Optical study on doped polyaniline composite films

• Published in: Journal of physics. Condensed matter Vol. 16; no. 34; pp. 6195 - 6204
• Main Authors: Li, G, Zheng, P, Wang, N L, Long, Y Z, Chen, Z J, Li, J C, Wan, M X
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.09.2004; Institute of Physics
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Electrical conductivity; Drude model; Doping; Electron localization; Order disorder; Composite material; Optical conductivity; Conducting polymers; Dielectric function; Metal insulator transition; Mott insulating; Exchange interaction; Water content; Anderson insulating; Anderson model; Microstructure; Kramers Kronig analysis; Aniline polymer; Reflectance
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/16/34/018

Localization driven by disorder has a strong influence on the conducting properties of conducting polymers. Some authors hold the opinion that disorder in the material is homogeneous and that the conducting polymer is a disordered metal close to the Anderson-Mott metal-insulator (MI) transition, while others treat the disorder as inhomogeneous and have the opinion that conducting polymers are a composite of ordered metallic regions and disordered insulating regions. The morphology of conducting polymers is an important factor that has an influence on the type and extent of disorder. Different protonic acids used as dopants and moisture have influence on the polymer chain arrangement and interchain interactions. We performed optical reflectance measurements on several PANI-CSA/PANI-DBSA composite films with different dopant ratios and moisture contents. Optical conductivity and the real part of the dielectric function are calculated by Kramers-Kronig (KK) relations. sigma 1(omega) and epsilon 1(omega) deviate from the simple Drude model in the low frequency range and the tendencies of the three sample are different and non-monotonic. The localization modified Drude model (LMD) in the framework of the Anderson-Mott theory cannot give a good fit to the experimental data. By introducing the distribution of relaxation time into the LMD, reasonable fits for all three samples are obtained. This result supports the inhomogeneous picture.