Preparation and characterization of conductive polyimide-graft-polyaniline

Polyimide graft polyaniline was successfully synthesized by a three step reaction. First, the polyimide backbone was prepared by reacting 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), 3,3′-dihydroxybenzidine (DHBD) with 4,4′-oxydianiline (ODA). Then, the hydroxyl groups of DHBD were reacted with 3-bromoaniline to link the polyimide backbone with the grafted chain. Finally, excess anilines were grafted into the polyimide chain at the prepared sites of DHBD to increase the conductive segment in the materials. The conductivities of the polyimide copolymer were in between 2.96 and 16.20 S/cm proportional to the amount of incorporated aniline in the reactions. The copolymers produced have higher thermal stability than pure polyaniline. However, the thermal stability depends on the polyimide structure and amount of polyaniline molecules cooperated. NMR spectroscopy, TGA and GPC confirmed the linkages of polyaniline grafted onto polyimide chains.

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► Successfully synthesized polyimide-g-polyaniline.
► The copolymer had higher thermal resistance while remained conductive.
► The conductivity depended on the length of the graft chain.
► The GPC and TGA results confirmed approximately same grafting amount.
► The NMR, GPC, TGA and FTIR confirmed the graft reaction.