## 3 Results and Discussion
### Structural and Morphological Characterization  
The successful inclusion of P(_bis_MEP) inside the BC network was demonstrated by ATR-FTIR spectroscopy. The infrared spectra of P(_bis_MEP), pure BC, and P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 nanocomposites are shown in Figure 2. The ATR-FTIR spectrum of P(_bis_MEP) shows all the relevant bands at 1714 cm\({}^{-1}\) (C=O stretching), 1159 cm\({}^{-1}\) (C=O stretching), 1054 cm\({}^{-1}\) (P=O(hydrogen bonded) stretching) and 976 cm\({}^{-1}\) (P-O-C stretching) [32]. The ATR-FTIR spectrum of BC displays the characteristic absorption bands of cellulose at 3340 cm\({}^{-1}\) (O-H stretching), 2900 cm\({}^{-1}\) (C-H stretching), 1310 cm\({}^{-1}\) (O-H bending) and 1030 cm\({}^{-1}\) (C-O stretching) [33]. Regarding the P(_bis_MEP)-based nanocomposites, their spectra clearly bear a resemblance to the sum of the vibration peaks of the corresponding individual components. Besides, the nonappearance of the band at about 1635 cm\({}^{-1}\) corresponding to the C=C double bond stretching of the methacrylic group of the monomer [32; 34], supports the occurrence of the in-situ free radical polymerization of _bis_MEP. Figure 1: Visual aspect of a dry pure BC (bacterial cellulose) membrane, and P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 nanocomposites. Furthermore, the augment of the intensity of the bands assigned to the polyelectrolyte agrees with the weight-gain (\(W_{\text{P({bisMEP)}}}/W_{\text{BC}}\)) determined for the nanocomposites (Table 1). The solid-state \({}^{13}\)C CP/MAS NMR spectroscopy also validated the composition of the nanocomposites through the presence of the representative resonances of both P(_bis_MEP) and BC, as depicted in Figure 3. Nanocomposites P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 exhibit the resonances of the BC at \(\delta\) 65.2 ppm (C6), 71.7-74.5 ppm (C2, C3, C5), 89.0 ppm (C4) and 105.1 ppm (C1) [35], jointly with those of P(_bis_MEP) at \(\delta\) 16.5 ppm (CH\({}_{3}\) of polymer backbone, C3\({}^{\prime}\)), 45.0 ppm (quaternary C of polymer backbone, C2\({}^{\prime}\)), 54.4 ppm (CH\({}_{2}\) of polymer backbone, C1\({}^{\prime}\)), 65.1 ppm (OCH\({}_{2}\)CH\({}_{2}\)O, C5\({}^{\prime}\)) and 177.2 ppm (C=O, C4\({}^{\prime}\)). The comparison between the spectra of P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 shows an increase of the intensity of the resonances allocated to P(_bis_MEP) with the increasing polymer content and are in accord with the \(W_{\text{P({bisMEP)}}}/W_{\text{total}}\) ratio (Table 1). The absence of the carbon resonances associated with the two double bonds (C=C) of the methacryloyl moiety of the monomer, is an additional evidence of the occurrence of the in-situ polymerization of _bis_MEP, as formerly shown by ATR-FTIR. The effect of the inclusion of P(_bis_MEP) within the nanocomposite three-dimensional network on the crystallinity of BC was assessed by XRD (Figure 4). P(_bis_MEP) exhibits a diffraction profile characteristic of amorphous polymeric materials, while the diffraction pattern of BC perfectly shows the three main characteristic reflections of cellulose I (native cellulose) at 2\(\theta\) values of about 14.5\({}^{\circ}\), 16.6\({}^{\circ}\) and 22.6\({}^{\circ}\) associated with the (100), (010) and (110) crystallographic planes [36]. The XRD diffractograms of the membranes display the main features of cellulose but the intensity of the peaks at ca. 2\(\theta\) 14.5\({}^{\circ}\) and 16.6\({}^{\circ}\) decreased relatively to the (110) crystallographic plane especially in the case of P(_bis_MEP)/BC_2 with 50 wt % of P(_bis_MEP), which might be an indication of higher disorder in the inter-sheet spacing with the addition of the amorphous polymer [37]. An analogous behavior was reported for nanocomposite membranes of a poly(ionic liquid) with BC [24]. Figure 2: ATR-FTIR spectra of P(_bis_MEP), pure BC, and P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 nanocomposite membranes. Figure 4: X-ray diffractograms of the P(_bis_MEP), pure BC, and P(_bis_MEP)/BC_1 and P(_bis_MEP)/BC_2 nanocomposite membranes.