| POLYMERS Vol.63 No.5 |
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COVER STORY
REVOLUTION IN MOLECULAR TRIBOLOGY: Lubricant Polymers and Interface Analysis |
| COVER STORY: Highlight Reviews |
| Highly Lubricating Property of Swollen Concentrated Polymer Brushes | Keita SAKAKIBARA, Yoshinobu TSUJII |
| <Abstract> Microtribological analysis using atomic force microscope (AFM) and surface forces apparatus (SFA) have revealed super-lubricating and ultralow-frictional properties of concentrated polymer brushes (CPBs), explaining the essential difference when comparing them to semi-diluted polymer brushes (SDPB). In this paper, tribological properties of confronted polymer brushes and their application to novel tribomaterials inspired by the articular cartilage of a human joint are described. Keywords: Polymer Brush / Tribology / Friction / Bottle-Brush / Cellulose Nanofiber / Bio-Compatibility |
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| Tribology on Prosthetic Polymer Materials | Yoshinori SAWAE |
| <Abstract> Ultra-high molecular weight polyethylene (UHMWPE) would be the most successful prosthetic polymer material and has been widely used in the articulating surface of hip and knee joint prostheses. However, fine wear particles released from polyethylene components of prosthtic joints cause osteolysis in the surrounded bone tissue and finaly induce the asseptic loosening of artificial joints. Therefore, the wear of UHMWPE used in joint prostheses are now recognized as a main factor limiting the joint lifetime. Many tribological researches have been conducted to understand the in vivo wear mechanism of UHMWPE and develop new prosthetic materials with improved wear resistance since 1990s. This manuscript review the knowledge accumulated during the past few decades and prospective now approaches for further improvement in the joint lifetime and functionalities. Keywords: Joint Prosthesis / UHMWPE / Wear / Wear Particles / Osteolysis / Cross-Linked PE / Oxidative Degradation |
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| Disk-to-Head Lubricant Transfer in Topical Hard Disk Drives | Paul H. KASAI |
| <Abstract> The lubricant layer atop the carbon overcoat on topical magnetic hard disks comprises a sub-mono molecular film and essentially all the lubricant molecular chains are bound to the carbon layer by a bona fide chemical bond. The disk-to-head lubricant transfer thus should not occur. The transfer still occurs. Severe and frequent disk/head interactions result in formation of Lewis acid centers of extreme acidity on the alumina surface of the slider. The observed transfer is due to mobile fragments generated by occurrences of multiple fragmentation reactions catalyzed by such centers on individual molecular chains. |
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| Analysis of Polymer Chains in the Adhesion and the Friction Processes using Theory and Simulations | Hiroshi MORITA |
| <Abstract> In 2002, OCTA, which is the simulation system for soft polymeric materials, was released and many researchers have applied OCTA to simulate the polymeric materials. Coarse-grained simulation became one of the important and the powerful tools to analyze the structure and the dynamics of these materials. The interfacial phenomena, such as adhesion or friction, are so complicated and coarse-grained simulations are expected to contribure to their analysis. Here we show examples of the simulation studies concerned with the friction and the adhesion phenomena on the basis of polymer chains, and discuss the applicability of the simulations. Keywords: Coarse-Grained Simulations / Polymer Chain / OCTA / Adhesion / Dynamics of Contact Line |
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| COVER STORY: Topics and Products |
| Structured Liquids Probed by Frequency-Modulation AFM | Hiroshi ONISHI |
| <Abstract> Frequency-modulation atomic force microscopy (FM-AFM) is a promising tool to observe the solid topography and the liquid structure at interfaces as well. The cantilever with a tip is resonantly oscillated and the shift of the resonance frequency represents liquid-induced force pushing or pulling the tip. Selected results observed on hydrophilic thiolate molecular monolayers are described. The observed, two-dimensional distributions of tip-surface force were sensitive to the composition of the solids and liquids, while insensitive to tips of different apex radii. This suggests that the observed force distribution was not much affected by the presence of the tip above the interface. Keywords: Liquid-Solid Interfaces / Liquid Structure / Thiolate Monolayers / Atomic Force Microscopy |
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| Soft Boundary Layers for Low-Friction Surfaces | Tomoko HIRAYAMA |
| <Abstract> b Tribologyb is one of the important engineering fields focusing on friction, wear and lubrication in sliding surfaces in machines. Soft boundary layer reducing friction under boundary lubrication has been recently attracting much attention, and new analytical approaches and developments of the layers have been proposed using interdisciplinary knowledge. Authors proposed to apply neutron reflectometry to solid-liquid interface to analyze the structure of soft boundary layer formed by oiliness additives. Fitting operation between the experimental and theoretical reflectivity profiles revealed that the oiliness additive layers on metal surfaces were very thin, less than several nanometers. To achieve much lower friction surfaces, the authors developed an oil-compatible concentrated polymer brush layer as a new soft boundary layer. Macro-tribological tests showed that the friction coefficients between the surfaces with polymer brushes under oil lubrication were less than 0.01, while those between the bare surfaces were larger than 0.1. Further development of soft boundary layers is a promising way for excellent tribological surfaces in near future. Keywords: Tribology / Lubrication / Soft Boundary Layer / Low-Friction / Lubricating Oil / Additive |
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| “See” Initiates “Learn”! Real Time TEM Observation of Actual Contact Area | Takaaki SATO, Tadashi ISHIDA, Hiroyuki FUJITA |
| <Abstract> The observation of nanoscale deformation in real time is a significant step toward understanding the mechanisms of friction and lubrication. Our micromachine combined with a TEM experimental setup allowed us to measure the deformation, force and cross-sectional area of the actual contact area. We have compared observations of several materials such as Ag, DLC and Si. Keywords: Nanotribology / Friction / TEM |
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| Polymer Science and I: A Personal Account |
| Successful Experience | Takeshi NAMIKOSHI |
| <Abstract> In the beginning of my studies I felt incompetent. Then success in research taught me the pleasure of research in polymer chemistry. I was able to change myself from this successful experience. I hope that it will continue to do so in the future and bring me a lot of success. |
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| Front-Line Polymer Science |
| Cylindrical Polymer Brushes as Shaped Molecular Nanoobjects | Yongming CHEN, Yechao YAN |
| <Abstract> As one kind of unimolecular nanoobjects with controlled shape from sphere to cylinder, molecular bottlebrush has a well-defined structure and tunable hierarchical functionalities. In this article, controlled synthesis of cylindrical polymer brushes and its application to fabricate unimolecular nanoobjects are described. Keywords: Cylindrical Molecular Brushes / Nanoobjects / Polymer Synthesis |
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