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Raman spectra and conformational relaxation in glassy molecular films

玻璃分子膜中的拉曼光谱和构象弛豫

基本信息

批准号：
02640355
负责人：
ISHII Kikujiro
金额：
$ 1.22万
依托单位：
Gakushuin University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

Structure and structural relaxation in amorphous molecular films were studied by Raman and, partly, infrared spectroscopies. The films were prepared by vacuum evaporation onto cold metal substrates. Three groups of substance, normal hydrocarbons, polyphenyls, and polyacenes, were studied. Major results are summarized below.1. Structural Relaxation in Amorphous n-C_<24>H_<50>The initial films evaporated onto cold substrates were amorphous containing molecules with a large number of gauche conformation. When the temperature of the film was elevated stepwise, the number of trans conformation increased. Then, molecules with the all-trans conformation appeared. The films finally changed into the structure of the crystalline state in the temperature region around 260-280 K.2.Structural Relaxation in Amorphous BiphenylBiphenyl molecules were found to be twisted to the angle of about 30ﾟ in the amorphous state, and were changed at about 140 K into the flattened structure as in the room-temperature crystal. The amorphous film was found to change into a crystalline phase with an unknown structure when it was kept for a long time at a temperature below 140 K.3. Structural Relaxation in Amorphous Films of Naphthalene and AnthraceneMolecules of this group of substance may be considered to be rigid bodies. It has been expected that amorphous states of this kind of substance can exist only at very low temperatures. However, an amorphous film of naphthalene kept a disordered structure to the temperature as high as 120 K. In amorphous films of anthracene, an anomalous interaction between molecules found to exist even at temperatures above 200 K. These are new findings on the structure of amorphous molecular states.

用拉曼光谱和部分红外光谱研究了非晶态分子薄膜的结构和结构弛豫。薄膜是通过真空蒸发在冷金属衬底上制备的。研究了三类物质：正构烃类、多苯类和多苯类。主要研究成果总结如下：1。非晶态n-C_&lt；24&gt；H_&lt；50&gt；蒸发到冷衬底上的初始薄膜为非晶态，含有大量的Guche构象的分子。随着薄膜温度的升高，反式构象数目增加。然后，具有全反式构象的分子出现了。在260-280K的温度范围内，薄膜最终转变为晶态结构。非晶态联苯分子的结构弛豫在非晶态下扭曲到约30ﾟ角，在140K左右转变为与室温晶体相同的扁平结构。在低于140K的温度下长时间放置时，非晶薄膜转变为结构未知的晶相。这类物质的无定形薄膜中的结构弛豫可认为是刚体。人们预计，这种物质的无定形状态只能在很低的温度下存在。然而，在菲的非晶薄膜中，在高达120K的温度下仍保持着无序结构，即使在200K以上也存在分子间的反常相互作用。这是关于非晶分子态结构的新发现。