| POLYMERS Vol.69 No.4 |
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COVER STORY
Life-Like Matter |
| COVER STORY: Highlight Reviews |
| Life with the Active Support of Macromolecules | Kenichi YOSHIKAWA |
| <Abstract> Living organisms on the earth maintain their lives with aqueous pools rich in various macromolecules. We discuss the intrinsic role of biomacromolecules on live activities. 1) It is argued that genome-size DNA exhibits the characteristic as a semiflexible polymer. It is well known that flexible polymers undergo continuous transition between coil and globule state. In contrast, semiflexible polymers undergo discrete, or on/off type, transitions. 2) DNA is a highly charged polyelectrolyte. Such a charge effect causes instability in the globule state. As a result, micro phase-segregation or intra-chain segregation is generated. 3) Crowding environment with macromolecules induces a depletion effect. Structure and function in cellular systems are expected to be supported by the depletion interaction. Keywords: Coil-Globule Transition / Higher-Order Structure / Counter-Ion Condensation / Crowding Effect / Phase Transition / DNA / Self-Organization |
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| COVER STORY: Topics and Products |
| Growing Gels that take “Nutrients” | Tasuku NAKAJIMA |
| <Abstract> Living tissues are growing materials. For example, our skeletal muscles grow bigger and stronger through physical exercise. In contrast, no synthetic materials can grow like muscles. Growth of living tissues are based on their dynamic and open nature. Their structures are continuously destructed and reconstructed by using nutrients supplied from outside. On the other hand, synthetic materials are close and static systems. They cannot take nutrients (building blocks) from outside and reconstruct their structure. In this work, we designed muscle-like self-growing materials based on tough double-network (DN) gels. DN gels can take monomers and cross-linkers from outside if immersed into their solutions. Also, given their unique internal fracture process, DN gels can autonomously construct new polymer networks upon mechanical stimuli. Based on these features, we succeeded in creating self-growing DN gels in response to mechanical stimuli similar to muscles. Polymer mass, Young’s modulus, and fracture strength of DN gels become continuously larger after repeated stretching. Keywords: Gel / Self-Growing / Self-Healing / Mechanochemistry / Metabolism / Radical Polymerization / Double Network / Muscle |
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| A Soft Actuator using PVC Gel | Minoru HASHIMOTO |
| <Abstract> Plasticized polyvinyl chloride (PVC) gel actuators exhibit a fast response in air, large deformation, and low power consumption under an electrical field, so it shows great potential for use as a new type of soft actuator. In this paper, we make a comparison between the characteristics of the PVC gel actuators and those of a muscle. PVC gel actuators are qualitatively close to the muscle, although they are a little inferior to those of the muscle in contraction strain and output stress. The elastic movement of the PVC gel actuators are similar to that of the living muscle, that is very flexible and no noise. Finally, the author believes that it is an important approach to learn the structure of a muscle to make a high performance soft actuator, and also the movement mechanism of a muscle is investigated. Keywords: Soft Actuator / Robotics / PVC / Polymer Gel |
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| Some Systems Showing Dynamic Adhesion | Takuya OHZONO |
| <Abstract> To realise smart adhesive systems that can change adhesive properties on demand as some biological systems are doing, gimmicks or tricks of the adhesive material systems that can manipulate the adhesion are required. As examples of such systems, here, two systems are briefly shown. First one is based on the topographical change of the surface that can alter the contact area of the adhesive interface. Second one is based on the viscoelasticity change of the nematic liquid crystal elastomers that affects the speed-dependent deformation property during peeling. Keywords: Dynamic Adhesion / Wrinkles / Topography / Liquid Crystal Etastomer / Viscoelasticity |
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| Spatial Hierarchical Structures and Motion of Living Systems: Spontaneous Deformation and Collective Motion | Yutaka SUMINO |
| <Abstract> Living systems produce macroscopic motion from microscopic flux of chemicals. Such spontaneous symmetry breaking can be possible under nonlinear nonequilibrium condition with autocatalytic processes. Thus, the motion of living systems should be recognized as a type of dissipative structures. As examples of biomimetic motion, here we show spontaneous deformation of oil droplets, as well as collective motion of self-propelled particles. One of the examples: an oil droplet generating an elastic aggregate at the surface shows spontaneous deformation characterized by circular extrudes. We should note that the formation process should be under nonlinear nonequilibirum conditions, and autocatalytic coupling of deformation and breakage of aggregates induces macroscopic interfacial deformation. The other examples: self-propelled particles show collectively ordered motion by local alignment of their neighbors. Interestingly, such macroscopically ordered motion can be realized just by having them in high enough density, inducing autocatalytic aligment. The nonlinear nonequilibrium condition imposed as the self-propulsion can be extracted as dissipative structure at enough high density. Keywords: Dissipative Structure / Nonlinear Nonequilibrium Conditions / Autocatalytic Process / Spontaneous Deformation / Self-Propelled Particle / Collective Motion |
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| Photocleavable Regenerative Polymeric Materials for the Solventless Tuning of Viscoelasticity | Satoshi HONDA, Minami OKA |
| <Abstract> Repeatable change in the rheological characteristic of materials caused by heat stimulation is one of the most fundamental phenomena we can experience in daily life. Yet, materials displaying a change in viscoelasticity upon photostimulation are rare. Various molecular systems have been proposed to date such as isothermal melting and crystallization of azobenzene-containing molecules upon photoisomerization. In this context, we have focused on polymeric materials containing reversibly cleavable and reformable covalent linking in molecular chains and have recently developed photocleavable regenerative polysiloxanes with hexaarylbiimidazoles (HABIs) linked in the chains. The photochemistry of HABI, i.e., cleavage of a covalent bond between two imidazoles in HABI into a pair of triphenylimidazolyl radicals (TPIRs) and recoupling of them into HABI upon irradiation and termination of photostimulation, enabled repeatable conversion of macromolecular architectures. Moreover, we have achieved solvent-free isothermal change in viscoelastic properties of PDMSs simply by photoirradiation. Keywords: Photoresponsive Polymers / Viscoelasticity / Network Polymers / Cyclic Polymers / Polysiloxane / Hexaarylbiimidazole |
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| Learn from Bone: Design of Self-Healing Ceramics | Toshio OSADA |
| <Abstract> Human bone are long lived and highly reliable due to their self-healing ability. Here, we show a new design approach for self-healing ceramics containing a 3D network of a healing activator. Keywords: Self-Healing / Ceramics / Fracture Mechanics / Microstructrue / Strength |
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| Adhesive Hydrogel Systems for using Hydrogels in Our Lives | Shingo TAMESUE |
| <Abstract> Gel materials like a jelly have high elasticity and softness. Thus, it is expected that they are used in various fields including engineering and medicals. Among them, hydrogels are excellent biocompatible materials as well as eco-friendly materials. To use hydrogel materials practically, superior adhesive hydrogel systems are required. For example, it is needed to bond hydrogels and biomaterils when we use hydrogels as artificial biomaterials, e.g. artificial muscles. However, development of adhesive hydrogel systems are difficult due to the specificity of water. Most of the adhesive hydrogel systems previously reported by researchers including us forcused on ease of preparation and strengh of adhesion. However, versatility of adhesive gel systems is also very important. Recently, we developed a versatile adhesive gel system, which can be prepared easily and has high adhesive strength, using in-situ synthesis of linear polymers inside gel networks. Keywords: Adhesive Hydrogel Systems / In-Situ Polymerization / Intercalation / Soft Materials |
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| Polymer Science and I: A Personal Account |
| Stem | Hironori MARUBAYASHI |
| <Abstract> Looking back on my research history, I have studied the polymer crystallization consistently while changing the environment. The beginning of my research is the encounter with poly(L-lactic acid). I would like to challenge unexplored areas of the polymer crystallization research by complementary use of real- and reciprocal-space multiscale analyses. |
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| Front-Line Polymer Science |
| MOF for Polymer Chemistry | Takashi UEMURA |
| <Abstract> An emerging trend in metal-organic frameworks (MOFs) is hybridization with polymers, which is the subject of this review. The use of designable MOF nanopores for polymer synthesis can facilitate multi-level structural control over the products. In addition, construction of the host-guest nanocomposites between MOFs and polymers provides unprecedented material platforms to accomplish many nanoscale functions. Keywords: Metal Organic Frameworks / Polymer / Nanochannel / Controlled Polymerization / Assembly / Nanocomposite / Separation |
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