AbstractThe thermal reaction of a bis(biphenylene) monomer,N,N′‐bis(biphenylene‐2‐yl)‐4,4′‐hexafluoroisopropylidenediphthalimide (3), with either of two diacetylenic monomers, bis(4‐ethynylphenyl) ether (4) or bis[4‐(phenylethynyl)phenyl] ether (5), gave polymers that contain phenanthrene units as a result of the reaction of the biphenylene groups with the acetylene groups. The reaction could be carried out in solution or in the melt, and in the latter case, reaction exotherms were found at 367°C and 386°C, respectively, for4and5. Polymer6, obtained from the melt reaction of3with5, is insoluble in all solvents and thermally stable, showing no weight loss in air up to 480°C and