Langmuir. 2018 Dec 18;34(50):15455-15461. doi: 10.1021/acs.langmuir.8b03318. Epub 2018 Nov 27.
The critical challenge to engineer the morphological structures in the strongly phase-segregated block copolymer thin film is to overcome the preferential wetting of the blocks at the interface and direct the self-assembly process. Herein, we utilize surface activity and selective solvation of a nematic (N) liquid crystalline (LC) solvent, 5CB, to facilely alter the LC anchoring and the orientation of the nanophase separated structures of the smectic-nematic (S-N) LC block copolymer thin film. For the neat S-N diblock copolymer thin film, the nanostructures are parallel aligned. In contrast, with continuous introduction of 5CB into the system, the orientations of the characteristic nanostructures and the morphologies of the LC thin film can be consequently changed, yielding the perpendicularly oriented lamellar or cylindrical structures with the feature size below 10 nm. The homeotropic alignment of the 5CB nematics near the air interface plays a critical role to induce this unique behavior in the S-N/5CB systems, which offers an opportunity to fine-tune the interfacial structures and the morphological patterning in the block copolymer thin film.
在强相分离嵌段共聚物薄膜中构建形态结构的关键挑战是克服嵌段在界面处的优先润湿，并指导自组装过程。在此，我们利用向列（N）液晶（LC）溶剂 5CB 的表面活性和选择性溶解，来轻松改变近晶-向列（S-N）液晶嵌段共聚物薄膜的 LC 锚定和纳米相分离结构的取向。对于纯 S-N 两嵌段共聚物薄膜，纳米结构是平行排列的。相比之下，随着 5CB 的连续引入，特征纳米结构的取向和 LC 薄膜的形貌可以随之改变，得到垂直取向的层状或圆柱状结构，特征尺寸低于 10nm。在空气界面附近的 5CB 向列的垂直取向在 S-N/5CB 体系中起着至关重要的作用，这为精细调整嵌段共聚物薄膜中的界面结构和形态图案提供了机会。
