Synthesis and characterization of fluorinated polyimide oligomers terminated with a phenylethynyl group

Novel all-aromatic phenylethynyl-terminated imide oligomers were prepared by the reaction of 4,4-oxydiphthalic anhydride (ODPA) or 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 1,4-(4-amino-2-trifluoromethyl-phenoxy)-2-(3′-trifluoro-methylphenyl) benzene and 4-(1-phenylethynyl)1,8-naphthalic anhydride (PENA). The resulting polymers were thermally crosslinked at 370 °C. The cured polymers exhibited good solvent resistance and high thermal stability up to 540 °C under nitrogen. They also exhibited small light absorption at 1.31 and 1.55 μm. The refractive index of the polymers was in the range of 1.5515-1.5976 at 1550 nm. The surface relief depth of the phenylethyl terminated imide (PETI) oligomer films before and after curing was less than 1 nm over a range of 1 μm × 1 μm.