A finger-jointing model for describing nanostructures of cellulose microfibrils

We propose a finger-jointing model to describe the possible nanostructures of native cellulose microfibrils based on new observations obtained through thermal decomposition of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofibers (CNFs) in saturated water vapor. We heated the micrometers-long TEMPO-CNFs in saturated water vapor (≥ 120 °C, ≥ 0.2 MPa) for ≤ 8 h. The long TEMPO-CNFs unzipped into short (100 s of nanometers long) cellulose nanowhiskers (CNWs). We characterized the CNWs using Raman spectroscopy and Fourier transform infrared spectroscopy, observing similar spectra as TEMPO-CNFs. Thus, the native cellulose microfibrils are not seamlessly long structures, but serial “jointed structures” of CNWs. The finger-jointing model implies a “working and resting rhythm” in the biosynthesis of cellulose. CNWs are highly dispersible in water and polar organic solvents, and are much easier to combine with other classes of polymers at nano-levels. The findings can enhance the feasibility and applicability of native cellulose to achieve sustainable development goals.