Electrophoresis of Colloidal Particles in Shear-Thinning Polymer Solutions

This thesis includes a theoretical and experimental analysis of electrophoresis of colloidal particles in non-Newtonian polymeric fluids with shear-rate dependent viscosities. A model is derived that predicts field dependent electrophoretic mobility in shear-thinning Carreau fluids. The latter effect is experimentally investigated for submicron particles in solutions of linear polyacrylamide using capillary electrophoresis. The mobilitiies of the particles studied in these solutions did not depend on field strength, yet the mobilities were consistently an order of magnitude greater than in water and glycerol solutions with similar bulk viscosities. The increase in particle mobility could be attributed to several mechanisms, however it is consistent with the depletion of polymer apparent viscosity of the fluid as it migrates by electrophoresis is the same as experienced by the particle in Brownian diffusion. A comparison of particle mobility in both glycerol and polyacrylamide solutions to diffusion coefficients of the particles measured by dynamic light scattering supports this conclusion.