## 3 Results and Discussion
### Infrared Spectroscopy  
The crystallinity and change in the molecular structure of cellulose were analyzed by infrared spectroscopy in the range from 800 to 1500 cm\({}^{-1}\)[22; 23]. As shown in Figure 3, the functional groups of the regenerated cellulose film (CNA-12) are very similar to those of the original cellulose. The major  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Crystal Phase** & **Crystallinity Index (\%)** \\ \hline MCC & & 68 \\ CW-5 & type I & 58 \\ CA-5 & & 44 \\ \hline CQA-5 & & 30 \\ CTA-5 & & 26 \\ CNA-5 & type II & 15 \\ CNA-2 & & 10 \\ CNA-10 & & 19 \\ CNA-12 & & 49 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Crystal phase and crystallinity index of cellulose samples prepared from different solvents.  
Figure 2: X-ray diffraction patterns of original cellulose and regenerated samples.  
characteristic peaks of cellulose are located in the range between 1465 and 1565 cm\({}^{-1}\). There was no new functional group appearing in this range, indicating that the dissolution and regeneration of cellulose in QA RTILs are physical reactions. However, a significant and sharp peak representing CNA-12 was found at 898 cm\({}^{-1}\); this peak is derived from the \(\beta\)-(1,4) glycosidic bond that corresponds to the C-H deformation with ring vibration contribution and O-H bending. This peak indicates that the cellulose was converted into cellulose II [22]. As compared to the original cellulose, the CH\({}_{2}\) bending vibration bonding of CNA-12 shifted from 1430 to 1424 cm\({}^{-1}\) with lower peak intensity. This reduction in CH\({}_{2}\) bending vibration intensity is due to the weakening of the C\({}_{3}\) and C\({}_{6}\) hydrogen bonds during the cellulose transformation from type I to type II. Furthermore, a peak at 1112 cm\({}^{-1}\) in the original cellulose curve disappeared in the CNA-12 curve. This was probably due to the difference of C-O stretching vibration caused by the cellulose ring skeleton and the weak hydrogen bond of cellulose II [23]. The IR (Infrared radiation) absorption peaks at 1432 and 898 cm\({}^{-1}\) are very different in the original cellulose and regenerated sample, so the intensity ratio of A\({}_{1432}\)/A\({}_{898}\) can be used as the crystallinity index (or named Lateral Order Index (LOI)). [PERSON] further claimed another index to represent the degree of crystallization of the regenerated cellulose: Total Crystallinity Index (TCI, A\({}_{1372}\)/A\({}_{2904}\)) [22]. Table 3 depicts that the LOI value of CNA-10 decreased from 2.525 to 0.534, and its TCI value also dropped from 0.118 to 0.022. As can be seen, the lower the cellulose content in QA RTILs, the smaller the values of LOI and TCI are. The results of the FTIR were consistent with their XRD patterns. As the cellulose structure is destroyed in the dissolution process, some defective areas will be produced to enhance the surface reactivity of cellulose in the applications, such as in the preparation of the polymer, paint, fiber, and membranes. In addition, the difference in the peak intensity at 1635-1645 cm\({}^{-1}\), indicating the O-H stretching vibration of the adsorbed water, was also observed. The absorption intensity of CNA-12 was significantly higher than that of the original cellulose. The reason for this phenomenon is that the amorphous structure of cellulose increased after dissolution in ILs, and then, the number of free hydroxyl bonds increased. Water molecules can easily penetrate the amorphous region to form temporary hydrogen bonds with free hydroxyls, thus enhancing its hygroscopicity.  
Figure 3: Fourier-transform infrared spectroscopy spectra of original cellulose and CNA-12 samples.