Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

Background Since at least 400 C.E., when the Mayans first used layered clays to make dyes, people have been harnessing the properties of layered materials. This gradually developed into scientific research, leading to the elucidation of the laminar structure of layered materials, detailed understanding of their properties, and eventually experiments to exfoliate or delaminate them into individual, atomically thin nanosheets. This culminated in the discovery of graphene, resulting in a new explosion of interest in two-dimensional materials. Layered materials consist of two-dimensional platelets weakly stacked to form three-dimensional structures. The archetypal example is graphite, which consists of stacked graphene monolayers. However, there are many others: from MoS 2 and layered clays to more exotic examples such as MoO 3 , GaTe, and Bi 2 Se 3 . These materials display a wide range of electronic, optical, mechanical, and electrochemical properties. Over the past decade, a number of methods have been developed to exfoliate layered materials in order to produce monolayer nanosheets. Such exfoliation creates extremely high-aspect-ratio nanosheets with enormous surface area, which are ideal for applications that require surface activity. More importantly, however, the two-dimensional confinement of electrons upon exfoliation leads to unprecedented optical and electrical properties. Liquid exfoliation of layered crystals allows the production of suspensions of two-dimensional nanosheets, which can be formed into a range of structures. (A) MoS 2 powder. (B) WS 2 dispersed in surfactant solution. (C) An exfoliated MoS 2 nanosheet. (D) A hybrid material consisting of WS 2 nanosheets embedded in a network of carbon nanotubes. Advances An important advance has been the discovery that layered crystals can be exfoliated in liquids. There are a number of methods to do this that involve oxidation, ion intercalation/exchange, or surface passivation by solvents. However, all result in liquid dispersions containing large quantities of nanosheets. This brings considerable advantages: Liquid exfoliation allows the formation of thin films and composites, is potentially scaleable, and may facilitate processing by using standard technologies such as reel-to-reel manufacturing. Although much work has focused on liquid exfoliation of graphene, such processes have also been demonstrated for a host of other materials, including MoS 2 and related structures, layered oxides, and clays. The resultant liquid dispersions have been formed into films, hybrids, and composites for a range of applications. Outlook There is little doubt that the main advances are in the future. Multifunctional composites based on metal and polymer matrices will be developed that will result in enhanced mechanical, electrical, and barrier properties. Applications in energy generation and storage will abound, with layered materials appearing as electrodes or active elements in devices such as displays, solar cells, and batteries. Particularly important will be the use of MoS 2 for water splitting and metal oxides as hydrogen evolution catalysts. In addition, two-dimensional materials will find important roles in printed electronics as dielectrics, optoelectronic devices, and transistors. To achieve this, much needs to be done. Production rates need to be increased dramatically, the degree of exfoliation improved, and methods to control nanosheet properties developed. The range of layered materials that can be exfoliated must be expanded, even as methods for chemical modification must be developed. Success in these areas will lead to a family of materials that will dominate nanomaterials science in the 21st century.

/pdf/liquid-exfoliation-of-layered-materials-3l83x6zg7f.pdf

Liquid Exfoliation of Layered Materials

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

Hyperbranched polymers: from synthesis to applications

Enzymatic Synthesis of Glyco-macromonomers

In this study, we found that hierarchically controlled assemblies from amylose analog aminopolysaccharides occurred by reductive amination to obtain nanoparticles, microaggregates, and macrohydrogels depending on reaction conditions. The polysaccharide substrate composed of α(1→4)-linked glucosamine residues was synthesized by thermostable phosphorylase (from Aquifex aeolicus VF5)–catalyzed enzymatic polymerization of α-d-glucosamine 1-phosphate according to the reaction manner reported in our previous study. The reductive amination of the produced polysaccharide was carried out in the presence of NaBH3CN as reductant in 0.1 mol/L acetic acid aq. at 60 °C for 1 h. When lower feed ratios of reductant to the reducing end of the substrate were employed for the reaction, nanoparticles were obtained. With increasing feed ratios of reductant, more α(1→4)-GlcNn molecules assembled to further form water-insoluble microaggregates and macrohydrogels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45890

Hierarchically controlled assemblies from amylose analog aminopolysaccharides by reductive amination: From nano- to macrostructures

Non-natural oligosaccharides can be expected to exhibit new functions and applications in glycoscience. Enzymatic glycosylation is a powerful tool for the preparation of oligosaccharides with well-defined structure. For example, α-(1→4)-glucosidic linkage can be constructed by α-glucan phosphorylase-catalyzed enzymatic glucosylation using α-D-glucose 1-phosphate (Glc-1-P) as a glycosyl donor. Because this enzyme expresses some loose specificity for recognition of substrate structures, the development of the α-glucan phosphorylase-catalyzed glycosylation using analogue substrates of Glc-1-P is the efficient approach to obtain new non-natural oligosaccharides. In this review, on the basis of above viewpoints, the facile synthesis of non-natural oligosaccharides by the α-glucan phosphorylase-catalyzed enzymatic glycosylations using such analogue substrates, i.e., hexose 1-phosphates as glycosyl donors is described. It has been found that α-Dxylose, α-D-mannose, 2-deoxy-α-D-glucopyranose, 3or 4-deoxyα-D-glucose, α-(N-formyl)-D-glucosamine, and α-D-glucuronic acid 1-phosphates are recognized by α-glucan phosphorylase as the glycosyl donor to occur the transfer reaction of the corresponding sugar residues to a non-reducing end of maltooligosaccharides (glycosyl acceptors), giving the non-natural oligosaccharides. Consequently, construction of the new oligosaccharide chains containing the different sugar residue at the non-reducing end by the α-glucan phosphorylase catalysis probably leads to development on new applications of non-natural glyco-substrates. A. Introduction Naturally occurring oligosaccharides in glycoproteins, glycolipids, and other glycoconjugates have important roles and funcMINIREVIEW doi: 10.4052/tigg.25.57 要 約 非天然型のオリゴ糖は、糖鎖科学において新しい機能や 応用を発現することが期待されている。そのような研究にお いて酵素的グリコシル化反応は構造明確なオリゴ糖を得る有 力な手法である。例えば、α(1→4)-グルコシド結合は、α-Dグルコース1-リン酸 (Glc-1-P) をグリコシル供与体に用いる α-グルカンホスホリラーゼを触媒とする酵素的グルコシル化 によって構築できる。この酵素は、ある程度の基質認識の緩 さを有しているので、Glc-1-Pのアナログ基質を用いるα-グ ルカンホスホリラーゼによるグリコシル化反応の開拓は新規 な非天然型オリゴ糖を得る有力な手法である。上記の観点か ら、本総説では、このようなアナログ基質、すなわち種々の ヘキソース1-リン酸をグリコシル供与体に用いたα-グルカン ホスホリラーゼによる酵素的グリコシル化反応による非天然 型オリゴ糖の簡便な合成について紹介する。α-D-キシロース、 α-D-マンノース、2-デオキシ-α-D-グルコピラノース、3-ある いは4-デオキシ-α-D-グルコース、α(N-ホルミル)-D-グルコサ ミンおよびα-D-グルクロン酸1-リン酸がグリコシル供与体と してα-グルカンホスホリラーゼに認識されることでマルトオ リゴ糖(グリコシル受容体)の非還元末端への対応する糖残 基の転移反応が起こり、非天然型のオリゴ糖が得られること が見いだされた。このようなことから、α-グルカンホスホリ ラーゼ触媒による異なった糖残基を非還元末端に有する新し いオリゴ糖鎖の構築は非天然型糖素材の新しい応用開拓につ ながると考えられる。 A. はじめに 糖タンパク質、糖脂質およびその他の複合糖鎖は種々の 生体経路において重要な役割や機能を担っている(1–5)。こ

Synthesis of Non-natural Oligosaccharides by α-Glucan Phosphorylase-Catalyzed Enzymatic Glycosylations Using Analogue Substrates of α-D-glucose 1-Phosphate.

This paper describes radical copolymerization of 2-methylene-1, 3-dithiane (a six-membered cyclic ketene dithioacetal, 1) with styrene and methyl methacrylate (MMA), The copolymerization proceeded without ring-opening of 1 to produce copolymer having dithioacetal group. The structure of the copolymer was determined by 1H, 13C NMR, IR, and UV spectroscopies. Polymerizability of 1 was higher than that of styrene and MMA. Monomer reactivity ratios determined are r1 = 3.35 and r2 = 0.03 (M2 = styrene) or r1 = 4.12 and r2 = 0.08 (M2 = MMA). The refractive index values of the resulting copolymers were also measured.

Jun-ichi Kadokawa

Papers

Enzymatic Synthesis of Glyco-macromonomers

Hierarchically controlled assemblies from amylose analog aminopolysaccharides by reductive amination: From nano- to macrostructures

Synthesis of Non-natural Oligosaccharides by α-Glucan Phosphorylase-Catalyzed Enzymatic Glycosylations Using Analogue Substrates of α-D-glucose 1-Phosphate.

Radical Copolymerization of 2-MEm-1,3-Dithiane with Styrene and Methyl Methacrylate

Preparation of Polysaccharide-Polymeric Ionic Liquid Composite Materials