Highly optically transparent/low color polyimide films prepared from hydroquinone- or resorcinol-based bis(ether anhydride) and trifluoromethyl-containing bis(ether amine)s

Abstract Two series of novel polyimides ( 5a – g and 6a – g ) containing flexible ether linkages and pendent trifluoromethyl (CF 3 ) groups were synthesized from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride ( 3a ) and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride ( 3b ) with various CF 3 -substituted aromatic bis(ether amine)s ( 4a – g ) via ring-opening polyaddition to poly(amic acid)s, followed by thermal or chemical imidization. These polyimides were readily soluble in a variety of organic solvents and could be solution-cast into flexible and tough films. The cast films exhibited high optical transparency and almost no color, with a UV–vis absorption edge of 368–382 nm and a very low b ∗ value (a yellowness index) of 6.2–15.5. They had good thermal stability with glass-transition temperatures of 186–288 °C, and most of them did not show significant decomposition before 500 °C. Moreover, these polyimide films also possessed low dielectric constants of 2.79–3.49 (at 1 MHz) and low water uptakes (