Friction and lubrication of hydrogels - its richness and complexity
Friction and lubrication of hydrogels - its richness and complexity
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DOI：
10.1039/b603209p
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发表时间：
2006-01-01
期刊：
影响因子：
3.4
通讯作者：
Gong, Jian Ping
中科院分区：
文献类型：
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作者：
Gong, Jian Ping
生物结缔组织，如软骨和角膜基质，本质上是由纤维性胶原和蛋白多糖组成的水凝胶。尽管我们在生物软组织中观察到了令人着迷的摩擦学行为，例如动物软骨之间极低的摩擦力，但人们对这种水凝胶的表面特性知之甚少。我们认为，以凝胶状态存在于细胞外基质中的溶剂化聚合物网络在软骨的特殊摩擦行为中起着至关重要的作用。为了阐明溶剂化聚合物基质的一般摩擦学特征，研究了各种水凝胶的摩擦行为，观察到了非常丰富和复杂的摩擦行为。摩擦力及其与载荷的依赖关系随凝胶的化学结构、相对衬底的表面性质和测量条件的不同而不同，这些与固体完全不同。最重要的是，凝胶的摩擦系数m在很大的范围内变化，并且呈现出非常低的值(u接近10(-3)-10(-4))，这是两种固体材料之间的摩擦所不能获得的。提出了一个排斥-吸附模型来解释凝胶摩擦，该模型认为，当凝胶的高分子链与基材非粘(排斥)时，摩擦是由于聚合物链水化层的润滑，而当吸附的高分子链与基材粘合时，摩擦是由于吸附的高分子链的弹性变形造成的。
Biological connective tissues, such as cartilage and corneal stroma, are essentially hydrogels consisting of fibrous collagen and proteoglycans. Little is known of the surface properties of the hydrogel, although we observe fascinating tribological behavior in biological soft tissues, such as extremely low friction between animal cartilages. We consider that the role of the solvated polymer network existing in the extracellular matrix as a gel state is critically important in the specific frictional behavior of cartilages. In order to elucidate the general tribological features of a solvated polymer matrix, the friction of various kinds of hydrogels has been investigated, and very rich and complex frictional behaviors are observed. The friction force and its dependence on the load differ with the chemical structure of the gels, surface properties of the opposing substrates, and the measurement conditions, which are totally different from those of solids. Most importantly, the coefficient of friction of gels, m, varies over a wide range and exhibits very low values (mu approximate to 10(-3)-10(-4)), which cannot be obtained from the friction between two solid materials. A repulsion-adsorption model has been proposed to explain the gel friction, which says that the friction is due to lubrication of a hydrated layer of polymer chains when the polymer chain of the gel is non-adhesive (repulsive) to the substrate, and the friction is due to elastic deformation of the adsorbed polymer chain when it is adhesive to the substrate.