Interactions between colloidal particles at oil-water interface

Ph.D. ; Colloidal particles at the fluid interface have constituted an enduring research interest in colloid science for their significance in theoretical study and practical applications. Theoretically, the observability of colloidal particles under an optical microscope renders them a model system for the study of phase behavior. Practically, colloidal particle systems at either a planar or curved interface can serve as templates for encapsulation and optical crystals, which can be used in the cosmetics and pharmaceuticals industries depending on designated ingredients. ; Despite the solid theoretical fundamentals of using a coarse-graining process and atom analogy to study the equilibrium properties of colloidal suspensions, no universal model yet exists to predict colloidal particle systems at the fluid interface, where particles are in a discontinuous environment. ; This thesis presents an experimental investigation of reported theories and models of colloids at the fluid interface along with a comparison with other published experimental systems. We seek to understand how the current experimentally prepared system may align with or deviate from theoretical predictions to determine affecting parameters to serve as the starting point for more complex practical application systems. ; By using video microscopy to record particle positions and reversible work theorem, we extract the effective pair potential U(r) of inter-particle mean force from the radial distribution function g(r). We start with the most frequently published model particles of polystyrene (PS) at the oil–water interface. With density-difference-induced buoyancy between D2O and polystyrene, we develop a new experimental method to prepare an interfacial colloidal system. By comparing the results of interfacial system preparation using a conventional spreading solvent, we reveal the origin of inconsistencies in published interactions between interfacial colloidal particles based on experimental techniques. We then extend our findings to more complex ...