Polymer particle interactions in nanocolloids

The rheological properties of complex fluids has been one of the interesting research subject due to the macroscopic behaviour (namely shear thinning and shear thickening) exhibited when they are subject to shear force. All concentrated suspensions under right conditions can exhibit the non-Newtonian flow behaviour, however, the required conditions and the underlying mechanism are not well understood in literature. To this respect, this study systematically investigates the effects of physicochemical parameters on the flow behavior of colloidal nanoparticle suspension (CNS) to shed a light on the mechanism behind the shear thickening behavior of CNS. We have also presented the outcomes of experimental studies of CNS with a low particle volume fraction, and anisotropic and flocculated microstructures through measuring their viscosity and electrical resistance under various shear forces together with utilizing several relevant characterization methods (i.e., Dynamic Light Scattering, Transmission Electron Microscopy and Capacitance Measurement). It is observed that studied CNS display shear thickening/thinning flow behavior depending on their microstructure forms due to the interaction forces among particles and associated changes in floc sizes, which are controlled by the shear induced hydrodynamical forces. The detailed evaluation of the experimental results indicates that the shear thickening phenomena in low volume fraction, anisotropic and flocculated systems is mainly attributed to the increase in the total surface area and the effective volume fraction of particles due to both hydrodynamic and interparticle forces