Wang Fei, Shao Leishan, Bai Qiyao, Che Xinyuan, Liu Bin, Wang Yinghan
State Key Laboratory of Polymer Materials Engineering of China; College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, China.
Research Institute of Maoming Petrochemical Company, SINOPEC, Maoming 525021, China.
Polymers (Basel). 2017 Jun 18;9(6):233. doi: 10.3390/polym9060233.
Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3'-dimethyl-4,4'-diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM), which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15° higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers.
通过一种简单有效的方法实现了液晶（LC）的垂直取向：以基于3,3',4,4'-二苯甲酮四羧酸二酐和3,3'-二甲基-4,4'-二氨基二苯甲烷（BTDA-DMMDA PI）的聚酰亚胺引发十二烷基丙烯酸酯（DA）单体的原位光聚合。通过偏光光学显微镜（POM）表征取向行为和取向稳定性，结果表明在热处理12小时后呈现稳定的垂直取向。分别用傅里叶变换红外光谱仪（FTIR）、扫描电子显微镜（SEM）和接触角测试仪分析了从含有和不含DA单体的液晶盒上剥离的取向膜的化学结构、形态和水接触角。结果证实，DA单体在紫外线照射下发生了由BTDA-DMMDA PI引发的自聚合和接枝聚合，并聚集在PI膜表面。取向膜的水接触角高出约15°，表明表面能相对较低。总之，LC的垂直取向是由接枝有DA聚合物的PI膜的低表面自由能以及LC与DA聚合物之间的分子间相互作用引入的。
