Departments of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Langmuir. 2011 Sep 6;27(17):10407-11. doi: 10.1021/la201306a. Epub 2011 Aug 3.
Azobenzene-based self-assembled monolayers (azo-SAMs) are photoactive and become orientationally ordered when illuminated with linearly polarized light (LPL), making them attractive as dynamic alignment layers in liquid crystal cells. Azo-SAMs, however, are chemically unstable when exposed to both air and light. We have characterized the photodegradation of a methyl red-based SAM by measuring with a high-sensitivity polarimeter the optical anisotropy induced by illumination with linearly polarized actinic light after the sample is irradiated with circularly polarized light (CPL) in air. The number of unbleached, photoactive molecules in the SAM decays exponentially with CPL exposure time, lowering the reorientation rate during photowriting with LPL. Azo-SAMs in an argon atmosphere, in contrast, are chemically stable and remain photoactive even after exposure to CPL.
基于偶氮苯的自组装单分子层（azo-SAMs）具有光活性，当用线偏振光（LPL）照射时会变得取向有序，因此它们作为液晶盒中的动态对准层很有吸引力。然而，当暴露于空气和光时，azo-SAMs 的化学稳定性较差。我们通过使用高灵敏度偏振计测量在空气中用圆偏振光（CPL）照射后用线偏振光照射时产生的光学各向异性，来表征基于甲基红的 SAM 的光降解。SAM 中未漂白的光活性分子的数量随 CPL 暴露时间呈指数衰减，从而降低了用 LPL 进行光写入时的重取向速率。相比之下，在氩气气氛中的 azo-SAMs 化学稳定，即使暴露于 CPL 后仍保持光活性。
