VISCOSITY OF MICROEMULSIONS

Microemulsions have been prepared from benzene and water using emulsifier blends of 5% Tween 20 + 1% Span 20 or 10% Tween 20 + 1% Span 20. The volume concentration of the dispersed phase (φ{symbol}) extended up to 0.406, and the mean particle diameter ranged from 543A-1245A. The steady-state viscosities of these microemulsions, as determined in a capillary viscometer, could not be represented by any equation which merely related viscosity and dispersed phase volume concentration. After allowing for the volume (φ{symbol}8) of benzene solubilized within the micelles of excess emulsifier, the relative viscosity (nrel) data conformed to Nrel=exp a(δ-δs) 1-k(δ-δs where k is a hydrodynamic interaction coefficient which depends empirically on mean particle size (Dm) according to k = 1.079 + exp( 0.01008 Dm) + exp ( 0.00290 Dm2. has a higher value (1.95-2.08) than predicted by Taylor's theory, although it is well below the value of 2.5 for solid spheres. Several factors may hinder fluid circulation within the droplets. © 1969.