Tang Yanhong, Wang Yan, Wang Xindong, Xun Shidi, Mei Chongyu, Wang Lixiang, Yan Donghang
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
J Phys Chem B. 2005 May 12;109(18):8813-9. doi: 10.1021/jp045427x.
Submonolayer thin films of a three-ring bent-core (or banana-shaped) compound, m-bis(4-n-octyloxystyryl)benzene (m-OSB), were vacuum-deposited on a mica surface, and a spontaneous transition from monolayer films to bilayer crystals was observed at room temperature, which was ascribed to the specific molecular shape and polar layered packing of the bent-core molecules [Tang et al. J. Phys. Chem. B 2004, 108 (34), 12921-12926]. The crystal nucleation and growth from the monolayer films as well as the melting phase transition from the bilayer crystals were investigated using atomic force microscopy (AFM). It was shown that after initial nucleation, the crystal growth was achieved through three pathways: direct absorption of molecules from monolayer films, molecular cluster diffusion, and quasi-Ostwald ripening. When annealing the bilayer crystals at elevated temperatures, morphological change from a bilayer to a monolayer was observed, and some new islands with fingerlike patterns were formed during this process, which resulted from a diffusion-controlled growth of the molten molecules. In general, the high-resolution AFM in combination with the molecularly thin m-OSB films provided us with direct visualization of nucleation, crystal growth, melting, and film morphology evolution on the mesoscopic scale, which are of fundamental interest from the theoretical viewpoint and are of central importance for the control of interfacial properties in practical applications.
将三环弯曲核（或香蕉形）化合物间双（4 - 正辛氧基苯乙烯基）苯（m-OSB）的亚单层薄膜真空沉积在云母表面，室温下观察到从单层薄膜到双层晶体的自发转变，这归因于弯曲核分子特定的分子形状和极性层状堆积[Tang等人，《物理化学杂志B》2004年，108 (34)，12921 - 12926]。使用原子力显微镜（AFM）研究了单层薄膜的晶体成核和生长以及双层晶体的熔融相变。结果表明，初始成核后，晶体生长通过三条途径实现：单层薄膜中分子的直接吸收、分子簇扩散和准奥斯特瓦尔德熟化。在高温下对双层晶体进行退火时，观察到从双层到单层的形态变化，在此过程中形成了一些具有指状图案的新岛，这是由熔融分子的扩散控制生长导致的。总体而言，高分辨率AFM与分子级薄的m-OSB薄膜相结合，为我们提供了介观尺度上成核、晶体生长、熔融和薄膜形态演变的直接可视化，从理论观点来看这些具有根本意义，并且对于实际应用中界面性质的控制至关重要。
