Iodination of poly(vinyl chloride) (PVC) was prepared by addition of 12 or I- through physical adsorption and chemical modification techniques forming (PVC-I-2) (composite I) and (PVC-I) (composite II), respectively. Investigations were performed using TGA, DSC, FTIR, UV-vis absorbance analyses and ac conductivity measurements. The activation energy of decomposition, Delta E-d, was found to be 215.15 kJ/mole and 43.1 kJ/mole for PVC and composite II, respectively. Both direct and indirect optical transitions near the absorption edge are observed. Addition of I-2 or I- decreases the optical energy gap for PVC. The chemical replacement of Cl- ion in PVC matrix with I- ion in composite II increases the electrical conductivity by two orders. A possible conduction mechanisms are suggested. (C) 2016 Elsevier B.V. All rights reserved.