Rheological measurement and microscopic observation were carried out to understand the shearing rate (
D) dependence of the shape of multilamellar structure which is made up of dialkyl (C
1618) dimethylammonium chloride (DADMAC).
Five percent DADMAC dispersion exhibited a pseudoplastic flow indicating reduction of apparent volume fraction of the DADMAC aggregate. Viscosity curve of the dispersion at 50°C (above the transition temperature of DADMAC : 37°C) was lower by 1 to 2 orders than that at 25°C when no remarkable shearing rate was applied. On the other hand, there was no significant difference between the viscosity at 25°C and that at 50°C after the dispersion was treated with
D of more than 10
5s
-1.
By an electron microscopy using a freeze-fracture replica method, a mixture of multilamellar vesicles with different numbers of bimolecular layers were observed in the dispersion not treated with remarkable
D. Both the number of bimolecular layers and the size of multilamellar vesicles were found to be reduced with an increase of an applied
D. Almost every vesicle became an aggregate with a few layers, especially when the dispersion was treated with
D of more than 10
5s
-1. Consequently a network structure was formed spontaneously among each vesicle which led to a slight increase of viscosity in relatively low
D region during storage period over a month. This phenomenon can be attributed to an electrostatic interaction between the small aggregates.
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