Soft matter systems have more complex interfaces than slab layers with gaussian roughness.
We will now model a data set for tethered deuterated polystyrene chains. The chains start out at approximately 10 nm thick in dry conditions, and swell to 14-18 nm thickness in toluene. Two measurements were made:
The chains are bound to the substrate by an initiator layer between the substrate and brush chains. So the model needs a silicon layer, silicon oxide layer, an initiator layer which is mostly hydrocarbon and scattering length density should be between 0 and 1.5 depending on how much solvent is in the layer. Then you have the swollen brush chains and at the end bulk solvent. For these swelling measurements, the beam penetrate the system from the silicon side and the bottom layer is deuterated or hydrogenated toluene.