## 2 Results and Discussion
### Effect of Composition of Copolymer Catalysts on Activity in Aerobic Oxidation of PMT
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Mol\%**} & \multicolumn{8}{c}{**mol\% of NHPI**} \\ \cline{2-10}  & **10** & **20** & **30** & **40** & **50** & **60** & **70** & **80** & **90** \\ \hline
1 & 0.91 & 0.64 & 1.96 & 2.83 & 4.51 & 4.37 & 5.44 & 6.46 & 5.06 \\ \hline
3 & 0.58 & 1.07 & 1.60 & 2.22 & 2.48 & 3.23 & 3.69 & 3.90 & 3.91 \\ \hline
5 & 0.48 & 1.21 & 2.84 & 3.19 & 3.23 & 3.78 & 4.55 & 4.66 & 5.89 \\ \hline
7 & 0.61 & 1.29 & 1.74 & 2.14 & 2.09 & 3.58 & 3.61 & 3.85 & 4.12 \\ \hline
9 & 0.58 & 1.23 & 1.66 & 2.19 & 2.53 & 2.92 & 3.27 & 3.67 & 3.90 \\ \hline
11 & 1.34 & 1.45 & 1.11 & 2.46 & 2.77 & n.m. & n.m. & n.m. & n.m. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Content of N (mmol/g catalyst) in the synthesized copolymer catalysts determined by elemental analysis. Figure 2: Dependence of equilibrium swelling degree in chloroform on the content of NHPI and DVB monomers in the studied copolymer catalysts. value with raising the NHPI content. The observed tendencies can certainly elucidate the catalytic behavior of the materials, but the deterioration of the swelling and catalytic properties for the copolymer catalysts with higher NHPI loadings is still unexplained. In order to clarify the above effects, spectroscopic studies of the fresh copolymer catalysts were carried out using FT-IR and XPS techniques. In Figure 3, the FT-IR spectra measured for the xNHPI_5%DVB series are presented. Many bands characteristic of C-H, C-C, as well as aromatic ring vibrations, can be easily identified, corresponding to all three monomers used to form the final copolymers. Nevertheless, there are also bands typical for NHPI groups, which confirm the presence of these functionalities [51]. Among them, first of all, we can point to the strong bands at 1713 and 1779 cm\({}^{-1}\) (the positions found for 90%NHPI_5%DVB) assigned to the C=O stretching vibrations. Furthermore, less intense bands, designated to the C-N stretching vibrations, appear at 1333 and 1378 cm\({}^{-1}\). The N-O vibrations occur in the region of lower wavenumbers and are manifested by the distinct band at 1146 cm\({}^{-1}\) (for 90%NHPI_5%DVB). As the NHPI monomer content decreases, the intensities of the individual bands decrease, as expected, but also some of them shift. This effect is especially distinct in the case of the bands corresponding to the vibrations of C=O (for the 20%NHPI_5%DVB sample they are found at 1720 and 1782 cm\({}^{-1}\)), as well as N-O (the band at 1143 cm\({}^{-1}\), respectively). Apparently, the chemical environment around these bonds changed. The explanation of this phenomenon may be the appearance of the band at 1534 cm\({}^{-1}\), observed for the catalyst with the highest content of NHPI monomer, which is attributed to the N=O stretching vibrations in (C=O)-N=O groups. Thus, these types of moieties had to be formed within the copolymer structure at the higher NHPI amounts. Taking into account the high concentration of NHPI groups in the copolymers with the high N loadings and high cross-linking degrees, it can be assumed that during the last stage of synthesis, carried out at a relatively high temperature, the formation of adjacent PINO radicals could have occurred. The self-decomposition reaction, described in Scheme 3, took place transforming a part of NHPI groups into catalytically inactive sites [50; 52; 53]. Figure 3: FT–IR spectra collected for the fresh xNHPI_5%DVB copolymer catalysts. In the shaded areas, the main vibrations of the NHPI groups are distinguished with the bands marked with asterisks (expected) and diamond (unexpected). XPS is another technique which confirms the formation of postulated NHPI dimers with the (C=O)-N=O groups. Figure 4 presents the XPS spectra collected in the N 1s and O 1s regions for three catalysts containing 60 mol% of NHPI monomer and differing in the cross-linking degree (the DVB content of 3, 5, or 7 mol%).