The dispersibility of Cellulose I and Cellulose II by tempo-mediated oxidation

ABSTRACT

Background:

The restricted dispersibility of cellulose in water has grown to be a significant problem which is a key step in making cellulose soluble in water and common solvent. To overcome the obstacle, cellulose structure is being modified to improve the surface properties and the utilization of the cellulose itself. In this study, cellulose I and cellulose II were examined after treated with water-soluble 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The hydrogen bond between chains and the crystallinity of the cotton linter (cellulose I) was first broken by NaOH/urea. Then, cellulose I and NaOH/urea-treated cellulose (cellulose II) were oxidized with sodium chlorite, sodium bromide, and TEMPO in a catalytic amount.

Results:

The success of oxidation is achieved when both cellulose I and II treated with TEMPO had preferentially converted the hydroxyl groups to carboxylate groups through Fourier Transform Infrared Spectrometer (FTIR). Besides, through X-ray diffraction analysis, cellulose I and II exhibited a decreased in the crystallinity. The scattered structure revealed through morphology analysis proved that cellulose treated with TEMPO had resulted in a more dispersed and separated cellulose fibre structure.

Conclusion:

The result showed, cellulose has been successfully modified using TEMPO-mediated oxidation with improved dispersion properties. The scattered structure revealed through morphology analysis proved that cellulose treated with TEMPO had resulted in a more dispersed and separated cellulose fibre structure. High cellulose dispersion ability will allow the manufacturing process of hydrogel, film and fibre to be much easier and faster. This is necessary for creating novel, environmentally friendly materials for various applications across numerous industries and future research anticipated to increase.

Keywords:
2,2,6,6-tetramethylpiperidine-1-oxyl radical; Bioresource based products; Carboxyl groups; Cellulose solubility; Crystallinity; Dissolution.

HIGHLIGHTS

2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) can modified cellulose with different molecular orientation (cellulose I and cellulose II). New functional group (-COOH) appeared after TEMPO oxidation has affected the crystalline structure of cellulose. TEMPO-modified cellulose experienced thermal degradation at lower temperature. Cellulose II-TEMPO is observed to have the highest stability and dispersibility with enhanced fibers dispersion and separation.