Oxone ®-Mediated TEMPO-Oxidized Cellulose Nanomaterials form I and form II

Molecules. 2020 Apr 17;25(8):1847. doi: 10.3390/molecules25081847.

Abstract

The 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation of cellulose, when mediated with Oxone® (KHSO5), can be performed simply and under mild conditions. Furthermore, the products of the reaction can be isolated into two major components: Oxone®-mediated TEMPO-oxidized cellulose nanomaterials Form I and Form II (OTO-CNM Form I and Form II). This study focuses on the characterization of the properties of OTO-CNMs. Nanoparticle-sized cellulose fibers of 5 and 16 nm, respectively, were confirmed through electron microscopy. Infrared spectroscopy showed that the most carboxylation presented in Form II. Conductometric titration showed a two-fold increase in carboxylation from Form I (800 mmol/kg) to Form II (1600 mmol/kg). OTO-CNMs showed cellulose crystallinity in the range of 64-68% and crystallite sizes of 1.4-3.3 nm, as shown through XRD. OTO-CNMs show controlled variability in hydrophilicity with contact angles ranging from 16 to 32°, within or below the 26-47° reported in the literature for TEMPO-oxidized CNMs. Newly discovered OTO-CNM Form II shows enhanced hydrophilic properties as well as unique crystallinity and chemical functionalization in the field of bio-sourced material and nanocomposites.

Keywords: TEMPO; cellulose; crystallinity; hydrophilicity; nanomaterials; oxone®.

MeSH terms

  • Cellulose, Oxidized / chemistry*
  • Densitometry
  • Hydrophobic and Hydrophilic Interactions
  • Nanostructures / chemistry*
  • Nanostructures / ultrastructure
  • Piperidines / chemistry*
  • Spectroscopy, Fourier Transform Infrared
  • Sulfuric Acids / chemistry*
  • Tensile Strength
  • X-Ray Diffraction

Substances

  • 2,2,6,6-tetramethyl-1-piperidine
  • Cellulose, Oxidized
  • Piperidines
  • Sulfuric Acids
  • potassium peroxymonosulfuric acid