高分子 Vol.70 No.8
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特集 力を可視化する
展望 COVER STORY: Highlight Reviews
Measuring Forces/Stresses Inside a Developing Embryo
杉村 薫
<要旨> アクチンフィラメントや核ラミナなどの生体高分子は、細胞の力の生成と情報応答の場である。本稿では、個体発生過程で細胞が生成、感知する力を計測する技術について解説する。とくに、高分子化学と親和性が高い力センサーを重点的に取り上げる。最後に、高分子化学と生命科学の融合研究の可能性について展望を述べる。
Keywords: Mechanics / Development / Morphogenesis / FRET
Effects of Polymer Deformation and Relaxation on Flow Characteristics
日出間 るり・鈴木 洋
<要旨> きわめて低濃度な高分子溶液であっても、流体中の高分子の変形と緩和は、流動場全体を大きく変化させ得る。本稿では、溶液の濃度からは予想されない、高分子溶液の非線形な流動現象について紹介する。とくに伸長流動に着目し、伸長流動下の高分子溶液の定量化、伸長流動場中の高分子挙動の可視化、これらが流体に与える影響について紹介する。
Keywords: Rheology / Complex Fluids / Extensional Flow / Drag Reduction / Microfluidics
トピックス COVER STORY: Topics and Products
Low Friction Polymer Additives for Oil-Based/Water-Based Lubrication
山田 真爾
<要旨> Recent nanotribological studies on the polymer additives which are useful to obtain low-friction surfaces in oil-based and water-based lubrication are described. The surface forces apparatus (SFA) technique was used to investigate the sliding film structures and friction properties of polymer additives adsorbed on mica surfaces from their oil-based/water-based solutions. By using the optical technique of the SFA (fringes of equal chromatic order, FECO), we measured the thickness of intervening lubricant films with the resolution of 0.1 nm simultaneously with the friction measurements. The results enabled us to discuss the molecular structures and sliding conformations that are suitable for reducing friction in boundary lubrication of oil-based/water-based systems.
Keywords: Polymer Additive / Nanotribology / Boundary Lubrication / Surface Forces Apparatus
Emissive Polymer Chemosensors that are Capable of Visualizing Pressures
中舍 琴恵・福原 学
<要旨> External stimulus-responsive polymers serve as great promises for wide applications in material science and practical diagnosis. In particular, pressure is one of the most ubiquitous external stimuli and can cause changes in polarity and viscosity of solvents used. Recently, hydrostatic pressure, or isotropic mechanical force, has attracted much attention in the fields of mechanochemistry and mechanobiology. We have also demonstrated the hydrostatic pressure-control concept. In this review, we want to highlight our recent studies on emissive polymer chemosensors controlled by hydrostatic pressure.
Keywords: Chemosensors / Hydrostatic Pressure / Pyrene / Aggregation-Induced Emission / Peptide / Polystyrene / Spectroscopy
蛍光Force Probeで高分子鎖のナノ応力集中を診る
Fluorescent Force Probe for Evaluating Nanoscale Stress Concentration of Polymers
小谷 亮太・齊藤 尚平
Ryota KOTANI, Shohei SAITO
<要旨> Understanding nanoscale force transmission in pico-to-nanoNewton range is important in polymer physics. While physical approaches have limitations to analyze local force distribution in condensed environments, chemical doping of force probe is promising. However, there are demanding requirements to probe the local force without structural damage, which corresponds to the force range below covalent bond scission (nanoNewton) and over thermal fluctuation (picoNewton). Here we report a conformationally flexible dual fluorescent force probe with 100-picoNewton threshold that realizes ratiometric analysis on nanoscale force distribution in stretched polymer chain network. Without changing original polymer properties, the force distribution has been reversibly monitored in real time. Chemical control of the probe location demonstrated that local stress concentration is twice more biased at crosslinkers than main chains particularly in a strain-hardening region. Due to the sensitive response, proportion of the stressed force probe was estimated more than 100 times higher than activation ratio of conventional mechanophores.
Keywords: Force Probe / Mechanophore / Polymer Physics / Rheology / Stress Concentration / Polyurethane / Fluorescent Probe / FLAP
Cellulose-Based Cholesteric Liquid Crystalline Elastomers for Visualization of Mechanical Stress and Strain
早田 健一郎・岩田 直人・古海 誓一
Kenichiro HAYATA, Naoto IWATA, Seiichi FURUMI
<要旨> Cellulose is the most abundant natural polymer on the Earth. Hydroxypropyl cellulose (HPC) derivatives are known to exhibit cholesteric liquid crystal (CLC) phase with visible Bragg reflection. Although the viscous CLCs of HPC derivatives show the changes in reflection color by mechanical compression, the changed reflection colors are not stable due to the molecular reorientation by diffusion. On the other hand, we successfully prepared the CLC elastomer (CLCE) films of crosslinked HPC derivatives with a capability to reversibly change the reflection colors by a compression-release process. Very recently, we have developed the CLCE films with high flexibility fabricated by new types of HPC derivatives, which thereby enable the reversible reflection color changes by not only compression, but also a stretch process. Finally, we demonstrated the visualization of both tension and strain by the CLCE films. Therefore, our cellulose-based CLCE films with capabilities to visualize mechanical stress and strain can be potentially applicable to a wide variety of industrial fields in the future.
Keywords: Cellulose / Cholesteric Liquid Crystal / Elastomer / Stretch / Bragg Reflection / Visualization / Mechanical Stress / Strain
Development of Mechano-Optical Sensing Materials for Polymer Robotics
久野 恭平・堤 治
<要旨> Strain sensors are a key component to develop next-generation robots – the soft robot. For such applications, the electronic sensing using flexible electronic materials are continuing to be at the forefront of the sensing technology. Recently, the optical sensing systems have attracted much attention because of their noninvasivity, sensitivity, and spatio-temporal resolution. Here, we introduce the trend in strain sensors, and propose a potential application of chiral-nematic liquid crystal elastomers. Indeed, there is remarkable maturity in the development of numerous stimuli-responsive liquid crystal elastomers. However, the control of the recovery process after the stimuli removal has not enjoyed comparable growth. Interestingly, our materials design concept of layering the elastomers with other materials allows us to arbitrary tune the rate of the recovery process in both macroscopic deformation and microscopic molecular orientation. Based on the concept, we have suceeded to fabricate a mechano-optical sensor with high sensitivity and high spatio-temporal resolution. This concept would open a pathway to control the recovery process in various stimuli-responsive liquid crystal elastomers.
Keywords: Chiral-Nematic Liquid Crystal / Liquid Crystal Elastomer / Soft Elasticity / Strain Sensor / Soft Robot
グローイングポリマー Polymer Science and I: A Personal Account
Physics Never Ends
作道 直幸
<要旨> I am researching gel physics at the Sakai-Chung group using “tetra gels,” which have controllable and homogenous networks. With the help of Prof. Sakai, Prof. Chung, Dr. Katashima, and students, we create new physics one after another. The physics of polymer gels never ends.
高分子科学最近の進歩 Front-Line Polymer Science
Structure and Dynamics of Macromolecules Observed by Terahertz Spectroscopy
保科 宏道
Hiromichi HOSHINA
<要旨> In this paper, polymer spectroscopy in the terahertz (THz) frequency region is reviewed. Due to the recent development of the THz spectroscopic technique, observation of polymer spectra in a lower frequency region has become much easier. THz vibrational spectra reflect intermolecular vibrational motion. Especially, crystalline polymers show characteristic vibrational bands in the THz region, which can be used for the quantitative analysis of polymer crystallinity and crystal structure. Interestingly, polymers with hydrogen bonds show characteristic bands in the frequency region of 2-4 THz. Water adsorption is also a good research target for THz polymer spectroscopy, because small amounts of bound water drastically changes the spectra. Dynamics of bound water in the polymer sample is studied by THz spectroscopy combined with ab initio molecular dynamics simulation. THz spectroscopy provides rich information about structure and dynamics of polymers, and is expected to become a novel tool for polymer science.
Keywords: Terahertz Spectroscopy / Polymer / Hydrogen Bonding / Bound Water / Dynamics