4.2 FTIR characterization

FTIR studies were performed on cellulose, chitin and chitosan powders. Figure 4 shows the UATR-FTIR spectra of cellulose, chitin, and chitosan collected in the wavenumber range of 4000–600 cm<sup>1</sup> . The peaks of cellulose at 3335 and 3234 cm<sup>1</sup> are attributed to the O-H stretching vibrations and the extensive interand intra-molecular hydrogen bonding network [55]. For chitin, the vibrations attributed to O-H and N-H stretching are visible at 3434 and 3256 cm<sup>1</sup> and for chitosan those peaks appear at 3434 and 3256 cm<sup>1</sup> [56, 57]. The bands in the region of 3000–2800 cm<sup>1</sup> correspond to the -CH2 symmetrical and asymmetrical stretching vibrations of polysaccharides [55–57]. Chitin exhibits the doublet amide I band at 1658 and 1619 cm<sup>1</sup> representing the presence of H-bonding in a C=O group with the NH group of the adjacent chain and the O-H group of the inter-chain [58]. The amide II band of chitin and chitosan is located at 1553 and 1586 cm<sup>1</sup> , respectively [56, 57]. The peak at 1307 cm<sup>1</sup> corresponds to the amide III band (in-plane mode of CONH2 group) of chitin. Respective, amide I and C-N stretching of amide III of chitosan appear at around 1647 and 1318 cm<sup>1</sup> . The vibrations at 1152 and 1110 cm<sup>1</sup> are attributed to the anti-symmetrical bridge of C-O-C stretching and anti-symmetric in-plane stretching. The peaks at 1060 and 1025 cm<sup>1</sup> correspond to the C-O stretching of the polysaccharide [55–57]. The band at 895 cm<sup>1</sup> is assigned to β-linkage of the polysaccharide [55–57].

Figure 4. FTIR spectra of cellulose, chitin, and chitosan in the wavenumber region of 4000–600 cm<sup>1</sup> .

Biopolymer-Based Materials from Polysaccharides: Properties, Processing, Characterization… DOI: http://dx.doi.org/10.5772/intechopen.80898
