COLL 439 |
| Darrell Velegol and Jason Feick. Chemical Engineering, Penn State University, University Park, PA 16802 |
| The classical models for colloidal forces have assumed uniform charge distributions on the particle surfaces. Recent papers have shown that a nonuniform charge distribution on two colloidal particles will significantly reduce colloidal stability from predictions based on a uniform charge distribution. Thus, nonuniform charge distributions can cause unexpected suspension stability, structure, and rheology. But using the technique of “rotational electrophoresis” (which combines video microscopy measurements of electrophoretic angular velocities with interpretations from electrokinetic theory), we have previously obtained data showing that particles are nonuniformly-charged on a nanoscale. Now we have examined the effects of adding surfactants (e.g., SDBS) and polyelectrolytes (e.g., sodium polystyrene sulfonate) on charge nonuniformity on polystyrene latex particles with sulfate charge groups. These additives have been found to reduce charge nonuniformity on the particles. |
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Colloidal and Molecular Electro-Optics
Division of Colloid and Surface Chemistry |