Synthesis and characterization of highly-fluorinated colorless polyimides derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) and aromatic dianhydrides

The authors report the synthesis and characterization of a polyimide (PI) series derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) (8FBPODMA). The 8FBPODMA monomer containing a perfluorobiphenyl group with two 2,6-dimethylaniline units connected by an ether bond was synthesized and polycondensed with several aromatic dianhydrides, including 4,4′-biphthalic anhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA), pyromellitic dianhydride (PMDA), and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), by the traditional two-step imidization procedure. All PIs shows high optical transparency, higher than 80% at 500 nm for a thickness of ca. 10 μm and good thermal properties. The thermal decomposition temperatures (T10%) of the PIs are in the range of 507–527 °C and the glass transition temperatures (Tg) are in the range of 280–345 °C. In addition, the PIs have low refractive indices because of their high fluorine contents. In particular, 8FBPODMA–6FDA shows a very low refractive index (1.5389) and a low birefringence (0.0054) at 637 nm. The authors describe the synthesis and characterization of a highly fluorinated polyimide (PI) series. The new diamine monomer based on perfluorobiphenyl derivative was synthesized and imidized with several aromatic dianhydrides. The resulting PIs exhibit high optical transparency and good thermal properties. In addition, the PIs have low refractive indices because of their high fluorine contents. [Display omitted] •We report the synthesis and characterization of a polyimide (PI) series.•All PIs shows high optical transparency and good thermal properties.•The PIs have low refractive indices because of their high fluorine contents.•8FBPODMA–6FDA shows a very low refractive index and a low birefringence.