Studies on Synthesis and Effect of Dopants on Conductivity and Morphology of Organically Soluble Poly(o-anisidine)

Abstract

Synthesis of poly(o-anisidine) doped with various protonic acids by using ammonium persulphate as oxidizing agent were carried out in aqueous acid media. Influences of protonic acids on the physicochemical properties were investigated. The various process parameters were optimized to obtain poly(o-anisidine) in the conducting salt phase form. The results are discussed with references to different protonic acids. It was observed that poly(o-anisidine) is highly soluble in organic solvents, such as m-cresol and N-methyl pyrrolidinone (NMP). The polymers were characterized by UV-Visible, FTIR, SEM, XRD and conductivity measurements. A result shows that, different types of dopant acids HCl, H₂SO₄ and HClO₄ affect the morphology and electrical conductivity of the polymer. The electrical conductivity of the polymer follows the order HCl >H₂SO₄>HClO₄. Thus the effect of dopant ion type and the size of its negative ions influence the physico-chemical properties. UV-Vis absorption spectra shows peaks at 740–783 nm with shoulder at 380–420 nm as characteristic peaks for the emeraldine salt (ES) phase of poly(o-anisidine) POA. The FTIR spectra show a broad and intense band at ∼2800–3001 cm⁻¹ and ∼1159–1170 cm⁻¹ that account for the formation of ES phase of the polymer. The X-ray diffraction spectra show a characteristic peak at 20–30^o, 2θ range which reveals partial crystalline structure. The conductivity of the poly(o-anisidne) salt was found to be in the range of 10⁻³ to 10⁻² S/cm. SEM studies of poly(o-anisidine) doped with HCl shows the continuous granular uniform morphology with sub-micrometer evenly distributed particles of size ∼100–200 nm.

Keywords:

• Poly(o-anisidine)
• conductivity
• morphology
• dopants effects

Acknowledgments

We sincerely acknowledge financial support from UGC, Nowrosjee Wadia College Pune, BCUD, Pune University and Indian Academy of Science Bangalore. Also, we are thankful to the National Chemical Laboratory, Pune for performing analysis. The authors are very thankful to Dr. V.T. Dangat for valuable suggestions.