Language：English   Publishing type：Research paper (scientific journal)  

In recent years, increased attention has been given to the effective use of chitin nanofibers (ChNFs). We have developed a method to fabricate thinner chitin nanomaterials, called scale-down chitin nanofibers (SD-ChNFs), by a bottom-up procedure at the nanoscale level, with subsequent disintegration by electrostatic repulsion. The surface modification of SD-ChNFs is anticipated to provide new properties and functions for their practical applications. Inspired by our previous reports, which found hydrophobicity in partially 2-deoxygenated (P2D-) amylose obtained by the glucan phosphorylase (GP)-catalyzed enzymatic copolymerization of α-d-glucose 1-phosphate/d-glucal as comonomers, this work investigated the hydrophobization of SD-ChNFs via an enzymatic approach. After the modification of maltooligosaccharide primers on SD-ChNFs was performed by a reductive alkylation toward ChNFs, the grafting of the P2D-amyloses was performed by GP-catalyzed enzymatic copolymerization. 1H NMR analysis supported the production of P2D-amylose-grafted SD-ChNFs with different d-glucose/2-deoxy-d-glucose unit ratios on SD-ChNFs. The X-ray diffraction analysis of the products confirmed that the chain lengths and unit ratios of the grafted polysaccharides strongly affected the entire crystalline structures. Water contact angle measurements of the cast films of the products indicated that successful hydrophobization was achieved by the grafting of P2D-amylose chains with a sufficient chain length, a relatively high 2-deoxy-d-glucose unit ratio, and low crystallinity.

DOI： 10.3390/molecules30010016

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

This study develops the efficient benzylation of chitin using benzyl bromide in the presence of LiOH in ionic liquids. Addition of amine bases, such as tributylamine, promotes the reaction to...

DOI： 10.1039/d5nj01789k

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.compositesa.2024.108511

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The aim of this study is to prepare new cellulose derivatives that show good feasibility and processability. Accordingly, in this study, we demonstrate Michael addition to hydroxyalkyl acrylates, that is, 2-hydroxyethyl and 4-hydroxybutyl acrylates (HEA and HBA, respectively), to synthesize amorphous cellulose derivatives under alkaline conditions. The reactions were carried out in the presence of LiOH in ionic liquid (1-butyl-2,3-dimethylimidazolium chloride)/N,N-dimethylformamide (DMF) solvents at room temperature or 50 °C for 1 h. The Fourier transform infrared and 1H nuclear magnetic resonance (NMR) measurements of the products supported the progress of Michael addition; however, the degrees of substitution (DS) were not high (0.3–0.6 for HEA and 0.6 for HBA). The powder X-ray diffraction analysis of the products indicated their amorphous nature. The cellulosic Michael adduct from HEA with DS = 0.6 was swollen with high polar organic liquids, such as DMF. In addition to swelling with these liquids, the cellulosic Michael adduct from HBA was soluble in dimethyl sulfoxide (DMSO), leading to its 1H NMR analysis in DMSO-d6. This adduct was found to form a cast film with flexible properties from its DMSO solutions. Furthermore, films containing an ionic liquid, 1-butyl-3-methylimidazolium chloride, showed thermoplasticity. The Michael addition approach to hydroxyalkyl acrylates is quite effective to totally reduce crystallinity, leading to good feasibility and processability in cellulosic materials, even with low DS. In addition, the present thermoplastic films will be applied in practical, bio-based, and eco-friendly fields.

DOI： 10.3390/polym16223142

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

We successfully synthesized a new unnatural polysaccharide, 2-deoxy-β(1→3)-glucan, by β−1,3-glucan phosphorylase-catalyzed enzymatic polymerization of a D-glucal monomer from a cellobiose primer, owing to recognition of such non-native substrates by the enzyme. Because of solubility of the product in several high polar organic solvents, acetylation as an example of its derivatizations smoothly occurred using acetic anhydride in the presence of base/catalyst in a DMF solvent. The NMR analysis of the acetylated derivative strongly supported the β(1→3)-linked chain structure.

DOI： 10.1093/chemle/upae167

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Other Link： https://academic.oup.com/chemlett/article-pdf/53/9/upae167/59363974/upae167.pdf

Language：Japanese   Publishing type：Research paper (scientific journal)  

Recently, attention has been paid to cellulose nanofibers, such as 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanofibers (TOCN), as new bio-based materials. In addition, hydrophobized surface on TOCNs can be expected to provide new applications. Based on our previous finding that partially 2-deoxygenated (P2D)-amylose, which was synthesized by GP-catalyzed enzymatic copolymerization of D-glucal with α-D-glucose 1-phosphate (Glc-1-P) as comonomers, was hydrophobic, in this study, hydrophobization of surfaces on TOCNs was investigated by the GP-catalyzed enzymatic grafting of P2D-amylose chains on TOCNs. After maltooligosaccharide primers were modified on TOCNs, the GP-catalyzed enzymatic copolymerization of D-glucal with Glc-1-P was performed for grafting of P2D-amylose chains. 1H NMR spectroscopic analysis confirmed the production of P2D-amylose-grafted TOCNs with different 2-deoxyglucose/Glc unit ratios. The powder X-ray diffraction profiles of the products indicated that the entire crystalline structures were strongly affected by the unit ratios and chain lengths of the grafted polysaccharides. The SEM images observed differences in nanofiber diameter in the reaction solutions and surface morphology after film formation, due to grafting of P2D-amylose chains from TOCNs. The water contact angle measurement of a cast film prepared from the product indicated its hydrophobicity.

DOI： 10.1016/j.carbpol.2024.122086

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

We prepared network polysaccharide nanoscopic hydrogels by crosslinking water-soluble chitosan (WSCS) with a carboxylate-terminated maltooligosaccharide crosslinker via condensation. In this study, the enzymatic elongation of amylose chains on chitosan-based network polysaccharides by glucan phosphorylase (GP) catalysis was performed to obtain assembly materials. Maltoheptaose (Glc7) primers for GP-catalyzed enzymatic polymerization were first introduced into WSCS by reductive amination. Crosslinking of the product with the above-mentioned crosslinker by condensation was then performed to produce Glc7-modified network polysaccharides. The GP-catalyzed enzymatic polymerization of the α-d-glucose 1-phosphate monomer from the Glc7 primers on the network polysaccharides was conducted, where the elongated amylose chains formed double helices. Enzymatic disintegration of the resulting network polysaccharide assembly successfully occurred by α-amylase-catalyzed hydrolysis of the double helical amyloses. The encapsulation and release of a fluorescent dye, Rhodamine B, using the CS-based network polysaccharides were also achieved by means of the above two enzymatic approaches.

DOI： 10.3390/molecules29081804

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41428-024-00911-y

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Other Link： https://www.nature.com/articles/s41428-024-00911-y

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Recently, environmentally degradable polymers have received great attention from the perspective of sustaining the aquatic environment. To control the degradation behavior of solid polymer materials in an aqueous phase, it is crucial to better understand the thermal molecular motion of polymer chains in water. We herein focus on polyglycolide (PGA), which is one of the representative aliphatic polyesters that are hydrolytically degradable. Three kinds of fiber mats of PGA with different fiber diameters and comparable crystallinities were prepared using an electrospinning method. Our choice of fiber mats was because the ratio of the surface area, where the hydrolytic degradation starts to occur, to the volume was larger than that for the films. Dynamic mechanical analysis (DMA) enabled us to gain direct access to the dynamic glass transition temperature (Tg & alpha;) of PGA in the fiber mats both in dry gaseous nitrogen and liquid water. The Tg & alpha; value varied not only with the presence of water molecules, but also with the fiber diameter, or the specific surface area. The degradation behavior of PGA fiber mats was examined by immersing the samples in phosphate-buffered saline at various temperatures. When the segmental motion of PGA in the fiber mats was released, the apparent crystallinity of the mats increased, meaning that PGA amorphous chains were cleaved and thus partially eluted into the aqueous phase. It was also shown that partially cleaved chains crystallized.The release of segmental motion of polyglycolide in fiber mats caused cleavage and partial elution of chains into aqueous phases.

DOI： 10.1039/d3sm00613a

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-23K04866/

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Polymer adhesion with inorganic materials is a key technology for realizing the diversification of materials. When a polymer contacts with inorganic materials, a layer containing strongly- and loosely-adsorbed chains is formed at the surface. The former and latter are chains that adopt mainly train and loop/tail conformations, respectively. To improve the interfacial adhesion, it is of pivotal importance to control the interaction between loosely-adsorbed chains, which are in part directly attached to the solid surface, and bulk free chains. We here succeeded in increasing the interfacial strength by chemically cross-linking them. Polymer chains were attached to the surface of a silicon wafer and then a film of isotactic polypropylene or polyamide 6 was mounted on it to produce our model system. As loosely-adsorbed chains have photo-cross-linkable moieties, the polyolefin or engineering plastic film could be strongly adhered to the silicon wafer via the adsorbed layer. On the other hand, the film could be easily detached from the wafer having loosely-adsorbed chains without photo-cross-linkable groups. Our facile idea that loosely-adsorbed interfacial chains chemically bond to the polymer bulk shows promise for the design and construction of not only interfacial adhesion but also composite materials.

DOI： 10.1016/j.polymer.2022.125581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

The mechanical properties in the outermost region of a polymer film strongly affect various material functions. We here propose a novel and promising strategy for the two-dimensional regulation of the mechanical properties of a polymer film at the water interface based on an inkjet drawing of silica nanoparticles (SNPs) underneath it. A film of poly(2-hydroxyethyl methacrylate) (PHEMA), which exhibits excellent bioinertness properties at the water interface, was well fabricated on a substrate with a pattern of SNPs. X-ray photoelectron spectroscopy and atomic force microscopy confirmed that the surface of the PHEMA film was flat and chemically homogeneous. However, the film surface was in-plane heterogeneous in stiffness due to the presence of the underlying SNP lines. It was also noted that NIH/3T3 fibroblast cells selectively adhered and formed aggregates on the areas under which an SNP line was drawn.

DOI： 10.1021/acs.langmuir.1c02776

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Tokyo : Springer Nature  

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publisher：Tokyo : Springer Nature  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGERNATURE  

A better understanding of the aggregation states of polymers in contact with water is a pivotal issue for the development of highly functional polymer devices that work under water. As a direct experimental method to achieve the above, we used near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) on a poly(methyl methacrylate) (PMMA) film mixed with a small amount of a bottlebrush-type methacrylate polymer with oligo(2-ethyl-2-oxazoline) in its side chain portions, referred to as P[O(Ox)(n)MA], in a hydrated state. The results showed that P[O(Ox)(n)MA] was segregated at the surface of the PMMA film and suppressed the adhesion and activation of platelets on the film.

DOI： 10.1038/s41428-021-00485-z

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I033417817

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGERNATURE  

Surface modification of versatile polymeric materials without changing their bulk properties is one of the essential techniques for regulating their physical and chemical characteristics, and this technique can improve the functions of materials. In this study, a bottlebrush-type poly[oligo(2-ethyl-2-oxazoline) methacrylate] (P[O(Ox)(n)MA]) (n = 7 and 19) was synthesized as a surface modifier. This compound was mixed into poly(methyl methacrylate) (PMMA) as a matrix (PMMA/P[O(Ox)(n)MA]) with a weight ratio of 15%, and the aggregation state in the surface region was examined under air and aqueous environments via atomic force microscopy, contact angle measurement, angular-dependent X-ray photoelectron spectroscopy, and neutron reflectivity. The surface of the PMMA/P[O(Ox)(n)MA] films was flat at the subnanometer level and covered with the PMMA-rich phase. However, once the films contacted water, the surface was reorganized due to the migration of P[O(Ox)(n)MA]. The extent of the surface segregation was more remarkable for P[O(Ox)(7)MA] than P[O(Ox)(19)MA] due to the entropic factor. Concurrently, NIH3T3 fibroblast adhesion and serum protein adsorption on the film were more strongly suppressed for P[O(Ox)(7)MA] than P[O(Ox)(19)MA] because it formed a thicker diffused interface in the film with water.

DOI： 10.1038/s41428-020-00459-7

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I033415543

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