Chito-g-AA-co-AM composite showed broad band at 3342 cm
−1 which corresponds to O–H and amide (-NH) groups stretching. The small peak at 2921 cm
−1 accredited to the asymmetric stretching frequency of -CH group, while peak at 1658 cm
−1 was assigned for N–H deformation bending of backbone (Figure S4). A very intense characteristic band at 1665 cm
−1 was observed due to C=O asymmetric stretching in carboxylate anion and was reconfirmed by peak at 1449 cm
−1. Chito-g-AA-co-AM, showed two additional peaks at 1726 cm
−1 (carboxylic acid) and 1564 cm
−1 (amide) which were absent in the IR spectrum of pure chitosan, this clearly indicates the formation of graft copolymer [
27]. FTIR spectrum of
Chito-g-AM composite showed two peaks at 3206 cm
−1 and 1660 cm
−1 corresponding to the primary amides and amide –NH stretching vibrations. Polyacrylamide can be identified by its characteristic amide C=O peak at 1660 cm
−1, which is also present in the spectrum of Chito-g-PAM.
Chito-g-AA—The peak at 1735 cm
−1 corresponds to the carboxyl absorption from grafted acrylic acid and the peaks at 821 cm
−1 and 619 cm
−1 were characteristic absorptions of acrylic acid.
Chito-g-NIPAAM—The FTIR spectrum of chitosan with a 75% deacetylation degree indicated that peaks appeared at 3436 cm
−1 (corresponding to OH stretching vibration, which indicated a chemical reaction between chitosan and N-isopropylacrylamide), 1658 cm
−1, and 1569 cm
−1 could be assigned to a hydroxyl group, carbonyl stretching vibration (amide I), and N–H bending vibration (amide II) of a primary amino group, respectively.
Chito-g-PMMA- The intense band at 3423 cm
−1 was assigned to the stretching vibrations of O–H group. The absorption bands at 1154 cm
−1 and 1033 cm
−1 were assigned for asymmetric stretching of the C–O–C bridge.
Chito-g-PAN- FTIR studies showed that peak of chitosan at 1164 cm
−1 disappeared indicating that this peak may be hindered by cross-linking. When crosslinker was used, FTIR showed appearance of new peak at 1550 cm
−1 which can be attributed to cross-linking reaction of chitosan with cross-linking monomer. A new sharp peak appeared at 1627 cm
−1 suggested, the stretching of N=C in composite form by the reaction of graft copolymerization. A band at 1564 cm
−1 indicated involvement of –NH
2 group during grafting.