J. Ind. Council Chem., Vol. 27, No. 2, 2010 128 J. Ind. Council Chem. Vol. 27, No. 2, 2010, pp. 128-133 Biological Activity of Emeraldine Bases of Polyaniline NARENDRA P. S. CHAUHAN, RAMESHWAR AMETA a , ROHIT AMETA b and SURESH C. AMETA Department of Polymer Science, University College of Science, M. L. Sukhadia University Udaipur-313 001 (Rajasthan) INDIA a Department of Chemistry, S. M. B. Govt. P.G. College, Nathdwara-313301 , (Raj.) INDIA b HASETRI, P. O. JK Tyre, Kankroli-313342 (Raj.) INDIA Polyaniline-emeraldine bases were synthesized in aqueous hydrochloric acid (HCl)/LiCl or CF 3 COOH medium by chemical oxidative polymerization with (NH 4 ) 2 S 2 O 8 as an oxidant. The viscosities and average molecular weight were measured by using Ubbelohde suspended level capillary viscometer (USLV). Antimicrobial properties of synthesized polymers have been tested for their antifungal and antibacterial activities. Keywords : Emeraldine base, Ammonium persulphate, Ubbelohde viscometry, Antimicrobial scanning. Received : 12-04-10; Revised : 06-02-10; Accepted : 10-10-10 Polyaniline (PANI) is unique among conducting polymers due to its electrical properties, which are reversibly controlled by both (i) changing the oxidation state of the main chain 1 and (ii) by protonation of the imine nitrogen atoms 2 . Its excellent environmental and thermal stability in the conducting form and the low cost makes PANI an attractive material for applications in several areas such as rechargeable batteries 3 , light emitting diodes 4 , anti- static packaging and coatings 5 , photonics 6,7 , chemical 8 and biochemical sensors 9-11 . One of the characterstic requirement of any polymer for technological application is, especially, its solution processability and therefore, intense efforts have been directed towards optimizing the processability, conductivity and stability of polyaniline through modification of the oxidation state, dopant and polymerization conditions. Dilute solution viscometry is concerned with accurate quantitative measurements of the increase in viscosity of polymer for particular solvent at a given temperature 14, 15 . It provides information relating to the size of the polymers in solution, including the effect on chain dimensions of polymer structure, molecular shape, degree of polymerization and polymer solvent interaction. Dilute solution viscosity is also used to estimate the molecular weight of a polymer. The intrinsic viscosity (η) of synthesized polyaniline was measured in N- methyl-2-pyrrolidone (NMP) at 30° C using Ubbelohde suspended level capillary viscometer 16 . The extent of polymerization and molecular weight of polyanilines were determined and these were found to depend on the ratio of aniline and ammonium persulphate, temperature, reaction time and pH 17 . A biocatalytic approach of conducting polyaniline nanoparticle has been summarized by Cholli et al 18 . Polyaniline from aniline and ammonium persulphate (APS) were synthesized at different temperatures (-15 ° C to +5°C) in different aqueous acidic media (1M HCl/ 6M HCl) or 1M CF 3 COOH 19 . These polyanilines were treated with NH 4 OH resulting in emeraldine bases (EB). These EB are soluble in aprotic solvent like NMP and dimethyl sulphoxide (DMSO). Their average molecular weights, viscosity and antimicrobial activity were also observed. EXPERIMENTAL Method Polymerization of aniline was carried out in different conditions as reported earlier 19 . The details are shown in Table 1. Table 1. Paolymers Monomer Oxidant Solvent Temperature A 1 Aniline (NH 4 ) 2 S 2 O 8 Mixture of -15°C A 2 (0.05 mol) ( 0.05 mol) 0.6M LiCl -5°C A 3 and 0.1M HCL +5°C B 1 Aniline (NH 4 ) 2 S 2 O 8 1M CF 3 COOH -15°C B 2 (0.05 mol) ( 0.05 mol) -5°C B 3 +5°C