1 H-NMR and 13 C-NMR spectroscopy were used as more in-depth methods of verifying the chemical structure of synthesized macromonomers. Overall, the analysis of NMR spectra confirmed the FT-IR findings. All of the obtained macromonomers had similar structure, consistent with our expectations based on prior work . As a representative example, Figure presents 1 H-and 13 C-NMR spectra of macromonomer obtained using 0.1 mol% Mg-Ti butoxide catalyst per step with peak assignments. The 1 H-NMR spectra for the other catalyst concentrations are available in the SI (see Figure ). The degree of acrylation (Fig. and Table ) was calculated based on NMR spectra which influences the crosslinking density of the obtained elastomeric networks. It can be observed that increasing the concentration of catalyst led to a decrease in the degree of acrylation, with the exception of sample PrMg-Ti_0.5 (0.5 mol% of catalyst). Higher catalyst concentration increases the reaction rate to achieve the equilibrium faster to the product which results in lower number of accessible NCO groups for methacrylate (HEMA) attachment. Lower catalyst concentration may result in reduced IPDI addition to polyester diol due to which some free terminal OH groups are still in the molecule which also leads to lower HEMA attachment. These data are also correlated with gel fraction of films after photocuring, which will be discussed in section 3.7.