Effect of polypyrrole on the morphology and ionic conductivity of TPU electrolyte containing LiClO4

The effect of conducting polypyrrole (PPy) on the morphology and ionic cond uctivity of thermoplastic polyurethane (TPU) doped with LiClO4 has been des cribed and compared with those of pure TPU system. The TPU-PPy composites w ere prepared by chemical polymerization of pyrrole inside TPU films. All sa mples were characterized by their swelling behavior in a liquid electrolyte (LiClO4/PC), thermogravimetric analysis (TGA), differential scanning calor imetry (DSC), scanning electron microscopy (SEM) and AC impedance measureme nts. Swelling studies indicate an improved chemical stability of the compos ite compared to TPU. From TGA, the thermal stability of the composite was f ound to be comparable to pure TPU. A decrease in Tg of the soft segment was observed in the composite from DSC experiments. This may be due to interac tion of PPy-NH groups with either carbonyl or ether oxygens of TPU, leading to phase separation of the hard and soft segments. The SEM micrograph of t he composite shows the presence of typical cauliflower-like morphology of P Py. The ionic conductivity of the composite was found to be about one order of magnitude higher than pure TPU having the same amount of LiClO4/PC. The enhancement of conductivity in presence of PPy may be associated with the increased mobility of ClO4- ions promoted by coordination of Li+ ions with PPB nitrogen atoms. (C) 2001 Elsevier Science B.V. All rights reserved.