|
چکیده
|
The colloidal assembly is a major route to fabricate materials with tailored functionality. Compared to other conventional colloidal dispersions, nanoemulsions have unique rheological behavior due to nanoscale droplets and significant interdroplet interactions. In this work, we investigate the complex colloidal behavior of nanoemulsions by controlling the depletion and electrostatic droplet interactions within the semi-dilute and concentrated regime. Therefore, the aggregation behavior, coalescence, and the structure-flow relationship of nanoemulsions are examined through flow curve and oscillatory shear measurements. We changed the interdroplet interactions as a function of surfactant types and concentrations for droplet sizes ranging from macro- to nano-droplets. Three regimes of colloidal interactions comprised of repulsive, attractive and Oscillatory structural forces in the presence of different amounts of surfactants are proposed. Therefore, the nature of the aggregation process and the cluster size distribution and its moments is identified. In the studied range of surfactant concentrations, rheology of emulsions with narrow size distribution shows the flocculation and transition from colloidal gels to a glassy state. In contrast to the macroemulsions, by inducing the depletion interaction at a high concentration of surfactants, the nanoemulsions exhibit very tenuous aggregation below the random close packing.
|