Polymers 2022 , 14 , 3309
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Figure3. The FTIR-ATR spectra of the original BEKP and celluloses cationized with CHPTAC and GT.
The chemical modifications induced in the cellulose were analyzed by FTIR-ATR. The FTIR spectra of the original BEKP and CCs, normalized by the highest peak of BEKP (1028 cm − 1 ), are presented in Figure 3. For the samples cationized with CHPTAC, it was possible to observe the appearance of a shoulder at 1473 cm − 1 related to the stretching vibration of the methyl groups of the quaternary ammonium [48], along with a small peak at 1638 cm − 1 due to the increased hydrophilicity and consequent water adsorption [49]. The changes are more evident for the sample known as CH0.16, with the highest DS. For the samples subjected to the two-step cationization, a new set of distinct peaks is visible (this is less evident for samples GT0.02_F and GT0.04_F, due to their low DS). The absorbance at 1683 cm − 1 can be assigned to the stretching of the carbonyl group on the GT structure [50]. The band at 1558 cm − 1 confirms the formation of the imine bond between DAC and GT [50]. The peaks found at 1473 cm − 1 and1414 cm − 1 are related to the asymmetric and symmetric bending of the methyl groups of GT, respectively [26]. The peak at 923 cm − 1 can be assigned to the asymmetric stretching of the C–N bond [26], the N–N bond [50,51], or to the stretching vibration of the C–C= bond [52] of the GT groups. The glucose ring-opening and subsequent oxidation of the hydroxyl groups into aldehyde groups during the periodate oxidation of cellulose can justify the decrease in intensity observed in the bands at 1158 cm − 1 and1052 cm − 1 [26,53]. The appearance of
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