Organosoluble, low-dielectric-constant fluorinated polyimides based on 9,9-bis[4-(4-amino-2-trifluoromethyI-phenoxy)phenyI]xanthene

摘要

A new trifluoromethylated bisfether amine) monomer, 9,9-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]xanthene (BATFPX), was prepared through the nucleophilic aromatic substitution reaction of 2-chloro-5-nitrobenzotrifluoride and 9,9-bis(4-hydroxyphenyl)xanthene in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of novel fluorinated polyimides were synthesized from BATFPX with various commercially available aromatic tetracarboxylic dianhydrides by one-step polycondensation in m-cresol. The resulting polyimides were readily soluble in many organic solvents such as N,N-dimethylacetamide and tetrahydrofuran, and afforded transparent, flexible and strong films with low moisture absorption (0.28-0.51%), low dielectric constant (2.85-3.26 at 1 MHz) and good optical transparency with UV-visible absorption cut-off wavelengths at 352-410 nm. All the polyimides were amorphous and exhibited high thermal stability, with glass transition temperatures of 282-330 °C, 5% weight loss temperatures above 520 °C in nitrogen or air and char yields higher than 55% at 800 °C in nitrogen. Also, these polyimides had good mechanical properties with tensile strengths of 93-118 MPa, elongations at break of 9-16% and initial moduli of 2.07-2.58 GPa.