Highly soluble polyimide based on asymmetric diamines containing trifluoromethyl group for high performance dielectric material

In this study, we report the newly synthesized asymmetric diamine monomers and polyimides (PIs). The new diamines containing a trifluoromethyl group, 4- (4-amino-3-(trifluoromethyl)phenoxy)-2,6-dimethylaniline (ARFPA) and 4-(4-amino-2-(trifluoromethyl)phenoxy)-2,6-dimethylaniline (ALFPA) were synthesized by the nucleophilic aromatic substitution reaction, followed by reduction of nitro groups. The new PIs were synthesized by the conventional polycondensation from the newly synthesized diamines and 6FDA (4,4′-(hexafluoroisopropylidene)diphthalic anhydride). The all PI films showed the improved thermal stability (a temperature of 5% loss in weight) in the range of 523-562 °C and high glass transition temperature (T_g>307 °C). The all PIs also exhibited good solubility in several solvents including chloroform, dimethyl sulfoxide, ethyl acetate, and acetone. Additionally, the PIs showed a low refractive index (1.5470-1.5475 at 637 nm) as well as a low dielectric constant. [Figure not available: see fulltext.].