Abstract
An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr·3.5H2O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.
Highlights
Cellulose is the most abundant renewable resource synthesized in the biosphere (Chandrakant & Bisaria, 1998, Dai et al 2020)
The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved
The natural cellulose could be readily dissolved in lithium bromide hydrates (LBHs), and cellulose chains were homogeneous dispersed with high accessibility to reagents
Summary
Cellulose is the most abundant renewable resource synthesized in the biosphere (Chandrakant & Bisaria, 1998, Dai et al 2020). TEMPO-mediated oxidation of cellulose has been primarily performed as liquid-solid heterogeneous reactions, where the reactivity of cellulose substantially differed within the crystalline and amorphous zones. The TEMPO-mediated oxidation of the natural cellulose cannot synchronously proceed among the crystalline and amorphous zones. The controllability of oxidation is inferior with extremely low degree of oxidation (DO) for the crystalline zone, and the oxidative groups are mainly distributed on the amorphous region and surface of crystalline cellulose (Isogai, Hänninen, Fujisawa, & Saito, 2018). TEMPO/NaClO/NaClO2 system was performed at weak acidic condition, and degradation of cellulose was significantly reduced by avoiding alkaline β-elimination reaction (Saito, Hirota, Tamura, & Isogai, 2010). Reports concerning TEMPO-mediated oxidation of cellulose was concentrated on heterogeneous conditions, and homogeneous reaction has not been reported hitherto. The homogeneous oxidized cellulose could be used for as a hemostatic for moderate bleeding which cannot be sutured or ligated in surgery
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Biological Macromolecules
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
