Synthesis of polyaniline-based inks, doping thereof and test device printing towards electronic applications

Polyaniline (PANI) was synthesised by oxidation polymerization starting from aniline dimer, thus avoiding the use of a toxic/mutagenic substance such as aniline. In order to work in an aqueous phase, polystyrene sulphonate (PSS) was used as an emulsioning/doping agent. The fine tuning of oxidant quantity allowed the production of PANI in the mixed leucoemeraldine/emeraldine oxidation states. PANI/PSS was solubilised in dimethylsulphoxide and used as ink for the fabrication of inkjet printed tracks, which showed an interesting negative capacitance effect that can be attributed to the presence of different oxidation states and the partial doping obtained by the use of PSS. Negative capacitance devices are extremely attractive in high frequency applications where positive parasitic capacitances have to be compensated.