Effect of annealing on structural and optical properties of polypyrrole doped with different acids

Abstract Polypyrrole (pure) and polypyrrole doped with different protonic acids (HCl and H₃PO₄) have been synthesized using NaOH as reducing agent in aqueous HCl medium and ammonium persulphate (APS) as an oxidant, respectively. These pure and doped samples were named as S1, S2, and S3 for further investigations. These pure and doped samples were annealed at 200^oC for 4 hr. The amorphous nature of these annealed and as‐prepared polypyrrole samples was confirmed by XRD. FTIR spectra and SEM images of all the samples were taken at room temperature, which indicate: significant change in annealed samples. To calculate the energy band gap of all the samples, the absorption spectra were recorded by USB‐2000 spectrophotometer at room temperature in the wavelength range 300–800 nm. From the analysis of absorption spectra, optical band gap of as‐prepared samples (S1–S3) was determined to be 2.64, 2.43, and 2.29 eV, respectively and for annealed samples A1–A3 values obtained were 2.30, 2.25, and 2.17 eV. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers