Synthesis of higher soluble nanostructured polyaniline by vapor‐phase polymerization and determination of its crystal structure

Higher soluble nanostructured polyaniline was prepared by vapor‐phase polymerization after passing aniline vapor through an aqueous acidic solution of ammonium persulfate (PANI‐V). Polyaniline was also synthesized by the conventional oxidative polymerization method (PANI‐C) in an aqueous medium for the comparison of its properties with PANI‐V. PANI‐V exhibited lower conductivity but higher hydrophilicity and higher solubility (2–3 times) in different solvents, such as tetrahydrofuran, N‐methyl‐2‐pyrrolidone, dimethylsulfoxide, N,N‐dimethyl formamide, and m‐cresol at room temperature compared with that of PANI‐C. The thermal stability of PANI‐V was higher than that of PANI‐C. In‐depth investigations of the crystal structures of PANI‐C and PANI‐V were performed through powder X‐ray diffraction analysis. The PANI‐V showed a less ordered structure with a lower crystallinity and crystallite size and with a higher d‐spacing and interchain separation compared with PANI‐C. The unit cell volume of PANI‐V was significantly higher with a greater number of atoms in the unit cell than that of PANI‐C.