Effect of structural anisotropy on electrical and magnetic properties of polyaniline conducting films

• Published in: Synthetic metals 2013-02, Vol.166, p.63-69
• Main Authors: Fedorko, P., Faure-Vincent, J., Fier, I., Walmsley, L., Sniechowski, M., Jacquot, J.F., Pron, A., Travers, J.P., Djurado, D.
• Format: Article
• Language: English
• Subjects: Anisotropy; Applied sciences; Conductivity; Electrical, magnetic and optical properties; Exact sciences and technology; Magnetic properties; Organic polymers; Physicochemistry of polymers; Polyaniline; Properties and characterization; Structure
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2013.01.017

► We measured high structural anisotropy of conducting films of PANI. ► The anisotropy concerns in-plane and out-of-plane molecular arrangements. ► We measured anisotropy comparing in-plane and out-of-plane electrical conductivities. ► We measured anisotropy by comparing the in-plane and out-of-plane magnetizations of films. It is shown that highly conducting films of polyaniline protonated with di-esters of sulfosuccinic and sulfophthalic acids which contain alkyl- or alkoxy-type substituents exhibit highly anisotropic structural, electrical and magnetic properties. The layered-like structure of these films can be described as consisting of polyaniline chains which are mainly oriented parallel to the plane of the film and form regular out-of-plane stacks. These stacks are separated by bilayers of the dopant anions. Accordingly, the main anisotropy observed for solution cast films implies in-plane and out-of-plane measurements. An electrical anisotropy of about 80 is found for the in-plane and out-of-plane electronic conductivities at 5K. The temperature dependences of the in-plane and out-of-plane conductivities are qualitatively similar and have been fitted as a series combination of variable-range-hopping-type and power law contributions. A maximum is observed in the temperature dependence of the electrical anisotropy at low temperature. The films also show a clear anisotropy of magnetization whose temperature and field characteristics depend on the chemical structure of the dopant anion.