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

过冷液体和玻璃的科学尚未得到充分发展，因为分子排列本质上是无序的，然而，我们提出，分子聚集的有序性对其在低温下的特性起着重要作用。在这项研究中，首先尝试实现二维玻璃并直接观察分子聚集及其变化，然后发现或阐明新的结构。 1）构建了在液氮温度下工作的扫描隧道显微镜，识别出沉积在石墨表面的邻三联苯分子，但尚未成功形成和观察其单层玻璃。 .2) 通过 1 和 3-位置取代基的系统变化，对简单苯衍生物的 α 和 β 弛豫时间进行了介电研究，而 β 弛豫时间与取代基的大小相当独立。异丙基以及是否存在氢键形成、-OH 和 NH_2 基团、α 弛豫时间取决于这些因素。在预先快速冷却的样品中，β 弛豫强度明显大于在 α 玻璃化转变区域中缓慢冷却的样品。 .3) 在七种带有苯环的化合物中总共发现了基于均相成核的结晶，这表明苯环的存在对其观察很重要。晶核的取向应与原始晶体的取向一致。4)在液体从熔点以上快速冷却至α玻璃化转变温度以下后，对邻苄基苯酚的晶体成核进行了跟踪发现。 5）除了正常的液相（L_N）相外，还证实了另一种非晶（L_C）相的存在基于L_N和L_C相的α弛豫性质，讨论了α分子重排过程一般由两个相对独立的因素控制：结构有序簇的大小和有序程度。簇，弛豫时间基本上由后者决定。