Structure Formation in Soft Material System : Structure Formation of Hydrocarbon Chains

用实验方法和计算机模拟的方法研究了在软材料体系结构形成中起重要作用的碳氢分子的结构形成。我们主要研究了正构烷烃薄膜体系、正构烷烃块体晶体特有的高温“旋转相”、正构烷基硫醇晶体、聚丙烯晶体以及一些链状分子模型体系。这些研究的主要结果如下。1.在链状分子薄膜体系中，分子链轴垂直于衬底表面的“法向取向”和分子轴平行于衬底表面的“平行取向”是常见的两种分子取向状态。系统地研究了分子取向与蒸发条件的关系。当蒸发速度较慢和/或衬底温度较高时，法向取向状态趋于…更多的内容将会出现。在本文所用衬底上的正构烷烃薄膜中，法向取向被认为是最稳定的状态。同时也证实了沉积过程中的动力学行为对衬底的强烈依赖性。2.在正构烷烃的旋转相，X-射线漫反射研究结果表明，碳氢链发生了两种涨落，即绕链轴的旋转运动和沿链轴的平移运动，并且它们之间存在着短程关联。3.在正硫醇体系中，碳链末端的弱SH-SH相互作用导致了复杂的多态现象。4.研究了以3/1螺旋结构为最稳定构象的等规聚丙烯中γ相的结晶行为。有趣的是，这些链是通过交叉它们的链轴来结晶的。5.通过计算机模拟，揭示了刚性棒状链模型体系中有序结构的形成机理。较少

Structure formations of hydrocarbon molecules, which are considered to play an important role in the structure formation in soft material systems, have been investigated by means of experimental methods and computer simulations. We mainly focus on n-alkane thin film system, characteristic high-temperature "rotator phase" of bulk n-alkane crystals, bulk n-alkanethiol ciystals, polypropylene crystals, and some chain molecular model system. The major results in these studies are as follows. 1. In chain molecular thin film system, typical two molecular orientation states, "normal orientation", in which the molecular chain axes are normal to the substrate surface, and "parallel orientation", in which the molecular axes are parallel to the substrate surface, are commonly observed. The evaporation condition dependence of the molecular orientation has been investigated systematically. When the evaporation rate is slow and/or the substrate temperature is high, the normal orientation state tends … More to appear. The normal orientation is considered to be most stable state in n-alkane thin film on substrates used here. The strong substrate dependence, which is caused by the kinetics during the deposition, is also confirmed. 2. In the rotator phase of n-alkanes, the results of the x-ray diffuse scattering study shows that the hydrocarbon chains make two kinds of fluctuations, the rotational motion around the chain axes and the translational motion along the axes, and they have short-range correlations each other. 3. In n-alkanethiol system, the complicated polymorphism, which is cased by the weak SH-SH interaction at the end of hydrocarbon chain, is observed. 4. In isotactic polypropylene, which is 3/1 helical structure as most stable conformation, the crystallization of γ phase has been investigated. It is interesting that the chains crystallize with crossing their chain axes. 5. The mechanism of the formation of the ordered structure in the rigid rod-like chain model system has been revealed by computer simulation. Less