A systematic approach is developed to study the ligno sulfonic acid sodium salt (LSA) protonation or doping process with polyaniline emeraldine base (Pani-EB) in organic solvents like dimethyl sulfoxide, and the influence of LSA-doping on the properties of polyaniline was investigated in detail. The composition of Pani-EB and LSA was varied in the weight ratio of 1:1 to 1:50 to investigate the effect of the dopant concentration on the conductivity and morphology. The doping process was confirmed by UV-vis and FTIR spectroscopes. The composition analysis indicates that only 50% of the LSA is used for the doping process irrespective of the weight ratio of LSA/Pani-EB in the feed. The four probe conductivity measurement suggests that the conductivity of the doped samples are increasing with the increase in the ratio of Pani-EB/dopant composition, and the high conductivity of the doped material was obtained in the range of 1.0 X 10(-2) S/cm. Scanning electron microscopy reveals that LSA induces a selective aggregation in the polyaniline chains to produce needlelike or rod-shape morphology of sizes having similar to 0.2 mu m diameter and 1 mu m length. At very higher amount of LSA, the microrods are completely collapsed and form uniform continuous morphology. (c) 2006 Wiley Periodicals, Inc.