Highly conducting and solution-processable polyaniline obtained via protonation with a new sulfonic acid containing plasticizing functional groups

New solution processing systems were studied with the goal to obtain highly conductive polyaniline films with good mechanical properties and its conducting blends with poly(methyl methacrylate). A new dopant, namely, 1,2-benzenedicarboxylic acid, 4-sulfo, 1,2-di(2-ethylhexyl) ester (DEHEPSA), was studied as a protonating agent. It was found that the use of this dopant together with dichloroacetic acid (DCAA) or difluorochloroacetic acid (DFCAA) as solvents leads to films showing conductivities of 180 and 100 S/cm, respectively. Films cast from DCAA are metallic in character down to 220 K. Since the protonation agent used exhibits doping as well as plasticizing properties, the resulting polyaniline films, in addition to high conductivity, show excellent flexibility and much lower glass-transition temperature, T-g, (280 K) as compared to polyaniline doped with other protonating agents. Moreover, the same processing system can be used for the fabrication of polyaniline-poly(methyl methacrylate) blends with low percolation threshold (much below 1 wt % of PANI). Upon casting, the overwhelming majority of the solvent can be efficiently removed from the polymer matrix, whereas the remaining residual solvent is strongly bound to the polymer matrix. For this reason, the resulting blends do not show the disadvantages of the blends cast from m-cresol which release the residual solvent upon aging.