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Attractive interactions between drops in which aggregation or adhesion occurs, rather than coalescence, govern the formation of microstructures that control the phase behaviour, stability, rheology and most importantly function of formulated products (e.g., food, personal care products, pharmaceutical formulations). These products are often multi-component emulsions where interactions between additives can mediate adhesion in complicated ways. The overarching objective of this thesis was to understand how polymer-surfactant (PS) complexes mediate adhesive interactions, with a focus given to the development of a novel microfluidic platform capable of investigating these systems using high throughput measurements. The attractive interactions between oil drops in poly(vinylpyrrolidone) (PVP) and sodium dodecyl sulphate (SDS) solutions were studied using both drop chaining in a microfluidic device and direct force measurements on an AFM. Links between the two methods were explored in detail with emphasis on understanding and establishing similarities in surface coverage and the structural composition of layers at the drops interface. Through interfacial tension measurements, direct force measurements and microfluidic observations a detailed investigation into drop-drop interactions was performed. Interfacial tension measurements confirmed the formation of PS complexes and the concentration region in which they exist for the PVP/SDS system. Rigid force measurements showed via a quantitative model that depletion and electrical double layer (EDL) forces dominate the interactions between two hydrophobic surfaces. Force measurements between two deformable oil drops using the same systems displayed similar depletion behaviour. A model used to describe deformable systems, also accounting for depletion and EDL forces, used the depletion length and osmotic pressure fit from the rigid surface analysis and showed reasonable agreement with the force data. A small under prediction b