Preparation of nanosize polyaniline by solid-state polymerization and determination of crystal structure

Background: Nanosize polyaniline has several advantages in both the fabrication of nanodevices and for preparing nanoscale electrical connections in highly conducting polymer composites. Results: Nanosize polyaniline with a diameter of 30-60 nm was prepared using a solid-state polymerization process (PANI-S) by mixing an equimolar quantity of ammonium persulfate and anilinium chloride crystals with a mortar and pestle. Polyaniline was also synthesized using a conventional oxidative polymerization method (PANI-C) in an aqueous medium for comparison. Conductivity and contact angle measurements, infrared spectroscopy, ultraviolet spectroscopy, transmission electron microscopy and thermogravimetric analysis were carried out. An in-depth investigation of the crystal structure of these polymers was carried out through powder X-ray diffraction analysis. Conclusion: PANI-S exhibited lower conductivity due to the presence of less emeraldine base form, lower crystallinity, greater d-spacing and greater inter-chain separation than PANI-C. The hydrophilicity and thermal stability of PANI-S were higher than those of PANI-C. The unit cell volume of PANI-S was much higher, resulting in a larger crystallite size and a greater number of atoms in the unit cell than PANI-C.