Conductive chitosan-graft-polyaniline copolymer: synthesis and characterization

Chitosan-graft-polyaniline (Chi-g-PANI) copolymer was successfully synthesized via the chemical oxidative polymerization method. The influence of various synthesis conditions, including the weight ratio of chitosan/aniline, amount of ammonium persulfate (APS), concentration of nitric acid ([HNO3]) and synthesis temperature, on grafting % and electrical conductivity of Chi-g-PANI copolymer was investigated. The synthesized Chi-g-PANI copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectrophotometer (UV–Vis), 13C solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffractometer (XRD), field-emittance scanning electron microscope (FE-SEM) and a four-point measurement method. The optimum synthesis condition was identified as the weight ratio of chitosan/aniline = 2, amount of APS = 0.49 g, [HNO3] = 0.1 M and synthesis temperature at 25 °C. The grafting % and electrical conductivity of the Chi-g-PANI copolymer at the optimized conditions were 92% and 8 × 10–3 S/cm, respectively. Results of FTIR and 13C solid-state NMR showed that PANI was successfully grafted onto the molecular chains of chitosan. UV–Vis analysis confirmed that the electronic transition behavior of Chi-g-PANI copolymer was similar to that of PANI. Meanwhile, XRD results revealed the crystallinity of chitosan was destroyed by PANI during copolymerization. Furthermore, FE-SEM results demonstrated that the morphology of the Chi-g-PANI copolymer was obviously different from that of chitosan or PANI.