## 2 Results and Discussion
### Chemical and Morphological Characterization of Et-DVB-AN Sample  
The FTIR spectra of the SV4 pure copolymer show the following bands (Figure 5). The bands found at 1448 cm\({}^{-1}\) and 709 cm\({-1}\) were assigned to N-H groups, while the bands situated at 3429 cm\({}^{-1}\) and 1643 cm\({}^{-1}\) were assigned to -NH\({}_{2}\) groups. The Et-DVB-AN sample's FTIR spectrum in Figure 5 displayed notable adsorption bands in the following areas: 3545-3350 cm\({}^{-1}\) attributed to (-OH and aliphatic-NH groups), 1660-1569 cm\({}^{-1}\) attributed to (NH in secondary and primary amines, respectively), 1460-1390 cm\({}^{-1}\) assigned to (\(\gamma\)N-C-aliphatic, \(\gamma\)P-OR), 1160-990 cm\({}^{-1}\) assigned to (\(\gamma\)P=O bond), and 800-690 cm\({}^{-1}\) assigned to (N-H groups in the amine primary and P-OR) [18; 19]. SEM images of the pristine SV4 copolymer and of the aminophosphate Et-DVB-AN copolymer are presented in Figure 6. It can be seen that both the pristine copolymer SV4 and the functionalized copolymer have a homogeneous surface morphology. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Type of Analysis**} & \multicolumn{5}{c}{**Wt\%**} \\ \cline{2-6}  & **C** & **N** & **O** & **P** & **H** \\ \hline \multirow{3}{*}{EDX} & \multirow{3}{*}{68.3} & \multirow{3}{*}{21.7} & \multicolumn{2}{c}{SV3} & \multirow{3}{*}{-} \\  & & & & Bz-DVB-AN & \\ \cline{1-1} \cline{4-6}  & & & & - & 7.48 \\ \cline{1-1} \cline{4-6}  & & & & 13.7 & 1.2 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Elemental analysis and semi-quantitative EDX-analysis of SV3 and Bz-DVB-AN copolymers. Figure 4: Thermogravimetric analysis of the pristine SV3 copolymer (**a**) and Bz-DVB-AN (**b**). Figure 5: FTIR spectra of SV4 copolymer and Et-DVB-AN sample. Figure 6: SEM images of SV4 (**a,b**) and Et-DVB-AN (**c,d**) copolymers; mag: 250\(\times\) (**a**), 4000\(\times\) (**b**), 250\(\times\) (**c**) and 5000\(\times\) (**d**). EDX spectra presented in Figure 7 show the result of functionalizing acrylonitrile-15%divinylbenzene copolymers (SV4) using diethylphosphite and 3-pyridine carboxayaldehyde, respectively. The values of elemental analysis and those obtained from the semi-quantitative EDX analysis and elemental analysis are presented in Table 2.  
The findings of the TG-DTG-DTA analysis of SV4 in nitrogen are displayed in Figure 8a. The mass loss of physically adsorbed water evaporating in the first stage (25-120 \({}^{\circ}\)C) was 5.6% (\(\sim\)60 \({}^{\circ}\)C); in the second stage (120-340 \({}^{\circ}\)C), it was 4.9% (\(\sim\)220.2 \({}^{\circ}\)C) due to pendant group degradation; and in the third stage (340-660 \({}^{\circ}\)C), it was 68.0% (\(\sim\)434.5 \({}^{\circ}\)C) due to DVB-AN degradation. A total of 21.5% of the residue remained after 78.5% of the total mass was eliminated at 800 \({}^{\circ}\)C. Figure 8b displays the TG-DTG-DTA study for the Et-DVB-AN sample. The synthesis product Et-DVB-AN was studied in nitrogen, and three steps of mass losses were noted: the evaporation of the physically adsorbed water was responsible for the first stage (25-140 \({}^{\circ}\)C), with--6.69% (\(\sim\)55.9 \({}^{\circ}\)C); the pendant group degradation was responsible for the second stage (140-360 \({}^{\circ}\)C), with--5.61% (\(\sim\)220.2 \({}^{\circ}\)C); and the DVB-AN degradation was responsible for the third stage (360-660 \({}^{\circ}\)C), with--65.37% (\(\sim\)422 \({}^{\circ}\)C). At 800 \({}^{\circ}\)C, 22.33% of the residue was still present after a total mass loss of 77.67%. Thus, the copolymer functionalized with the aminophosphonate group Et-DVB-AN shows a good thermal stability.