Ternary phase separation during spin casting

旋涂是一种广泛用于制造非常光滑和非常薄的聚合物膜的工具。例如，它通常被大规模地用于制造集成电路和液晶显示器的滤色器。这可能是聚合物电子学新兴领域中的一个重要加工步骤。最常见的情况是旋涂聚合物溶液（溶解在溶剂中的聚合物）。一个已经充满溶液的扁平圆盘以每分钟10,000转的速度旋转。这导致溶液的均匀涂层。然后溶剂迅速蒸发，留下非常光滑且高质量的纯聚合物膜。当两种聚合物从一种共同的溶剂中纺丝时，会出现一种具有巨大技术潜力的更复杂的情况。大多数化学性质不同的聚合物不喜欢混合，但如果在对两种聚合物都有利的溶剂中充分稀释，则形成混合溶液。然而，随着溶剂蒸发，两种聚合物将彼此分离。值得注意的是，这可以在最终膜中产生各种各样的微结构。这些范围可以从两个明确定义的层到横向相分离发生在从纳米到许多微米的各种长度尺度上的情况。例如，在发光二极管和光伏器件中使用的半导体聚合物薄膜中，器件效率关键取决于微结构。因此，如果人们了解如何控制微观结构，就可以在单个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.