Shear degradation as a probe of microalgal exopolymer structure and rheological properties
The bulk rheological properties of exopolymers produced by three species of microalgae are destroyed by shear stress. The properties are drag reduction in capillary pressure flow and low shear rate viscosity. As such, shear stress constitutes an experimental probe into the macromolecular structure which effects bulk rheological properties. Native and sheared exopolymer solutions were subjected to analysis by electrophoresis, size exclusion chromatography, hydrolysis, dialysis, and reducting end-group analysis. The evidence indicates that shearing did not break the glycoside backbone of these exopolymers; rather, shearing disrupted subtle interactions between copolymers. The interactions necessary for bulk rheological properties are likely at the quaternary level of macromolecular organization, specifically weak aggregations.
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