Defectless and Uniform Single-Crystallite Dispersions of Sustainable Wood Nanocellulose with a Regulated Right-Handed Twist Periodicity

Controlling the quality of cellulose nanofibers (CNFs), such as dispersibility and defects, is crucial for fully exploiting sustainable wood-derived CNFs. The dispersibility of CNFs is now tailorable, whereas the defects are still uncontrollable. This study is the first to demonstrate defect suppression through the selection of raw material species and the chemical pretreatment for cellulose. Two raw materials of softwood pulp and holocellulose are chosen from the perspective of the nanoscale supramolecular structure of plant celluloses. These two materials are subjected to regioselective surface oxidation using 4-acetamido-2,2,6,6-tetramethylpiperidinyl-1-oxyl as a catalyst at two different pHs to prepare four types of CNFs. Through statistical analysis of the CNF morphology using atomic force microscopy (AFM) image processing, we found a process yielding defectless CNF dispersions comprising uniform single crystallite units of cellulose. Wavelet transform analysis of AFM height profiles further revealed that the defectless CNFs exhibit regulated twist periodicity along much of their length.