POLYMERS　Vol.68　No.11
>> Japanese >> English
COVER STORY
Forefront of Polymers’ Termini
COVER STORY: Highlight Reviews
Telechelic Polymer Products and their Applications Yoshiki NAKAGAWA
<Abstract> A telechelic polymer having a crosslinkable functional group at both ends and having a low Tg main chain is a representative example of a industrial product that successfully utilizes the terminal structure of the polymer. The end functional groups are crosslinked each other to afford network structure of low Tg polymer, which can have elastomeric property. Since the functional group at the end of the polymer is constrained to the polymer, its reactivity is generally reduced compared to that of a similar structure of low molecular weight compound. Moreover, since it exists only at the terminal of the polymer, the concentration of the functional group is very low. However, it has been confirmed that it has sufficient reactivity for industrial use. Kaneka has developed telechelic polyethers, telechelic polyisobutylenes, and telechelic polyacrylates using controlled polymerization technology. The products are used for many purposes around the world, mainly sealant and adhesive applications utilizing features of the main chain structure.
Keywords: End Functional Group / Telechelic / Polyether / Polyisobutylene / Polyacrylate / Controlled Polymerization / Sealant / Adhesive
Top of the Page▲
Role of Chain Ends in Dynamics of Entangled Polymers Takashi UNEYAMA
<Abstract> We discuss the role of chain ends in the dynamics of entangled polymers. In entangled polymers, a polymer chain motion is strongly constrained and a chain can move only along the chain itself (the reptation motion). We consider how the chain end works during the reptation motion, and which role it plays. We also consider the relation between the diffusion behavior of the center of mass of a chain can and the end-to-end vector motion. We show that the instantaneous diffusion coefficient can be directly related to the end-to-end vector dynamics.
Keywords: Entangled Polymer / End-to-End Vector / Reptation / Diffusion
Top of the Page▲
End-Functionalization of Semiconducting Polymers and Their Functions in Organic Devices Keisuke TAJIMA
<Abstract> Electronic devices using thin films of semiconducting polymers have been attracting much attention along with the recent development of flexible electronics that can be mass-produced by printing. From the viewpoint of the material design, terminal structures of the semiconducting polymers have a considerable influence on the device performance. Several examples for the effects of the terminal modificaton on the electronic properties of the films are introdued. Various methods to control the terminal structure of the semiconductor polymers during the polymerization reactions are reviewed. The influence on the polymer structures such as the chain orientations in the thin film, and their effects on the organic electronic device are discussed. Further developments of precise controls of end-groups would lead to high performance organic electronic devices with high stability.
Keywords: Semiconducting Polymers / Thin Films / Organic Electronics / Polymerization / Interface Modification / Self-Organization / Crystallization
Top of the Page▲
COVER STORY: Topics and Products
Terminal-Group Effect of a Triptycene Derivative that has a Dominant Influence on the Physical Properties of a Polymer Fumitaka ISHIWARI, Takanori FUKUSHIMA
<Abstract> A surprising terminal-group effect on the assembly and rheological properties of PDMS is described. We have recently demonstrated that 1,8,13-trisubstituted and 1,8-disubstituted triptycenes show remarkable self-assembly behavior resulting in a highly ordered “2D＋1D” structure based on nested hexagonal packing of the three blades of triptycene. We found that when a 1,8-disubstituted triptycene is attached to the termini of a liquid polydimethylsiloxane (PDMS, Mn = 18－24 kDa), a highly viscous solid polymer with birefringence is obtained. Surprisingly, the telechelic PDMS, despite a low content of the triptycene termini (6 wt%) and a large distribution of Mw/Mn (ca. 2), can form a well-ordered “2D＋1D” structure, where layers of the PDMS domains that are formed between 2D triptycene arrays stack into a 1D multilayer structure with a layer spacing of 18－20 nm. Consequently, the complex viscosity of the telechelic PDMS was dramatically enhanced. Notably, PDMS functionalized with 1,4-disubstituted triptycenes, hardly form such an ordered structure.
Keywords: Spuramolecular Polymers / Self-Assembly / Tripodal Triptycene / Terminal Effect / PDMS
Top of the Page▲
Dynamics of the Polymer Chain End Yohei MIWA, Shoichi KUTSUMIZU
<Abstract> The chain end is present as unique local structure in polymers; the chain end often affects the physical properties of polymeric materials. On the other hand, the quantitative physical property of the chain end is still unclear. Here, the molecular motion at the chain end of polystyrene (PS) has been studied by the combination of three kinds of labeling techniques: spin-, dielectric-, and deuterium-labeling. The segmental mobility at chain end above the glass transition temperature (Tg) was determined by electron spin resonance measurement with the spin-labeling and dielectric spectroscopy with dielectric-labeling. The segmental mobility at the chain end is roughly double compared to that at the midchain sites at Tg＋50 K. On the other hand, the local Tgs at the regions around the chain end and midchain site determined by the spin-labeling and FT-IR with deuterium-labeling techniques were comparable with each other. This result reveals that the chain ends move cooperatively with numerous neigboring other segments around the Tg.
Keywords: Chain End / Labeling / Electron Spin Resonance / Dielectric Spectroscopy / FT-IR / Glass Transition Temperature / Segmental Mobility
Top of the Page▲
Control of Silica Dispersibility Using End-Modified Polymer Takuo SONE
<Abstract> The reduction of rolling resistance of tires has become a more important aspect of the tire development. Rolling resistance is primarily related to the hysteresis loss in the tire tread compounds and silica has been widely used in them. The dispersibility of silica is considered to affect hysteresis loss. Some modified styrene butadiene rubbers (SBRs) with functional groups at the polymer chain ends have been prepared by living anionic polymerization. They showed significant reduction in the hysteresis loss of rubber compounds by achieving interaction with silica. To investigate the hierarchical structure of the silica filler in rubber compounds with modified SBR small angle X-ray scattering (SAXS) was used. The distribution of particle size of silica aggregates can be obtained by the analysis of the scattering profile, and the result was that the radius of the silica aggregate is smaller and the distribution of particle size is narrower in modified SBR as compared to non-modified SBR.
Keywords: End-Modified SBR / Living Polymerization / Rubber Compound / Silica Dispersion / SPring-8 / Reverse Monte Carlo Method
Top of the Page▲
Polymer Science and I: A Personal Account
Angels & Demons Takayuki NONOYAMA
<Abstract> We do not know what will happen in the future. There are many events that we cannot control ourselves. However, your future leads not only to darkness but also to light. Be optimistic for your life.
Top of the Page▲
Front-Line Polymer Science
Progress of Cyclic Polymer Synthesis and Potentials to Functional Materials Takuya YAMAMOTO
<Abstract> The basic properties of cyclic polymers were comprehensively studied, and the synthesis of not only monocyclic but also multicyclic homopolymers and copolymers has been established. Comprehensive and rigorous investigations on topology effects are currently in progress. In particular, it is worth noting that more and more studies are focused on topology effects on various self-assembled states, i.e., micelles, gels, LB films, etc. These studies indicate that the topology effects derived from the difference between linear and cyclic can be amplified by self-assembly. It was also reported that reversible linear–cyclic topological conversion was succeeded, and special characteristics were found in π-conjugated cyclic polymers.
Keywords: Cyclic Polymer / Self-Assembly / Amphiphile / Reversible Topological Conversion / π-Conjugated Polymer
Top of the Page▲
 
Copyright(C) 2019 The Society of Polymer Science, Japan All Rights Reserved.