Synergistic effect of copolymers composition on the electrochemical, thermal, and electrical behavior of 5-lithiosulphoisophthalic acid doped poly(aniline-co-2-isopropylaniline): synthesis, characterization, and applications

The paper reports the synergistic effect of substituent, i.e. isopropyl group on electrical, thermal, and processability of polyaniline in the presence of 5-lithiosulphoisophthalic acid (LiSIPA). The presence of substituent not only affects the electrochemical redox behavior of polyaniline but also brings changes in the optical and electronic properties of polyaniline. Evaluation of the copolymers as corrosion inhibitor for iron in 1.0 N HCl using electrochemical impedance spectroscopy and Tafel extrapolation method shows that the copolymers and homopolymer show corrosion inhibition efficiency ranging from 69 to 80% depending upon the composition of the copolymers. The copolymers doped with LiSIPA were soluble in organic solvents like methanol, ethanol, isopropanol, N-methyl pyrrolidinone, and chloroform. The compositions of the copolymers were determined by H-1 NMR spectroscopy. The conductivity of the polymers was found to be in the order of 4.9 to 10(-3) S cm(-1) depending upon the comonomer ratios and concentration of dopant. Cyclic voltammetry of the copolymers shows a shift in peak potential value from 0.157 to 0.398 V when the monomer ratio of aniline to 2-isopropylaniline in the polymerization reaction was changed from 0.9:0.1 to 0.5:0.5. The polymers were characterized by FTIR and UV-visible spectroscopy, NMR, X-ray diffraction, TGA, DSC, and cyclic voltammetry. Copyright (C) 2008 John Wiley & Sons, Ltd.