| POLYMERS Vol.70 No.11 |
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COVER STORY
Polymers with Conductivities are Communicative |
| COVER STORY: Highlight Reviews |
| Metallic Plastic Mediated by Ion Exchange Doping | Yu YAMASHITA, Shun WATANABE |
| <Abstract> Chemical doping of polymeric semiconductors involves the electron transfer between the host polymer and the guest dopant, representing a host-guest binary system. The successful introduction of functional dopant molecules or ions into an interstice of crystalline polymers improves the doping level. A metallic state with degenerated electrons is realized particularly via ion exchange doping. The resulting high doping level and enhanced conductivity obtained could allow an in-depth understanding of electronic states in polymeric semiconductors, and may possibly open up opportunities for exploring novel functionalities of conductive polymers. Keywords: π-Conjugated Polymers / Chemical Doping / Ion Exchange / Metallic Conduction |
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| MOF Glass and Liquid for Electric/Ionic Conductivity | Satoshi HORIKE |
| <Abstract> Many crystal structures of coordination polymers (CPs) and metal-organic frameworks (MOFs) exhibiting electric/ionic conductivity have been explored in recent years. It involves metallic conductivity and superconductivity. As well as crystalline state, glass and liquid states of MOFs are developed. It attracts attention as amorphous materials for electro/ionics devices such as fuel cell and secondary battery. Synchrotron X-ray, solid-state NMR, and computational studies have revealed that MOF glass and liquid structure are correlated with their structures in crystalline states. Some examples of MOF glass and liquid possess coordination bond-network structures. MOF glasses show unique characteristics compared with conventional glasses (ceramics, organic polymers, metals, and so on) in mechanical property, phase transition, and conductivity. The soft and moldable nature of MOF glass/liquid provides more opportunity for electrochemical application. Keywords: Ion Conductivity / Electric Conductivity / Metal-Organic Frameworks / Coordination Polymers / Glass / Functional Liquid / Mechanical Property / Fuel Cell |
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| Transmitting Heat by Controlling Higher Order Structures of Polymers | Yoshitaka TAKEZAWA |
| <Abstract> Polymers are superior electrical insulating material but also are thermal insulators. Most conventional polymers do not transmit the heat well and therefore polymers are generally used as composites containing ceramics powders to improve their low thermal conductivities. Recently, renowed journals have published articles about the high thermal conductive polymers that are not composites. One report is about the widely used thermoplastic polymer, polyethylene as an ultra-drawn nano-fiber, which has the high thermal conductivity of 104 W･m－1･K－1, which is behavior like conductive metals. The other is a thermosetting polymer used in electronic devices, especially in mesogenic epoxy resin, that shows the high thermal conductivity of 5.8 W･m－1･K－1 in cross-plane direction in the interface on the substrate by controlling higher order structure. These thermal conductivities have been achieved by controlling the higher order structures of polymers. In this article I will explain the latest technologies of controlling the higher order structures of polymers to increase the thermal conductivities. Keywords: Higher Order Structure / Phonon / Thermal Conductivity / Molecular Orientation / Mesogen / Epoxy / Polyethylene |
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| COVER STORY: Topics and Products |
| Hydrogen-Bonding Conductive Polymer Electrocatalysts for Conversion and Storage of Renewable Electricity | Yuya HARADA, Tsukasa YOSHIDA |
| <Abstract> Metal-free hydrogen-bonding conductive polymer electrocatalysts (HCPCs) are promising and sustainable candidates for conversion of renewable electricity into storable chemical energies to be used on demand. This article gives a short review on our recent explorations for the HCPCs. While the π-conjugated system of the polymer main chain affords electrical conductivity, the presence of hydrogen-bonding substituents are also essential for stabilization of reaction intermediates to exhibit electrocatalytic activities for the hydrogen evolution reaction (HER) and the CO2 reduction reaction (CO2RR). Such HCPCs are obtained either by oxidative chemical vapor deposition or electropolymerization deposition. Taking poly-dopamine (PDA) as an example, the reasons for selectivities of HER and CO2RR are discussed to project possible future challenges to obtain useful hydrocarbons as products. Keywords: Hydrogen Bonding Conductive Polymer Catalysts (HCPC) / Electrocatalysis / Energy Conversion / Hydrogen Evolution Reaction/ CO2 Reduction Reaction |
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| Development of 3D Gyroid-Nanostructured Proton Conduction Pathway | Takahiro ICHIKAWA, Tsubasa KOBAYASHI |
| <Abstract> In situ polymerization of liquid-crystalline monomers in the self-assembled states is a unique strategy for creating highly-ordered-nanostructured polymer membranes. We have focused on the use of this strategy for developing gyroid nanostructured polymer films having a 3D continuous proton conduction pathway. A gemini-type amphiphile zwitterion monomer has been designed and synthesized. It forms bicontinuous cubic phases in the presence of appropriate amounts of bis(trifluoromethanesulfonyl)imide and water. By carrying out polymerization for the mixture in the liquid-crystalline state, a gyroid nanostructured polymer film with self-standing properties has been obtained. It shows a high ionic conductivity on the order of 10－1 S cm－1 when it is placed under high relataive humidity of 90%. The high ionic conductivity can be attributed to the formation of a proton hopping conduction pathway that is composed of hydrogen-bonding networks of water molecules along a gyroid minmal surface. Keywords: Gyroid / Bicontinuous Cubic Phase / Liquid Crystal / Self-Organization / Proton Conduction |
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| 2D, 3D Electron and Ionic Conductive Materials | Taichi IKEDA |
| <Abstract> This article introduces two-dimensional electron conductive materials so-called “thiophene nanosheets” and ion conductive materials based on cationic glycidyl triazolyl polymers (cationic GTPs) with three-dimensional branched side chains. Thiophene nanosheets are made from foldable polymers consisting of phenyl-capped bithiophene, oligo(ethylene glycol) and turning units via intra- and inter-molecular self-assemblies. Thiophene units form two-dimensional crystals sandwiched by ethylene glycol layers, which can exhibit comparable carrier mobility as that observed in thiophene film prepared by vacuum vapor deposition. Cationic GTPs are synthesized using copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) between glycidyl azide polymer and alkyne derivatives of ionic liquids. Thanks to the high reactivity of Cu-AAC, poly(ionic liquid)s with branched side chains were successfully prepared. It was confirmed that the glass transition temperature decreases and the ionic conductivity increases with increasing the degree of the side chain branching. In case of cationic GTP with tri-branched side chains, the highest ionic conductivity of 3.6×10－5 S/cm was recorded (at 298 K, anhydrous condition). Keywords: 2D Materials / Functional Polymers / Self-Assembly / Foldamer / Poly(Ionic Liquid)s / Ion Conductive Materials / Polyelectrolytes / Glycidyl Polymer |
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| Phase-Change Materials Using Plastic Crystals | Kensuke NAKA |
| <Abstract> Phase-change materials (PCMs) have drawn great interest in the past few decades due to their capability of absorbing and releasing latent heat within a narrow temperature interval during phase change. The design of molecular alloys using n-alkanes are often used for this purpose. Encapsulation of this system constitutes an efficient way to prevent the leakage of melted PCMs. We found that mono-functionalized heptaisobutyl-substituted polyhedral octasilsesquioxane (POSS) derivatives (R-POSSs) exhibited orientationally disordered (OD) phase transition depending on their substitutions. The tested POSS derivatives showed variable sharp endothermic peaks between －29 to 60℃. The composite films were prepared by drop-casting of a chloroform solution of PMMA with R-POSS. No appearance change of films was observed despite the heating and cooling of the films on the hotplate due to no drastic density difference below and above the OD phase transition. This result suggests that the isobutyl-substituted POSS derivatives are expected to be good candidates for PCMs. Keywords: POSS / Orientationally Disordered Phase / Plastic Crystals / Silsesquioxane / Phase-Change Materials |
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| Polymer Science and I: A Personal Account |
| Try Something New to Build Strengths | Tomoki NISHIMURA |
| <Abstract> The author has worked in different research fields at three different universities. He feels that challenging himself in new research fields has built up the author’s strengths as a researcher. In this column, he will introduce his past research experience and show the importance of taking on new challenges. |
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| Front-Line Polymer Science |
| Polymers and Supramolecules with Helical or Twisted Conformation | Tamaki NAKANO |
| <Abstract> Polymers and supramolecules with helical or twisted conformation are reviewed focusing on construction of novel chemical structure and conformational control over existing chain structure as well as novel applications and analytical methodologies. Keywords: Circular Dichroism / Catalysis / π-Stack / Cyclopolymerization / Circularly Polarized Light / Covalent Organic Framework / Aggregation / Polymer Reaction |
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