of monomeric solutions and non-interacting micelles

3 Rheological behaviour of monomeric solutions and non-interacting micelles 

Solutions below the cmc contain only monomeric surfactant molecules. To a first approximation these dissolved molecules do not influence the viscosity which is the same as for pure water (1 mPa s at room temperature) [37]. 

The influence of non-interacting micelles (i.e. spherical micelles or small rod-like micelles not far beyond the cmc) on the viscosity r] of a solution can be described by the Einstein equation  

In the case of non-interacting anisometric aggregates, the situation becomes more complex. Such aggregates rotate in a shear flow with the consequence that their effective volume is much larger than the volume fraction of the micelles. Hence, the viscosity as a function of concentration increases with a larger slope once rod-like micelles are formed. 

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