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Realization of a two-dimensional glass, and the direct observation of its ordered-cluster structure and structural change

二维玻璃的实现及其有序簇结构和结构变化的直接观察

基本信息

批准号：
10440169
负责人：
OGUNI Masaharu
金额：
$ 8.58万
依托单位：
Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Science of Supercooled liquids and glasses has not been developed enough because of the aspect that the arrangement of molecules is essentially disordered. The development of ordering in the molecular aggregation, however, plays an important role in their characteristic properties at low temperatures. We have proposed an "ordered-clusters aggregation model" for the structure of those systems. In this research, it was tried first to realize a two-dimensional glass and observe directly the molecular aggregation and its change, and second to discover or elucidate new phenomena based on the proposed model.1) A scanning tunneling microscope was constructed which works at liquid nitrogen temperature. o-Terphenyl molecules deposited on a graphite surface was identified, but it has not been succeeded yet to form and observe its mono-layer glass.2) α and β relaxation times of simple benzene-derivatives were investigated dielectrically with systematic change of the substituent groups at 1 and 3- … More positions. While the β relaxation times were rather independent of the size of substituents to within isopropyl group and the presence/absence of hydrogen-bond forming, -OH and NH_2, groups, α relaxation times depended strongly on those factors. The β relaxation strength was appreciably large in the sample cooled rapidly than slowly in the α glass transition region in advance.3) Homogeneous-nucleation-based crystallization was found in total in seven compounds with phenyl rings, indicating that the presence of the ring is important for its observation. It was also indicated to be important for the observation that the orientation of the crystal nucleus should coincide with that of the original crystal.4) Crystal nucleation was followed for o-benzylphenol after the liquid was cooled very rapidly from above fusion point to below the α glass transition temperature. It was found in a certain temperature region that the crystal nuclei were formed, then extinguished, and formed again after further long duration.5) In addition to a normal liquid (L_N) phase, another amorphous (L_C) phase was confirmed to exist in triphenylphosphite. Based on the α relaxation properties of the L_N and L_C phases, it was discussed that, in general, the α molecular rearrangement process is controlled by two relatively independent factors : the size of structurally ordered cluster and the degree of the order in the cluster, and that the relaxation time is basically determined by the latter factor. Less

由于分子的排列本质上是无序的，过冷液体和玻璃的科学还不够发达。然而，分子聚集中有序性的发展对它们在低温下的特性起着重要作用。对于这些系统的结构，我们提出了一个“有序簇聚集模型”。在本研究中，首先尝试实现二维玻璃，直接观察分子聚集及其变化，然后基于所提出的模型发现或解释新的现象。1)搭建了一台工作在液氮温度下的扫描隧道显微镜。发现了沉积在石墨表面的邻三联苯分子，但还没有成功地形成并观察到它的单层玻璃。2)用介电方法研究了简单苯衍生物的α和β弛豫时间，并系统地改变了1和3-…上的取代基更多的职位。虽然β弛豫时间与异丙基内取代基的大小以及氢键形成与否、-OH和NH_2基团的存在与否无关，但α弛豫时间强烈地依赖于这些因素。在β玻璃化转变区，快速冷却的样品的α驰豫强度明显大于缓慢冷却的样品。3)7个含苯环的化合物均相成核结晶，这表明环的存在对其观察是重要的。4)当液体从熔点以上快速冷却到α玻璃化转变温度以下时，邻苯基苯酚发生晶核形核。发现在一定的温度范围内，晶核形成，然后熄灭，并在较长时间后再次形成。5)除了正常的液体相(L_N)外，还证实了亚磷酸三苯酯中存在另一个非晶相(L_C)。根据L_N相和L_C相的α驰豫性质，讨论了α分子重排过程一般由两个相对独立的因素控制：结构有序团簇的大小和团簇中的有序度，驰豫时间基本上由后者决定。较少