| POLYMERS Vol.63 No.12 |
| >>Chinese | >>English | >>Japanese | >>Korean |
COVER STORY
What Are Polymer-like Features?: Studies on Assemblies and Behaviors |
| COVER STORY: Highlight Reviews |
| Self-Organization in a Single Molecular Chain | Kenichi YOSHIKAWA |
| <Abstract> Living cels maintain their lives based on the information embedded in genomic DNA, exhibiting the length of the order of mm-cm. Unique bahavior of giant DNA is described by focusing the topics: 1) Nanoscaled ordered structures generated from single DNA molecules, 2) Emergenve of intrachain segregation, with the coexistence of compact and relaxed conformation, 3) Cell-sized confinement under crowding condition. It is suggested that the unique crowding propertied of giant DNA molecules introduced in the present article would be reproduced for various synthetic polymers in a near future. Keywords: Genomic DNA / Single Macromolecules / Self-Organization / Nano-Ordered Structure / Folding Transition / Micro-Confinement |
| Top of the Page▲ |
| Cooperative Effects in Photoresponsive Liquid Crystalline Polymers | Takahiro SEKI |
| <Abstract> Photoreactions in ordered media have been the subject of numerous studies. In liquid crystalline polymer systems, molecules are packed with substantial motional freedom, and photoreactions trigger changes in the packing state or the collective molecular orientation. The effects can be amplified from molecular motions to the mesoscopic, microscopic, and even macroscopic levels due to strong motional cooperativity. These processes can provide various types of smart, light-responsive materials. This review introduces, three research areas, photoalignment, photo-driven migrations, and photomechanical systems, focusing onto azobenzene-containing liquid crystalline polymer systems. Light can trigger motions in a non-contact manner, thereby, precise evaluations of the hierarchical motions become available. It is expected that continuing efforts in these areas will provide precise understandings on the motility and cooperativity in liquid crystal polymer materials, and extend this gained knowledge into numerous applications. Keywords: Liquid Crystalline Polymers / Photoresponsive Films / Azobenzene / Linearly Polarized Light / Photoalignment / Photo-Driven Migrations / Photomechanical Effects |
| Top of the Page▲ |
| Novel Molecular Design for Thermo-Sensitive Polymers on the Basis of Supramolecular Interaction | Kazuki SADA, Kenta KOKADO |
| <Abstract> A new molecular design for thermo-sensitive polymers on the basis of supramolcular interactions is proposed. Our design is based on a ternary system that consists of (1) a polymer bearing strong associative functional groups to provide an attractive interaction between the polymer chains, (2) an “effector” that can interact with the functional groups in the polymer chains and affect the solubility of the polymer, and (3) a solvent as a background medium that rarely interferes with the polymer-polymer or polymer-effector interactions. Two typical examples that use hydrogen bond and charge-transfer interactions are shown in this mini-review. Keywords: Thermo-Sensitive Polymer / Supramolecular Interaction / LCST(Lower Critical Solution Temperature) / UCST(Upper Critical Solution Temperature) / Solubility / Hydrogen Bond / Charge Transfer Interaction |
| Top of the Page▲ |
| Polymer Characteristics Observed in Associating Polymers | Tsuyoshi KOGA |
| <Abstract> Polymer characteristics are suppressed by intramolecular association in polymers with many associative groups along the chain. When such intramolecular association is destroyed by external stimuli, drastic changes of physical properties occur in the associating polymers. This article reviews recent developments in the study on the mechanical and rheological properties of such associating polymers with paying special attention on polymer characteristics. Keywords: Associating Polymer / Intramolecular Micelle / Force-Elongation Relation / Rheology / Shear Thickening / Shear-Induced Gelation / Shake Gel / Molecular Simulation |
| Top of the Page▲ |
| Living Supramolecular Polymerization | Kazunori SUGIYASU, Soichiro OGI, Masayuki TAKEUCHI |
| <Abstract> In contrast to conventional polymer chemistry, an important challenge in realizing living polymerization still remains in the field of supramolecular polymer chemistry. Herein, we briefly discuss the possibility of living supramolecular polymerization based on the supramolecular polymerization mechanisms: i.e., isodesmic and cooperative models. On the basis of this consideration, we present the first reported living supramolecular polymerization that we have recently achieved. Considering the tremendous contribution of living polymerization techniques to conventional polymer science so far, our finding should be a significant step forward toward the further development of supramolecular polymer chemistry. Keywords: Supramolecular Polymerization / Living Polymerization / Far-from-Equilibrium Thermodynamic Systems |
| Top of the Page▲ |
| COVER STORY: Topics and Products |
| Chiral Discrimination Materials Based on Dynamic Nature of Helical Polymers | Katsuhiro MAEDA |
| <Abstract> Here we describe a unique polyacetylene-based chiral stationary phase (CSP) whose elution order can be reversibly switched. The macromolecular helicity was induced in a polyacetylene bearing 2,2’-biphenol-derived pendants in the solid state as well as in solution by noncovalent interactions with a nonracemic alcohol through significant amplification of the chirality, which could be retained even after complete removal of the alcohol. The helical handedness of the polymer could be further reversibly switched in the solid state upon interaction with the opposite enantiomeric alcohol and its subsequent removal, which enabled this polymer to be the first switchable CSP for HPLC. Keywords: Helical Polymer / Memory / Chiral Stationary Phase / Enantioseparation / Chiral Discrimnation |
| Top of the Page▲ |
| Dimension-Controlled Assemblies of Orderly Arranged Charged π-Electronic Systems | Hiromitsu MAEDA |
| <Abstract> Arrangement of well-designed charged π-electronic systems in ordered structures is highly important for the introduction of multiple π-systems in supramolecular assemblies. Ion binding enables the fabrication of charged π-systems by complexation of electronically neutral π-systems with (inorganic) ions. In fact, anion complexes of anion-responsive π-systems have been found to provide various ion-based assembled structures as supramolecular gels and thermotropic liquid crystals by combination with appropriate cationic species. Derived from favorable overlap of charged π-planes, ion-based materials with the contributions of charge-by-charge and charge-segregated arrangements provided effective charge carrier mobilities, showing semi-conductive properties. Highly ordered arrangement of charged π-electronic systems has been found to be a key factor to exhibit the enhanced performance as fascinating electronic materials. Keywords: π-Electronic Systems / Ion Binding / Soft Materials / Supramolecular Assemblies |
| Top of the Page▲ |
| Relationship Between Physical Properties of Tetra-PEG Gels and Polymer Chains | Takamasa SAKAI, Takuya KATASHIMA |
| <Abstract> Polymer gels are swollen 3D polymer networks. Because a polymer network consists of polymer chains connected by crosslinks, the physico-chemical properties of polymer gels are inherently related to those of a polymer chain. However, the full understanding of these relationships have been inhibited by the inherent heterogeneity of polymer networks. In this paper, in order to discuss the relationship between the mechanical properties of polymer gels and the single polymer chain, we utilize Tetra-PEG gels, which are polymer gels with well-controlled network structures. The ultimate elongation ratio of the Tetra-PEG gels increased with increases in polymer volume fraction and degree of polymerization of network strands, and was independent of the connectivity. These results do not obey the Kuhn model, in which the principal concept is based on a single polymer chain. We propose a new semi-empirical model, where the initial length of a network strand is not defined only by the degree of polymerization of a network strand, but influenced by the polymer volume fraction. Keywords: Tetra-PEG Gel / Polymer Gels / Ideal Network / Ultimate Elongation Ratio |
| Top of the Page▲ |
| Controlling a Molecular Assembly by Light | Shiki YAGAI |
| <Abstract> Diarylethenes have rarely been used in the design of photoresponsive molecular assemblies featuring a well-defined morphology transition because of rather small structural changes upon photoisomerization. We demonstrate that a supramolecular design based on the parallel conformation of diarylethenes enables the construction of photoresponsive dye assemblies that undergo a remarkable nanomorphology change. The parallel conformer of diarylethene was stabilized by cooperative stacking of perylene bisimide dyes through complementary hydrogen bonds. UV/Vis spectroscopy, atomic force microscopy, and molecular modeling showed that our diarylethene and perylene building blocks coassembled in nonpolar solvent, affording well-defined helical nanofibers comprising dimeric J-aggregates of perylene dyes. Upon irradiating the coassembly solution with UV and visible light in turn, a reversible morphology transition between nanofibers and nanoparticles took place. Furthemore, our system involves the generation of a new self-assembly pathway by means of photocontrol. Keywords: Supramoleuclar Polymer / Functional Dye / Photochromism / Self-Assembly / Hydrogen Bond / Nanostructures / Supramolecular Chemistry |
| Top of the Page▲ |
| Polymer Science and I: A Personal Account |
| Leave My Life to Intuitions | Yuji HIRAI |
| <Abstract> Now I’m satisfied with my research situation, which is the results of leaving my life to intuitions. My research will be moving ahead at an accelerated pace by the beautiful nature of Hokkaido and my students. |
| Top of the Page▲ |
| Front-Line Polymer Science |
| Recent Progresses in Organic Field Effect Transistors Based on π-Conjugated Organic Molecules | Hiroki MORI, Yasushi NISHIHARA |
| <Abstract> Organic field-effect transistors (OFETs) have gained considerable interest as the key elements for realizing future ubiquitous electronics because they have a large number of advantages such as the flexibility, light-weight, and ease of design. In this article, recent material developments in this field, including phenacene-type molecules, thienoacene derivatives, and a series of donor-acceptor (D-A)-type polymers, are summarized. Phenacene-type molecules possess a low HOMO level and a wide band gap. Recently, among phenacene-type molecules, picene, [6]phenacene, and [7]phenacene have been recognized as unique molecules because using them high field-effect mobility in the transistors can be realized. In addition, in some cases the FET properties were found to be highly improved by an incorporation of alkyl chains to the parent motif and one can expect to apply these molecules to a solution-process owing to a high solubility in common organic solvents. Furthermore, recent progress of diketopyrrolopyrrole (DPP) and isoindigo (IID)-based D-A polymers showing high mobility are introduced. Keywords: Phenacene / Organic Field-Effect Transistors / High Mobility / p-Channel Characterictics / Picene / Cross-Coupling / Polymers |
| Top of the Page▲ |
| Copyright(C) 2014 The Society of Polymer Science, Japan All Rights Reserved. |