## 3 Results and Discussion
### Alginate-Glycerol Films  
In Figure 3, we present Raman spectra at room temperature for the 5% alginate films, glycerol and 5% alginate-glycerol films in the spectral range 1700-700 cm\({}^{-1}\). We report in Table 2 the values of each of the observed or adjusted peaks. Subtraction spectra are helpful to determine the contributions of each of the elements in the 5% alginate and glycerol mixture. The difference spectrum between 5% alginate-glycerol films and glycerol is shown in Figure 4 (spectral data from the sample scans were baseline-corrected and normalized against band at 1085 cm\({}^{-1}\) using Origin 5.0). From Figures 3 and 4, we can observe that the Raman spectrum of 5% alginate-glycerol films seems to be superposition of the Raman spectra of two elements taken separately. In Figure 4, the subtraction Raman spectrum highlights the vibrational modes exclusively linked to glycerol (peaks at 1463 and 845 cm\({}^{-1}\) assigned to CH\({}_{2}\) bending deformation and CH\({}_{2}\)-OH twisting mode, respectively) and to 5% alginate (peaks at 1414 and 956 cm\({}^{-1}\) assigned to hydrogen bond and C-O-C stretching mode, respectively. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**5\% Alginate** & **Glycerol** & **Starch** & \
\begin{tabular}{c} **5\%** \\ **Alginate–Glycerol** \\ \end{tabular} & **Alginate–Starch** &
\begin{tabular}{c} **5\%** \\ **Glycerol–Starch** \\ \end{tabular} & **Assignments** \\ \hline
343 & & & 346 & 348 & 343 & \(\delta\)(C-O) out of plane \\  & 376 & & & & \(\delta\)(C-O) in plane \\  & 414 & 409 & & 413 & 415 & \(\delta\)(C-O) in plane \\
428 & & 441 & & 440 & 440 & \(\delta\)(C-O) in plane \\  & 483 & 480 & & 480 & \(\delta\)(C-O) in plane \\
491 & & 494 & 488 & & \(\delta\)(C-O) in plane \\  & & 520 & & 521 & 521 & \(\
u\)(C-O-C) \\  & 546 & & 550 & & \(\
u\)(C-O-C), \(\delta\)(O-H) \\  & & 577 & & 577 & 576 & \(\delta\)(O-H) out of plane \\
710 & & 711 & 720 & 720 & 720 & \(\delta\)(O-H) out of plane \\  & & 765 & 762 & 763 & & \(\delta\)(O-H) out of plane \\
805 & & & 795 & & \(\
u\)(C-O-C) \\  & 818 & & 814 & & 814 & \(\
u\)(C-O-C) \\  & 845 & 848 & 847 & 850 & 850 & \(\tau\)(CH\({}_{2}\)-OH) \\  & & 865 & 861 & 867 & 866 & \(\tau\)(CH\({}_{2}\)-OH) \\
885 & & 890 & 890 & 889 & & \(\
u\)(C-O-C) \\
922 & 920 & 921 & 922 & 923 & 923 & \(\
u\)(C-O-C) \\
954 & & & 956 & & 956 & \(\
u\)(C-O-C) \\
980 & & & 1002 & & & \(\
u\)(C-O-C) \\
1032 & 1040 & & 1041 & & 1032 \({}^{*}\) & \(\
u\)(C-O-C) \\
1067 & & & 1062 & & & \(\
u\)\({}_{\rm as}\)(C-C)\({}_{\rm T}\) \\
1094 & 1088 & 1083 & 1096 & 1082 & 1084 & \(\
u\)(C-C)\({}_{\rm G}\) \\
1127 & & 1132 & 1124 & 1130 & 1127 & \(\
u\)(s\(\rm C\)-C)\({}_{\rm T}\), \(\
u\)(C-O)\({}_{\rm T}\) \\
1160 \({}^{*}\) & & 1155 & & 1154 & 1154 & \(\
u\)(s\(\rm C\)-C)\({}_{\rm T}\), \(\
u\)(C-O)\({}_{\rm G}\) \\  & 1202 \({}^{*}\) & 1203 & & 1203 & \(\
u\)(s\(\rm C\)-C) \\  & 1252 & 1258 & & 1256 & 1259 & \(\tau\)(CH\({}_{2}\)) \\
1275 \({}^{*}\) & & & & & \(\
u\)(s\(\rm C\)-C)\({}_{\rm G}\) \\
1310 & 1315 & 1303 \({}^{*}\) & 1315 & 1311 & 1308 & \(\delta\)(O-H) in plane \\
1340 & 1344 & 1340 & 1340 & 1340 & 1340 & \(\delta\)(O-H) in plane \\
1360 \({}^{*}\) & & 1361 \({}^{*}\) & 1362 \({}^{*}\) & & & \(\delta\)(O-H) in plane \\  & 1374 & 1380 & & 1379 & 1381 & \(\delta\)(O-H) in plane \\
1412 & 1414 & 1404 \({}^{*}\) & 1412 & 1414 & 1418 & \(\
u\)(s\(\rm C\)OO\({}^{-}\)), H- \\  & 1463 & 1461 & 1465 & 1460 & 1460 & \(\delta\)(CH\({}_{2}\)) \\
1500 & & & & & & hydrogen bond \\
1570 & & & & & & hydrogen bond \\  & & 1612 & & & & \(\
u\)\({}_{\rm as}\)(COH) \\
1630 & & & & & & \(\
u\)\({}_{\rm as}\)(COO\({}^{-}\)) \\  & 2882 & & & & & \(\
u\)\({}_{\rm as}\)(CH\({}_{2}\)) \\  & 2905 & 2902 & 2905 & 2903 & \(\
u\)(s\(\rm CH\)\({}_{2}\)) \\
2934 & 2935 & & & & & \(\
u\)(CH-OH), \\  & & 2945 & 2946 & 2946 & 2946 & \(\
u\)(CH-OH) \\  & 2961 & & & & & \(\
u\)(CH-OH) \\ \hline \end{tabular}
\end{table}