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Grain Growth and Coarsening Dynamics in a Compositionally Asymmetric Block Copolymer Revealed by X-ray Photon Correlation Spectroscopy
Macromolecules ( IF 5.5 ) Pub Date : 2020-09-17 , DOI: 10.1021/acs.macromol.0c01676
Ronald M. Lewis , Grayson L. Jackson 1 , Michael J. Maher , Kyungtae Kim , Suresh Narayanan 2 , Timothy P. Lodge , Mahesh K. Mahanthappa , Frank S. Bates
Affiliation  

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.

中文翻译:

X射线光子相关光谱揭示的组成不对称嵌段共聚物的晶粒长大和粗化动力学

纳米结构软材料的动力学至关重要地影响了其相关的宏观材料性能,但是由于常规仪器的时空限制,它们通常很难测量。在本文中,我们使用X射线光子相关光谱法直接观察以体心立方形成的二嵌段聚合物熔体在晶粒长大和粗化过程中的粒子尺度动力学,尤其要注意与晶面间相关的结构弛豫时间的分布(110 )距离。在样品从无序状态淬灭后,这些动力学现象出乎意料地表现出对时间和热淬灭深度的依赖性很小。我们假设这些弛豫源于晶粒旋转过程中的集体粒子运动。我们还观察到异常的内部参考外差相关性,可以测量样品中的速度分布。与先前在微相分离的嵌段聚合物熔体中晶粒成核和生长期间报道的那些速度相比,这些速度明显更慢并且出现的退火时间长得多。利用多晶硬质和软质材料之间的类比,我们将这些速度分布归因于有序畴粗化期间异常取向相关的晶界迁移以及沿着晶界的异常快速,协作的串状粒子运动。因此,这些相干的X射线测量提供了质疑多晶软材料中晶界结构和动力学的新机会。与先前在微相分离的嵌段聚合物熔体中晶粒成核和生长期间报道的那些速度相比,这些速度明显更慢并且出现的退火时间长得多。利用多晶硬质和软质材料之间的类比,我们将这些速度分布归因于有序畴粗化期间异常取向相关的晶界迁移以及沿着晶界的异常快速,协作的串状粒子运动。因此,这些相干的X射线测量提供了质疑多晶软材料中晶界结构和动力学的新机会。与先前在微相分离的嵌段聚合物熔体中晶粒成核和生长期间报道的那些速度相比,这些速度明显更慢并且出现的退火时间长得多。利用多晶硬质和软质材料之间的类比,我们将这些速度分布归因于有序畴粗化期间异常取向相关的晶界迁移以及沿着晶界的异常快速,协作的串状粒子运动。因此,这些相干的X射线测量为质疑多晶软材料中的晶界结构和动力学提供了新的机会。我们将这些速度分布归因于有序畴粗化过程中与取向错误有关的晶界迁移,以及沿晶界异常快速,协作的串状粒子运动。因此,这些相干的X射线测量为质疑多晶软材料中的晶界结构和动力学提供了新的机会。我们将这些速度分布归因于有序畴粗化过程中与取向错误有关的晶界迁移,以及沿着晶界的异常快速,协作的串状粒子运动。因此,这些相干的X射线测量提供了质疑多晶软材料中晶界结构和动力学的新机会。
更新日期:2020-10-13
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