A series of fluorinated copolyimides containing phthalazinone moieties were prepared from 2

2-bis(3

4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)

3

3'4

4'-benzophenone-tetracarboxylic dianhydride (BPDA) and 2-(4-aminophenyl)-4-[4-(4-aminophenoxyl)phenyl]-2

3-phthalazin-1-one (DHPZ-2NH2) for making polymeric optical waveguides. The resulting copolymers containing 050 mol% BPDA/ DHPZ-2NH2 show good solubility and are soluble in some organic polar aprotic solvents. The copolyimides also present excellent thermal stability. These polymers possess high glass transition temperature higher than 603 K and high decomposition temperature above 742 K determined by differential scanning calorimetry and thermogravimetric analysis

respectively

under a nitrogen atmosphere. Their refractive indices could be controlled by varying the ratio of 6FDA and BPDA in the copolymer from 0.5 to 1.0

and the in-plane refractive indices (nTE) range from 1.6366 to 1.6668 and the out-of-plane refractive indices (nTM) from 1.6024 to 1.6280 at 632.8 nm. The polymers birefringence (0.03420.0388) is almost independent of the 6FDA content of copolymer

which indicated that the phthalazinone-containing copolyimides could be suitable to fabricate optical waveguides possessing a low polarization dependent loss (PDL).