含氟基团对液晶垂直排列的作用

实验发现双酚A双肉桂酸酯和六氟双酚A双肉桂酸酯单体在线偏振紫外光作用下发生光交联,形成的薄膜对液晶分子的排列效果截然不同,分别诱导液晶分子沿面平行排列和垂直排列.红外光谱分析表明光交联的类型均为2+2]环加成反应.利用原子力显微镜观察薄膜表面,没有发现明显的各向异性拓扑分布.通过测量非含氟和含氟两种交联膜的表面能大小,发现氟的引入使薄膜的表面能降低,同时表面能中的极性作用明显降低.实验结果表明,氟基团的引入导致液晶分子垂直排列.本文探讨了这种垂直排列的原因.

THE ROLE OF FLUORINATED GROUPS IN HOMEOTROPIC ALIGNMENT OF LIQUID CRYSTALS

Photosensitive monomers of bisphenol A dicinnamic ester and hexafluorobiphenol A dicinnamate ester were used for preparation of films by photo-crosslinking reaction initiated by irradiation of linearly polarized ultraviolet light.Homogeneous and homeotropic alignments of molecules of a nematic liquid crystal 5CB were obtained on the two resultant films respectively. The structure change due to the photo-crosslinking reaction process was revealed by Fourier transform infrared spectra.The surface of these films didn't show clear morphological anisotropy through atomic force microscope analysis.It was found that the surface energy,especially its polar componeut of these aligned films decreased with introduction of the fluorine groups.These results indicated that it was the fluorinated groups that caused the homeotropic alignment of liquid crystal molecules.