Mokarian-Tabari P, Geoghegan M, Howse J R, Heriot S Y, Thompson R L, Jones R A L
Department of Physics and Astronomy, University of Sheffield, S3 7RH, Sheffield, UK.
Eur Phys J E Soft Matter. 2010 Dec;33(4):283-9. doi: 10.1140/epje/i2010-10670-7. Epub 2010 Nov 18.
Thin films of polymer mixtures made by spin-coating can phase separate in two ways: by forming lateral domains, or by separating into distinct layers. The latter situation (self-stratification or vertical phase separation) could be advantageous in a number of practical applications, such as polymer optoelectronics. We demonstrate that, by controlling the evaporation rate during the spin-coating process, we can obtain either self-stratification or lateral phase separation in the same system, and we relate this to a previously hypothesised mechanism for phase separation during spin-coating in thin films, according to which a transient wetting layer breaks up due to a Marangoni-type instability driven by a concentration gradient of solvent within the drying film. Our results show that rapid evaporation leads to a laterally phase-separated structure, while reducing the evaporation rate suppresses the interfacial instability and leads to a self-stratified final film.
形成横向畴，或分离成不同的层。后一种情况（自分层或垂直相分离）在许多实际应用中可能具有优势，例如聚合物光电子学。我们证明，通过控制旋涂过程中的蒸发速率，我们可以在同一系统中获得自分层或横向相分离，并且我们将此与先前假设的薄膜旋涂过程中的相分离机制相关联，根据该机制，由于干燥薄膜内溶剂浓度梯度驱动的马兰戈尼型不稳定性，瞬态润湿层会破裂。我们的结果表明，快速蒸发会导致横向相分离结构，而降低蒸发速率会抑制界面不稳定性并导致自分层的最终薄膜。
