Polymer grafted hard carbon microspheres at an oil/water interface

Pickering emulsions offer an established method of stabilizing oil-in-water emulsions as either an alternative to surfactants or as an additive together with surfactants, providing greater colloidal stability even at low particle concentrations. This work presents a novel experimental approach to study the influence of several system parameters on the effectiveness of Pickering emulsion systems. Specifically, a dodecane oil drop stabilized by hard carbon microspheres in an aqueous saline solution is used as a model system to obtain both quantitative and qualitative information on the effectiveness of the microspheres as a function of their surface wetting properties. The test setup, in which a macroscopic oil drop is brought into contact with a test surface in a controlled motion and environment, allows for several aspects of the test (for e.g., oil drop size, approach velocity, normal force, solution ionic strength, temperature, pH, and presence of surfactants) to be potentially controlled and studied precisely. To demonstrate the capabilities of the experimental set-up, hard carbon microspheres are modified with a poly(styrenesulfonate) shell through ATRP in order to tune the wettability of the particles through choice of polymer, which are then used to stabilize a dodecane oil drop in an aqueous saline solution. The particles effectively form a steric barrier preventing the spreading of an oil drop on hydrophobic surfaces and also preventing the coalescence of stabilized oil drops.