Articles in 2021

Cellulose chains with a reducing-end thiol group are of interest to install a controllable topochemical pattern of site-selective modification into nanocellulose materials. Selection of the polymerizing enzyme (cellodextrin phosphorylase; CdP) was pursued here to enhance the synthetic precision in the preparation of 1-thio-cellulose. The CdP from Clostridium stercorarium (CsCdP) was identified as a practical catalyst for 1-thio-cellulose synthesis in high purity (≥95%) directly from β-1-thio-glucose. The synthesis proceeds without the need of cellobiose phosphorylase (CbP) and minimizes the contamination (plain cellulose; ≤5%) in the product.

A series of polyacrylamide/polyanionic cellulose/Zr–CP (PAM/PAC/Zr–CP) composite hydrogels were prepared via acrylamide polymerization in aqueous solution of PAC and disodium terephthalate (Na₂BDC), followed by posttreatment in 0.1 M ZrOCl₂ solution. The coordination of Zr(IV) clusters with carboxylates on PAC and BDC²⁻ endows the hydrogels with improved strength and adsorption of methyl orange (MO). Specially, over 5 MPa of compressive strength and 500 mg MO/g Zr of MO-adsorption capacity are attained. This work provides a facile and green approach to synthesize CP-based composite hydrogels with enhanced mechanical and adsorptive properties through strong metal–ligand coordination.

The self-assembly of biomolecules is an important strategy for fabricating structurally ordered artificial nanomaterials. In this study, we investigated the cellodextrin phosphorylase-catalyzed synthesis and self-assembled structures of cellulose oligomers in the presence of protein denaturants. The modulation of intermolecular interactions between oligomers by protein denaturants under adequate synthesis conditions resulted in the production of oligomers with greater degrees of polymerization and different crystal structures.

Utilizing the emulsion-forming ability of partially deacetylated chitin nanofibers, a composite with polystyrene (PS) was prepared. A partially deacetylated chitin nanofiber aqueous dispersion was added to styrene to obtain an oil in a water-type Pickering emulsion. Using the emulsion, suspension polymerization was performed to obtain PS fine particles covered with chitin nanofibers. This composite could be molded by hot pressing, and the molded product was transparent to some extent. Mechanical properties of PS were greatly improved. When the composite was molded again, the mechanical properties did not decrease.

Using a facile method, a gelatin hydrogel with anisotropic gel properties was prepared on a substrate via hydrogelation to induce self-assembly. Three kinds of surface properties (structural control factors) of the template induce the formation of an anisotropic gelatin network by self-assembly. The swelling behavior and mechanical properties of the anisotropic and isotropic gelatin hydrogels are different. When the hydrogel is compressed in a direction perpendicular to the tube-like gelatin network, the inner space of the network is compressed.

A supramolecular complex termed “hemoCD1” was constructed as the aqueous synthetic Hb/Mb model using a 1:1 inclusion complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(II) with a per-O-methylated β-cyclodextrin dimer with a pyridine linker. HemoCD1 was used as a selective CO scavenger in vivo due to its extremely high binding affinity to CO. In addition, hemoCD1 was utilized to quantify the accumulation of endogenous and exogenous CO in organs/tissues. Finally, hemoCD1 was employed as an antidote for CO poisoning in animals.

In this article, a series of thermo-driven self-healable organic/inorganic nanohybrid polyurethane (WMPUS-x) films were prepared with different addition amount of furfuryl modified silica nanoparticles (furan@SiO₂). The self-healable system was constructed via a DA/retro-DA process among furan@SiO₂ and maleimide-terminated waterborne polyurethane. The results exhibited the addition of furan@SiO₂ enhanced the mechanical behavior of all WPU samples.

Hydrophobically modified polysaccharides have attracted considerable attention in the biomedical field because of their biocompatibility, biodegradability, and nontoxicity. This article reviews previous studies on micellar structures formed by hydrophobically modified polysaccharides (pullulan and amylose) in aqueous solutions by static and dynamic light scattering, small angle X-ray and neutron scattering, and fluorescence from pyrene solubilized in the polymer solution. Depending on the degree of substitution, the hydrophobically modified polysaccharides exist in aqueous solution as full or loose flower necklaces or as nanogels made up of randomly branched polymers.

TEMPO-catalyzed oxidation enables efficient and position-selective conversion of primary hydroxy groups in water-soluble and -insoluble polysaccharides to sodium carboxylate groups. TEMPO/NaBr/NaClO in water at pH 10 is an advantageous system in terms of the degrees of oxidation and reaction rates. Various new water-soluble TEMPO-oxidized polysaccharides have been prepared by TEMPO-catalyzed oxidation, and they have unique properties and functionalities. When crystalline native cellulose and chitin are oxidized by the TEMPO/NaBr/NaClO system under suitable conditions, the obtained water-insoluble oxidized products can be converted to characteristic nanomaterials by mechanical disintegration in water.

We estimated the configurational heat capacity above a glass transition temperature (T_g) of 21 types of polymers for which molecular vibration analysis was already completed. The polymers for which the configurational heat capacity was determined are six types of linear polymers with a carbon backbone, eight types of polyesters, and seven types of poly(oxide)s. As temperature increases, the configurational heat capacity of all polymers decreases. Based on Landau’s theory, the obtained heat capacity can be well reproduced by the power and logarithmic functions.

Effect of graphene (rGO), as the secondary filler, in rubber compounds filled with silica was investigated. Scanning electron microscopy showed that silica dispersion was improved in the presence of small quantities of rGO, but it deteriorated at higher loadings of rGO due to the formation of compact hybrid filler network. This morphological development affects dynamic-mechanical properties such that the Payne effect reduces in the presence of low concentrations of rGO. Using these observations, the underlying mechanism was explained based on how rGO hinders silica reagglomeration thermodynamically after the mixing.

Novel alcohol-derived degradable acetal-linkage-containing epoxy resins HBA–CHDMVG and HOBA–CHDMVG were synthesized. The thermal decomposition temperature of HOBA–CHDMVG was higher than 300 °C; moreover, HOBA–CHDMVG exhibited excellent Charpy impact strength. The cured HOBA–CHDMVG was completely decomposed during the hydrolysis reaction under acidic conditions, and the reaction products were soluble in a tetrahydrofuran/H₂O mixed solvent. Furthermore, the carbon fibers in the carbon-fiber-reinforced plastic with a HOBA–CHDMVG matrix were recovered via the complete decomposition of HOBA–CHDMVG.

The isothermal crystallization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was evaluated using a range of models namely, Avrami, simplified Hillier, Tobin, Malkin, Urbanovici-Segal, Velisaris-Seferis and Hay. The Hay model was found to generate the best fit, closely followed by the Velisaris-Seferis parallel model, suggesting that primary and secondary crystallization occur concurrently. This work highlights the importance of selecting the most appropriate model for analyzing isothermal crystallization kinetics, especially when high levels of secondary crystallization occur.

Poly(vinyl alcohol) (PVA) was crosslinked via catalyst-free solid-state esterification at 120 °C with 2,5-furandicarboxylic acid (FDCA) at concentrations ranging from 1 to 10%. The thermal stability of PVA was improved significantly, especially at low FDCA concentrations of 1 and 5%, where degradation maximums occurred at 354 and 371 °C, respectively, compared to 267 °C for unmodified PVA. A twofold increase in tensile strength for the biodegradable PVA was achieved by crosslinking with 5% FDCA. A twofold increase in tensile strength for the biodegradable PVA was achieved by crosslinking with 5% FDCA.

A simplified multi-ion network is presented, which can toughen and modulate the spontaneous self-healing capability of dry-solid Zn(II)-carboxylate polyamic acid under ambient conditions.

Regenerated fibers of β-1,3-glucan (curdlan) and α-1,3-glucan were fabricated by dry-jet wet spinning, and the fiber properties and structures are summarized in this review. The flexible and water-absorbent curdlan and the stiff and strong α-1,3-glucan would be utilized in different applications from conventional cellulose. As a new type of post-treatment, a two-step stretching method in water was developed for α-1,3-glucan by utilizing its crystal transition. This can be applied to various polysaccharides for future production of high-performance fibers.

Organogel formation was observed immediately during the addition of diisocyanate to a solution of para-substituted bis(3-aminopropyl)hexaisobutyl-substituted cage octasilsesquioxane (T₈ cage) monomer at room temperature when above the critical gel concentrations (C_gs). T₈-polyureas with phenylurea moieties promoted organogel formation in comparison with T₈-polyureas with nonphenylurea moieties. The substitution of methyl groups at the ortho position of the phenylurea groups provided lower C_gs. Increasing the intermolecular interaction between the ureido groups in the T₈-polyurea enhanced organogel formation, which was supported by the FT-IR analysis of the dried gels.

To clarify the role of lateral deformation of condensed polymer surface on cell adhesion, the responses of cell spreading were characterized at a cell culture temperature on the poly(N-isopropylacrylamide)-grafted surfaces with different degree of graft-polymerization (DGP). A clear negative correlation between cell spreading and DGP of PNIPAAm was found regardless of the amount of fibronectin adsorbed on the substrates. The microscopic local strain of the condensed polymers by cellular traction forces was considered to modulate the density distribution of adsorbed adhesive ligands beneath the focal adhesions and the cell spreading.

Bis(indolyl)-coordinated titanium dichlorido complexes were applied for ethylene polymerization. The results showed that [{bis(indolyl)}TiCl₂]₂ activated by modified methyl aluminoxane (MMAO) exhibited ethylene polymerization activity up to 2494 (kg of polyethylene)/(mol of Ti)·h·atm. This activity is comparable to the highest known activity in catalyst systems based on diamido-supported titanium complexes. The [{bis(indolyl)}TiCl₂]₂/MMAO catalyst system was also active for propylene polymerization (344 (kg of polypropylene)/(mol of Ti)·h·atm) to furnish atactic polypropylene.