Rheological study of fumed silica suspensions in chitosan solutions

In this article, the linear and nonlinear rheological properties of fumed s ilica suspensions are studied in the presence of a cationic polysaccharide, chitosan. Chitosan is shown to adsorb on silica aggregates, and the viscoe lastic properties of chitosan/silica systems are shown to depend strongly o n the chitosan concentration regime. For silica volume fractions greater th an 2%, addition of chitosan in the semidilute regime leads to rheological p roperties attributed to the formation of a colloidal suspension of percolat ing silica aggregates that interact through hydrogen bonds mediated by sili ca and adsorbed chitosan; whereas addition of chitosan in the concentrated regime leads to rheological behaviors attributed to the formation of a chit osan entanglement network reinforced by silica aggregates that behave as fi llers.