Charge transport and electrical conductivity studies on poly(aniline-co-p-nitroaniline)

Author(s): YahyaA.Ismail*, FaizMohammad, AfaqAhmad

Copolymers of aniline with p-nitroaniline were synthesized for different molar ratio of the respectivemonomers in acidicmediumusingK2S2O8 as oxidant. The two probe electrical conductivitywasmeasured on the pressed pellets of the polymers at frequencies of 100Hz and 10 KHz. The relative frequency dependence of electrical conductivity on the pH of the reaction media as well as on the copolymer composition and the temperature dependence of electrical conductivities were studied. All the copolymers showed lower electrical conductivity than that of polyaniline which decreased as the ratio of the nitroaniline units increased in the copolymer backbone. The electrical conductivity at the 10 KHz was greater than that measured at 100 Hz. The frequency dependence increased as the ratio of the nitroaniline units increased as well aswith the increase in the pH of the reaction medium. The decrease of electrical conductivity is explained in terms of the decreased extent of conjugation, increase in the band gap caused by the increased phenyl ring torsional angles, decreased inter chain diffusion of the charge carriers and greater electron localization. The observation on frequency dependence of electrical conductivity suggested the evidence of greater electron localization in copolymers. We suggested that greater the electron localization greater will be frequency dependence of electrical conductivity. Temperature dependence of electrical conductivity showed that the effect of moisture on electrical conductivity has a negligible effect on both the polyaniline and copolymers and a combination of conduction mechanism are operating depending on the temperature ranges.

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