Recently, we demonstrated that conjugated sequences of unsaturated double bonds can be introduced into co-polymers such as styrene butadiene rubber (SBR), which contains isolated double bonds along the polymer backbone through conjugation reactions induced by iodine [Sreeja R. Submitted for publication [1]]. Here, we report for the first time the doping reaction in another notable co-polymer nitrile rubber, a copolymer of acrylonitrile and butadiene. The conductivity reaches a value of about 0.01 S/cm with the characteristic color change from colorless to dark red upon doping. Fr-IR and UV/VIS studies of the polymer film establish the formation of conjugated sequences of the unsaturated double bonds followed by the formation of charge transfer complexes with the dopant ion. The reaction is analogous to the iodine doping of SBR for longer doping period and retained flexibility of the film after doping. However, the band gap evaluated is greater for NBR and this increase can be explained as due to the presence of electron withdrawing -CN groups in place of electron releasing phenyl group in the SBR backbone, which can cause a partial influence on the chemical reaction along the polymer backbone. The excellent oil resistance, abrasion resistance and mechanical properties of NBR combined with the newly developed semi conducting behaviour can be utilized for fabricating various electronic and optical devices based on this elastomer. (c) 2005 Published by Elsevier Ltd.