Aniline has been polymerized in the presence of a novel dopant sodio-5-sulfo-isophthallic acid (NaSIPA), via the chemical oxidative polymerization route. The thermal stability and processability of polyaniline prepared by indirect method (PD1) have been improved significantly (290 degrees C) as compared to polyanilme doped with conventional inorganic dopants like HCl or H2SO4, without much loss of electronic conductivity (5.07 S/cm in PD1). This suggests its use for melt blending with engineering thermoplastics. However, polyaniline prepared by direct method (PD2) can be melt-blended only with conventional thermoplastics like polyethylene, polypropylene, polystyrene, etc. Low-temperature studies reveal the 1-D variable range hopping as a conduction mechanism for direct polymer (PD2), with parameters T-0 and sigma(0) as 4112 K and 15.1 S/cm, respectively. However, for indirectly doped polymer (PD1) Arrhenius-type model, having parameters vertical bar (E-F - E-C) vertical bar and sigma(C) as 0.04 eV and 28.4 S/cm, respectively, it suited well. The coherence length as found from XRD data was around 28.8 nm for PD1 and 25.2 nm for PD2. (c) 2008 Wiley Periodicals.