高分子　Vol.70　No.4　2021年4月

高分子　Vol.70　No.4

特集　薄くて熱い！二次元材料が創る未来

展望　COVER STORY: Highlight Reviews

二次元共有結合性有機骨格の化学
The Chemistry of Two-Dimensional Covalent Organic Frameworks

江　東林
Donglin JIANG

＜要旨＞共有結合で構成ユニットを二次元的に規則正しく連結するとシート状高分子が形成され、重合反応の進行にともなって積層・結晶化し、共有結合性有機骨格を生成する。従来の鎖状高分子とは異なり、二次元共有結合性有機骨格は特異な原子層構造、πカラム構造および一次元チャンネル構造を創り出す。本稿では分子設計、合成、機能開拓および今後の課題について概説する。
Keywords: Two-Dimensional Polymers / Covalent Organic Frameworks / Polycondensation / Topology Diagram / Adsorption / Mass Transport / Catalysis / Semiconductors

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二次元高分子の合成
Synthesis of Two-Dimensional Polymers

坂本　純二
Junji SAKAMOTO

＜要旨＞シート状の二次元高分子には従来の紐状高分子とは大きく異なる性質が期待できる。その反面、二次元高分子を安価に大量合成する技術は未だ開発の発展途上にある。本記事では二次元高分子の合成アプローチについて、これまでのマイルストーンと最近の研究例を交えて解説し、今後の展望と課題について述べる。
Keywords: Graphene / Nanosheet / Monolayer / Exfoliation / Crystal / Topochemical Polymerization / Dynamic Bond Formation / Cohelical Crossover

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無機ナノシートのナノ～メソスケール配列制御と機能開拓
Organization of 2D Inorganic Nanosheets into Nano- to Mesoarchitectures and Their Functions

佐々木　高義
Takayoshi SASAKI

＜要旨＞最近グラフェンをはじめとしたさまざまな二次元物質をビルディングブロックとして配列・累積・接合させ、ナノ～メソスケールの階層構造を構築・設計することが可能となり、それら人工構造をベースとする斬新な機能の発現が多数報告されている。本稿では、二次元物質におけるこのような最新の研究動向について概説する。
Keywords: 2D Materials / Nanosheets / Colloid Processes / Layer-by-Layer Assembly / Artificial Lattice / Liquid Crystal / Nano- to Mesoarchitectures / Electronics / Energy Storage and Conversion

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トピックス　COVER STORY: Topics and Products

擬ポリロタキサンナノシートの創製と機能
Creation of Pseudo-Polyrotaxane Nanosheet and Its Function

上沼　駿太郎
Shuntaro UENUMA

＜要旨＞ Nanosheets are 2D structures with thicknesses of up to 100 nm and lateral dimensions of over a few hundred nanometers. Herein, we report a novel nanosheet, called pseudo-polyrotaxane nanosheet （PPRNS）, which is fabricated via hierarchical self-assembly of bio-safe and accessible compounds. The PPRNS was formed by mixing β-cyclodextrin （CD） and carboxyl-terminated poly（ethylene oxide）₇₅-b-poly（propylene oxide）₂₉-b-poly（ethylene oxide）₇₅ （EO₇₅PO₂₉EO₇₅） in water. The β-CDs localized on a central PO segment of the axis and formed the thin layer with a thickness of 11 nm and the side length of ca. 2 μm. The thickness corresponded to the length of PO₂₉ with all trans conformation. The PPRNS was isolated by Coulombic repulsion forces between the nanosheet surfaces. Interestingly, PPRNS exhibited a structural coloration and those orientations could be controlled by a strong magnetic field. Owing to the mass-producibility and biocompatibility, PPRNS has a great potential to develop new nanosheet engineering applications, particularly in optical materials, biomaterials, and drug delivery systems.
Keywords: Supramolecules / Self-Assembly / Cyclodextrin / Structural Coloration / Magnetic-Field-Induced Orientation

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二次元炭素ナノシートのトップダウン合成
Top-Down Approaches for 2D Nanocarbons

仁科　勇太
Yuta NISHINA

＜要旨＞ Methods for preparing 2D nanocarbon from graphite are summarized. To obtain 2D nanocarbons in a stable state, it is necessary to weaken the interaction between graphene layers. Here chemistry-based methods that utilize chemical functionalization, electrochemical functionalization, and mixing with dispersants are discussed. Although these treatments enable us to produce 2D materials on a large scale, the obtained materials lack outstanding physical properties expected for high crystalline graphene. Nevertheless, the sophisticated use of these materials will bring the path to practical applications.
Keywords: Graphene / Functionalization / Electrochemistry / Dispersant / Graphite / Exfoliation / Oxidation

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無機原子層シートの合成と物性
Synthesis and Properties of Inorganic Atomic Sheets

神戸　徹也・山元　公寿
Tetsuya KAMBE, Kimihisa YAMAMOTO

＜要旨＞ In this report, we describe the bottom-up synthesis and properties of 2D materials focusing on borophene and metalladithiolene sheets. Such 2D atomically thin sheets, a representative analog of graphene, are attractive materials showing unique mechanical and electronic properties. The synthesized borophene-like sheet was found to have a completely planar skeleton with hexagonal network. Potassium cations between the layers enabled crystalline stacking of the layers, as well as dissolution in solvents as atomically thin layers. In contrast, stacked or atomically thin metalladithiolene sheets were prepared at the interface of solution of the organic ligand and corersponding metal salt. Metallic properties of both bottom-up sheets were revealed. Almost zero activation energy like a metal was suggested in the borophene-like sheet. In the case of metalladithiolene sheet, metallic nature was revealed by photoelectron emission spectroscopy.
Keywords: 2D Sheet / Atomic Layer / Bottom-Up Synthesis / Borophene / Electronic Properties

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ポリイミド薄膜の高温焼成による二次元グラファイトの作製と用途展開
Two-Dimensional Carbon Material (Graphite) Made from Polyimide and its Applications

立花　正満
Masamitsu TACHIBANA

＜要旨＞ Highly crystalline artificial graphite thin films, which are two-dimensional carbon materials produced by the pyrolysis of polyimide films, are being developed for various applications due to advances in thinning and improvement of surface smoothness. For example, a graphite thin film with a size of 10 cm square and a thickness of 1.0 μm has been realized, and a graphite thin film with a mirror-like surface and 1.0 μm thickness has also been materialized. These graphite thin films have been commercialized as electrode membrane of ion beam shape measurement sensors and ion beam charge stripping foils for particle accelerators, taking advantage of their thinness and high heat durability in vacuum. Graphite thin films are also expected to be used as thermal interface material (TIM) with low thermal resistance due to their thinness and high thermal conductivity, and as high-frequency vibrators by making use of their lightness and large Young’s modulus.
Keywords: Graphite / Polyimide / Particle Accelerator / TIM / Vibrator

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グローイングポリマー　Polymer Science and I: A Personal Account

おもしろさの発見
Discovery of Interest

日比野　利保
Toshiyasu HIBINO

＜要旨＞ Looking back on my research life, when the research moves forward, it is a common situation where I am persistently struggling. In order to do that, I think it is necessary to find it interesting.

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高分子科学最近の進歩　Front-Line Polymer Science

速度論的制御に基づく超分子金属錯体の化学
Kinetically Controlled Supramolecular Coordination Chemistry

酒田　陽子
Yoko SAKATA

＜要旨＞ While molecular recognition and self-assembly are generally thermodynamically controlled events, kinetic control of such processes is essential for the development of new supramolecular functional systems. This review summarizes the recent development of the kinetic control of functions in supramolecular coordination chemistry. The introduction of caps or gates into the apertures of the host molecules enables the kinetic control of guest uptake/release of host-guest system. The methodology to investigate protein-ligand binding mechanism in biological system can be applied to unveil the mechanism of artificial host-guest binding where the host molecule uptakes the guest accompanied by the structural change. Investigation of coordination-driven self-assembly processes and control of kinetic stability of self-assembled metal complexes are also important for the design of well-defined new supramolecular hosts.
Keywords: Supramolecular Chemistry / Metal Coordination / Kinetic Control / Host-Guest Binding / Molecular Recognition Mechanism / Self-Assembly

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ポリマーセレクト　Polymer Select

シクロオレフィンポリマーの開発史と最新開発状況
Development History and Latest Development Status of Cyclo Olefin Polymers

寳川　卓士
Takashi HOUKAWA

＜要旨＞ Cycloolefin polymer is a thermoplastic developed by Zeon Corporation for optical use and it was released in 1991. It was predominantly developed for optoelectronics application, mainly represented by CDs, digital cameras, LCD televisions, and smartphones. This paper introduces the initial development process, features, and the latest development status of cycloolefin polymer produced by Zeon Corporation.
Keywords: COP / Tacticty

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