| Abstract
| - A protocol is described for measuring and analyzing neutron reflectivity data from a buried oil−waterinterface. A hexadecane−water interface is considered, and data from the bare interface and from filmsof polybutadiene−poly(ethylene oxide) linear diblock copolymers with Mw ∼ 60 000 g mol-1 and containing∼50 mol % poly(ethylene oxide) spread (with interfacial concentrations of Γ = 4 and 10 mg m-2) at theinterface are reported. From the analysis, it emerges that the hexadecane−water interface is “rougher”than capillary wave theory based expectations. This could be attributable to the influence of molecularsize and shape on the intrinsic thickness of the interface. When present, the amphiphilic copolymerssegregate at the interface with the blocks occupying a concentrated region (∼20% polymer) with thickness∼20 Å and a dilute region (≪10% polymer) of thickness ∼50 Å on either side of a nominal dividing surface.The amount of copolymer at the interface, determined using a Guinier-type analysis, is in line with thespread amount at the interface at a moderate (Γ = 4 mg m-2) interfacial concentration but is consistentwith a more expanded configuration at Γ = 10 mg m-2.
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