Controlling a block copolymer “grain”, in which the microdomains are regularly ordered in a single lattice, is important for developing high-performance polymeric materials. This is because the grains, which are several micrometers in size, can directly affect the properties of the materials. In this regard, we focused on grain coarsening on the free surface and in the thickness direction of a sphere-forming triblock copolymer film. We evaluated the grain size on the free surface using atomic force microscopy combined with image processing, and in the thickness direction, we used small-angle X-ray scattering edge-view measurements. It was found that the grain growth in the direction parallel to the free surface was very slow in the early stage of thermal annealing. Then, the grain growth shifted to a rapid growth mechanism with a power-law relationship (grain size ~tα, with α = 0.7) after ~30 min. Based on the value of the growth exponent α, the grain growth mechanism is considered to fall between the random and deterministic processes. In contrast, for the thickness direction, a much larger value (α = 1.72) was obtained. For such a large α value, it is impossible to consider the growth mechanism of the grain within the conventional to framework of the growth of domains and droplets. Therefore, our results may require a new framework to explain the behavior of the grain growth in the spherical microdomain system. Another notable finding is that the thickness of the oriented layer near the free surface or near the surface in contact with the substrate can be as thick as 9.5 µm, which is substantially larger than the reported values of the propagation distance of surface-induced orientation of microdomains in block copolymers. Based on the results of the current study, it is speculated that grain growth serves as a propagator for the regular ordering of spherical microdomains and the orientation of the lattice.The grain size was quantitatively evaluated on the free surface, and in the thickness direction. The grain growth on the free surface was very slow in the early stage of thermal annealing, then it shifted to a rapid mode with a power law (~t0.7). While in the thickness direction, the growth followed a power law of t1.72 until 1180 min, then it shifted to a slow mode with t0.21. Furthermore, the oriented layer near the free surface was found to be as thick as 9.5 µm, indicating that grain growth serves as a propagator for the regular ordering of spherical microdomains and orientation of the bcc lattice.

中文翻译：

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球形三嵌段共聚物薄膜自由表面和厚度方向的晶粒粗化

控制嵌段共聚物“晶粒”，其中微域在单个晶格中规则排列，对于开发高性能聚合物材料非常重要。这是因为几微米大小的晶粒可以直接影响材料的性能。在这方面，我们专注于形成球体的三嵌段共聚物膜的自由表面和厚度方向的晶粒粗化。我们使用原子力显微镜结合图像处理评估了自由表面的晶粒尺寸，并且在厚度方向上，我们使用了小角度 X 射线散射边缘视图测量。发现在热退火初期，平行于自由表面方向的晶粒生长非常缓慢。然后，在~30 分钟后，晶粒生长转变为具有幂律关系（晶粒尺寸~tα，α = 0.7）的快速生长机制。根据生长指数 α 的值，晶粒生长机制被认为介于随机和确定性过程之间。相反，对于厚度方向，获得了更大的值（α = 1.72）。对于如此大的 α 值，不可能在域和液滴生长的常规框架内考虑晶粒的生长机制。因此，我们的结果可能需要一个新的框架来解释球形微畴系统中晶粒生长的行为。另一个值得注意的发现是，自由表面附近或与基板接触的表面附近的取向层的厚度可高达 9.5 µm，这大大大于所报道的嵌段共聚物中微域表面诱导取向的传播距离值。根据目前的研究结果，推测晶粒生长是球形微畴规则排列和晶格取向的传播者。在自由表面和厚度方向上定量评估晶粒尺寸。在热退火的早期阶段，自由表面上的晶粒生长非常缓慢，然后转变为具有幂律 (~t0.7) 的快速模式。而在厚度方向，生长遵循 t1.72 的幂律，直到 1180 分钟，然后它转移到 t0.21 的慢速模式。此外，发现自由表面附近的取向层厚达 9.5 µm，