Electrochemical polymerization of 2-methoxynaphthalene B. Meana-Esteban a , C. Kvarnstro ¨m a,* , B. Geschke b , J. Heinze b , A. Ivaska a a Process Chemistry Group, c/o Laboratory of Analytical Chemistry, A ˚ bo Akademi University, FIN-20500 Turku-A ˚ bo, Finland b Institut fu ¨r Physikalische Chemie, Universita ¨t Freiburg, Freiburg, Germany Received 18 October 2002; accepted 16 January 2003 Abstract Electropolymerization of 2-methoxynaphthalene in TBAPF 6 -ACN and characterization of the formed film were studied by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), Fourier transform infrared spectroscopy (FT-IR) and by scanning electron microscopy (SEM). Oxidation of 2-methoxynaphthalene at a Pt electrode was performed by CV in a three-electrode electrochemical cell. EQCM was used during polymerization as an in situ technique, detecting the continuous mass increase with the number of potential cycles. The redox behavior (both p- and n-doping) of the film was studied by CV in monomer-free, TBAPF 6 -ACN, electrolyte solution. The electrochemical response from the anodic charging (p-doping) of the film was found to consist of a strongly increasing current but with no well-defined oxidation peak. Upon discharging a distinct reduction peak was observed. The cathodic charging and discharging (n-doping) responses consisted of well-resolved redox peaks. Both the anodic and the cathodic reactions are reversible and the film did not show any evidence of degradation when cycled between 2.4 and þ1.3V. Transmission FT-IR spectra of the freshly prepared neutral film of 2-methoxynaphthalene and of the neutral polymer after n-doping were recorded. These results gave evidence of oligomer and macromolecular formation due to the fact that new bands in the region of 600–900 cm 1 were observed. The morphology of the electrosynthesized film was studied by SEM. # 2003 Elsevier Science B.V. All rights reserved. 1. Introduction The electrical conductivity, fast and reversible redox response and optical responses of polyconjugated organic materials [1] have been the center of interest of basic and applied sciences in the development of new materials for new technologies. Polymers with fused ring systems and ladder type polymers have been studied by many groups [2]. One reason for this extensive research is the expected suppression of the band gap and improved electronic proper- ties in these materials due to the rigid planar polymer backbone in the form of a double-stranded molecule. Electrochemical polymerization of aromatic compounds has been proven to be a useful method for obtaining con- ducting polymer films. Electrochemistry allows convenient control of the polymerization process. The synthesis per- formed in this way can in many cases result in a more selective reaction leading to higher yields of the desired product. Electrosynthesis has been frequently used in pro- duction of poly(naphthalene) type polymers [3–5], poly- naphthol containing polymers [6,7] and double-stranded polymers of poly(peri-naphthalene) type [8]. In this work poly(2-methoxynaphthalene) will be synthesized by anodic electropolymerization in organic solvents. The resulting film will be characterized electrochemically by SEM and FT-IR. 2. Experimental 2.1. Apparatus The electrochemical polymerization of 2-methoxy- naphthalene was performed in a conventional three-elec- trode one-compartment cell at room temperature. A Pt disk (area 0.07 cm 2 ) was used as working electrode and a Pt wire as counter electrode. A Ag/AgCl wire was used as quasi- reference electrode, calibrated versus the ferrocene/ferroci- nium couple. All the data reported are, if not differently stated, given versus this reference electrode. Before poly- merization the working electrode was polished mechanically with alumina (0.3 mm). The voltammograms were recorded with an Autolab potentiostat PASTTAT 100 with the pro- gram GPES. FT-IR spectra were recorded from KBr pellets with a Bruker, IFS66S FT-IR instrument equipped with a DTGS-detector and the resolution used was 4 cm 1 . The surface of the formed films was studied by using scanning Synthetic Metals 139 (2003) 133–143 * Corresponding author. Tel.: þ358-2-215-4419; fax: þ358-2-215-4479. E-mail address: ckvarnst@abo.fi (C. Kvarnstro ¨m). 0379-6779/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0379-6779(03)00079-1