Synthesis and characterization of conducting substituted polyanilines

Poly(2-flouroaniline) (P2FAn), poly(2-chloroaniline) (P2ClAn), poly(2-bromoaniline) (P2BrAn) and poly(2-iodoaniline) (P2IAn) were synthesized chemically using K2Cr2O7, (NH4)(2)S2O8, and FeCl3 as oxidizing agents in acidic media. The effects of halogen atoms bonded to aromatic ring on the electrical and structural properties of polymers obtained were investigated. The polymers synthesized using FeCl3 have the lowest yields. The polymers were characterized by FT-IR and UV-Vis spectroscopies, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and conductivity measurements. From FT-IR spectra of polymers, it was revealed that polymerization reaction occured by head-to-tail mechanism. The UV-Vis spectra demonstrated that when the halogen atoms bonded to aromatic ring changed, the wavelenghts belong to pi --> pi* transitions were also observed to shift. The solubility tests of substituted polyanilines showed that they were highly soluble in some organic solvents. The conductivities of polymers synthesized using three different salts were measured by four-probe technique. The effects of salts and halogen groups on the conductivities were investigated. The variations in conductivities were explained with respect to electronic, steric, and anion effect. Among the polymers, P2ClAn synthesized using (NH4)(2)S2O8 salt has the highest conductivity with values of 1.32 x 10(-3) S cm(-1). Magnetic properties of the polymers salts were analyzed by Gouy scale measurements and were found that their conducting mechanism is of polaron and bipolaron nature. The thermal properties of polymers were investigated by DSC and TGA analyses and found that they had shown adequate thermal stability. Furthermore, the effects of halogen Groups and salts on the degradation temperatures were elucidated. (C) 2003 Elsevier B.V. All rights reserved.