open access

https://hdl.handle.net/2115/57276

両性イオン性ゲルの表面摩擦に関する研究 [全文の要約]

英語

2014-09-25

Hokkaido University

https://www.lib.hokudai.ac.jp/dissertations/copy-guides/

Scientists in polymer science are attempting to provide synthetic tissues that serve as alternative biomechanical role in the body, such as articular cartilage, semilunar cartilage, tendons, and ligaments. To effectively replace the natural tissues with artificial materials , a number of significant engineering challenges like suitable elastic modulus, high mechanical strength, appropriate water content, low surface friction and wear are to be solved . Hydrogels have provided most of these demands until now. an articular cartilage,that is a kind of hydrogel containing 70% water exhibits little wear under a load as high as several to a hundred megapascals and millions of cycles with a wide range of sliding velocities. Gong and co-workers have reported a unique method of obtaining hydrogels with extremely high mechanical toughness which is a composition of two networks-a polyelectrolyte and a neutral polymer (double-network hydrogel).Later on a number hydrogels with different characteristics have been designed for different various purposes. Some of them show low friction and low wear properties which opens a new era of soft and wet materials as substitutes for articular cartilage and other tissues. Studies on the surface sliding friction of various types of bulk hydrogel revealed very rich and complex frictional behavior In previous studies on the friction of gels against solid substrates in water, a complicated velocity dependence of the frictional stress was observed, and the frictional behavior was strongly dependent on the interfacial interaction between the gel and the solid substrate. On a repulsive surface such as a negatively charged polyelectrolyte gel on a piece of glass that has negative charges on its surface in water, we observed a monotonic increase in the friction with velocity. On an adhesive substrate, we often observed a distinct friction transition with velocity.The transition behavior was influenced by various parameters such as the chemical combination of the gel and the substrate, the viscosity of the aqueous liquid, the elastic modulus of the gel, and the normal strain (pressure) applied on the gel.This friction transition in liquids appears to be similar to the elasto hydrodynamic transition observed for solid friction in liquids. Mechanistic models have been proposed to explain the friction transition for adhesive and non adhesive interfaces. However, different hydrogels have different mechanical strength, swelling degree and chemical composition. So, it was not possible to compare the frictional characteristics of adhesive and non adhesive interfaces on a same platform. To overcome this problem using zwitterionic hydrogels can be an effective solution, which can be made adhesive and non-adhesive by altering the pH. Moreover,the swelling and mechanical properties of polyelectrolytes are susceptible to ionicstrength and pH of the swelling medium. Recently zwitterionic hydrogel composed of poly carboxymethyl dimethyl (methacryloyloxy) ethanaminium, inner salt (PCDME) is designed, which can keep its swelling and mechanical properties unchanged over a wide range of pH and ionic strength. This provides us an excellent opportunity to study the friction with various ionic strength and pH as well as to understand the adhesive and non adhesive interface in a microscopic view

甲第11552号

博士(生命科学)

(主査) 教授 龔 剣萍, 教授 芳賀 永, 特任教授 佐々木 直樹, 准教授 黒川 孝幸

生命科学院（生命科学専攻）

博士論文

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