Polyaniline (PANI) is one of the most common polymers known for its conducting properties. However, poor water solubility limits its applications. In this work, PANI has been functionalized with sulfonic acid groups to produce sulfonated PANI (SPANI) offering excellent solubility in water. To compensate for the decrease of electrical conductivity due to functionalization, SPANI was combined with reduced graphene oxide (RGO) to form SPANI/RGO composites with interesting optical, thermal, and electrical properties. The composites have been characterized using X‐ray diffraction (XRD), field emission scanning electron microscopy, UV–vis absorption spectroscopy, Raman spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, and four probe electrical conductivity measurement. The SPANI/RGO composites show increased thermal stability, reduced optical band gap and improved electrochemical properties compared with the pure polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42766.

Abstract. Polyaniline (PANI) is the most important conducting polymer with excellent electrochemical properties. So PANIbased biosensors may find wide applications in medical diagnostics. We report here a ternary nanocomposite of gold nanoparticle-decorated single-walled carbon nanotubes (SWCNTs) embedded in sulfonated polyaniline matrix, prepared using a simple solvothermal chemical route. The structural and morphological characteristics have been determined by electron microscopy, X-ray diffraction and Raman spectroscopy. Optical characteristics of the nanocomposite have been determined by ultraviolet (UV)-visible absorption spectroscopy and photoluminescence spectroscopy. The direct current (DC)-conductivity measurement of the material shows a significant increase in electrical conductivity at 353 K from 7.80·10 -2 S/m for pure SPANI to 10.91 S/m for the 3-phase nanocomposite as synthesized in the present investigations. Thus the incorporation of SWCNT/Au nanohybrid fibers in the PANI matrix enhanced its electrical properties. Sulfonation increased the processability of the material, as the samples have now been found to be soluble in water and common organic solvents like DMSO. Such a functional nanocomposite will make an excellent biosensor electrode material.

Sulfonated polyaniline (SPANI) has emerged as a promising polymer in the past few decades due to its solubility in water and relatively moderate conductivity. However, to date, literature data on the optical characterization of SPANI are very limited and preliminary in nature. In the present work, SPANI is synthesized by direct sulfonation of emeraldine salt form of polyaniline with chlorosulfonic acid in an inert solvent. Detail photophysical properties of SPANI are investigated in aqueous medium by using steady state (concentration, temperature, pH, and excitation wavelength dependence) and time-resolved spectroscopic techniques. The steady state fluorescence emission measurements are carried out carefully to avoid inner filter effect (especially secondary inner filter effect or reabsorption effect) as well as scattering. Two ground state conformations of SPANI are suggested to exist in aqueous medium. Excitation wavelength dependence of the fluorescence emission spectra is attributed to red-edge effect. All these observations are nicely corroborated by the fluorescence lifetime data of SPANI obtained from time-resolved measurements. All these new findings are extremely important in view of the potential applications of SPANI in polymer optoelectronics.