Organosoluble and light-colored fluorinated polyimides based on 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-1-phenylethane and various aromatic dianhydrides

To investigate the CF3 group affecting the coloration and solubility of polyimides (PI), a novel fluorinated diamine 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-1-phenylethane (2) was prepared from 1,1bis(4-hydrophenyl)-1-phenylethan and 2-chloro-5-nitrobenzotrifluoride. A series of light-colored and soluble PT 5 were synthesized from 2 and various aromatic dianhydrides 3a-f using a standard two-stage process with thermal 5a- f(H) and chemical 5a-f(C) imidization of poly(amic acid). The 5 series had inherent viscosities ranging from 0.55 to 0.98 dL/g. Most of 5a-f(H) were soluble in amide-type solvents, such as N-methyl-2-pyrrolidone (NMP), N,N- dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF), and even soluble in less polar solvents, such as m-Cresol, Py, Dioxane, THF, and CH2Cl2, and the 5(C) series was soluble in all solvents. The GPC data of the 5a-f(C) indicated that the and Mw values were in the range of 5.5-8.7 x 10(4) and 8.5-10.6 x 10(4) respectively, and the polydispersity index (PDI) Mw/Mn values were 1.2-1.5. The PT 5 series had excellent mechanical properties. The glass transition temperatures of the 5 series were in the range of 232-276 degrees C, and the 10% weight loss temperatures were at 505-548 degrees C in nitrogen and 508-532 degrees C in air, respectively. They left more than 56% char yield at 800 degrees C in nitrogen. These films had cutoff wavelengths between 356.5-411.5 nm, the b* values ranged from 5.0-71.1, the dielectric constants, were 3.11-3.43 (1MHz) and the moisture absorptions were in the range of 011-0.40%. Comparing 5 containing the analogous PI 6 series based on 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenylethane (BAPPE), the 5 series with the CF3 group showed lower color intensity, dielectric constants, and better solubility. (c) 2005 Wiley Periodicals, Inc.