Ternary phase separation during spin casting

自旋镀膜是一种广泛应用于制造非常光滑和非常薄的聚合物薄膜的工具。例如，它通常被大规模用于制造集成电路和液晶显示器的彩色滤光片。在新兴的聚合物电子学领域，这可能是一个中心重要的加工步骤。最常见的情况是聚合物溶液（溶解在溶剂中的聚合物）的自旋涂层。一个被溶液浸透的圆盘，以每分钟10000转的速度旋转。这就形成了均匀的溶液涂层。然后溶剂迅速蒸发，留下非常光滑和高质量的纯聚合物薄膜。当两种聚合物从一种共同的溶剂中纺成时，会出现一种更复杂的情况，这种情况具有很大的技术潜力。大多数化学性质不同的聚合物不喜欢混合，但如果在对这两种聚合物都有利的溶剂中充分稀释，就会形成混合溶液。然而，随着溶剂的蒸发，这两种聚合物将彼此分离。值得注意的是，这可以在最终的薄膜中产生各种各样的微观结构。这些范围可以从两个定义良好的层到在各种长度尺度（从纳米到许多微米）上发生横向相分离的情况。例如，在用于发光二极管和光伏器件的半导体聚合物薄膜中，器件效率主要取决于其微观结构。因此，如果人们了解如何控制微观结构，人们可以在一个单一的、廉价的加工步骤中获得优化的薄膜。

Spin coating is a widely used tool in the manufacture of very smooth and very thin polymer films. For example, it is routinely used on a massive scale for making integrated circuits and colour filters for liquid crystal displays. It is likely to be a centrally important processing step in the emerging field of polymer electronics. The most common situation is the spin coating of a polymer solution (a polymer dissolved in a solvent). A flat disc, which has been flooded with the solution, is rotated at speeds of up to 10,000 revolutions per minute. This results in a uniform coating of solution. The solvent then rapidly evaporates to leave a very smooth and high quality film of pure polymer. A more complicated situation, that has great technological potential, occurs when two polymers are spun from a common solvent. Most chemically different polymers do not like to mix, but if diluted enough in a solvent favourable to both polymers a mixed solution forms. However, the two polymers will separate from each other as the solvent evaporates. Significantly, this can result in a wide variety of microstructures in the final films. These can range from two well defined layers to situations in which lateral phase separation takes place on a variety of length-scales, from nanometres to many micrometres. In thin films of, for example, semiconducting polymers used in light emitting diodes and photovoltaic devices, the device efficiency depends critically on the microstructure. Hence, if one understands how to control the microstructure, one can achieve an optimised film in a single, inexpensive processing step.