Precise analysis of coating defect formation on nanoparticles/polymer composite thin films

我们工作的最终目的是获得正确的理解纳米粒子/聚合物复合薄膜的去湿行为，以确定无缺陷和光滑的薄膜涂层的最佳条件。本文首先研究了以下几个方面的问题：利用相移干涉显微镜、激光扫描共聚焦显微镜和原子力显微镜观察了在表面涂有十八烷基三乙氧基硅烷的石英玻璃板上的含CeO_2纳米颗粒的聚苯乙烯（PS）薄膜的去湿行为，然后在353 K退火。采用有机配体辅助的超临界水热法对CeO_2纳米粒子进行表面改性，得到的纳米粒子为平均边长为4-6 nm的球形纳米粒子，在有机溶剂中可以完全分散。日 关于我们 膜厚度约为20-30 nm。结果，几个孔，即，在含有纳米颗粒的PS膜上出现的由去湿过程引起的具有边缘的干燥斑块膨胀并彼此接近。然后，接近的孔变成桥接细丝，最后断裂并在基底上留下孤立的小液滴。此外，似乎含有纳米颗粒的PS膜的去湿过程比没有纳米颗粒的PS膜的去湿过程更快，尽管我们不能定量地讨论有和没有纳米颗粒的去湿行为之间的比较，因为在初始阶段没有纳米颗粒的去湿行为不能被观察到。结果表明，纳米粒子的加入使基底上残留的小液滴尺寸变小;此外，基于润滑近似对去湿过程进行了数值模拟，认为纳米粒子的加入增强了去湿过程，这是由于薄膜表观Hamaker常数的变化。少

The ultimate aim of our work is to acquire correct understandings for the dewetting behavior of nanoparticles/polymer composite thin films in order to determine the optimum conditions for a defect-free and smooth coating of the films. In the present work, the following points were investigated as the first step.The dewetting behavior of polystyrene (PS) thin films containing CeO_2 nanoparticles on a silica glass plate coated with octadecyltrietoxysilane was observed using a phase-shifting interference microscopy, a laser scanning confocal microscopy and an atomic force microscopy, where the PS film was spin coated on the silane-coated substrate, and then was annealed at 353 K. The surface of the CeO_2 nanoparticles used here were modified with decanoic acid through the organic-ligand-assisted supercritical hydrothermal process, and consequently, the nanoparticles obtained were cubic-shaped ones with average edge length of 4-6 nm and could be dispersed completely in organic solvents. Th … More e film thickness was approximately 20-30 nm. As a result, several holes, i.e., dry patches with a rim, caused by the dewetting process appeared on the PS film containing nanoparticles, expanded and approached one another. Then, the approaching holes became a bridging filament, and finally, broke and left behind isolated small droplets on the substrate. Also, it seemed that the dewetting process of the PS film containing nanoparticles was faster than that without nanoparticles, although we could not discuss quantitatively the comparison between the dewetting behaviors with and without nanoparticles because the dewetting behavior without nanoparticles at the initial stage could not be observed. It was found that the size of the small droplets left on the substrate became smaller when the nanoparticles were added.In addition, numerical simulations of dewetting process based on the lubrication approximation were carried out, considering that the enhancement of dewetting by addition of nanoparticles was due to the variation of apparent Hamaker constant of the film. Less