Preparation of polyaniline–titanium dioxide hybrid materials in supercritical CO2

Polyaniline–titanium dioxide (PANI–TiO2) hybrid materials were synthesized in supercritical CO2 using two different methods. In the first method, separately synthesized TiO2 particles were mixed with aniline to perform polymerization in supercritical CO2. The second method included the preparation of aniline–TiO2 hybrids through a sol–gel reaction of titanium isopropoxide in the presence of aniline. Further polymerization of aniline–TiO2 hybrids in supercritical CO2 produced PANI–TiO2 hybrid particles. The final products showed the intrusion of PANI into the internal structure of TiO2. The PANI–TiO2 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–TiO2 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% TiO2 by mass and showed a strong interaction at the interface of TiO2 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% TiO2 by mass. Through SEM and TEM analyses it was confirmed that the PANI has been interpenetrated into the three-dimensional network of the TiO2 when the second method was used.