Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
South China Advanced Institute for Soft Matter Science and Technology, School of Emergent Soft Matter, South China University of Technology, Guangzhou, Guangdong 510640, China.
J Phys Chem Lett. 2023 Mar 9;14(9):2402-2409. doi: 10.1021/acs.jpclett.3c00299. Epub 2023 Mar 1.
Plastic crystals formed from anisotropic molecules or particles are an important state of matter characterized by the presence of long-range positional order and the lack of long-range orientational order. The rotational motion of molecules or particles in plastic crystals is the most attractive characteristic of the system. Here the rotational dynamics of the discoid particles in quasi-two-dimensional colloidal plastic crystals stabilized via depletion interactions are quantitatively studied using time-resolved confocal microscopy. The measured probability distribution of particle orientation reveals the existence of a strong coupling between the lattice symmetry and particle rotation, resulting in anisotropic rotational dynamics modes resembling the underlying hexagonal crystalline symmetry. Furthermore, the orientational distribution function provides information about the potential surface of rotational dynamics. The observed slow rotational diffusion can be attributed to the presence of orientational minima and potential barriers on the potential surface. Our findings with a real experimental system provide important insights into the role of attraction in the phase behaviors of plastic crystals.
各向异性分子或粒子形成的塑料晶体是一种重要的物质状态，其特征是具有长程位置有序和缺乏长程取向有序。塑料晶体中分子或粒子的旋转运动是该体系最吸引人的特点。在这里，通过耗散相互作用稳定的准二维胶体塑料晶体中圆盘粒子的旋转动力学使用时间分辨共焦显微镜进行了定量研究。测量得到的粒子取向概率分布揭示了晶格对称性和粒子旋转之间存在强耦合，导致各向异性旋转动力学模式类似于潜在的六方晶体对称性。此外，取向分布函数提供了关于旋转动力学势表面的信息。观察到的缓慢旋转扩散可以归因于势表面上的取向极小值和势垒的存在。我们在真实实验系统中的发现为了解吸引力在塑料晶体相行为中的作用提供了重要的见解。
