Organosoluble and colorless fluorinated poly(ether imide)s containing a bulky fluorene bis(ether anhydride) and various trifluoromethyl-substituted aromatic bis(ether amine)s: synthesis and characterization

A series of fluorinated aromatic poly(ether imide)s (PEIs)(IV) containing bulky fluorene bis(ether anhydride) [(9,9-bis[4-(3,4-dicarboxyphenoxy)-phenyl]fluorene, (I)] with various fluorinated diamines (II) were prepared through polyaddition and chemical, or, thermal imidization two-stage process. The resulting PEIs have inherent viscosities of 0.50-0.58 dL/g and are readily soluble in various organic solvents. Both chemically and thermally imidized PEI films are colorless and highly transparent with cut-off wavelengths below 375 nm and yellowness index ranging from 5.4 to 13.4. They also exhibited excellent thermal stability with glass transition temperatures (T(g)s) up to 297 ? and 10% weight loss temperatures (T(d)s) up to 583 ? in nitrogen atmosphere. Furthermore, the films have tensile strengths of 90-147 MPa and initial modulus of 2.0-2.6 GPa. Meanwhile, all the obtained fluorinated PEIs exhibited low dielectric constant of 2.69-3.19 at 1 MHz and low water uptake of 0.17-0.34%. Finally, the non-fluorinated counterparts derived from similar bis(ether anhydride) (I) with various bis(ether amine)s were prepared and compared. The results demonstrate that the fluorinated PEIs are promising candidates for high-performance films due to the bulky fluorene bis(ether anhydride) and trifluoromethyl substituted along the polymer repeat unit chain.