## 3 Results and Discussion  
### Transmission Contribution to GIS Pattern  
GISANS experiments together with the corresponding simulations with BornAgain were performed on samples of PEG-microgels adsorbed at a silicon interface and are presented in Figure 2. The same GISANS data have been presented in Ref. [11], with a preliminary evaluation of the line cuts which did not cover all details of the experimental data. The angle of incidence \(\alpha_{i}=0.7^{\circ}\) at a wavelength of 5 A slightly above the critical angle of total reflection has been chosen to strongly illuminate the microgels. The analysis of 2D GISANS detector images is mainly focused on the part containing the totally reflected beam above the sample horizon, whereas the part below the sample horizon, where the transmitted beam and small angle scattering still reaches the detector, is often ignored. A first analysis of the experiments on PEG-microgels at the interface was done in this way (as presented in Ref. [11]). Figure 2: Experimental (**a**) and simulated with BornAgain (**b**) 2D grazing incidence small-angle neutron scattering (GISANS) scattering pattern of adsorbed p(MEO2 MA-co-OEGMA) microgels. White dashed lines in (**a,b**) correspond to the cuts depicted in (**c,d**). In (**c,d**) the perpendicular (along \(q_{x}\)) and the parallel (along \(q_{y}\)) to the sample surface cuts are presented, dots and solid lines in (**c,d**) correspond to experimental and simulated data, respectively. Grey masks in (**a–c**) is beam-stop that blocks direct beam. The red dashed line in (**c**) represents the sample horizon. If the incident angle \(\alpha_{i}\) was slightly above the critical angle of total reflection (\(\alpha_{c}\)) as in case of PEG-microgels, transmission scattering (TS) occurred in addition to the specular and diffusive signal. Therefore, in the following analysis of the scattering 2D pattern, it was recognized that the transmitted scattering may in particular also have extended into the detector half of the GIS signal, contributing to the diffuse scattering as a background. The transmission signal was reconstructed with BornAgain by applying the PEG-microgel model [26], and included into the GIS simulation. The scattering below the sample horizon in the TS part corresponded to the scattering of a transmission experiment at the surface layer with a slightly inclined beam. Thus, the incident angle \(\alpha_{i}\) was set to \(90^{\circ}\) for the transmission scattering simulation. A direct calculation in grazing incidence geometry would be more appropriate, but is at the moment not yet implemented in the BornAgain software. Accounting for the SANS signal in this way well explained in our case the scattering contributions of the GISANS pattern and seemed to be adequate in this case. It should be noted, that such a sample rotation in virtual experiment is possible in case of an isotropic system in the probed length-scale. If structural anisotropy at the considered length scale comes into play, care has to be taken concerning details of the transmission scattering pattern. In contrast to the highly collimated and monochromatic beam of grazing incidence small angle X-ray scattering experiments, GISANS experiments normally use a neutron beam with a much broader width and a wavelength distribution of 10-20% in order to obtain enough intensity. This leads to some peculiarities, which should not be overlooked during the data treatment and simulations. The influence of the beam divergence on the scattering volume of the sample and on the footprint of the beam on the detector is depicted in Figure 3. The difference in scattering volume of areas 1 and 2 corresponded to the different scattering intensity on the 2D scattering pattern in the regions AB and BC. Angles are expanded in Figure 3 compared to a real experiment. The difference in the intensity distribution in area AB and BC (Figure 3) was taken into account in the following way.