In this review, I describe stimuli-responsive colloidal assemblies prepared from a rigid rod-like clay mineral called imogolite, and relate them to their structural characteristics. When combined with dicarboxylic acids, imogolite formed gels that exhibited keen thixotropy, and physical anisotropy via orientation of the imogolite particles after flowing and subsequent standing. Robust hydrogels were also obtained by in-situ polymerization of vinyl monomers in imogolite aqueous dispersion. Under strain, these hydrogels showed a reversible isotropic–anisotropic structural transition.
As a reinforcing filler for polymer composite materials, cellulose nanofiber (CNF) is a promising alternative to conventional fillers from the viewpoints of its low cost, low density, biodegradability, high stiffness, and safety. A promising strategy for the preparation of CNF-reinforced polymer composite materials involves in-situ nanofibrillation, in which as-received wood pulp fibers are nanofibrillated into CNFs during the melt-compounding process. To further streamline this process, in this study, we used low-molecular-weight polyols, such as glycerol and glucitol, as nanofibrillation-assisting plasticizers, since polyols are expected to migrate and plasticize into the spaces between cellulose microfibrils in wood cell walls and break down the wood pulp fibers into CNFs. Never-dried needle-leaf bleached kraft pulp (NBKP), high-density polyethylene (HDPE), and a diblock copolymer (BCP), were used as the CNF resource, polymer matrix, and dispersant,respectively. The isolated cellulose fibers produced by the in situ process had diameters of between 200 and 500 nm. Furthermore, under the optimized conditions, the prepared composite material exhibited superior mechanical properties, with a Youngʼs modulus and tensile strength of 3 GPa and 44 MPa, respectively, when produced with 10 wt% NBKP. These values correspond to a four-fold higher Youngʼs modulus and a two-fold higher tensile strength than neat HDPE. Finally, the plasticization effects of glucitol and urea are compared and discussed from the viewpoints of the mechanical properties against the degree of nanofibrillation. This study provides a potential approach for an industrial-scale process.
Plant fibers used for paper and textile are mainly composed of cellulose microfibers which are gathered in the form of hierarchical structures in the plant cell wall. The microfibers are often obtained in the form of pulp from wood, sisal, abaca, and bamboo. Cellulose nanofibers (CNFs) are able to separate from the microfibers. This paper reports that the microfibers are composed of lots of CNFs oriented parallel to the microfiber axis, using electron microscopes. The morphological properties of the microfibers mentioned above are almost retained after the chemical carbonization at a temperature of 800℃ using methane sulfonic acid (MSA) or Iodine (I2) as a catalyst for the carbonization. MSA is more effective for the carbonization than Iodine. CNFs added to bamboo papers are enhanced the mechanical and electrical properties of the bamboo papers in both of the case before and after the carbonization. CNFs obtained from wood pulp, so called, TEMPO oxidized CNFs, show a needle-like structure in nanometer-size after the chemical carbonization.
Air quality is particularly important to public health. Therefore, effective purification and filtration of indoor and outdoor air has become an urgent need. Metal-organic frameworks (MOFs) have been used in the field of gas adsorption because of their superior specific surface area and porosity. However, MOFs are generally presented in powder form, which is not conducive to practical application. In this study, to expand the practical application of MOFs, polystyrene (PS) was used as raw material to prepare PS/Co(AC)2 nanofiber membrane as the matrix material through electrostatic spinning. By soaking method, Co2+ in the nanofiber was coordinated with 2-methylimidazole (2MI) ligand in the soaking solution to make Zeolitic imidazolate framework-67 (ZIF-67) grow on the nanofiber in situ, and ZIF-67@PS composite membrane was prepared. The results of this study showed that the formaldehyde adsorption and filtration properties of the ZIF-67@PS nanofiber membrane were significantly better than those of pure PS nanofiber membrane.
For eight types of knitted fabrics for summer garments and, for comparison, one type of winter garment fabric, subjective hand evaluations were performed under dry and wet conditions, and the fabricsʼ physical properties, such as their tensile strength, shear strength, and surface properties, were evaluated under dry conditions using the Kawabata evaluation system for fabrics (KES-FB). Three factors related to “pleasant, slippery dry feeling,” “smooth, flexible feeling,” and “cool feeling” were extracted following factor analysis of ratings obtained from the subjective hand evaluations. Each factor score exhibited a difference depending on the state of the sample (dry or wet) and the type of material in the fabric. For a plain knitted fabric consisting of 87% polyester and 13% polyurethane (Sample H), each factor score tended to be high under dry conditions. In comparison to other samples, Sample H exhibited higher slipperiness, smoothness, elasticity under shear deformation, tensile recovery, thermal conductivity, and maximum heat flux (qmax) for the contact temperature sensation indicated and lower shear rigidity. For all of the samples, except for the two evaluation description pairs “sticky-slippery” and “dislike-like,” the subjective evaluation values estimated from multiple regression analysis using measurements of physical properties and subjective hand evaluations were similar to the experimental subjective evaluation values for both dry and wet conditions. Hence, the fact that subjective hand evaluation results can be predicted from the objective measurements of physical properties indicate the possibility of practical implications of the fiber product design.
Sulfated heptakis-6-[4-(β-D-maltopyranosyloxymethyl)-1H-1, 2, 3- triazoyl-1-yl)-β-CD (6-O-maltosyl β-CD) was prepared by the sulfation of 6-O-maltosyl β-CD that had been synthesized by click reaction of acetylated 1-O-propagyl-β-D-maltoside with heptakis-6-azido β-CD and then deacetylation. Sulfated 6-O-glucosyl β-CD was also synthesized from 6-O-glucosyl β-CD. These sulfated β-CDs were found to have potent anti-HIV activity (EC50) of 1.3 and 27.9 µg/mL, respectively, however, sulfated β-CD had low anti-HIV activity,>200 µg/mL. The surface plasmon resonance against poly-L-lysine as a model of HIV surface glycoprotein gp 120 indicated that the apparent association- (ka) and dissociation-rate (kd) constants increased and decreased, respectively, ka=0.21×103, 6.24×103, 1.46×104 1/Ms and kd=6.70×10－4, 3.92×10－4, 3.03×10－4 1/s, by depending on the number of branched glucose units. The particle size of the sulfated β-CDs was 13.7 nm, 6.2 nm, and 3.3 nm,respectively, measured by dynamic light scattering. These results suggest that the particle size of the sulfated β-CDs also played an important role in the strength of anti-HIV activity. The highest anti-HIV activity of sulfated 6-O-maltosyl β-CD was expressed by the electrostatic interaction with HIV gp 120 putting on sulfated 6-O-maltosyl β-CD like a cap, because the particle size (13.7 nm) was somewhat larger than that of HIV gp 120 (8 to 10 nm).