Macromolecules 2006, 39, 7193-7195
Solution-Surface Electropolymerization: A Route to Morphologically Novel Poly(pyrrole) Using an Ionic Liquid Jennifer M. Pringle,*,† Maria Forsyth,† Gordon G. Wallace,§ and Douglas R. MacFarlane‡ Australian Centre of Excellence in Electromaterials Science, Department of Materials Engineering and School of Chemistry, Monash UniVersity, Wellington Road, Clayton, VIC 3800, Australia, and Australian Centre of Excellence in Electromaterials Science, Intelligent Polymer Research Institute, UniVersity of Wollongong, Northfields AVenue, Wollongong, NSW 2522, Australia ReceiVed June 22, 2006 ReVised Manuscript ReceiVed September 1, 2006 The continually increasing interest in the use of conducting polymers, which now encompasses a wide range of applications,1,2 is fuelling a continued need for materials with improved physical and chemical properties. In particular, there is a recent drive toward nanostructured and reduced dimensionality materials, such as thin films, nanotubes, wires, particles, etc., which can exhibit markedly different properties from those of the bulk materials.3-5 The use of a template can be effective in such synthesis, but with the disadvantage of having to subsequently remove the template to obtain the nanostructured polymer. We have been investigating the use of ionic liquids for the electrochemical synthesis of conducting polymers,6 and here we report an unusual growth process of poly(pyrrole) in this medium, which can result in the formation of a free-standing polymer film with an extended fine structure, without the aid of a template. In addition, SEM analysis of the materials provides insight into the growth mechanism of such electrochemically synthesized poly(pyrrole) films. Ionic liquids are a relatively new class of solvent, composed entirely of ions, whose advantageous physical properties can in some cases include negligible vapor pressure, nonflammability, and good electrochemical stability.7-9 The use of ionic liquids as the supporting electrolyte for conducting polymers has been shown to be extremely beneficial to performance and device lifetimes,10,11 and studies have more recently focused on the potential benefits of using ionic liquids as the growth media for conducting polymers.12-15 We have previously observed significant morphological differences between poly(pyrrole) films grown onto a stainless steel working electrode from ionic liquids compared to those grown in conventional molecular solvent/electrolyte systems.6 However, if the electrochemical polymerization of pyrrole in the ionic liquid is performed using a platinum wire as the working electrode, the polymer forms an initial layer on the section of working electrode that is submerged into the monomer/ionic liquid solution, but then grows along the surface of the ionic liquid. This solution-surface electropolymerization is explored in more detail in this paper. The ionic liquid used here was 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, prepared using the literature †
Department of Materials Engineering, Monash University. School of Chemistry, Monash University. § University of Wollongong. * Corresponding author: e-mail
[email protected]; Fax (+613) 9905 4597; Tel (+613) 9905 4599. ‡
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procedure,16 dried (water typically
