Polypyrrole films electropolymerized from ionic liquids and in a traditional liquid electrolyte: A comparison of morphology and electro-optical properties

Polypyrrole (ploy) films have been formed by electropolymerization from a conventional media: lithium triflate in acetonitrile and in room temperature ionic liquids: 1-ethyl-3-methyl imidazolium bis(perfluoroethanesulfonyl)imide (EMIPFSI) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITF). The well ordered nodular morphology of the ploy film grown in EMIPFSI with significantly low roughness endows these films with superior redox activity and electro-optical properties. Ambient temperature do conductivities of 43, 15 and 13 S cm(-1), for films grown in EMIPFSI, EMITF and control solutions have seen obtained. The well-organized particulate morphology of the ploy film grown in EMI-PFSI seems to be responsible for its enhanced conductivity, as also better interfacial charge transfer capabilities as compared to their counterparts derived. Under an external bias of +/- 2.2 V, the sluggish switching kinetics shown by the films under scrutiny presumably are due to the (i) resistive barriers formed at the two interfaces of the pPy electrode (ii) a plausible passivation layer on the solution side of the film during electrochemical cycling. This demonstrates the need to further improve the interfacial properties of pPy so as to obtain a consistent and stable electrochromic response. (C) 2008 Elsevier Ltd. All rights reserved.