Detailed Structural Analyses of Nanofibrillated Bacterial Cellulose and Its Application as Binder Material for a Display Device.

Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium under agitated aerobic conditions in a carboxymethylcellulose (CMC)-supplemented medium. Detailed structural analyses revealed that NFBC fiber widths varied with the degree of substitution of the CMC used, and zeta potential values decreased with the increment of CMC concentration in the medium. Transmission electron microscopy observation after immunostaining demonstrated that CMC molecules were present on the NFBC microfibril surfaces. We tested NFBC for utility as a binder for a display device that uses electrochromic (EC) material. Introduction of a quaternary ammonium group into the EC molecules enhanced their interactions with the negatively charged NFBC microfibrils. A casting process homogeneously adsorbed the EC molecules onto the surface of a transparent electrode with NFBC. A homogeneous color change was successfully observed upon applying an electric field, suggesting that NFBC could be used as a binder material for uniform surface adsorption.

One-Step Production of Amphiphilic Nanofibrillated Cellulose Using a Cellulose-Producing Bacterium.

Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium (Gluconacetobacter intermedius NEDO-01) with rotation or agitation in medium supplemented with carboxymethylcellulose (CMC). Despite a high yield and dispersibility in water, the product immediately aggregates in organic solvents. To broaden its applicability, we prepared amphiphilic NFBC by culturing strain NEDO-01 in medium supplemented with hydroxyethylcellulose or hydroxypropylcellulose instead of CMC. Transmission electron microscopy analysis revealed that the resultant materials (HE-NFBC and HP-NFBC, respectively) comprised relatively uniform fibers with diameters of 33 ± 7 and 42 ± 8 nm, respectively. HP-NFBC was dispersible in polar organic solvents such as methanol, acetone, isopropyl alcohol, acetonitrile, tetrahydrofuran (THF), and dimethylformamide, and was also dispersible in poly(methyl methacrylate) (PMMA) by solvent mixing using THF. HP-NFBC/PMMA composite films were highly transparent and had a higher tensile strength than neat PMMA film. Thus, HP-NFBC has a broad range of applications, including as a filler material.

Relationship between wettability of pulp fibers and tensile strength of paper during recycling.

The wettability of the paper surface is greatly affected by the wettability of the pulp fibers. We conducted this study in order to understand the relationship between the wettability of a single fiber of recycled pulp and the strength of recycled paper, as well as the inter-fiber bonding strength. The contact angle was determined from a series of photographs of the pulp fiber and the water silhouettes at the point of contact. The contact line and profile history were continuously photographed in every 1 s after the initial contact. The recycled softwood kraft pulp fibers were clearly much less hydrophilic than the original fibers, regardless of whether the fibers had been bleached or not. The contact angle of the original chemi-thermomechanical pulp fiber was much higher than that of the original softwood bleached kraft pulp fiber. Furthermore, increased number of recycling decreased the contact angle of the chemi-thermomechanical pulp fiber. The Page equation was used to evaluate the strength contributions of single fiber and fiber-fiber bonding to tensile strength of paper. As a result, an increase in weakness factor of fiber-fiber bonding strength was obtained for the recycled softwood kraft pulp handsheet. On the other hand, the weakness factor of the original chemi-thermomechanical pulp handsheet decreased with recycling. In addition, the weakness factor of fiber-fiber bonding strength and the contact angles of the provided softwood bleached kraft pulp fibers bore a proportional relationship to each other.

"Nanocellulose" as a single nanofiber prepared from pellicle secreted by Gluconacetobacter xylinus using aqueous counter collision.

This study attempted to prepare a single cellulose nanofiber, "nanocellulose", dispersed in water from 3D networks of nanofibers in microbial cellulose pellicle using aqueous counter collision (ACC), which allows biobased materials to be down-sized into nano-objects only using water jets without chemical modification. The nanocellulose thus prepared exhibited unique morphological properties. In particular, the width of the nanocellulose, which could be controlled as desired on nanoscales, was smaller than that of just secreted cellulose nanofiber, resulting in larger specific surface areas. Moreover, ACC treatment transformed cellulose I(α) crystalline phase into cellulose I(ß) phase with the crystallinity kept >70%. In this way, ACC method depending on the treatment condition could provide the desired fiber width at the nanoscale and the different ratios of the two crystalline allomorphs between cellulose I(α) versus I(ß), which thus opens further pathways into versatile applications as biodegradable single nanofibers.

Aqueous counter collision using paired water jets as a novel means of preparing bio-nanofibers.

This study involved a detailed investigation of a novel approach to reducing naturally occurring cellulose fibers into nanofibers solely by the use of aqueous counter collision (ACC) without any chemical modification. In this process, equivalent aqueous suspensions of cellulose are ejected from dual nozzles and collide at high speed and pressure. Even a few repetitions of the collision process are sufficient to produce nano-sized fibers dispersed in water. This work compared the ACC nano-pulverization of stable Iß-rich and meta-stable Iα-rich cellulose samples. The ACC method is applicable to various kinds of polymeric materials with hierarchical structures, either natural or synthetic, as a means of preparing aqueous dispersions of nano-sized structures.