Polyoxyalkylene block copolymers adsorbed in hydrocarbon and fluorocarbon oil-in-water emulsions

Small-angle neutron scattering has been used to investigate the structure of the adsorbed layers formed by three poly(oxyethylene)-poly(oxypropylene) block copolymers (Poloxamer 188, Poloxamer 407 and Poloxamine 908) in two similar oil-in-water emulsions; one with a fluorocarbon oil phase, the other with a hydrocarbon oil phase. We find that the structure of the buoy layer is remarkably similar in the two cases. Since previous work has shown that the fluorocarbon/water interface is impenetrable to these polymers, these new findings also suggest that there cannot be significant penetration of the hydrocarbon/water interface. This is discussed in relation to the findings from other studies. The effects of added electrolyte and temperature on the adsorbed layer structure are also reported.