Organosoluble and light-colored fluorinated polyimides from 4-tert-butyl-[1,2-bis(4-amino-2-trifluoromethylphenoxy)phenyl]benzene and aromatic dianhydrides

A novel fluorinated diamine monomer with the tert-buty group, 4-tert-butyl-[1,2-bis(4-amino-2-trifluoromethylphenoxy)phenyl]benzene (2), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride with 4-tert-butylcatechol in the presence of potassium carbonate to the yield intermediate dinitro (1), followed by catalytic reduction with hydrazine and Pd/C. Polyimides 5a-f were synthesized from diamine 2 and various aromatic dianhydrides 3a-f via thermal imidization with inherent viscosities ranging from 0.53 to 0.89 dL/g. These polymers showed well solubility together with good tensile strengths. Glass transition temperatures of 5a-f were in the range of 230-286 °C, and the 10% weight loss temperatures were almost above 500 °C. Compared with the polyimides 6 series based on 4-tert-butyl-1,2-bis(4-aminophenoxy)benzene, the 5 series showed better solubility and lower color intensity, dielectric constant, and moisture absorption. Their films had cutoff wavelengths between 354 and 402 nm, the b* values (yellow index) of 6-50, dielectric constants of 2.83-3.19 (1 MHz), and moisture absorptions of 0.08-0.18 wt%.