A novel diamine monomer, containing fluorine and phosphine oxide, bis(3-aminophenyl) 3,5-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO), was prepared via Grignard reaction, and utilized to prepare polyimides with dianhydrides such as PMDA, 6FDA, BTDA or ODPA, by the conventional two-step route; preparation of poly(amic acid), followed by solution imidization. The polyimides were characterized by FT-IR, NMR, and DSC with intrinsic viscosity and refractive index also being evaluated. A phosphine oxide containing monomer, bis(3-aminophenyl)phenyl phosphine oxide (mDAPPO) and a commercial 3,3-diaminodiphenyl sulfone (mDDS) were also used for comparison. The polyimides derived from mDA6FPPO exhibited high T$sub$g/, excellent solubility and low birefringence.