# A View on the Synthesis and Characterization of Porous Microspheres Containing Pyrrolidone Units
## 3 Results and Discussion
Figure 6: DTG curves of the investigated copolymers: (**a**) poly(NVP-_co_-EGDMA)\_1 (pink line); (**b**) parent poly(GMA-_co_-EGDMA)\_1 (green line), modified poly(GMA-_co_-EGDMA)\_1+p (blue line). As follows from the presented results, the best thermal resistance was obtained for the poly(NVP-co-EGDMA)_1 copolymer. Its decomposition began at a temperature exceeding 300 \({}^{\circ}\)C, and the temperatures of 20% and 50% mass loss were the highest among all of the studied copolymers. What is important is that the decomposition process proceeded in a single stage. The poly(GMA-co-EGDMA)_1 copolymer demonstrated a reduced thermal resistance. It started to decompose at about 250 \({}^{\circ}\)C, and this process underwent two steps, with maxima at 272 and 369 \({}^{\circ}\)C. Although the main thermal degradation step corresponded to the first maximum. Increasing the amount of functional monomer into the polymeric matrix (poly(GMA-co-EGDMA)_2 copolymer) resulted in a further decrease in its thermal properties. The opposite effect was triggered by the modification process. The modification process with pyrrolidone improved the thermal resistance of the materials under study. The T5% parameter increased by about 30 \({}^{\circ}\)C for both modified copolymers. The changes were even more profound with respect to the maxima of decomposition. After modification, T1 max increased by 78 \({}^{\circ}\)C for the poly(GMA-co-EGDMA)_1+p copolymer and by 69 \({}^{\circ}\)C for poly(GMA-co-EGDMA)_2+p. For these copolymers, the major mass loss occurred during the second decomposition stage. The decomposition of the copolymers was monitored by infrared spectroscopy to identify the evolved gases. Figure 7 presents the FTIR spectra of the gaseous degradation products emitted during the heating of poly(VP-co-EGDMA)_1. **In this copolymer, NVP-based units** promoted \(\alpha\)-scission due to **polar functional groups** that **stabilized transition states** or favored radical delocalization. The main products of \(\alpha\)-hydrogen bond scission are carbon oxide, carbon dioxide, water, and aldehydes. Aldehydes are formed when \(\alpha\)-scission occurs near the ester group between the backbone and the ester carbon. Consequently, in Figure 7, the bands characteristic of the asymmetric stretching vibrations of CO2 (at 2359-2310 cm\({}^{-1}\)), CO (at 2181 and 2114 cm\({}^{-1}\)), and H2O (at \(\sim\)4000-3500 cm\({}^{-1}\)), as well as the bending vibrations of H2O (at \(\sim\)1800-1300 cm\({}^{-1}\)), are noticeable. Additionally, carbonyl absorption in the range of 1772-1770 cm\({}^{-1}\), corresponding to C=O stretching, is evident and is likely due to \(\alpha\)-hydrogen bond cleavage. In Figure 8, the infrared spectra of the gaseous products released during the thermal degradation of poly(GMA-co-EGDMA)_1 recorded across the full heating range (a) and  
Figure 7: Infrared spectra of gaseous products released during thermal degradation of poly(VP-co-EGDMA)_1: (a) recorded across the full heating range and (b) extracted at the maximum of degradation (417 \({}^{\circ}\)C). extracted at temperatures of the degradation maxima (b) are presented. As can be seen, the spectrum obtained at the first degradation maximum exhibited absorption bands characteristic of carbonyl compounds, including -C=O stretching at 1742 cm\({}^{-1}\) and -C-O stretching at 1150 cm\({}^{-1}\). Evidence of vinyl compound formation was also observed in the spectrum, with absorption bands at 3110 cm\({}^{-1}\) (-C-H stretch), 939 and 1017 cm\({}^{-1}\) (-C-H out-of-plane deformation), and 1693 cm\({}^{-1}\) (-C=C stretch). The presence of aliphatic groups was supported by spectral bands at 2964 and 2989 cm\({}^{-1}\). They were related to the symmetric and asymmetric C-H stretching vibrations of the methylene and methyl groups. What is extremely important is that an oxirane-related peak at 850 cm\({}^{-1}\) is clearly visible. This suggests that during the first degradation step, depolymerization occurs and emission of the GMA monomer takes place.