Grain Growth and Coarsening Dynamics in a Compositionally Asymmetric Block Copolymer Revealed by X-ray Photon Correlation Spectroscopy
Grain Growth and Coarsening Dynamics in a Compositionally Asymmetric Block Copolymer Revealed by X-ray Photon Correlation Spectroscopy
复制标题
DOI：
10.1021/acs.macromol.0c01676
复制
发表时间：
2020-10-13
期刊：
影响因子：
5.5
通讯作者：
Bates, Frank S.
中科院分区：
文献类型：
--
作者：
Lewis, Ronald M., III;Jackson, Grayson L.;Bates, Frank S.
纳米结构软材料的动力学对其相关的宏观材料性质具有至关重要的影响，但由于传统仪器的时空限制，它们通常难以测量。在这里，我们使用X射线光子相关光谱直接观察颗粒尺度的动态过程中的晶粒生长和粗化的体中心的双嵌段聚合物熔体中，特别注意与面间（110）距离的结构弛豫时间的分布。在样品从无序状态淬火后，这些动力学现象令人惊讶地表现出对时间和热淬火深度的依赖性很小。我们认为，这些弛豫源于集体粒子运动在晶粒旋转。我们还观察到不寻常的内部参考外差相关性，使样品内的速度分布的测量。这些速度是显着较慢，出现在更长的退火时间比那些先前报道的在微相分离的嵌段聚合物熔体中的晶粒成核和生长。绘制多晶硬材料和软材料之间的类比，我们归因于这些速度分布的取向不良依赖于晶界迁移有序域粗化和快速，合作的弦状粒子运动沿着晶界。因此，这些相干X射线测量提供了新的机会，询问晶界结构和多晶软材料的动力学。
The dynamics of nanostructured soft materials crucially impact their associated macroscopic material properties, yet they are often difficult to measure due to spatiotemporal limitations of conventional instrumentation. Herein, we use X-ray photon correlation spectroscopy to directly observe particle-scale dynamics during grain growth and coarsening in a body-centered cubic-forming diblock polymer melt, with specific attention to the distribution of structural relaxation times associated with the interplanar (110) distance. Following sample quenching from the disordered state, these dynamical phenomena surprisingly exhibit little dependence on time and thermal quench depth. We posit that these relaxations stem from collective particle motions during grain rotation. We also observe unusual internally referenced heterodyne correlations, which enable measurements of speed distributions within the sample. These speeds are significantly slower and appear at much longer annealing times than those previously reported during grain nucleation and growth in microphase-separated block polymer melts. Drawing on analogies between polycrystalline hard and soft materials, we ascribe these speed distributions to misorientation-dependent grain boundary migration during ordered domain coarsening and anomalously fast, cooperative stringlike particle motion along the grain boundaries. Thus, these coherent X-ray measurements provide new opportunities to interrogate grain boundary structure and dynamics in polycrystalline soft materials.