Synthesis and characterization of transparent copolyimide films containing CF3 groups: Comparison with copolyimide nanocomposites

Copolyimides (Co-PIs) were synthesized from 2,2′-bis(trifluoromethyl)-benzidine (TFB), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 2,2′-bis(4-(4-aminophenoxy)-phenyl)hexafluoropropane (BAPP). Five Co-PIs were prepared, with 6FDA:TFB:BAPP mole ratios of 1:1:0, 1:0.8:0.2, 1:0.5:0.5, 1:0.2:0.8, and 1:0:1. The Co-PI films were obtained from poly(amic acid) (PAA) by solution casting through thermal imidization on a glass plate. The thermomechanical properties and optical transparencies of the Co-PI films with various BAPP monomer contents were investigated. Compared to conventional PI Kapton® films, all of the Co-PI films exhibited superior optical transparency. Hybrids of the Co-PI with a 6FDA:TFB:BAPP mole ratio of 1:0.5:0.5 and the organoclay dodecyltriphenyl phosphonium-mica (C12PPh-Mica) were prepared by the solution intercalation method. The thermomechanical properties, morphology, and optical transparency of the hybrids were examined as a function of organoclay content.