# A View on the Synthesis and Characterization of Porous Microspheres Containing Pyrrolidone Units
## 3 Results and Discussion
The spectrum of the parent copolymer collected at 272 \({}^{\circ}\)C is analogous with the GMA spectrum in the NIST database [42]. In the spectrum recorded at the second maximum of degradation, the bands connected with CO\({}_{2}\) stretching vibrations (2360-2311 cm\({}^{-1}\)) and CO stretching vibrations (2181 and 2114 cm\({}^{-1}\)) are mainly visible. Additionally, ester-related vibrations at 1745 cm\({}^{-1}\) (-C=O stretching) and at 1154 cm\({}^{-1}\) (-C-O stretching) are present. The absorption bands mentioned above suggested that the thermal degradation of the poly(GMA-_co_-EGDMA) copolymers was driven by the breakdown of their ester functionalities. The infrared spectra of gases that evolved during the heating of the modified poly(GMA-_co_-EGDMA)_1+P copolymer are presented in Figure 8. The spectrum collected at the first maximum of decomposition (350 \({}^{\circ}\)C) shows bands associated with CO\({}_{2}\) (2359-2310 cm\({}^{-1}\)) and CO (2186 cm\({}^{-1}\)) as well as carbonyl-related (1748 cm\({}^{-1}\) and 1133 cm\({}^{-1}\)) and water-related (4000-3500 cm\({}^{-1}\) and 1700-1300 cm\({}^{-1}\)) bands. What's more, bands that can be connected with the appearance of amide (3587-3567 cm\({}^{-1}\) and 1767 cm\({}^{-1}\)) are noticeable. In the second spectrum, extracted at the maximum of degradation (417 \({}^{\circ}\)C), mainly water and carbon dioxide are visible. Figure 9 shows infrared spectra of gaseous products released during thermal degradation of poly(GMA-_co_-EGDMA)_1+p copolymer. The characteristic absorption bands observed in FTIR spectra of the all investigated copolymers are summarized in Table S1. Figure 8: Infrared spectra of gaseous products released during thermal degradation of poly(GMA-_co_-EGDMA)_1: (**a**) recorded across the full heating range and (**b**) extracted at the temperatures of degradation maxima. The thermal decomposition behavior of the investigated copolymer elucidated using TG-FTIR analysis of the evolved gases confirmed a multi-step degradation mechanism under inert (helium) conditions, consistent with the behavior of other functional methacrylate-based microspheres. The infrared spectra of gases collected throughout the heating program revealed distinct absorption bands corresponding to carbon monoxide, carbon dioxide, and water vapor, along with organic fragments showing C=O, N-H, and vinyl (C=C) vibrations, suggesting progressive breakdown of the pyrrolone ring and the main backbone. In light of recent findings [43] on thiol-functionalized GMA copolymers, a self-decomposition mechanism appears plausible in our nitrogen-containing systems as well. In the referenced study, decomposition was initiated by transesterification between thiol and ester groups, producing carbonyl sulfide (COS), acrolein, and CO\({}_{2}\), with subsequent fragmentation driven by radical pathways. Analogously, in our system, the presence of -C=O and -N-H bonds in pyrrolone may promote intramolecular hydrogen abstraction and radical-driven cleavage, initiating degradation without the need for external oxidants. These polar groups likely lower the activation energy for chain scission, enabling decomposition to begin at relatively modest temperatures. Notably, the FTIR spectra obtained during decomposition revealed strong bands associated with amide carbonyls (around 1680-1720 cm\({}^{-1}\)) and decomposition products such as acrolein (2810-2780 cm\({}^{-1}\)), indicating that ring-opening and chain unzipping dominate the early stages of decomposition. As in thiol-containing systems, we propose that decomposition proceeds via (i) endothermic scission of methacrylate backbones, (ii) partial oxidation and isomerization of the pyrrolone ring, and (iii) release of small-molecule volatiles (CO, CO\({}_{2}\), and aldehydes), culminating in a carbon-rich, unsaturated residue.