A new unsymmetrical diamine monomer, 2,4-diaminophenyl [4'-(2",6"-diphenyl-4"-pyridyl)phenyl]ether, was successfully synthesized by nucleophilic substitution of 1-chloro-2,4-dinitrobenzene with 4-(2',6'-diphenyl-4'-pyridyl) phenol. The diamine monomer was characterized by FTIR, H-1 and C-13 NMR, and elemental analysis techniques and used for the preparation of novel polyimides (Pis) by reaction with commercially available tetracarboxylic dianhyd rides such as pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and bicyclo12.2.21-oct7-ene-2,3,5,6-tetracarboxylic dianhydride. These Pis with inherent viscosities ranged from 0.43 to 0.48 dL/g were readily soluble in many organic solvents and afforded tough and flexible films by solution casting. These polymers exhibited To between 237 and 294 degrees C, and 10% weight loss temperatures in excess of 500 degrees C with up to 56% char yield at 600 degrees C in air. Their maximum fluorescence emission in dilute (0.2 g/dL) NMP solution appeared at 450 run. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3407-3415, 2010