S. M. Kwak, J. H. Yeon and T. H. Yoon
A novel diamine, bis(3-aminophenyl)-4-(1-adamantyl)phenoxyphenyl-phosphine oxide (mDAATPPO), was synthesized via the Williamson ether reaction of 4-(1-adamantyl)phenol and bis(3-nitrophenyl)-4-fluorophenyl phosphine oxide, followed by reduction. The monomer was utilized to prepare polyimides with 6FDA, BTDA, ODPA, and PMDA by the conventional two-step synthesis, and the molecular weight was controlled to 20,000 g/mol by off-stoichiometry. In addition, solubility, intrinsic viscosity, dielectric constant, and birefringence of polyimides were also evaluated. Novel polyimides with mDAATPPO exhibited good solubility, high glass-transition temperatures (290–330 °C), excellent thermal stability (>500 °C), low dielectric constants (2.77–3.01), low refractive indices, and low birefringence values (0.0019–0.0030).