| For polymerically stabilized colloids, we incorporate the thermodynamic and hydrodynamic effects of the grafted polymer chains into a statistical mechanical theory relating microscopic interactions to rheological properties. The long range repulsion between polymer layers is either estimated via mean field theory or extracted from surface force measurements in the literature. Monte Carlo simulations with this potential yield the equilibrium radial distribution function. Treating the polymer layer as a Brinkman medium allows one to determine the hydrodynamic mobilities of interacting particles. A weak shear flow perturbs the structure slightly from equilibrium and determines the high frequency shear modulus and zero shear viscosity for several permeabilities and ratios of particle radius to layer thickness. Comparison with experimental data clarifies the subtle interplay between the interparticle potential and hydrodynamic interactions.; The same basic theory predicts the high frequency shear modulus for micellar solutions of associative polymer, which have a soluble midblock and two insoluble end groups. A variational approach systematically accounts for curvature and predicts the repulsive component of the pair interaction potential, while the entropic bridging attraction is estimated from the results of Milner and Witten (1992). Predictions of the modulus show not only the direct importance of the attraction but also its effect on the structure in influencing the number of nearest neighbors.; Our experimental system consists of commercial poly(methyl methacrylate) particles and a triblock copolymer composed of a poly(isoprene) midblock and two poly(ethylene oxide) end blocks dispersed in decahydronapthalene (decalin). The triblocks associate into micelles in solution, but do not adsorb onto the particles. Steady shear measurements on mixtures of the triblock and particles reveal highly non-Newtonian viscosities dramatically larger than either the particle dispersion or the polymer solution. The zero shear viscosities correlate reasonably well with the exponent of the potential minimum estimated for depletion attractions. Linear viscoelastic measurements detect loss and storage moduli that are power law functions of frequency, indicating the formation of a percolation network or weak gel. Although there was no detectable dichroism for the mixtures, birefringence appeared in the thinning region and increased with shear rate. |
