液晶分子吸附引起的排列记忆效应

In the work, wedge cells were adopted and the orientational order parameters distributed in the liquid crystal interface layer was investigated. It was clarified that the surface order parameter is about 1/2 of that in bulk when the surface rubbing treatment is very strong, and the surface order parameter becomes 1/6 of that in bulk when without any alignment treatment on alignment films that means by memory effect. It was also obtained that the surface anchoring strength is proportional to square of surface order parameters. It is very important to understand the mechanism of the memory effect, and we realized that the stability of liquid crystal alignment is mainly determined by the order parameter of alignment films. In the experiment we observed that the surface anchoring strength increased from 2mm-1 to 30mm-1 with memory time. It indicates that the orientational order is able to transfer from liquid crystals to polymer films through the interaction between the both. In fact 30mm-1 is the saturation value. It means that the anchoring strength caused by memory effect is rather weak, only 1/10 of the strength caused by rubbing treatment. In order to quantitatively describing the interaction between liquid crystals and polymer films, we measured the molecular adsorption energy, as 1.0eV that is the effective value because a liquid crystal molecule has multi-adsorption-points. The value of adsorption energy suggests the interaction between liquid crystal molecules and polymer film is very strong. It is the reason why the orientational order can be induced from liquid crystals to polymer film. However the adsorption energy doesn't matter with alignment anchoring strength. 30mm-1 of the memory anchoring strength is not strong enough coming into practice..Through above work, we realized that the alignment films should have molecular orientation in itself. And then, we challenged a new alignment method, photo-alignment. Photo-alignment is a kind of method without touch with each other, in which there will be no electric charges or dusts brought into liquid crystal cells as rubbing treatment does. The method of photo-alignment was proposed in the beginning of 1990's, but it has not come into practice, yet. We designed the molecule with photo-sensitive parts in both ends of the molecule and made the photo-polymerization in a common direction. A good alignment result was obtained..The above are the frontier results in the world. They give important contribution to understanding mechanism of liquid crystal alignment, and guidance to designing or renovating the alignment method..

本研究将剖析液晶记忆排列机理，澄清高分子取向膜与被吸附液晶分子之间的相互作用。具体解析分子排列有序度、测量表面处的取向锚定能、探讨液晶分子预倾角在高分子膜上的记忆强度及稳定性。本项目的研究结果，不仅会对液晶界面的物理化学理论做出贡献，而且为记忆排列在产业上的应用，提供理论依据，使液晶显示器件的成品率发生革命性飞跃。