| A series of new 2,7-diamino-9,9'-bis(4-substituted)fluorenes was prepared. The diamines were polymerized with 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BisADA). A series of known 9,9'-bis(4-diamnno)-2,7-disubstituted fluorenes was also prepared and polymerized with these dianhydrides under the same environmental conditions. The properties of the polyimides obtained from both series of monomers were determined and compared. The intrinsic viscosities of the 2,7-fluorene catenated polymers ranged from 0.30 to 1.45 dl/g while those of their 9,9'-catenated analogs ranged from 0.69 to 2.33 dl/g. The glass transition temperatures of the 2,7-fluorene catenated polymers ranged from 199 to 374°C, while those of their 9,9 '-catenated analogs ranged from 275--398°C. The 9,9 '-fluorene catenated polymers were more thermally and thermo-oxidatively stable displaying 5% weight losses from 373 to 512°C in nitrogen and 354--502°C in air, respectively, when subjected to TGA. The temperatures at which the 2,7-catenated series underwent such losses in these atmospheres were 338 to 505°C and 360 to 500°C, respectively. Both series of polymers were soluble in common organic solvents and could be solution cast into flexible thin films. Thin films of the 9,9'-catenated series were more transparent than those of the 2,7-catenated series. The films of the 2,7-catenated series displayed higher negative birefringences (0.0128 to r 0.0289) than those of the 9,9'-catenated series (0.0011 to 0.0126). A study was carried out to determine the effects of two different catalysts, isoquinoline and benzoic acid, on the polymerization of the 9,9 '-fluorene catenated diamines with 6FDA and BisADA. The use of isoquinoline resulted in polymers with higher intrinsic viscosities (0.69 to 2.33 dl/g) compared to (0.55 to 1.80 dl/g). The thermal and optical properties of the polymers obtained with the two catalysts were very similar. |
