A novel fluorinated diamine monomer, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)-3,3',5,5'-tetramethylbiphenyl, was prepared by a nucleophilic chloro-displacement reaction of 3,3',5,5'-tetramethyl-4,4'-biphenoI with 2-chloro-5-nitrobenzotrifluoride and subsequent reduction of the intermediate dinitro compound. The diamine was reacted with aromatic dianhydrides to form polyimides via a two-step polycondensation method; formation of poly(amic acid)s, followed by thermal imidization. All the resulting polyimides were readily soluble in many organic solvents and exhibited excellent film forming ability. The polyimides exhibited high T-g (312-351 degreesC), good thermal stability, and good mechanical properties. Low moisture absorptions (0.2- 1.1 wt%), low dielectric constants (2.54-3.64 at 10 kHz), and low color intensity were also observed.