Hexachloroplatinate-Initiated Synthesis of Polyaniline/Platinum Composite

The chemical synthesis of polyaniline (PANI) is explored using hexachloroplatinate, PtCl6 2. These studies provide a simple method for the spontaneous oxidation of aniline by PtCl6 2- and simultaneous formation of gram quantities of PANI/Pt composite. The degree of Pt incorporation and subsequent encapsulation is based on a multistep reduction/oxidation process. The first step involves the reduction of PtCl6 2- to PtCl4 2- or Pt(0) and formation of the aniline radical cation in solution. The further reduction of PtCl4 2- to Pt(0) can also occur after aniline oligomers and polymer are formed in solution. The platinum colloids act as nucleation sites for the polymer forming the PANI/Pt composite, which precipitates from solution. Elemental analysis, XPS, and FTIR studies of the material indicate the properties of the polymer are consistent with the formation of a polymer salt containing metallic Pt. SEM images indicate that the Pt particles have maximum diameters on the order of 0.5−1 μm with some aggregation of clusters on the surface of the polymer. The formation of the PAN/Pt composite salt influences the electronic properties of PANI/Pt lowering the conductance by ∼107 relative to PANI without Pt. The conductivity in solution is sufficient such that the representative acid doping and PANI/Pt electrochemistry is observed in HCl.