B. Y. Myung, J. S. Kim, J. J. Kim and T. H. Yoon
A novel diamine monomer, 2,2-bis[4(4-aminophenoxy)phenyl]phthalein-3′,5′-bis(trifluoromethyl)anilide (6FADAP) was synthesized via the Williamson ether condensation reaction from 1-chloro-4-nitrobenzene and phenolphthalein-3′,5′-bis(trifluoromethyl)anilide (6FAP), followed by hydrogenation. The monomer was characterized by Fourier transform infrared (FTIR), 1H NMR, 19F NMR, elemental analysis (EA), and titrator, and then utilized to prepare polyimides with 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). The polyimides were characterized by FTIR, NMR, gel permeation chromatography (GPC), differential scanning calorimetry, and thermogravimetric analysis. Their solubility, water absorption, CTE, dielectric constant, and refractive index were also evaluated. The polyimides prepared with 6FADAP provided excellent solubility, high glass-transition temperature (290 °C), good thermal stability (>500 °C in air), low water absorption (1.9 wt %), a low dielectric constant (2.81), a low refractive index, and low birefringence (0.0041).