Zou Qing-Zhi, Li Zhan-Wei, Zhu You-Liang, Sun Zhao-Yan
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
Soft Matter. 2019 Apr 17;15(16):3343-3352. doi: 10.1039/c9sm00165d.
We perform dynamics simulations to investigate the translational and rotational glassy dynamics in a glass-forming liquid of monodisperse soft Janus particles. We find that, with decreasing temperature, the mean-square angular displacement shows no clear plateau in the caging region, in contrast with the apparent caging behavior of translational motion. By defining a reorientational mean-square angular displacement, the caging behavior of rotational motion can be recognized. On approaching the glass transition (decreasing temperature), the coupling between translational and rotational relaxation increases, while the coupling between translational and rotational diffusion decreases, whereas the coupling between translational and reorientational diffusion increases. The strong decoupling between translational and rotational diffusion is due to the suppressed translational mobility but promoted rotational mobility of soft Janus particles. We think that the low-T SE and SED decoupling is mainly attributed to hopping motion of soft Janus particles, whereas the high-T SE and SED decoupling is mainly attributed to collective cage motion of soft Janus particles. Our results demonstrate that interaction anisotropy has a critical effect on the translational and rotational dynamics of soft Janus particles.
我们进行动力学模拟，以研究单分散软Janus粒子的玻璃形成液体中的平动和转动玻璃态动力学。我们发现，随着温度降低，均方位移在笼蔽区域没有明显的平台期，这与平动的明显笼蔽行为形成对比。通过定义一个重取向均方位移，可以识别转动运动的笼蔽行为。在接近玻璃化转变（温度降低）时，平动和转动弛豫之间的耦合增加，而平动和转动扩散之间的耦合减小，而平动和重取向扩散之间的耦合增加。平动和转动扩散之间的强解耦是由于软Janus粒子的平动迁移率受到抑制但转动迁移率得到促进。我们认为，低温下的自扩散系数（SE）和自扩散系数与扩散系数之比（SED）解耦主要归因于软Janus粒子的跳跃运动，而高温下的SE和SED解耦主要归因于软Janus粒子的集体笼运动。我们的结果表明，相互作用各向异性对软Janus粒子的平动和转动动力学有关键影响。
