Preparation, Characterization, and Conductivity of Polyaniline Doped with 12-Tungstoboric Acid

The Keggin type 12-tungstoboric acid (H5BW12O40) was prepared. Aniline was oxidized in an aqueous solution of H5BW12O40 to synthesize a series of polyanilines doped with the 12-tungstoboric acid (PANI-[H5BW12O40]), using ammonium persulfate as an oxidant. The effects of the initial weight ratio x (x=0.005 similar to 0.100) of H5BW12O40 to aniline on the properties of PANI-[H5BW12O40] were investigated by FTIR, UV-vis, XRD, and conductivity measurement. The results showed that PANI in PANI-[H5BW12O40] was in the emeraldine salt state, and the 12-tungstoboric anions were incorporated into the chains of PANI more and more with increasing values of x. The oxidation degree of PANI in PANI-[H5BW12O40] was strongly dependent on x. As the weight ratio x reached 0.040, the oxidation degree of PANI in PANI-[H5BW12O40] increased obviously. The reason that electrical conductivity of PANI-[H5BW12O40] decreased sharply at x=0.040 was attributed to the increase of the oxidation degree resulted by the excess of H5BW12O40 used in the preparation.