Monitoring the stability of nanosized silica dispersions in presence of polycations by a novel centrifugal sedimentation method
Gudrun Petzold¹, Christine Goltzsche¹, Mandy Mende¹, Simona Schwarz¹, Werner Jaeger² ; Journal of Polymer Science (2009) submitted.
Abstract: The stability of Aerosil -silica dispersions is analyzed in dependence on the addition of polycations with different charge density and hydrophobic modification using the analytical centrifuge LUMiSizer. This novel centrifugal sedimentation method allows the direct calculation of the stability parameters like sedimentation velocity and prediction of the shelf life. The highly charged polycation poly(diallyl-dimethylammonium chloride) (PDADMAC) is compared with tailored cationic polyelectrolytes of equal degree of polymerization but lower and different charge density as well as various hydrophobic substitution. The used technique allows to accelerate demixing and to quantify the stability of dispersions in a direct way. All polymers under study are able to stabilize Aerosil dispersions, but the shelf life strongly depends on the polymer concentration. Typically for polycations the stability increases with the polymer concentration whereas at low polymer content flocculation can be detected. In this context the behavior of PDADMAC and three cationic PVB derivatives is similar, but, whereas the stability of PDADMAC containing dispersions decreases at higher polymer concentrations, two of the PVB derivatives are effective stabilizers at higher concentrations too. The highest increase of the stability with increasing polymer concentration is obtained with the ampholytic terpolymer TP which has the lowest cationic charge.
Key words: Polyelectrolyte stabilization • Dispersion stability • Silica • Centrifugation • Adsorption
¹ Leibniz Institut fur Polymerforschung Dresden, Department of Surface Modification, Hohe Strasse 6, D-01069 Dresden, Germany².Contact us
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