| Polyimide is widely used as one kind of liquid crystal alignment material. Pretilt angle is the key parameter to evaluate the property of this material. The uniformity and the photoelectric performance of the display will be affected by the selection of the pretilt angle directly. Also, the transparency and the thermal stability of the material are significant influencing factors.Polyimide generally contains with the imide group in the principal chain. In this paper, 5,5'-oxydiisobenzofuran-1,3-dione (ODPA) was synthesized as dicarboxylic acid anhydrides, and the best condition of this reaction was found out. 4,4'-(propane-2,2-diyl)dianiline (IPDA) was synthesized as aromatic diamine, propane-2,2-diyldibenzene was fabricated as the intermediate of IPDA, and this product was purified by distillation, the best conditions were 103～105℃of the temperature and 5 Pa of the pressure. After Nitration and Hydrogenation IPDA was successfully prepared. 4-(decyloxy)phenyl-3-amino-5-(methylamino)benzoate (DOP-DABO) and 3-amino-N-(4-(decyloxy)phenyl)-5-(methylamino)benzamide (DOP-DABA) were designned and synthesized as two kinds of side-chain polyimide to improve the pretilt angle, aromatic structure of the side-chain were connected with ester bond and amide bond, respectively. And each of these compounds was connected with ten carbon chain. These reactions were refered to Acylation reaction, Williamson synthesis, Hydrogenation reaction, Esterification reaction and Amidation reaction. The structure of the compounds was detected by GC, LC, MS, IR and DSC.After preparation of the monomers, five kinds of straight-chain polyamic acid (PAA) and side-chain polyamic acid were synthesized through condensation polymerization. Side-chain polyamic acid contained four kinds of ester bond and amide bond polymers. Ubbelohde viscometer was utilized to measure the viscosimeter of these solutions, and the result was discussed about the effect of the viscometer with chemical structure. All the solutions were satisfied with the range of liquid crystal alignment. Later, in the appearance of the polyamic acid, the transparency of ester bond side-chain polyamic acid is much better than amide bond side-chain polyamic acid. After imidization of the PAA, IR was used to detect the cyclization of polyimide. The conditions were 0.02 MPa vacuum and 2 h in 180℃, and polymer imidized incompletely. Therefore, the polymer was imidized in higher temperature (350℃) in muffle furnace.Liquid crystal cells were fabricated to research the alignment material, and the pretilt angle was detectd through rotating-crystal method. After that, the relation between rubbing strength and pretilt angle was disscused in this section. The pretilt angle of the ester bond side-chain polyimide is 19.1°and the pretilt angle of the amide bond side-chain polyimide is 9.4°, all the result accord with our anticipation, that this kind of material can satisfy the mode of the LCD which needs larger pretilt angle. But the polyimide which synthesized with side-chain diamine and anhydrides can not coincidence to the expected requirements of the MVA mode. The opinion to improve the capability of material was given finally.
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