Effects of diamines and their fluorinated groups on the color lightness and preparation of organosoluble aromatic polyimides from 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy) phenyl]-hexafluoropropane

摘要

To investigate the position and amount of the CF3 group affecting the coloration of polyimides (PIs), we prepared 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane (2) with four CF3 groups with 2-chloro-5-nitrobenzotrifluoride and 2,2-bis(4-hydroxyphenol)hexafluoropropane. A series of soluble and lightcolored fluorinated PIS (5) were synthesized from 2 and various aromatic dianhydrides (3a-3f). 5a-5f had inherent viscosities ranging from 0.80 to 1.19 dL/g and were soluble in amide polar solvents and even in less polar solvents. The glass-transition temperatures of 5 were 221-265 degreesC, and the 10% weight-loss temperatures were above 493 degreesC. Their films had cutoff wavelengths between 343 and 390 nm, b* values (a yellowness index) ranging from 5 to 41, dielectric constants of 2.68-3.01 (1 MHz), and moisture absorptions of 0.03-0.29 wt %. In a comparison of the PI series 6-8 based on 2,2-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl] propane, and 2,2-bis [4-(4-aminophenoxy)phenyl] propane, we found that the CF3 group close to the imide group was more effective in lowering the color; this means that CF3 of 5, 7, and 8f was more effective than that of 6c. The color intensity of the four PI series was lowered in the following order: 5 > 7 > 6 > 8. The PI 5f, synthesized from diamine 2 and 4,4'-hexafluoroisopropylidenediphthalic anhydride, had six CF3 groups in a repeated segment, so it exhibited the lightest color among the four series. (C) 2003 Wiley Periodicals, Inc. [References: 21]