Synthesis and characterization of asymmetric diamine for transparent polyimide film

Polyimide is widely used in microelectronic applications because there’re good mechanical, electrical and thermal properties. However, most polyimides colour are yellow-orange that limiting to use in optical application. The colour in polyimide occurs from electron charge transfer between amine groups and benzene ring. To reduce it, the asymmetric diamine was induced to polymer backbone. In this study, aiming to synthesis new asymmetric diamines by apply the Williamson’s ether synthesis and hydrogenation reaction. For 1st Diamine monomer, the sample from conversion of 2,2 Dinitrobiphenyl to 2,2’ Diaminobiphenyl was successfully prepared by hydrogenation reaction in hydrogen atmosphere. For 2nd Diamine monomer, the reactant including 2-Nitrophenol and 4-Chloro-3-nitrobenzotrifluoride was reacted by Williamson’s ether synthesis reaction to create asymmetric dinitro, then converse the dinitro to diamine as 2-(2-aminophenoxy)-5-(trifluoromethyl)aniline by hydrogenation reaction. Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectrometers then examined the product structureandthey were confirmed. The transparent film was made by thermal imidization, PI-1 and PI-2 were created from copolymer of 1st Diamine: 6F-Diamin: 6FDA and 2nd Diamine: 6FDiamine: 6FDA, respectively. The obtained films were characterized by Thermogravimetric analysis (TGA), Ultraviolet-Visible spectrophotometer (UV-vis) and solubility test. The target of cut off wavelength below 350 nm can be obtained. However, the synthesized film could not separate from glass substrate because of it’s brittle.