## 3 Results and Discussion  
### Alginate Films  
Raman spectra at room temperature for the five alginate films relative the proportion by mass of alginate in the water from 1% to 5% are represented in Figure 1 in the spectral range 1700-700 cm\({}^{-1}\). In this spectral region, we observe numerous vibrational modes corresponding to the carboxylate stretching, the O-H deformation with the existence of possible hydrogen bonds, the v(C-C) skeletal and v(C-O) stretching modes [24; 25; 28]. We report in Table 1 the values of the wavenumbers by pointing or by fitting for each vibrational mode. The frequency values indexed by * are fitted values (Curve fitting was performed as per [PERSON] et al. [29]). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Alginate 1\%** & **Alginate 2\%** & **Alginate 3\%** & **Alginate 4\%** & **Alginate 5\%** & **Assignments** \\ \hline
345 & 345 & 345 & 345 & 343 & \(\delta\)(C-O) out of plane \\
430 & 431 & 431 & 430 & 428 & \(\delta\)(C-O) in plane \\
497 & 496 & 496 & 498 & 491 & \(\delta\)(C-O) in plane \\
733 & 730 & 730 & 731 & 710 & \(\delta\)(O-H) out of plane \\
806 & 806 & 806 & 806 & 805 & \(\
u\)(C-O-C) \\
889 & 889 & 889 & 889 & 885 & \(\
u\)(C-O-C) \\
920 * & 920 * & 921 * & 920 * & 922 & \(\
u\)(C-O-C) \\
955 & 954 & 954 & 953 & 954 & \(\
u\)(C-O-C) \\
982 & 983 & 983 & 982 & 980 & \(\
u\)(C-O-C) \\
1034 & 1034 & 1035 & 1034 & 1032 & \(\
u\)(C-O-C) \\
1067 & 1068 & 1068 & 1069 & 1067 & \(\
u_{\rm ss}\)(C-C)T \\
1096 & 1097 & 1096 & 1096 & 1094 & \(\
u\)(C-C)G \\
1130 & 1129 & 1130 & 1128 & 1127 & \(\
u_{\rm s}\)(C-C)T\({}_{\rm r}\) (C-O)T \\ \hline \end{tabular}
\end{table} 
Table 1: Assignments of Raman modes of alginate films at room temperature; \(\delta\) = bending, \(\
u\) = stretching; s = symmetric; as = asymmetric; T = trans; G = gauche; * = fitted value [22; 25; 28; 30]. Figure 1: The 1700–700 cm\({}^{-1}\) Raman spectral range of the five alginate films: 1%, 2%, 3%, 4% and 5% alginate in proportion by mass in water. From Figure 1 and Table 1, it appears that in the spectral range 1650-1500 cm\({}^{-1}\), the proportion of alginate in the water is a marker of differentiation: for 5% alginate, we observe three peaks (1630, 1570 and 1500 cm\({}^{-1}\)), whereas for the others samples we observe only one at 1612 cm\({}^{-1}\). The modes at 1570 and 1500 cm\({}^{-1}\) should be assigned for a hydrogen bond [28]. We note that the last peak at 1612 cm\({}^{-1}\) assigned to asymmetric COO\({}^{-}\) stretching vibration shifts to 1630 cm\({}^{-1}\) for alginate 5% films. The shift of this band to 1630 cm\({}^{-1}\) can be attributed to hydrogen bond [22]. It seems that the hydrogen bonds are more important for the 5% alginate films which is consistent with an increase in the mass proportion of alginate in the water. To assess the impact of the mass proportion of alginate on the existence of hydrogen bonding, we studied the area ratio \(\tau=Area_{1414}/Area_{1340}\) between the mode 1414 cm\({}^{-1}\) assigned to the hydrogen bonds and 1340 cm\({}^{-1}\) assigned to \(\delta\)(O-H) in plane. The areas of these vibrational modes are obtained from an adjustment by Lorentzian functions with Origin 5.0 software in the spectral range 1450-1300 cm\({}^{-1}\). In Figure 2, we present the evolution of the ratio \(\tau\) according to the mass proportion of alginate in the water. From Figure 2, it appears that \(\tau\) remains more or less equal to 4 up to 3% of alginate in the water before it suddenly increases to 4% and 5% to reach a value close to 11. Thus, it would seem that the vibrational contribution of hydrogen bonds has been multiplied by almost 3 between 1% and 5% alginate films. This development should be compared with the appearance of additional peaks in the spectral region 1650-1500 cm\({}^{-1}\) for 5% alginate films.