Organo-soluble and lightly-colored fluorinated polyimides based on 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

Two series of soluble and light-colored poly(ether imide)s (III and IV) were synthesized from 2,2-bis[4-(3,4-dicarboxyphenoxyl)phenyl]hexafluoropropane dianhydride (1) and various fluorinated and non-fluorinated aromatic diamines (IIa-g and II'(a-g)) by a conventional two-step procedure that included a ring-opening polyaddition to give poly(amic acid)s, followed by chemical cyclodehydration to poly(ether imide)s. The III series were lighter-colored and higher optical transparency as compared with the non-fluorinated IV series. On comparing the IV series with the common lightly-colored aromatic polyimides (V series) based on 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), the IV series revealed less colored than the V series. This indicated that both the III and IV series were lightly-colored poly(ether imide)s. These polymer films showed the cutoff wavelength in the range of 364-371 nm. The III series showed good solubility in all testing solvents at a concentration of 5-10 wt/v % and most of IV series was soluble. These polymers exhibited glass-transition temperatures in the range of 194-264 degrees C, and the 10% weight-loss temperatures were higher than 492 degrees C under either nitrogen or air atmosphere. The III series also showed lower dielectric constants of 3.01-3.65 at 1 MHz and lower moisture absorption of 0.09-0.44 wt % than IV series.