Department of Physics & Astronomy, McMaster University, Hamilton, ON, L8S 4M1, Canada.
Polymer Science & Engineering Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
Nat Commun. 2018 Mar 21;9(1):1172. doi: 10.1038/s41467-018-03610-4.
Hydrodynamic slip, the motion of a liquid along 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 polymer reptation implies 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 low 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 a model that includes physical adsorption of polymer chains at the solid/liquid interface.
流体动力学中的动力学滑动，即液体沿固体表面的运动，是一种基本现象，它控制着小尺度下的液体输运。对于聚合物液体，de Gennes 预测，Navier 边界条件与聚合物蠕动相结合，意味着在理想表面上缠结聚合物熔体的界面滑动非常大；这种 Navier-de Gennes 模型已通过在超低能基板上进行的超光滑脱湿实验得到证实。在这里，我们使用毛细平整-表面张力驱动流动的薄膜，这些薄膜最初具有不均匀的厚度-在相同的基板上的聚合物薄膜。通过对润滑模型进行稳健的单参数拟合来测量滑移长度。我们表明，与脱湿实验相比，在平整实验中涉及的低剪切速率下，所使用的基板不再被认为是理想的。相反，数据与一个模型一致，该模型包括聚合物链在固/液界面的物理吸附。
