纳米级润滑膜分子排列取向的拉曼光谱表征技术

Molecular alignment of nano-thin film using Raman spectroscopy

利用激光拉曼散射技术,对剪切作用下受限于钢球与石英盘之间的纳米级液晶5CB的分子排列取向进行研究.结果表明,在特定的实验条件下,可以得到高信噪比的纳米级润滑膜的拉曼散射信号(20∶1).同时发现,当激光偏振方向与剪切运动方向平行(垂直)时,所得拉曼信号强度达到最大(小)值,表明纳米级液晶5CB分子在剪切诱导作用下,沿剪切运动方向趋于定向排列.另外,当钢球与石英盘之间的剪切速度逐渐增大时,受限的纳米级液晶5CB的拉曼信号强度也逐渐增大.最后,利用根据相对光强干涉原理研制的纳米膜厚测量仪对纳米级液晶5CB润滑膜的膜厚值进行了初步测试与分析.

Molecular alignment of nano-thin liquid crystal 5CB film confined between highly polished steel ball and quartz disk under shear is studied using Raman spectroscopy. The results show that an acceptable signal-to-noise ratio as high as 20：1 can be obtained under certain experimental conditions. In addition, the intensity of the Raman spectrum reaches its peak （minimum） value when polarization of the laser is parallel （perpendicular） to the direction of shear motion. This indicates that the molecules of liquid crystal 5CB film are oriented along the direction of shear motion. Furthermore, the influence of shear speed on the intensity of Raman spectroscopy of nano-thin liquid crystal 5CB film was investigated, and its film thickness was analyzed based on a relative optical interference intensity technique.