论文标题
半脱水聚合物溶液的近地表流变学和流体动力边界条件
Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions
论文作者
论文摘要
理解复杂流体的限制流需要同时访问液体的机械行为和界面处的边界条件。在这里，我们使用evaneScent的波显微镜研究半脱水的，未进入的聚丙烯酰胺溶液的近表面流。通过同时使用中性和阴离子聚合物，我们表明单体电荷在受限聚合物动力学中起关键作用。对于与玻璃接触的溶液，中性聚合物显示链条大小的吸附层，而对于阴离子聚合物溶液，观察到剪切率依赖的明显滑动长度。当使用具有非Newtonian粘度的简单两层耗竭模型缩放时，在所有浓度下测量的滑动长度崩溃了。此外，通过在阴离子聚合物溶液中用额外的盐筛选电荷，从表观滑移边界条件到链式吸附层的过渡也可以突出显示。我们预计，我们的研究将成为更复杂的研究的起点，该研究将界面的聚合物动力学与它们的化学和物理组成有关。
Understanding confined flows of complex fluids requires simultaneous access to the mechanical behaviour of the liquid and the boundary condition at the interfaces. Here, we use evanescent wave microscopy to investigate near-surface flows of semi-dilute, unentangled polyacrylamide solutions. By using both neutral and anionic polymers, we show that monomer charge plays a key role in confined polymer dynamics. For solutions in contact with glass, the neutral polymers display chain-sized adsorbed layers, while a shear-rate-dependent apparent slip length is observed for anionic polymer solutions. The slip lengths measured at all concentrations collapse onto a master curve when scaled using a simple two-layer depletion model with non-Newtonian viscosity. A transition from an apparent slip boundary condition to a chain-sized adsorption layer is moreover highlighted by screening the charge with additional salt in the anionic polymer solutions. We anticipate that our study will be a starting point for more complex studies relating the polymer dynamics at interfaces to their chemical and physical composition.
