A series of substituted poly(biphenylene oxide)s (PBPOs) was synthesized via nucleophilic nitro displacement reactions. High molecular weight PBPO's with nitrile groups were effectively synthesized from the polymerization of A-B type monomers with K2CO3 as a base in N-methyl-2-pyrrolidinone (NMP) at 140 degrees C. The polymers are completely amorphous. soluble in polar aprotic solvents, and formed flexible films on solution casting. Para-linked PBPO with nitrile groups showed excellent thermal properties such as high 5% weight loss temperature above 530 degrees C and T-g at 241 degrees C which is higher than those of commercially available PPO (TM) (T-g = 210 degrees C). The pendent nitrile groups of PBPO were easily transformed to carboxylic acid groups by acidic hydrolysis. (c) 2006 Elsevier Ltd. All rights reserved.