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Volume 78, Issue 4
Displaying 1-9 of 9 articles from this issue
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[in Japanese]2005 Volume 78 Issue 4 Pages 129
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSDownload PDF (142K) -
Jian Ping GONG2005 Volume 78 Issue 4 Pages 130-134
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSThe author's research group have systematically studied the surface sliding friction of hydrogels, and various unique features in gel friction have been discovered. The frictional force and its dependencies on the load are quite different depending on the chemical structures of the gels, surface properties of the opposing substrates, and the measurement condition, which are completely different from those of solids. Most importantly, the friction coefficient of gels exhibits a value as low as 0.001, which cannot be obtained from the friction between two solid materials.
Therefore, gels have a high potential as a low friction material, such as an artificial cartilage. However, conventional gels are mechanically too weak to be used as load bearing materials. The author's research group recently developed a general method to obtain very strong gels by introducing a double network structure of the gel. These high strength hydrogels, containing 90% water, sustain a compressive pressure as high as decades of MPa and show a high wear resistance due to their extremely low friction. These gels might open new era of soft and wet materials for substituting articular cartilage and other tissues.View full abstractDownload PDF (1101K) -
Takashi MIYATA2005 Volume 78 Issue 4 Pages 135-141
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSStimuli-responsive gels have attracted considerable attention as smart materials in the biochemical and biomedical fields, since they can sense environmental changes and induce structural changes by themselves. This paper provides an overview of the important research regarding the design and applications of stimuli-responsive gels that undergo volume changes in response to pH, temperature, electric fields, specific molecules, etc. Especially, the synthetic strategies of molecule-responsive gels that exhibit swelling changes in response to a specific molecule are summarized on the basis of molecular complex and molecular imprinting. This article focuses on two types of molecule-responsive gels, that is, biomolecule-cross-linked gels and biomolecule-imprinted gels as the stimuli-responsive gels that have molecular recognition functions. The stimuli-responsive gels reviewed in this paper are expected to contribute significantly to the development of newer generations of smart biomaterials and self-regulated drug delivery systems.View full abstractDownload PDF (1303K) -
Ryojiro AKASHI, Hiroaki TSUTSUI2005 Volume 78 Issue 4 Pages 142-146
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSWe have developed “Smart Gel” light-modulation material and system, which imitate the manner of pigment cells of cephalopods, such as octopus or squids. This material exhibits tremendous ability to modulate the absorption of visible light. This material consists of stimuli-responsive polymer gel particles and pigments dispersed in the gels with a high concentration. The light-modulation mechanism of the system is a synergic effect between change of light absorption area and absorption efficiency of pigments according to reversible volume change of the colored gel particles. The essential factors dominating the light modulation ability are the concentration of pigment, the volume change ratio and size of gel particles. A test sample of the light modulator indicated supreme light modulation ability. Furthermore, a flexible and durable light-modulation film could be assembled using the light-modulation layer, which the gel particles dispersed in resin matrices. The novel light-modulation material and system own various advantages such as excellent light-modulation ability, high durability and color varieties. We anticipate the light-modulation material and system may find applications in display devices, light-modulator or other optical devices.View full abstractDownload PDF (1086K) -
Naruhiko MASHITA, Xiaorong WANG2005 Volume 78 Issue 4 Pages 147-152
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSNovel non-aqueous physical gels based on a small amount of semi-crystalline thermoplastic elastomers and a large amount of oils of low molecular weight were studied. Morphological investigation of the gels by means of X-ray CT confirmed that the gels had three-dimensionally continuous polymer cells. We name this a “Microcellular Porous Structure”. The network structure was formed by the phase separation of a homogeneous mixture of TPE/oil. It was observed that modulated structure due to spinodal like decomposition appeared in the initial stage of the phase separation; however, the modulated structure changed to the clear network structure of polymer-rich phase and clusters of spherical oil-rich phase in the late stage. Time evolution of the size D of a typical structure during the phase separation process at a constant temperature was estimated as D∝t1 in the initial stage and D∝t1/3 in the late stage. Industrial potentials of the gels and/or its super-structure were introduced. A cushion for medical and welfare use, a soft damping material made of physical gel and comb-like polymer for wide service temperature ranges, and thin film or coating having network structure were introduced.View full abstractDownload PDF (2027K) -
Kunihiko MITA2005 Volume 78 Issue 4 Pages 153-157
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSSilicone polymer which features excellent characteristics such as heat resistance, cold resistance, electrical insulation, and flame retardancy is widely used as the polymer binder for high performance thermal interface materials. There are several forms of TIM such as elastomer sheet, phase change sheet, and grease material. Recently, gel type TIM such as gel sheet, gel-forming grease, and gel type adhesive have been developed, which feature low contact resistance for lower thermal resistance and highly stable performance for long term due to gel-forming crosslinking networks.
In addition, silicone gel sheet has advantage such as excellent handling characteristics and highly electrically insulative properties suitable for power supply application. Gel-forming silicone grease material has advantage of extremely low contact resistance with very high thermal performance, which is the most suitable for computer CPU type applications. Silicone gel type adhesive has advantage of self bonding properties for metals and lastic substratum. Mainly, addition cure system has been adopted for the design of silicone gel type TIM formulation because addition cure enables much controled crosslinking networks for realizing low modulus of gel materials.View full abstractDownload PDF (878K) -
Hiroyuki OHNO2005 Volume 78 Issue 4 Pages 158-162
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSIonic liquids, room temperature molten salts, were coupled with polymer matrices to prepare gel type polymer electrolytes. The obtained films exhibited high ionic conductivity and excellent thermal stability. Since ionic liquids are non-volatile, they are used as inflammable electrolyte membrane. Performance of these gel type polymer electrolytes should deeply depend on the characteristics of the applied ionic liquids. Accordingly, some basic and advanced studies on these ionic liquids were also summarized. Well-designed ionic liquids and polymers were mixed to examine the basic characteristics such as thermal stability, ionic conductivity, etc. Some applications with these gel type polymer electrolytes were also briefly introduced.View full abstractDownload PDF (1021K) -
Kazuharu NIWA2005 Volume 78 Issue 4 Pages 163-167
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSA plastic intraocular lens (IOL) is implanted in the eye during cataract surgery to replace the human lens. Improvements in microsurgical techniques make it possible to remove a cloudy lens through a small incision. Thus, foldable IOLs that are made of soft materials were developed. Today materials for foldable IOLs are classified in three groups: silicone elastomers, hydrophobic acrylic rubbers, and hydrophilic acrylic gels. Recently, it has been reported good results from the clinical studies performed on the hydrophobic acrylic foldable IOLs (acrylic IOLs). These results suggest that hydrophobic acrylic rubbers have suitable biocompatibility to be used as material for IOLs. Actually the acrylic IOLs are made of acrylate-methacrylate copolymers. Small amount of water in these polymers induces phase transitions by temperature change, and small vacuoles called glistening appear. Effective ways to prevent glistening are the production of uniform polymer and the control of water absorption by the polymers.
The final goal of IOLs is to restore ocular accommodation. Accordingly high performance gels are required.View full abstractDownload PDF (1355K) -
[in Japanese]2005 Volume 78 Issue 4 Pages 168-169
Published: 2005
Released on J-STAGE: May 19, 2008
JOURNAL FREE ACCESSDownload PDF (290K)
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