The synthesis,characterization,thermal degradation and stability of polyaniline(PANI),poly(m-nitroaniline), poly(m-chloroaniline) and poly(o-methylaniline) were reported.Different properties were measured and compared with PANI to find out the effect of electron donating groups(-CH_3) and electron withdrawing groups(-Cl,- NO_2).It was found that the presence of any type of substitution in the benzene ring of aniline increased the solubility but reduced the yield,thermal stability and electrical conductivity.Two probe methods were used to measure the electrical conductivity of these polymers.The structural properties of these polymers were characterized by using FTIR and UV-Vis spectroscopic methods.Thermal degradation and stability of these polymers were explained by using thermogravimetric analysis(TGA) and conductivity measurements. The synthesis, characterization, thermal degradation and stability of polyaniline (PANI), poly (m-nitroaniline), poly (m-chloroaniline) and poly (o-methylaniline) were reported. Different properties were measured and compared with PANI to find out the effect of electron donating groups (-CH_3) and electron withdrawing groups (-Cl, - NO_2) .It was found that the presence of any type of substitution in the benzene ring of aniline increased the solubility but reduced the yield, thermal stability and electrical conductivity.Two probe methods were used to measure the electrical conductivity of these polymers. Structural properties of these polymers were characterized by using FTIR and UV-Vis spectroscopic methods. Thermal degradation and stability of these polymers were explained by using thermogravimetric analysis (TGA) and conductivity measurements.