Preparation of polyaniline–titanium dioxide hybrid materials in supercritical CO2

Abstract Polyaniline–titanium dioxide (PANI–TiO 2 ) hybrid materials were synthesized in supercritical CO 2 using two different methods. In the first method, separately synthesized TiO 2 particles were mixed with aniline to perform polymerization in supercritical CO 2 . The second method included the preparation of aniline–TiO 2 hybrids through a sol–gel reaction of titanium isopropoxide in the presence of aniline. Further polymerization of aniline–TiO 2 hybrids in supercritical CO 2 produced PANI–TiO 2 hybrid particles. The final products showed the intrusion of PANI into the internal structure of TiO 2 . The PANI–TiO 2 hybrid materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), electrical conductivity (EC), Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) measurements. PANI–TiO 2 nano-composites synthesized with the first method showed a relatively low electrical conductivity of 3.78 × 10 −2  S/cm at 20 °C. TGA suggested that the particles contained 40.6% TiO 2 by mass and showed a strong interaction at the interface of TiO 2 and PANI. The electrical conductivity of the hybrid particles produced using the second method increased to 7.75 × 10 −2  S/cm and the TGA results showed 34.4% TiO 2 by mass. Through SEM and TEM analyses it was confirmed that the PANI has been interpenetrated into the three-dimensional network of the TiO 2 when the second method was used.