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Lubrication by charged polymers

机译：带电聚合物润滑

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摘要

Long-ranged forces between surfaces in a liquid control effects from colloid stability to biolubrication, and can be modified either by steric factors due to flexible polymers, or by surface charge effects. In particular, neutral polymer 'brushes' may lead to a massive reduction in sliding friction between the surfaces to which they are attached, whereas hydrated ions can act as extremely efficient lubricants between sliding charged surfaces. Here we show that brushes of charged polymers (polyelectro-lytes) attached to surfaces rubbing across an aqueous medium result in superior lubrication compared to other polymeric surfactants. Effective friction coefficients with polyelectrolyte brushes in water are lower than about 0.0006-0.001 even at low sliding velocities and at pressures of up to several atmospheres (typical of those in living systems). We attribute this to the exceptional resistance to mutual interpenetration displayed by the compressed, counterion-swollen brushes, together with the fluidity of the hydration layers surrounding the charged, rubbing polymer segments. Our findings may have implications for biolubrication effects, which are important in the design of lubricated surfaces in artificial implants, and in understanding frictional processes in biological systems.
机译：液体控制表面之间的远距离作用力从胶体稳定性到生物润滑作用，并且可以由于柔性聚合物引起的空间因素或表面电荷作用而改变。特别是，中性聚合物“刷子”可能会导致与其连接的表面之间的滑动摩擦大大降低，而水合离子可以在带电的滑动表面之间充当极其有效的润滑剂。在这里，我们表明，与其他聚合物表面活性剂相比，附着在表面上横跨水性介质摩擦的带电聚合物（聚电解质）的刷子可产生优异的润滑效果。即使在低滑动速度和高达数个大气压的压力下（典型的生物系统中），使用聚电解质刷在水中的有效摩擦系数也低于约0.0006-0.001。我们将其归因于压缩，抗衡离子膨胀的刷子表现出的对互穿的出色抵抗力，以及围绕带电，摩擦聚合物链段的水合层的流动性。我们的发现可能会对生物润滑效果产生影响，这对于人工植入物的润滑表面设计以及对生物系统中的摩擦过程的理解至关重要。

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