环丁醇温致相变的原位拉曼光谱研究

发布时间：2018-02-15 06:05

本文关键词： 环丁醇拉曼光谱相变差示量热扫描　出处：《光谱学与光谱分析》2016年02期 　论文类型：期刊论文

【摘要】：采用拉曼光谱和红外光谱解析了常温条件下环丁醇的各个振动模式及其与分子构象间的关联,结果表明液态环丁醇以赤道反式构象为主,并含有少量的赤道间扭式构象。在此基础上结合差示扫描量热技术和变温拉曼光谱,原位研究了环丁醇的温致相变过程和分子构象随温度的变化。结果表明,冷却至140K的过程中,环丁醇并未结晶固化,而是保持亚稳定的无序液体状态,即出现过冷现象,继续降温至138K出现玻璃化转变。升温过程中,在170K时出现放热峰,同时有新的拉曼峰出现,并且拉曼峰的半高宽和强度发生明显的突变,表明环丁醇由无序结构转变为有序的结晶相。因此,我们获得了环丁醇的温致相变序列:液态→过冷液体→玻璃态→结晶态→液态。通过对环丁醇不同分子构象的拉曼特征峰的定量分析,证实环丁醇在降温过程中,反式构象和间扭式构象的比例未发生明显改变,即没有发生构象变化。然而升温时,伴随170K时结晶态的转变,反式构象特征峰的相对强度减小,表明部分分子由赤道反式构象转变为赤道间扭式构象。该研究结果对进一步理解和研究其他有机小分子的温致相变和构象变化具有指导意义。
[Abstract]:The vibrational modes of cyclobutanol at room temperature and their correlation with molecular conformation were analyzed by Raman and infrared spectra. The results show that the liquid cyclobutanol is mainly equatorial trans-conformation. On the basis of differential scanning calorimetry (DSC) and variable-temperature Raman spectroscopy, the temperature induced phase transition of cyclobutanol and the variation of molecular conformation with temperature are studied in situ. In the process of cooling to 140 K, cyclobutanol did not crystallize and solidify, but maintained a metastable disordered liquid state, that is, the phenomenon of undercooling, and then the glass transition occurred at 138K. During the heating process, the exothermic peak appeared at 170 K. At the same time, a new Raman peak appeared, and the peak width and intensity of the Raman peak changed obviously, which indicated that cyclobutanol changed from disordered structure to ordered crystalline phase. Therefore, we obtained the temperature induced phase transition sequence of cyclobutanol: liquid phase change. 鈫扴upercooled liquid. 鈫扜lass state. 鈫扖rystalline state. 鈫扡iquid state. By quantitative analysis of Raman characteristic peaks of cyclobutanol in different molecular conformations, it is proved that the ratio of trans-conformation to inter-torsional conformation does not change obviously during the cooling process of cyclobutanol, that is, no change of conformation occurs. With the transition of crystalline state at 170 K, the relative strength of the trans-conformational characteristic peak decreases. The results show that some of the molecules are transformed from the equatorial trans conformation to the equatorial torsional conformation. The results of this study are useful for further understanding and studying the thermo-induced phase transitions and conformation changes of other organic small molecules.
【作者单位】：郑州轻工业学院物理与电子工程学院;
【基金】：国家自然科学基金项目(11404292)资助
【分类号】：TQ233.1;O657.37

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