Dielectric behavior of polyaniline synthesized by different techniques

• Published in: European polymer journal Vol. 42; no. 3; pp. 676 - 686
• Main Authors: Soares, Bluma G., Leyva, Maria Elena, Barra, Guilherme M.O., Khastgir, Dipak
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2006; Elsevier
• Subjects: Applied sciences; Conductive polymer; Dielectric properties; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polyaniline; Properties and characterization; Polyaniline; Conductive polymer; Dielectric properties; Experimental study; Sulfonic acid; Dielectric relaxation; Conducting polymers; Emulsion polymerization; Dispersion polymerization; Doped polymer; Oxidative polymerization; Activation energy; Comparative study; Aniline polymer
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2005.08.013

Polyaniline doped with dodecylbenzenesulfonic acid (Pani.DBSA) was synthesized by different procedures: by a dedoping–redoping process, by one step inverted emulsion polymerization and by one step aqueous dispersion polymerization. The effect of these different techniques on the electric properties (dielectric constant, dielectric losses, and complex electric modulus) of the corresponding emeraldine base has been studied by thermal dielectric analyzer (DETA) in the temperature range −130
°C to 200
°C and in frequency range 0.03–10
5
Hz. It was found that the preparation technique has significant influence on the dielectric properties of Pani. The different synthetic routes give rise to polyaniline with different distribution of electric relaxation process, indicating different chain structure. Emeraldine base from Pani.DBSA prepared by one step aqueous dispersion polymerization exhibits one single relaxation peak with narrow distribution whereas that prepared by inverted emulsion polymerization exhibits two relaxation peaks, indicating two-phase structure as indicated by a bimodal distribution of relaxation process. Emeraldine base from Pani.DBSA prepared by dedoping–redoping process presents an intermediary behavior. Percentage crystallinity of Pani.DBSA samples has also been investigated using wide-angle X-ray diffraction analysis. Pani.DBSA prepared by aqueous dispersion exhibited higher crystallinity degree, which agrees with the higher conductivity.