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We have measured the apparent critical exponent y characterizing the divergence of the viscosity η∝(T-Tc)-y near the liquid–liquid critical point of the mixture polystyrene in diethyl malonate. The data span the range in reduced temperature of 10-4<(T-Tc)/Tc<10-1. The sample was prepared from the same materials used by Gruner et al. in their capillary viscometer [Macromolecules 23, 510 (1990)]; however our torsion oscillator viscometer had a shear rate 80 times lower. This increased the range of reduced temperatures where shear effects could be neglected. In spite of the large reduction in shear rate and the different viscometry technique, the parameters fitted to our data and those of Gruner et al. are in agreement. For this polymer solution, y is in the range 0.028±0.003, close to recent results for two other polymer solutions measured in capillary viscometers. However, it is significantly smaller than the exponent for pure fluids (0.041± 0.001) and simple binary mixtures (0.042±0.002). It appears that polymer solutions are in a dynamic universality class different from that of simpler fluids. [ABSTRACT FROM AUTHOR]

The flow of the microemulsion dioctylsulfosuccinate (AOT)/decane/water through 0.1 and 1.0 μm diameter pores was studied for water droplet volume fractions ranging from 0 to 0.5. The viscosity of these microemulsions, as measured in a capillary viscometer with a bore of ≊1 mm diameter, exceeds by as much as a factor of 4 theoretical predictions of the viscosity of suspensions of hard or liquid spheres. If droplet clustering causes this viscosity enhancement, then flow of the microemulsions through pores with diameter small compared to the characteristic cluster size should display a large finite-size effect. The apparent viscosity of the microemulsions in pores differed from the viscosity measured in the capillary viscometer by less than 40% for 0.1 μm diameter pores and by less than 8% for 1.0 μm diameter pores. These differences are of the same scale as estimates of two effects: adsorption of droplets on the pore wall and the enhanced flow of suspensions near a wall. The absence of larger finite-size effects implies that clustering of droplets on length scales of 0.1 μm or larger does not contribute substantially to the microemulsion viscosity. [ABSTRACT FROM AUTHOR]

We have measured the viscosity of four binary mixtures near their consolute points: (1) methanol+cyclohexane, (2) isobutyric acid+water, (3) nitroethane+3-methylpentane, and (4) 2-butoxyethanol+water. The viscosity data are consistent with the power-law divergence: η∼|T-Tc|-y, with an apparent viscosity exponent in the range 0.0404

We have measured the viscosity of the three-component microemulsion water/decane/AOT as a function of temperature and droplet volume fraction. At temperatures well below the phase-separation temperature the viscosity is described by treating the droplets as hard spheres suspended in decane. Upon approaching the two-phase region from low temperature, there is a large (as much as a factor of 4) smooth increase of the viscosity which may be related to the percolation-like transition observed in the electrical conductivity. This increase in viscosity is not completely consistent with either a naive electroviscous model or a simple clustering model. The divergence of the viscosity near the critical point (39 °C) is superimposed upon the smooth increase. The magnitude and temperature dependence of the critical divergence are similar to that seen near the critical points of binary liquid mixtures. [ABSTRACT FROM AUTHOR]

Examines the measurements of the viscosity near the consolute point of triethyl n-hyxel ammonium triethy n-hyxel borate in diphenyl ether. Analysis on coexistence for a mean-field ionic fluid; Composition of mean-field ionic fluid; Indication for mean-field static behavior; Presence of critical viscosity enhancement.