CONICET | Buscador de Institutos y Recursos Humanos

Nanocellulose (nanocrystals, microfibrilar or bacterial) presents excellent properties and possibilities to be modified with relative facility, for which has been proposed for use in such diverse applications as electrodisplays, scaffolds for the growth of biological tissues, biodegradables food packaging, or as viscosity modifiers and emulsion stabilizers. The attractiveness of using cellulose fibers is based on its mechanical properties at the nanometer level (lower probability to show defects than macroscopic fibers), reaching, theoretically, Young modulus above 100 GPa. The aim of this study is to obtain surface-modified cellulose-nanofibers in order to extend their field of applications. The modification was done on cellulose nanocrystals (NCC) obtained by acid hydrolysis, using 2,2,6,6-tetramethylpiperidin-1-oxi radical (TEMPO) as oxidant, by a catalytic cycle which also includes NaBr and NaClO. The product of this reaction is an oxidized NCC, with the C6 as a carboxylate that becomes protonated after the neutralization of the reaction medium to pH 7. This carboxylate group is identifiable by FTIR. Also, X-ray studies were performed to evaluate the change in the crystallinity index of the NCC. Subsequently, a conductimetric titration yielded information on the number of units of oxidized cellulose. This measurement allows calculating the amount of surface-OH in the NCC.It was also possible to follow the advance of reaction by Electron Paramagnetic Resonance (EPR) spectroscopy, through the signal emitted of the TEMPO radical. If the reaction is carried out without NaBr and NaClO, the catalytic cycle is not followed and there is a consumption of TEMPO, that generates a decreasing signal as the reaction proceeds, allowing exactly knowing the value of the surface-OH in the NCC.