(634g) Structure to Function of Polymer-Surfactant Complexes Coating Emulsion Drops

Polymers and surfactants are commonly used to control the phase behaviour, stability, rheology, and other functions of formulated products such as shampoos, processed foods, and pharmaceuticals. With a focus on emulsions, understanding how the polymers and surfactants form complexes, coat emulsion drops, and mediate drop interactions is critical to controlling the function of these multi-component systems. In addition, the increasing demand for formulated products to become more sustainable, moving to greener or less fossil fuel dependent feedstocks, has created a more immediate need to approach ingredient replacement on faster pathway than traditional formulation approaches or using traditional colloid and interfacial characterisation methods. Our group has focused on developing innovative methods and tools to study colloidal, hydrodynamic and nanomechanical interactions in soft systems, ranging from fundamental molecular and colloidal scale measurements to more applied microfluidic platforms. We will discuss how polymer-surfactant (PS) complexes comprised of anionic surfactants and cationic polymers or neutral polymers mediate the interactions between drops measured using atomic force microscopy (AFM) methods pioneered by our group. We will show how the attractive or adhesive interactions between drops with PS complex coatings exhibit a strong dependence on surfactant concentration and type as well as being able to respond to step changes in solution conditions. We will also present data on the insights that can be gained by using single molecule force spectroscopy to probe the molecular structure of individual PS complexes. Finally, we will show how the rich information in these detailed AFM measurements can be accessed through a novel microfluidic platform allowing for faster measurement of larger parameter spaces for use in practice or as a screening tool for more detailed AFM measurements.