Mechanochemical synthesis of polyaniline in the presence of polymeric sulfonic acids of different structure

Abstract

We demonstrate that the solvent-free mechanochemical method, previously used for the synthesis of polyaniline (PANI) protonated with low molecular weight inorganic acids, can be extended to the preparation of conductive, all-polymeric PANI/polyacid molecular composites. Two polymeric sulfonic acids differing in their chain rigidity were selected as PANI protonating agents, namely: poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA, flexible backbone polyacid) and poly(p,p′-(2,2′-disulfonic acid)-diphenylene-tere-phthalamide) (t-PASA, rigid backbone polyacid). Spectroscopic (UV–vis–NIR, FTIR, EPR), morphological, structural (TEM), electrochemical and spectroelectrochemical properties of the mechanochemically prepared molecular composites were compared with those determined for their analogs synthesized by oxidative polymerization in aqueous solution. The mechanochemically synthesized molecular composites show a characteristic layer-type morphology, distinctly different from that observed for the composites prepared chemically in aqueous solutions. UV–vis–NIR and FTIR spectroscopy clearly indicate better polaron delocalization in the mechanochemically prepared samples. These results are in line with those obtained in ESR, electrochemical and spectroelectrochemical investigations unequivocally showing better charge carrier delocalization in the mechanochemically prepared composites. The measured dc-conductivity of the mechanochemically prepared samples is 24mS/cm and 31mS/cm for PANI/PAMPSA and PANI/t-PASA, respectively.