FTIR spectroscopy was chosen as an easy and readily available method to investigate the chemical changes during crosslinking. The employed polyperoxides have an amphiphilic character bearing hydrophilic MA groups and hydrophobic peroxide/BA, respectively. According to the suggested crosslinking mechanism (Figure ), both reactive groups can partake in the crosslinking process. The IR spectrum of polyperoxide/PEtOx blends also show the absorption bands at 1860, 1782 and 1707 cm -1 , which were attributed to the antisymmetric stretching of the carbonyl moieties in MA, while the band at 1730 cm -1 corresponds to the C=O stretching of the butyl ester group (Figure , blue). The signals at 1200 and 1156 cm -1 are attributed to the C-O-stretching in MA and butyl ester, respectively . Even though the polyperoxides containing blends show only weak signals in IR spectra due to the symmetric nature and low concentration of the peroxides, we can attribute a weak absorption bands between 870-880 cm -1 in our polymers to the peroxides (Figure , red). Therefore, we expect that this signal should decrease during crosslinking . Similarly, the signals attributed to the anhydride motif in MA should also decrease . IR spectra of PEtOx crosslinked with P[PM-co-MA] (Figure ) and P[PM-co-BA-co-MA] (Figure ), respectively, before and after crosslinking at 120 °C -160 °C showed ambiguous results. An increase in temperature to 120 °C is accompanied by an increased signal attributed to ester groups with a corresponding decrease in the signal attributed to MA. An interesting observation was made in the region of 800 -900 cm -1 (Figure , red band). Before heating, the spectra exhibit a broad peak in this region. With increasing temperature, a splitting of the peak is observed concomitant with a minor increase of peak intensity at 880 cm -1 and decrease at 860 cm -1 (Fig 5A ). The increase at 880 cm -1 can be attributed to symmetric stretching of ether bonds that are formed during the crosslinking . This observation was less noticeable when using P[PM-co-BA-co-MA] as a crosslinker (Figure ). This may be due to the lower mol% of peroxide groups. Changes of a band at 1065 cm -1 (asymmetric stretching of the C-O-C group) can be explained with changes in the maleic anhydride and ether contents . The signals at 1780 and 1725 cm -1 , which correspond to C=O groups of MA and esters, respectively, initially increased with temperature (Figure , blue). However, after treatment at 200 °C, the intensities at 1780 and 1725 cm -1 as well as at 800-900 cm -1 decreased. This corroborates that peroxides groups decomposed during heating. Decreasing intensity at 1780 and 1725 cm -1 could be explained due to decomposition of ester groups under these conditions.