Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Langmuir. 2013 Feb 12;29(6):1841-9. doi: 10.1021/la304829s. Epub 2013 Jan 31.
Colloidal particles spontaneously attach to the interface between two immiscible fluids to minimize the interfacial area between the two phases. The shape and wettability of particles have a strong influence on their configuration and interactions at fluid-fluid interfaces. In this study, we investigate the behavior of asymmetrically hydrophilic Janus cylinders (or double hydrophilic Janus cylinders with two different hydrophilic regions) trapped at an air-water interface. We find that these double hydrophilic Janus cylinders with aspect ratios of 0.9, 1.2, and 2.4 adopt both end-on and tilted configurations with respect to the interface. Our numerical calculations show that the coexistence of these configurations is a result of multiple energy minima present in the attachment energy profile that can be represented as a complex energy landscape. Double hydrophilic Janus cylinders with tilted orientations induce hexapolar interface deformation, which accounts for the pair interactions between the particles as well as the nondeterministic assembly behaviors of these particles at the interface.
胶体粒子会自发地附着在两种不混溶流体的界面上，以最小化两相之间的界面面积。粒子的形状和润湿性对它们在流体-流体界面上的配置和相互作用有很强的影响。在这项研究中，我们研究了在气-水界面捕获的不对称亲水 Janus 圆柱（或具有两个不同亲水区域的双亲水 Janus 圆柱）的行为。我们发现，这些双亲水 Janus 圆柱的纵横比为 0.9、1.2 和 2.4 时，相对于界面采取了端对端和倾斜两种配置。我们的数值计算表明，这些配置的共存是由于附着能谱中存在多个能量极小值所致，这些能量极小值可以表示为复杂的能量景观。具有倾斜取向的双亲水 Janus 圆柱诱导六极界面变形，这解释了颗粒之间的相互作用以及这些颗粒在界面上的非确定组装行为。
