Clearly transparent and air-permeable nanopaper with porous structures consisting of TEMPO-oxidized cellulose nanofibers

Electrodeposition of cellulose nanofibers as an efficient dehydration method

Dehydration of a cellulose nanofiber (CNF)/water dispersion requires large amounts of energy and time due to the high hydrophilicities and high specific surface areas of the CNFs. Various dehydration methods have been proposed for CNF/water dispersions; however, an efficient dehydration method for individually dispersed CNFs is needed. Here, electrodeposition of CNFs was evaluated as a dehydration method. Electrodeposition at a DC voltage of 10 V on a 0.2 wt% CNF/water dispersion resulted in a concentration of ∼1.58 wt% in 1 h. The dehydration energy efficiency was ∼300 times greater than that of dehydration by evaporation. The concentrated CNF hydrogels recovered after electrodeposition were redispersed with a simple neutralization process, and clear transparent films were obtained by drying after redispersion. This work provides a new method for dehydration and reuse of individually dispersed CNF/water dispersions and provides new insights into control of the hierarchical structures of CNFs by electrodeposition.

Effect of Adding Bentonite to Porous Silica via the Sol-Gel Method

The control of specific surface area and pore size of porous materials is essential for applications such as optics, medicine, and food technology. Here, the interspace between nanomaterials such as nanoparticles and nanosheets was studied. Nanoparticle-nanosheet interspaces were formed by incorporating bentonite nanosheets to the preparation of porous silica by the sol-gel method. The product had micropore and mesopores, which originated from internanoparticle space and nanoparticle-nanosheet spaces, respectively. These two types of pores had not only different sizes but also different aspect ratios. Time-domain nuclear magnetic resonance evaluation of the bentonite dispersion revealed that the dispersion state of bentonite in water prior to composite fabrication affected the formation of the pore structure. The pore size distribution could be easily changed by adding two-dimensional and flexible nanosheets owing to the change in the physical properties of the product. The silica-bentonite composite had a significantly larger specific surface area and pore volume than porous silica without bentonite. Water vapor adsorption measurements showed that the composite exhibited a larger maximum adsorption in comparison to porous silica. Therefore, a large improvement in the physical properties can be achieved by combining nanomaterials with different geometries.

The Critical Roles of Water in the Processing, Structure, and Properties of Nanocellulose

The cellulose industry depends heavily on water owing to the hydrophilic nature of cellulose fibrils and its potential for sustainable and innovative production methods. The emergence of nanocellulose, with its excellent properties, and the incorporation of nanomaterials have garnered significant attention. At the nanoscale level, nanocellulose offers a higher exposure of hydroxyl groups, making it more intimate with water than micro- and macroscale cellulose fibers. Gaining a deeper understanding of the interaction between nanocellulose and water holds the potential to reduce production costs and provide valuable insights into designing functional nanocellulose-based materials. In this review, water molecules interacting with nanocellulose are classified into free water (FW) and bound water (BW), based on their interaction forces with surface hydroxyls and their mobility in different states. In addition, the water-holding capacity of cellulosic materials and various water detection methods are also discussed. The review also examines water-utilization and water-removal methods in the fabrication, dispersion, and transport of nanocellulose, aiming to elucidate the challenges and tradeoffs in these processes while minimizing energy and time costs. Furthermore, the influence of water on nanocellulose properties, including mechanical properties, ion conductivity, and biodegradability, are discussed. Finally, we provide our perspective on the challenges and opportunities in developing nanocellulose and its interplay with water.