POLYMERS　Vol.69　No.10
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COVER STORY
Cutting-Edge Polymer Reaction Research
COVER STORY: Highlight Reviews
Mechanochromic Polymers Driven by Polymer Reactions Hideyuki OTSUKA, Daisuke AOKI
<Abstract> Mechanical forces applied to polymeric materials, including compression, tension, shear, and so on, cause defects to the polymer chains, resulting in the deterioration in the material properties and reducing their reliability. Therefore, stress or damage detection is expected to enable the repair or replacement of materials, improving their lifetimes and durability and increasing the understanding of the failure and deterioration mechanisms of polymeric materials. In this paper, mechanochromic polymers driven by polymer reactions are systematically described. The mechanochromophore incorporation system helps us to comprehend stress or degradation at the molecular level. Typical recent examples of mechanochromic polymers based on isomerization or cleavage of mechanochromophores are introduced. In the final part, the recent progress of radical-type mechanophores and the related mechanochromic polymers are reported. The relationship between mechano-responsive behavior and polymer architectures is also discussed.
Keywords: Polymer Reactions / Mechanochromism / Mechanochromic Polymers / Mechanofunctional Polymers / Stress Visualization / Isomerization / Polymer Chain Scission
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Recent Advances in Macromolecular Coupling Reactions Tomohiro KUBO, Brent S. SUMERLIN
<Abstract> As the toolbox of established polymer reactions is expanded, we can use more tailored approaches to meet various synthetic needs. Herein, we highlight polymer-polymer coupling reactions that demonstrate efficacy for block copolymer synthesis and bioconjugation.
Keywords: Polymer-Polymer Coupling / Block Copolymers / Living Polymerization / Functional Polymers
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COVER STORY: Topics and Products
Molecular Conjugation by Controlled Click Chemistry Suguru YOSHIDA
<Abstract> On the basis of diverse reactivities of azides and azidophiles including terminal alkynes and cyclooctynes, we have developed several methods for controlling click chemistry. Indeed, the transformations involving selective triazole formations allowed for the efficient preparation of unsymmetric bis(triazole)s using diverse platform molecules.
Keywords: Click Chemistry / Azide / Alkyne / Cycloalkyne / Triazole
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Reversible Transformation Between Ionic Liquids and Coordination Polymers Tomoyuki MOCHIDA
<Abstract> We synthesized ionic liquids and poly(ionic liquid)s containing cationic ruthenium sandwich complexes. These liquids formed coordination polymers upon photoirradiation, accompanied by changes in ionic conductivity and viscoelasticity. The products underwent reverse reactions upon heating, thereby enabling the reversible control of the physical properties by the application of light and heat.
Keywords: Ionic Liquids / Poly(ionic liquid)s/ Ruthenium Complexes / Photochemical Reaction / Ionic Conductivity
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Controlled Degradation by Polymer Reaction Nobuhiro KIHARA
<Abstract> Degradation should be suppressed during use even for the highly degradable polymer. Since all-or-nothing control is impossible when a natural stimulus is used to initiate the degradation, an artificial stimulus must be applied. We have reported that diacylhydrazine is stable in air although it degrades rapidly by the action of sodium hypochlorite solution. Polydiacylhydrazine is a typical high performance polymer, while it is oxidized to carboxylic acid and nitrogen gas. Novel bisphenols bearing the diacylhydrazine moiety were developed as the curing agent for epoxy resins, and the cured resin can be used as an adhesive. The adhered materials can be dismantled spontaneously by sodium hypochlorite solution to recover the original materials without the trace of the adhesive on the surface. Diacylhydrazine-crosslinked gel was prepared. When starting from the copolymer of methyl acrylate, the original polymer can be recovered after the crosslinking-decrosslinking cycle. A crosslinked transparent monolith, which undergoes oxidative degradation, can be prepared by bulk copolymerization with bifunctional monomer bearing diacylhydrazine.
Keywords: Artificial Stimulus / Sodium Hypochorite / Oxidative Degradation / Diacylhydrazine / Epoxy Resin / Degradable Adhesive / Reversible Crosslinking / Crosslinked Monolith
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Analysis of Polymer Degradation Reactions Shogo YAMANE, Junji MIZUKADO
<Abstract> Recently the application of polymer materials to transportation equipment such as automobiles and airplanes has been expanding, and deterioration and stability of polymer have become more important. This paper introduces the latest research of polymer degradation and stability evaluation using mass spectrometry. Degradation analysis using high-resolution MALDI-TOFMS has the feature that the structure can be determined from the composition formula. Furthermore, it becomes possible to easily classify each degraded structure by KMD analysis. LC-MS is effective for qualitative / quantitative analysis of additives that have a great influence on the stability of polymer materials, however, there are some points to note in quantitative analysis. The mass spectrometry methods introduced in this paper are effective not only for degradation analysis but also for structural analysis of polymers and analysis of polymer reactions.
Keywords: Polymer Degradation / Stability / Mass Spectrometry / MALDI-TOFMS / LC-MS
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Material Development in New Polyurethane Synthesis Reactions using CO2 Gas as Raw Material Kazuya KIMURA
<Abstract> Recently, the development of sustainable polymers has gained great attention. We focused on the urethane synthesis reaction using CO2 as a raw material and tried to use it for creating a new material. Our developed materials were polyurethane resin obtained from epoxy, CO2, and amine. Major features of this materials are not only using of CO2 in its production but they also have unique chemical structures. They are a new type of polyurethane resins having hydroxyl groups, so we call them HPUs. Compared to conventional urethane resin, HPU has a higher mechanical strength, and has excellent gas barrier properties and metal adhesion. On the other hand, HPU has some weak points in handling when used in similar ways as existing polyurethane (PU) substitute applications. Therefore, we tried to develop a new material that eliminates the drawbacks by copolymerizing PU. As a result, we have achieved the development of a new polyurethane product that can be differentiated in terms of performance and can be used in the same way as conventional PU.
Keywords: Sustainable Polymers / Polyurethane Resine / Gas Barrier / Metal Adhesion
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Polymer Science and I: A Personal Account
Growing Sulfur Yuki ARAKAWA
<Abstract> This introduction describes the very small journey of my research on sulfur-containing liquid crystal materials and the associated factors that inspired my research.
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Front-Line Polymer Science
Recent Progress in Alternative Copolymerization of Carbon Dioxide and Epoxide Masayoshi HONDA, Hiroshi SUGIMOTO
<Abstract> Recent advances in aliphatic polycarbonate synthesis via alternating copolymerization of CO2 and epoxide are summarized. First, the development of the catalyst is described. In addition to the widely used Co salen and porphyrin catalysts, various elements such as Cr, Al, Fe, Ni, Zn, B based catalysts with various ligands have been reported. Binary Co and bimetallic catalyst systems have been intensively researched. Secondly, the improvement of the properties of aliphatic polycarbonate is described to develop appropriate applications. Epoxides with sterically bulky pendant groups drastically improved the glass transition temperature. The controll of stereoregularity and the formation of the stereocomplex gave a cristallinity that cannot be observed in atactic polymers. The pendant hydroxy or carboxyl groups have an interesting effect on hydrophilic-hydrophobic and thermal properties. At last, other types of polymerization are introduced: copolymerization of CO2 and oxetane, and polycondensation of CO2 and diol.
Keywords: Alternative Copolymerization / Carbon Dioxide / Epoxide / Aliphatic Polycarbonate
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