Fig. 2: Grazing-incidence small-angle X-ray scattering patterns and the extracted domain sizes with increasing polymerization time as well as a schematic representation of the polymerization process.

a, b Show the summed scattering patterns for each individual polymerization time, LT in a (pristine = 0 s, 0.1 s, 0.3 s, 0.6 s, and 1 s) and HT in b (0 s, 0.1 s, 0.2 s, 0.5 s, 1 s). The vertical red arrow marks the feature peak position in the pristine and the 1 s polymerized sample. The white dashed box in 0.1 s shows the Yoneda region which is integrated in q_y-direction for fitting. c shows the extracted in plane length scale for LT (black) and HT (red) with an exponential fit which follows the same trend as the conversion in the FTIR spectra, see also Supplementary Fig. 1. The error bars are fit errors. d, e show schematically the network formation inside the film during the photo-initiated polymerization for LT and HT, respectively. On the left the pristine film with small domains, which increase in size and merge till the film is fully polymerized. We propose that the length scale growth is restricted due to the confined thickness of the film of around 140–160 nm. We interpret the peak shift in the GISAXS patterns with in plane length scale growth which is shown with the circles with increasing size when irradiated with UV light. The blue matrix is the unpolymerized surroundings, which is also correlated with the not full conversion followed by FTIR.