Urata Chihiro, Masheder Benjamin, Cheng Dalton F, Miranda Daniel F, Dunderdale Gary J, Miyamae Takayuki, Hozumi Atsushi
Materials Research Institute for Sustainable Development, National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 , Anagahora, Shimoshidami, Moriyama, Nagoya 463-8560, Japan.
Langmuir. 2014 Apr 15;30(14):4049-55. doi: 10.1021/la500548v. Epub 2014 Apr 2.
The dynamic dewettability of a smooth alkyl-terminated sol-gel hybrid film surface against 17 probe liquids (polar and nonpolar, with high and low surface tensions) was systematically investigated using contact angle (CA) hysteresis and substrate tilt angle (TA) measurements, in terms of their physicochemical properties such as surface tension, molecular weight/volume, dielectric constant, density, and viscosity. We found that the dynamic dewettability of the hybrid film markedly depended not on the surface tensions but on the dielectric constants of the probe liquids, displaying lower resistance to liquid drop movement with decreasing dielectric constant (ε < 30). Interfacial analysis using the sum-frequency generation (SFG) technique confirmed that the conformation of surface-tethered alkyl chains was markedly altered before and after contact with the different types of probe liquids. When probe liquids with low dielectric constants were in contact with our surface, CH3 groups were preferentially exposed at the solid/liquid interface, leading to a reduction in surface energy. Because of such local changes in surface energy at the three-phase contact line of the probe liquid, the contact line can move continuously from low-surface-energy (solid/liquid) areas to surrounding high-surface-energy (solid/air) areas without pinning. Consequently, the organic probe liquids with low dielectric constants can move easily and roll off when tilted only slightly, independent of the magnitude of CAs, without relying on conventional surface roughening and perfluorination.
通过接触角（CA）滞后和基底倾斜角（TA）测量，系统研究了光滑的烷基封端溶胶 - 凝胶杂化膜表面对17种探针液体（极性和非极性，具有高和低表面张力）的动态润湿性，涉及它们的物理化学性质，如表面张力、分子量/体积、介电常数、密度和粘度。我们发现，杂化膜的动态润湿性明显不取决于探针液体的表面张力，而是取决于其介电常数，随着介电常数降低（ε < 30），对液滴运动的阻力减小。使用和频产生（SFG）技术进行的界面分析证实，与不同类型的探针液体接触前后，表面连接的烷基链的构象发生了明显变化。当低介电常数的探针液体与我们的表面接触时，CH3基团优先暴露在固/液界面，导致表面能降低。由于探针液体三相接触线处表面能的这种局部变化，接触线可以连续地从低表面能（固/液）区域移动到周围的高表面能（固/气）区域而不被钉扎。因此，低介电常数的有机探针液体可以很容易地移动，并且仅轻微倾斜时就会滚落，与接触角的大小无关，无需依赖传统的表面粗糙化和全氟化处理。
