Interfacially polymerized polyaniline/dodeca tungstophosphoric acid nanocomposites: Enhancement of conductivity and humidity sensing

Polyaniline (PAni) doped with dodeca tungstophosphoric acid (12TPA) nanomaterials prepared by interfacial polymerization are characterised via UV-vis spectroscopy, X-ray diffraction, thermogravimetry and ac impedance analysis. From the X-ray diffraction pattern, the crystallite size of the nanomaterials is found to be around 10-50 nm. The ac impedance studies on these materials in the temperature range 300-398 K show that the conductivity in PAni is due to the hopping of polarons following correlated barrier hopping model whereas in PAni doped with 12TPA (P12TPA) it is due to the tunneling of large polarons. It gives an understanding on the role of thermal annealing over the conductivity of the P12TPA, which arises from the presence of hydroxyl groups and is also evident from the thermogram. The humidity sensing behaviour of the nanomaterial elucidates the P12TPA as a good humidity sensor. The results of optical, structural and thermal analysis illustrate that PAni and 12TPA are not simply blended or mixed up, but a strong interaction is there between the polymer backbone and the polyanion. (C) 2010 Elsevier B.V. All rights reserved.