Study on Infrared Spectrophotometer for Langmuir monolayer

1采用带路滤波器改变辐射能量，研究了红外辐射对硬脂酸和硬脂酸锌Langmuir单层FT-IR外反射光谱的影响。如果使用正常FT-IR测量水平的辐射能量，则由于辐照区温度升高和随之而来的表面密度急剧下降，无法观察到大表面积上硬脂酸Langmuir单层的亚甲基拉伸带。相反，硬脂酸锌的Langmuir单层带在任何表面区域都被观察到。结果表明，单层硬脂酸锌是刚性的，分子不容易移动。预计硬脂酸盐分子之间通过锌离子紧密结合研究了不同表面积下，红外辐射对硬脂酸和硬脂醇Langmuir单层FT-IR外反射光谱影响的时间依赖性。在较低的表面压力下，Langmuir单层膜条带的峰值强度随着时间的推移而减小，最终峰值消失。此外，在较大的表面积和硬脂酸Langmuir单层中，这种下降速度比硬脂醇更快。这种下降速度的差异似乎取决于朗缪尔单分子层粘度的差异记录了硬脂酸锌Langmuir单层膜在不同表面积和表面压力松弛下的FT-IR外反射光谱，并估计了碳氢链和羧酸基的结构变化。此外，还证实了12-羟基硬脂酸锌单分子层中碳氢链的取向与硬脂酸锌单分子层中不同。

1 Effect of infrared radiation on FT-IR external reflection spectra of Langmuir monolayers of stearic acid and zinc stearate were examined by changing the amount of radiation energy with a band path filter. If the radiation energy at the level of normal FT-IR measurements was used, the methylene stretching bands of the Langmuir monolayers of stearic acid at large surface areas could not be observed, owing to the temperature increase in the irradiated region and the enormous surface density decrease which follows it. On the contrary the bands of the Langmuir monolayers of zinc stearate were observed at any surface areas. The result means that the monolayer of zinc stearate is rigid and the molecules do not move easily. It is expected that the stearate molecules bind strongly each other through the zinc cations.2 Time dependence of the effect of infrared radiation on FT-IR external reflection spectra of Langmuir monolayers of stearic acid and stearyl alcohol were examined under various surface areas. At low surface pressures, the peak intensities of the bands of the Langmuir monolayers decreased with the time lapse, and finally the peak disappeared. Moreover the decrease occurred more quickly at larger surface areas, and in the Langmuir monolayer of stearic acid than that of stearyl alcohol. This difference of the decrease speed seems to depend on the difference of the viscosity of the Langmuir monolayers.3 FT-IR external reflection spectra of Langmuir mono layers of zinc stearate were recorded under various surface areas and under surface pressure relaxation, and the structural changes of the hydrocarbon chain and the carboxylate group were estimated. Moreover it was elucidated that the orientation of hydrocarbon chain in the zinc 12-hydroxystearate monolayer was different from that in the zinc stearate monolayer.