Polymers 2022 , 14 , 3309
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a small peak at 868 cm − 1 can be associated with the existence of hemiacetal bonds that formed between the remaining aldehyde groups and nearby hydroxyl groups [54]. The content of quaternary ammonium groups introduced into the cellulose structure was quantified in terms of DS and CD (Table 2) via elemental analysis and potentiomet- ric titration, respectively. The samples cationized with CHPTAC presented a DS in the range of 0.08–0.16, while for those prepared by the two-step reaction with GT, a range of 0.02–1.06 was obtained. The CD of the CCs was estimated in the range of 0.23–3.44 mmol/g. 3.2. Morphological Analysis Figure 4 displays optical microscopy images of the original BEKP and the produced CCs, all at the same magnification. For the samples CH0.08 and CH0.16, no visible mor- phological changes are observed in the cellulose fibers, keeping their structure intact and similar to that of the original BEKP. The HPH treatment of the original fibers led to the par- tial disruption of the cellulose structure, inducing the formation of long micro/nanofibrils, as visible in sample CH0.13_F.
Figure4. Optical microscopy images of the original BEKP and celluloses cationized with CHPTAC and GT (* Residual cellulose fiber fragments). For the samples obtained by the two-step reaction, sample GT0.32 presents fibers with an increased diameter and the appearance of balloons along the fibers, without the noticeable release of fibrils into the medium, while sample GT1.06_P, reveals that the initial cellulose fibers were almost completely solubilized (with the exception of some small, visible fibers fragments remaining, probably due to some cross-contamination).
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