Polymer熔体在理想基体上的吸附诱导滑移抑制
Adsorption-Induced Slip Inhibition for Polymer Melts on Ideal Substrates
摘要：
液体在固体表面的流体动力学滑移代表了流体动力学中的基本现象，其在小尺度下控制液体输运。对于聚合物液体，de Gennes预测，Navier边界条件与聚合物动力学理论一起意味着理想表面上缠结聚合物熔体的界面滑移非常大;使用超光滑低能基底上的去湿实验证实了Navier-de Gennes模型。在这里，我们使用毛细管流平-表面张力驱动的膜流动，具有初始不均匀的厚度-在这些相同的基板上的聚合物膜。实现了从稳健的单参数拟合到润滑模型的滑移长度的测量。我们表明，在较低的剪切速率涉及流平实验相比，去湿的，所采用的基板可以不再被认为是理想的。相反，数据与聚合物链在固/液界面处的物理吸附一致。我们扩展的Navier-de Gennes描述使用一个额外的参数，即每单位表面的物理吸附链的密度。由此产生的配方被认为是在良好的协议与实验观察。
英文摘要：
Hydrodynamic slip of a liquid at a solid surface represents a fundamental phenomenon in fluid dynamics that governs liquid transport at small scales. For polymeric liquids, de Gennes predicted that the Navier boundary condition together with the theory of polymer dynamics imply extraordinarily large interfacial slip for entangled polymer melts on ideal surfaces; this Navier-de Gennes model was confirmed using dewetting experiments on ultra-smooth, low-energy substrates. Here, we use capillary leveling - surface tension driven flow of films with initially non-uniform thickness - of polymeric films on these same substrates. Measurement of the slip length from a robust one-parameter fit to a lubrication model is achieved. We show that at the lower shear rates involved in leveling experiments as compared to dewetting ones, the employed substrates can no longer be considered ideal. The data is instead consistent with physical adsorption of polymer chains at the solid/liquid interface. We extend the Navier-de Gennes description using one additional parameter, namely the density of physically adsorbed chains per unit surface. The resulting formulation is found to be in excellent agreement with the experimental observations.
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