Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, MA 01003, USA.
Nanoscale. 2017 Oct 12;9(39):14888-14896. doi: 10.1039/c7nr05394k.
A simple and robust method has been developed for the generation of macroscopically ordered hexagonal arrays from the directed self-assembly (DSA) of cylinder-forming block copolymers (BCPs) based on minimal trench patterns with solvent vapor annealing. The use of minimal trench patterns allows us to probe the guided hexagonal arrays of cylindrical microdomains using grazing incidence small angle X-ray scattering (GISAXS), where the sample stage is rotated on the basis of the six-fold symmetry of a hexagonal system. It is found that the (10) planes of hexagonal arrays of cylindrical microdomains are oriented parallel to the underlying trench direction over macroscopic length scales (∼1 × 1 cm). However, there are misorientations of the hexagonal arrays with short-range ordering. GISAXS patterns show that the hexagonal arrays on the minimal trench pattern are distorted, deviating from a perfect hexagonal lattice. This distortion has been attributed to the absence of topographic constraints in the unconfined direction on the 1-D minimal trench pattern. Also, the frustration of BCP microdomains, arising from the incommensurability between the trench pitch and natural period of the BCP at the base of the trench, influences the distortion of the hexagonal arrays.
已经开发出一种简单而稳健的方法，用于通过溶剂蒸气退火从基于最小沟槽图案的圆柱形嵌段共聚物（BCP）的定向自组装（DSA）生成宏观有序的六边形阵列。使用最小沟槽图案允许我们使用掠入射小角 X 射线散射（GISAXS）探测圆柱形微域的导向六边形阵列，其中根据六边形系统的六重对称性旋转样品台。结果发现，在宏观长度尺度（约 1×1cm）上，圆柱形微域的六边形阵列的（10）面平行于下面的沟槽方向取向。然而，存在短程有序的六边形阵列的取向失配。GISAXS 图案表明，最小沟槽图案上的六边形阵列被扭曲，偏离了完美的六边形晶格。这种扭曲归因于在 1-D 最小沟槽图案的无约束方向上不存在地形约束。此外，由于沟槽底部的 BCP 沟槽间距和自然周期之间的不协调性，BCP 微域的受挫也会影响六边形阵列的变形。
