## 3 Results and Discussion  
### FTIR Analysis  
Chemical modifications of PVA was monitored by FTIR. Figure 2 represents FTIR spectrum of: (a) unmodified PVA; (b) toyslated PVA (PVA-Ts); (c) azidated PVA (PVA-N\({}_{3}\)) and (d) PVA after the click reaction with propargylamine (PVA-NH\({}_{2}\)).  
Figure 2: FTIR spectra of (**a**) unmodified PVA; (**b**) toyslated PVA (PVA-Ts); (**c**) azidated PVA (PVA-N\({}_{3}\)) and (**d**) PVA after click reaction with propargylamine (PVA-NH\({}_{2}\)).  
The FTIR analysis of unmodified PVA (Figure 2a) revealed characteristic PVA spectra that are in agreement with the literature [18]. We can clearly see the presence of a large peak at 3400 cm\({}^{-1}\). This peak is linked to the stretching of O-H from the intramolecular and intermolecular hydrogen bonds. The peaks observed at 2840 cm\({}^{-1}\) and 2920 cm\({}^{-1}\) are respectively related to the symmetric and antisymmetric stretching vibrational of C-H from alkyl groups. Comparing with the unmodified PVA, after reaction with the tosyl group (Figure 2b), one can observe the appearance of new peaks. The new peaks appeared mainly at 1600 cm\({}^{-1}\), 1365 cm\({}^{-1}\), 1175 cm\({}^{-1}\) and 816 cm\({}^{-1}\). The peak at 1600 cm\({}^{-1}\) may be assigned to the aromatic C=C stretching group. The two new peaks at 1365 cm\({}^{-1}\) and 1175 cm\({}^{-1}\) can be related to the S=O group, and the peak at 816 cm\({}^{-1}\) can be related to the C-O-S bonds [19].  
Two ways were investigated for the azidation reaction after the tosylation. The FTIR spectra of the PVA-N\({}_{3}\) are similar and compared to the Figure 2c. Indeed, Figure 2c showed the disappearance of the entire peaks related to the presence of tosyl and the appearance of a new peak at 2106 cm\({}^{-1}\). The peak at 2106 cm\({}^{-1}\) is assigned to the azide antisymmetric stretch. These results suggested the consumption of the tosyl group and confirmed the introducing of the azide function on the PVA backbone. This result indicated that, for azidation reaction, the precipitation of PVA-Ts is not necessary. Moreover, the presence of Et\({}_{3}\)N does not influence the azidation reaction. In addition, avoiding the precipitation allowed gain time and used less energy. Also, in the case of using a click reaction to introduce amine function on the PVA backbone, two ways were investigated after azidation. The first one consisted of undertaking the reaction in the presence of the excess of NaN\({}_{3}\). The second way consisted of removing NaN\({}_{3}\) excess by dialysis. FTIR analysis (Figure 2d) showed identical results. We mainly notice the decreased intensity of the peak at 2106 cm\({}^{-1}\) and the appearance of a new peak at 1560 cm\({}^{-1}\). This new peak should be related to the primary amine function. This result confirms the introducing of the amine function on the backbone of PVA. The first way enables us to gain the time wasted during the dialysis step. A comparison between the mass yield for way a (75%) and the way b (40%) showed that the filtration offered another advantage compared to the precipitation.  
The FTIR analysis proved that the chemical modification of PVA was confirmed. The different step of the chemical modification was also supported by XPS analysis.