Applications of polyaniline doubly doped with p-toluene sulphonic acid and dichloroacetic acid as microwave absorbing and shielding materials

Doped-polyanilines (PAnis) were prepared at O degrees C using different synthesized parameters such as different ratio of dopants like p-toluene sulphonic acid (pTSA) and dichloroacetic acid (DCA), oxidant (ammonium peroxydisulfate, APS) and various kind of solvents (H2O, HCl aqueous and H3PO4 aqueous). The doped-PAnis were then characterized by UV-vis, FTIR and thermogravimetric analysis. Generally, it is important to control the synthesized parameters to get the expected value of dielectric constants and conductivities in order to improve the microwave behavior of PAnis. Microwave behaviors of PAnis were studied using a microwave vector network analyser from 0.3 GHz to 13.5 GHz. Sample E with Ani/pTSA/DCA ratio of 1/1/1 and synthesized in H-2,O with APS ratio of I posses most efficient doping during polymerization, thus it has a maximum conductivity of 9.86 S cm(-1). This sample has a lower dielectric loss (epsilon(r)" = 5. 1) and negative dielectric constant (epsilon(r)' = -15.2), thus leading to more disordered movement of charge carriers along the backbone of polymer. Consequently, this sample exhibited better microwave property since only 1.07-4.90% of the microwave energy was being transmitted in frequency range of 4-13.5 GHz. In conclusion, this sample is a good microwave shielding and absorbing, materials at higher frequency. (c) 2007 Elsevier B.V. All rights reserved.