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An inverted emulsion process for the synthesis of the emeraldine salt of polyaniline using a novel oxidizing agent, namely benzoyl peroxide, is described. The polymerization is carried out in a nonpolar solvent in the presence of a functionalized protonic acid (sulfosalicylic acid) as the dopant and an emulsifier (sodium lauryl sulfate). The influence of synthesis conditions such as the duration of the reaction, temperature, concentration of the reactants, etc., on the properties of polyaniline was investigated to determine the optimum conditions for the synthesis of polyaniline salt in high yield and conductivity. Using different substituted anilines and dopants, the synthesis of polyaniline derivatives was also carried out. The polymer salt and its base were characterized by a number of techniques such as UV-vis, FT-IR, FT-Raman, NMR and EPR spectroscopies, conductivity, particle size, SEM, X-ray powder diffraction, and TGA-DTA. The polyaniline-sulfosalicylic acid salt synthesized shows a conductivity of 2.53 S cm-1 , which is a marked increase over the ones synthesized employing ammonium persulfate as the oxidant and sulfosalicylic acid as the dopant (2 × 10-2 S cm-1).

SYNOPSISFive different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. Polyaniline samples have been heat treated at four different temperatures (150, 200, 275, and 375°C) and characterized by electron paramagnetic, electronic absorption, and infrared spectral measurements. Thermal stabilities of the chemically synthesized polyaniline salts have been studied by thermal analysis and spectral methods. Polyaniline salts undergo a three-step weight-loss process in the heating cycle. The first step (up to 110°C) corresponds to the loss of water molecules from the polymer chain. In the second step ( 110-275"C), a small amount of acid escapes as volatile gas, and after 275°C the polymer undergoes oxidative thermal degradation in the third step. It was found that thermal stability of polyaniline salts depends on the counteranion used and the polymer is apparently stable up to 25OoC. No structural changes have taken place up to 200°C and this has been confirmed from infrared and electronic absorption spectra. No definite correlation exists between conductivity and spin concentration. 0 1994