In living organisms, nanoscale building blocks are well organized into a nearly defect-free arrangement, leading to sophisticated hierarchical structures that exhibit high mechanical strengths and functionalities. Cellulose nanofibrils are representative building blocks in nature and have raised great interest as excellent structural materials, originating from the most abundant bioresource, wood biomass. Here, we report integration controls of the cellulose nanofibrils that have been completely dispersed in water through the specific surface-carboxylation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. The dispersed nanofibrils spontaneously align in water. The integration controls of the self-aligned nanofibrils, i.e., careful adjustment of the pH and evaporation of the solvent in the nanofibril dispersions, produce a wide range of artificial bulk materials with outstanding properties. Examples include unprecedentedly stiff hydrogels that are freestanding with a water content of 99.9%, ultralow-density, tough aerogels with large surface areas, and transparent films with exceptionally high oxygen-barrier properties. These materials are expected to further develop as robust frameworks of polymer nanocomposites or high-capacity supports of catalysts and the other functional materials. For the sustainable development of society, we propose a methodology for producing sophisticated, high-performance bio-based materials.

SUMMARY Fiber orientation is a criterion used to ascertain the manufacturing district and manufacturing technique of ancient paper as a material of cultural properties. Image analysis using fast Fourier transform with suitable modifications was demonstrated to be an applicable and nondestructive method to determine the orientation angle and anisotropy. In order to improve its accuracy, two new procedures—the binarization process of the microscopic images of the paper surface and precise calculations of the average Fourier coefficients as an angular distribution by linear interpolation—have been introduced to the existing procedures. This analytical method was applied to digital optical micrographs of paper surfaces. As predicted, the method was able to distinguish among laboratory handsheet, copier paper, Japanese paper, and wood-containing paper in terms of the papermaking processes. Traditionally manufactured Korean and Japanese papers showed their own characteristic orientation behavior in accordance with the motion of the bamboo wire in papermaking.

To expand the application field of the pulping industry, this study conducted a series of sample preparations for processing cellulose nanocrystals (CNCs) from a dry hardwood pulp to achieve optimal sulfuric acid hydrolysis. The properties of laboratory-prepared pulp CNCs (P-CNCs) were investigated with different preparation conditions including sulfuric acid concentrations, hydrolysis temperatures, and hydrolysis durations. Results showed a gradient of color changes observed with the increase of hydrolysis duration and temperature. Under certain conditions, the derived P-CNCs exhibited nanoscale dimensions, detected by transmission electron microscopy, and a crystallinity index similar to commercial products. In addition, the surface sulfate groups were assumed to be contributed by sulfuric acid hydrolysis. However, a high acid concentration and long hydrolysis processing duration introduced more sulfate groups on the derived P-CNCs, which may have acted as flame retardants and, thus, increased the amount of char residue.