硬脂酸亚甲基面外弯曲振动红外光谱研究

Study on Stearic Acid Methylene Out-of-Plane Wagging Vibration by Two-Dimensional Infrared Spectroscopy

在20~120℃的温度范围内,采用一维红外光谱和四阶导数红外光谱测定硬脂酸亚甲基面外弯曲振动模式（ωCH2）,研究温度对硬脂酸分子结构的影响。实验结果表明,在1 180~1 320 cm^-1的频率范围内,硬脂酸存在＂第一特征频率红外吸收谱带＂和未见文献报道的＂第二特征频率红外吸收谱带＂。硬脂酸脂肪链由全反式有序构象改变为无序构象的临界温度为80~85℃。进一步采用二维红外光谱技术研究了温度对于硬脂酸ωCH2红外吸收强度变化趋势的影响。

The out-of-plane wagging vibration mode（ωCH2） of stearic acid methylene was determined by onedimensional infrared spectroscopy and fourth-derivative infrared spectroscopy,and the effect of temperature on the molecular structure of stearic acid was studied. The experimental results have shown that stearic acid has a first characteristic frequency infrared absorption spectrum band as well as a second characteristic frequency infrared absorption spectrum band that has not been found to be published in literature in the frequency range of 1 180 to 1 320 cm^-1. The critical temperature at which the aliphatic chain of stearic acid changes from all-trans ordered conformation to disordered conformation is 80 to 85 ℃. In addition,two-dimensional infrared spectroscopy was used to study the effect of temperature on the infrared absorption intensity variation trend of stearic acid ωCH2.