Concentration and carbon chain length effects of cationic surfactant in enzymatic production of cellulose nanostructures

This work evaluated the effect of cationic surfactants [cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TDTAB), and dodecyltrimethylammonium bromide (DTAB)], and its concentration (0.03, 0.30, and 3.00 mM) on the production by enzymatic hydrolysis and surface modification of cellulose nanostructures (CNSs), from the one-step method. From FTIR spectra, changes and surfactant peaks and bands for modified CNSs compared to CNS were observed. For XRD results, the crystalline structure was more altered for CTAB and TDTAB, especially for higher concentrations, not changing cellulose's crystalline structure. The surfactants affected colloidal stability, which CTAB promoted a higher shielding effect than DTAB and TDTAB, reducing the negative charges present in nanocellulose, while high concentrations lead to saturation of colloidal system, creating micelles and causing agglomerates. However, CNS CTAB showed smaller particle sizes for lower concentrations (90-100 nm), lower sugar production (50 mg g(-1)) for high concentrations, and cellulose nanocrystals obtaining. CNS DTAB and CNS TDTAB did not present statistical differences for particle size. Thermal stability was also affected. CNS DTAB presented the highest T-onset (250-254 degrees C) compared to CNS TDTAB and CNS CTAB. Thus, these results prove and suggest the possible application of these modified CNSs to develop nanocomposites with excellent dispersion, resulting in promising properties. Crown Copyright (C) 2021 Published by Elsevier B.V. All rights reserved.