Soft interfaces constituted by molecular assemblies in interfacial geometries play important roles in a multitude of technological applications, for instance in the fields of liquid purification, separative chemistry, and lubrication. The term "soft interfaces" broadly covers flexible interfaces and interfaces composed of molecular groups with considerable conformational degrees of freedom. In contrast to the case of "rigid" interfaces, the interaction characteristics of soft interfaces depend on the conformation of their constituents. The interaction between polymer-decorated interfaces, for instance, will be crucially influenced by the ability of the polymer chains to mutually intercalate. With the planned experiment we aim at the structural characterization of hydrophilic PEG polymer brushes in an aqueous environment under confinement and while interacting with a second brush. This scenario is of great relevance in context with biological and technological soft interfaces, but so far largely unexplored. Sensitivity to the conformation of individual brushes will be achieved by the simultaneous use of hydrogenated and deuterated PEG brushes.