The associations of triblock copolymer made of acrylic acid, methyl acrylic acid and butyl acrylate in aqueous solution as well as in NaCl and CaCl 2 solutions were studied by using fluorescence. The micelle like clus...
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The associations of triblock copolymer made of acrylic acid, methyl acrylic acid and butyl acrylate in aqueous solution as well as in NaCl and CaCl 2 solutions were studied by using fluorescence. The micelle like clusters(MLCs) of copolymer formed is able to solubilize non polar material. A little electrolytes added in the copolymer solution can increase the value of critical aggregation concentration( ρ ac ) and micropolarity. But with the increase of the concentration of electrolytes, the value of ρ ac and micropolarity will decrease. When there is NaCl with fixed concentration in the systems, the process of the MLCs loosening is relaxed because of the charge screening. In the systems with fixed CaCl 2 concentration, Ca 2+ induced the cross link of -COO - groups, so the interface between the MLCs and the water is not obvious and the big MLCs is formed between the clusters.
Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspensio...
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Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspension. In this paper, the shear thickening was observed in colloidal dispersion gel, with very lower volume fraction, of partially hydrolyzed polyacrylamide(PHPA)/aluminum citrate. Colloidal dispersion gels are made of low concentrations of polymer and crosslinker. Polymer mass fractions normally range from 0.01% to 0.12%. In this concentration regime, there is not enough polymer to form a continuous network, so a conventional bulk type gel cannot form. Instead of a solution of separate gel bundles forms, and it is a mixture of predominantly intramolecular and minimal intermolecular crosslinks. In the work reported here, the colloidal dispersion gels are made of PHPA of 0 03%, KCl of 0.5%, thiourea of 0.1% and Al 3+ with a mass fractions range of 0—0 003%, the Al 3+ ∶PHPA mass ratio changes from 0 to 0.1. The critical shear rates(CSR) for the onset of shear thickening are about 200 s -1 for all CDG systems studied, i.e ., the Al 3+ ∶PHPA mass ratio don’t affect the CSR. In the lower shear regime than CSR shear thinning was observed and in the higher shear regime than CSR the shear thickening was observed. The shear thickening may be explained with cluster formation mechanism.
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