Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , Los Angeles, California, 90089, United States.
Langmuir. 2013 Sep 17;29(37):11640-5. doi: 10.1021/la402538e. Epub 2013 Sep 5.
We have observed that the vapor-phase deposition of polymers onto liquid substrates can result in the formation of polymer films or particles at the liquid-vapor interface. In this study, we demonstrate the relationship between the polymer morphology at the liquid-vapor interface and the surface tension interaction between the liquid and polymer, the liquid viscosity, the deposition rate, and the deposition time. We show that the thermodynamically stable morphology is determined by the surface tension interaction between the liquid and the polymer. Stable polymer films form when it is energetically favorable for the polymer to spread over the surface of the liquid, whereas polymer particles form when it is energetically favorable for the polymer to aggregate. For systems that do not strongly favor spreading or aggregation, we observe that the initial morphology depends on the deposition rate. Particles form at low deposition rates, whereas unstable films form at high deposition rates. We also observe a transition from particle formation to unstable film formation when we increase the viscosity of the liquid or increase the deposition time. Our results provide a fundamental understanding about polymer growth at the liquid-vapor interface and can offer insight into the growth of other materials on liquid surfaces. The ability to systematically tune morphology can enable the production of particles for applications in photonics, electronics, and drug delivery and films for applications in sensing and separations.
我们已经观察到聚合物在液相基底上的气相沉积可以在气液界面形成聚合物薄膜或颗粒。在这项研究中，我们证明了聚合物在气液界面上的形态与液体和聚合物之间的表面张力相互作用、液体的粘度、沉积速率和沉积时间之间的关系。我们表明，热力学稳定形态由液体和聚合物之间的表面张力相互作用决定。当聚合物在液体表面上扩展在能量上有利时，稳定的聚合物薄膜形成，而当聚合物在能量上有利时，聚合物颗粒形成聚集。对于不太有利于扩展或聚集的体系，我们观察到初始形态取决于沉积速率。在低沉积速率下形成颗粒，而在高沉积速率下形成不稳定的薄膜。当我们增加液体的粘度或增加沉积时间时，我们还观察到从颗粒形成到不稳定薄膜形成的转变。我们的结果提供了对聚合物在气液界面上生长的基本理解，并可以深入了解其他材料在液体表面上的生长。系统地调节形态的能力可以使生产用于光子学、电子学和药物输送的颗粒以及用于传感和分离的薄膜成为可能。
