含氟光敏单体的液晶光控取向研究

Alignment Behavior of Liquid Crystals on the Crosslinked Film of Monomers with Fluorinated Groups

制备了系列含氟光敏单体材料,六氟双酚A双肉桂酸酯(6F-BADE)与含二氟亚甲基结构的肉桂酸酯(FDE-n,n=2,3,4).材料在线性偏振紫外光辐照下均可发生定向光交联反应,通过红外光谱和凝胶渗透色谱跟踪检测,表明光交联类型为[2+2]环加成.单体光聚后形成的取向膜对液晶分子排列效果不同,6F-BADE取向膜诱导液晶分子垂直排列,FDE-n取向膜诱导液晶分子平行排列.用原子力显微镜对取向膜表面进行表征,均未观察到明显的各向异性分布现象.应用量子力学半经验方法AM1分析发现单体分子极性有较大差异,认为分子极性的差异是诱导液晶取向不同的主要原因.

A series of photosensitive monomers, including hexafluorobiphenol A dicinnamate ester （6F-BADE） and fluorinated dicinnamate esters （FDE-n, n=2, 3, 4）, were synthesized. These monomers could be crosslinked under irradiation of linearly polarized ultraviolet light. FTIR spectra and GPC spectra were used to measure the results in real time. The results indicated that the crosslinking reaction was [2＋2] cycloaddition. The photoalignment films formed by monomers under the ultraviolet light could induce different types of liquid crystal （LC） alignments ： 6F-BADE and FDE-n films resulted in vertical and parallel alignments, respectively. AFM images of the surfaces of the alignment showed no obvious anisotropy on the surfaces of these films. Finally, it was found that, using semiempirical method AM1 of quantum mechanics, the difference of the polarities among different monomer molecules was large, which was considered to be the main cause resulting in different LC alignments.