Molecular weight distribution and functional group profiles of TEMPO-oxidized lyocell fibers

•The effects of TEMPO-mediated oxidation were studied on lyocell fibers.•CHO and COOH profiles were analyzed in relation to the MWD of TEMPO-oxidized lyocell.•Significant decrease in the Mw was obtained during the first hour of TEMPO-oxidation.•COOH groups were introduced in the high molecular weight fractions.•The amount of functionalities can be controlled by selecting the oxidative conditions. The effects of TEMPO-mediated oxidation, performed with NaClO, a catalytic amount of NaBr, and 2,2′,6,6′-tetramethylpiperidine-1-oxy radical (TEMPO), were studied on lyocell fibers by means of GPC using multiple detection and group-selective fluorescence labeling according to the CCOA and FDAM methodology. The applied method determines functional group content as a sum parameter, as well as functional group profiles in relation to the molecular weight of the cellulose fibers. Both the CHO and COOH profiles, as well as molecular weight alterations, were analyzed. A significant decrease in the average molecular weight was obtained during the first hour of TEMPO-mediated oxidation, but prolonged oxidation time resulted in no strong additional chain scission. Significant amounts of COOH groups were introduced in the high molecular weight fractions by the oxidation with higher concentrations of NaClO (2.42–9.67mmol NaClO/g fiber) after modification times of 1h or longer.