Vertical Domain Orientation in Cylinder-Forming Diblock Copolymer Films upon Solvent Vapor Annealing
Vertical Domain Orientation in Cylinder-Forming Diblock Copolymer Films upon Solvent Vapor Annealing
复制标题
DOI：
10.1021/acs.macromol.5b01771
复制
发表时间：
2016-01-12
期刊：
影响因子：
5.5
通讯作者：
Potemkin, Igor I.
中科院分区：
文献类型：
--
作者：
Berezkin, Anatoly V.;Papadakis, Christine M.;Potemkin, Igor I.
应用耗散粒子动力学模拟圆柱体二嵌段共聚物薄膜中的溶剂蒸气退火。我们的模拟揭示了多种条件，在这些条件下，快速溶剂蒸发促进了垂直畴取向。首先，必须在薄膜膨胀时诱导有序到无序的转变。该条件确保了干燥过程中结构形成与历史（即制备条件）的独立性。其次，在蒸发过程中必须能够实现弱偏析状态。这种条件为结构转变提供了更多的“途径”，而不会伴随着界面能的强烈惩罚。圆柱形纳米域垂直取向的第三个条件是溶剂的弱选择性。在溶胀状态下，大多数域的更强溶胀导致球形胶束（而不是圆柱形）的形成。薄膜干燥后，这些球形胶束结合形成圆柱体，与（垂直）溶剂流平行排列。讨论了对齐的可能机制。此外，还研究了不同膜厚度、溶胀程度、偏析状态和膜自由表面选择性的影响。对等效干膜的溶剂蒸气退火和热退火的计算机模拟揭示了最终膜结构的显着差异。
Dissipative particle dynamics was applied to simulate solvent vapor annealing in films of cylinder-forming diblock copolymers. Our simulations reveal a wide range of conditions, under which the vertical domain orientation is promoted by the fast solvent evaporation. First, the order-to-disorder transition must be induced upon swelling of the film. This condition ensures the independence of the structure formation during drying on the history, i.e., the preparation conditions. Second, the weak segregation regime has to be achievable during the evaporation process. This condition provides more "pathways" for structural transformations which are not accompanied by a strong penalty in the interfacial energy. The third condition for vertical orientation of the cylindrical nanodomains is a weak selectivity of the solvent. In the swollen state, a stronger swelling of the majority domains results in the formation of spherical micelles (rather than cylindrical). Upon drying of the film, these spherical micelles join to form cylinders, which align in parallel to the (vertical) solvent flow. Possible mechanisms of the alignment are discussed. In addition, the effects of varying film thickness, the degree of swelling, segregation regime, and the selectivity of the free surface of the film are studied. Computer simulations of the solvent vapor annealing and thermal annealing of equivalent dry films reveal considerable differences in the final film structures.