Nanoscale Discontinuities at the Boundary of Flowing Liquids: a Look into Structure and Dynamics

通常液体被表征为3D各向同性系统。然而，边界，如自由液体表面或固-液界面，区分空间方向并引起各向异性。这种降低的对称性可能限于靠近表面/界面区域的纳米尺寸长度尺度，或者它可能以大得多的长度尺度渗透到液体中。相关的有序现象在液体中已经很好地建立起来，最近的研究表明，近界面结构关键取决于固体边界的化学终止。它进一步确立了在流动的液体剪切可能有一个显着的影响，散装结构，更戏剧性的效果可能会发生近表面的异常或界面处的不连续性，通过表面滑移证明。虽然这些不连续性可能具有有限的空间延伸，但对结构和动力学的影响可能与大得多的体积相关。我们建议通过表面敏感中子和X射线散射来研究聚合物溶液中基本未知的近表面区域的结构和动力学性质，从而可以访问迄今为止未探索的流动液体的时间和空间制度。

Usually liquids are characterized as 3D isotropic systems. However a boundary, like the free liquid surface or a solid-liquid interface, distinguishes a spatial direction and induces anisotropy. This reduced symmetry may be limited to a nanosize length scale next to the surface/interface region or it may penetrate into the liquid on a much larger length scale. Related ordering phenomena in liquids are well established, and more recently it was shown that near-interface structures depend crucially on the chemical termination of the solid boundary. It is further established that shear in flowing liquids may have a pronounced influence on bulk structures, and more dramatic effects may occur as near-surface anomalies or discontinuities at interfaces as evidenced through surface slip. Although these discontinuities may have a limited spatial extension, there consequences on structure and dynamics may be relevant for much larger volumes. We propose to study both the structural and dynamical properties of the largely unknown near-surface regions in polymer solutions by surface sensitive neutron and x-ray scattering which allow to access a so far unexplored time and spatial regime of flowing liquids.