## 3 Results and Discussion
The lack of the absorption bands originating from the oxirane groups in this spectrum confirms that the depolymerization and emission of the GMA monomer occur in the first stage of copolymer degradation. In the spectrum of the copolymer heated to 360 \({}^{\circ}\)C, there is no band at 1500 cm\({}^{-1}\) originating from C=C vibrations of the aromatic ring [46]. The disappearance of bands at 1174 and 1123 cm\({}^{-1}\) originating from -C-O-C-stretching vibrations in the ester can also be observed. Simultaneously, a sharp band with a maximum at 1168 cm\({}^{-1}\) appears and a shift of the C=O group band from 1732 to 1720 cm\({}^{-1}\) and a decrease in its intensity take place, indicating partial decarboxylation (CO\({}_{2}\) emission) and the formation of an aldehyde group. In addition, a band at 1604 cm\({}^{-1}\) originating from the C=C vibration can be observed [47]. The disappearance of bands at 1451, 1389 and 2995 cm\({}^{-1}\) associated with vibrations of methyl and methylene groups is also visible [48]. Based on the obtained spectroscopic results, a mechanism for the decomposition of the poly(GMA-\(co\)-1,4 DMB) copolymer (Figure 6A) in the initial step of pyrolysis was proposed. This mechanism leads to the emission of monomers, acrolein, carbon dioxide and the formation of unsaturated bonds in the solid residue. In the FTIR spectrum of the gaseous poly(GMA-\(co\)-TRIM) decomposition products collected at the first emission maximum value at 255 \({}^{\circ}\)C (Figure 7A), bands characteristic of polyGMA decomposition by depolymerization can be observed. The absorption bands at 849 cm\({}^{-1}\) associated with oxirane ring vibrations [41], those at 1160 cm\({}^{-1}\) from C-O-C vibrations in the ester, those at 1744 cm\({}^{-1}\) from vibrations of the C=O group and those at 3057 cm\({}^{-1}\) related to the methylene group vibrations in the oxirane ring indicate the emission of GMA monomers [39; 42]. For the TRIM-crosslinked copolymer, the bands characteristic of acrolein are not as intense as in the case of the copolymer with 1,4 DMB, but bands in the spectrum region of 2700-2800 cm\({}^{-1}\) can still be observed (Figure 5) [16]. Since an overall endothermic peak is observed in the DSC curve in the temperature region of the first degradation step, it can be assumed that the possible isomerization of  
Figure 3: Three-dimensional FTIR diagrams of gaseous products of poly(GMA-\(co\)-TRIM) (**A**) and poly(GMA-\(co\)-1,4 DMB) (**B**) degradation. oxirane groups is not as intense as in the case of the 1,4 DMB-crosslinked copolymer and methacrolein is probably released due to the polymer network breakdown. In addition, at higher decomposition temperatures, mainly bands characteristic of water (3500-3600 and 1500-1600 cm\({}^{-1}\)), carbon dioxide (2360 cm\({}^{-1}\)) and carbon monoxide (2180 and 670 cm\({}^{-1}\)) formed by decarboxylation and dehydration processes of the created solid products of pyrolysis are observed [39; 40; 46]. Moreover, in order to follow the changes in the chemical structure of the copolymer during heating, it was heated to 245, 370 and 510 \({}^{\circ}\)C in a helium atmosphere, and then FTIR/ATR spectra of the preheated samples were recorded. These spectra were compared with the FTIR spectrum of the initial sample (Figure 7B). For the sample preheated to 245 \({}^{\circ}\)C, bands characteristic of oxirane ring vibrations at 846 and 908 cm\({}^{-1}\)[41] and a band at 1256 cm\({}^{-1}\) associated with oxirane ring stretching vibrations were not observed [45]. At 370 \({}^{\circ}\)C, a decrease in the intensity of the bands caused by the vibrations of the methyl and methylene groups (2965-3000 cm\({}^{-1}\)) and a shift in the band of C-O-C group vibrations from 1158 cm\({}^{-1}\) to 1138 cm\({}^{-1}\) can be observed [48]. Moreover, at 1604 cm\({}^{-1}\), a new band appears indicating the formation of unsaturated C=C groups. Figure 6B proposes a decomposition scheme for the TRIM-crosslinked copolymer [47].