以4,4′二氨基二苯醚(ODA)、 3,5-二氨基苯甲酸{6-[4′-(苯基)苯氧基]}己基)酯(C6-DABBE)、4,4′-二苯醚四羧酸二酐(ODPA) 为单体,分别采用一步法和两步法共聚合成一系列含有联苯侧链的聚酰亚胺。采用衰减全反射红外光谱(ATR-FTIR)、表面能、原子力显微镜(AFM)、光电子能谱(XPS)等测试手段对薄膜的基本性能进行了研究。通过对预倾角的测量考察了液晶分子在联苯侧链聚酰亚胺薄膜上的取向性能。结果表明,一步法和两步法合成的聚酰亚胺表面分子结构基本一致,都能使液晶分子表现出良好的取向性能;液晶分子的预倾角随着聚酰亚胺侧链含量的增加而增加;由于两步法更有利于侧链在表面富集,所以采用两步法可获得更大的预倾角。

Polyimide(PI) is widely used as alignment layers in liquid crystal display industry,owing to their many excellent properties,such as heat resistance,dielectric properties,mechanical properties,chemical resistance,film-forming ability. One of the important parameters of alignment layers is pretilt angles of liquid crystal molecules.In this paper,a series of PIs containing biphenyl side chain polymerized from C6-DABBE/ODA/ODPA were synthesized via one-step method and two-step method.By means of ATR-FTIR,atomic force microscope (AFM),surface energy,X-ray photoelectron spectroscopy(XPS),the basic characters of PI films were investigated.The LC molecule alignment ability induced by polyimide alignment films and the profile of polyimide surfaces rubbed were also studied through pretilt angles.The results showed that liquid crystal on PI (C6-DABBE/ODA/ODPA) prepared by both one-step method and two-step method both could get good alignment.The pretilt angles of LC increased along with the density of side chain for higher enrichment of side chain on the surface, polyimides prepared by two-step method could show bigger pretilt angles.