Electrochimica Acta 49 (2004) 3671–3686 Novel synthetic methods to produce functionalized conducting polymers I. Polyanilines César Barbero ∗ , Horacio J. Salavagione, Diego F. Acevedo, Doris E. Grumelli 1 , Fernando Garay, Gabriel A. Planes, Gustavo M. Morales 2 , Mar´ ıa C. Miras Departamento de Qu´ ımica, Universidad Nacional de R´ ıo Cuarto, Agencia Postal 3, 5800 R´ ıo Cuarto, Argentina Received 20 October 2003; received in revised form 5 November 2003; accepted 10 November 2003 Available online 2 June 2004 Abstract Recent results, part of an ongoing research programme aimed to develop synthetic methods which could be used to functionalise conducting polymers, are described. Among those methods are the copolymerization of aniline with substituted anilines and post-modification reactions of polyaniline, such as: electrophilic substitution, nucleophilic addition and coupling with diazonium salts. Some of those methods could be chemically or electrochemically controlled allowing a quantitative tailoring of the modification. The effect of the added functionalities on the electrochemical properties of the polymers is investigated using spectroscopic and electrochemical techniques. The extension of the synthetic methods to combinatorial modification of conductive polymers is also discussed. © 2004 Elsevier Ltd. All rights reserved. Keywords: Synthesis; Conductive polymers; Polyanilines 1. Introduction Conducting polymers are very interesting materials for electrochemical applications: batteries, supercapacitors, electrochromic devices, conductive support of fuel cell electrodes, wiring of biosensors, desalination systems, drug release devices, ion sensitive electrodes, electrochemome- chanical actuators, etc. The properties of simple conductive polymers (e.g. polypyrrole) could be improved by func- tionalization adding novel properties. In that way, polymers with redox sensing [1], complexing [2], non linear optics [3], charge storage [4] or memory [5] capabilities could be produced. Among conducting polymer, polyaniline (PANI) is one of the most extensively studied conductive redox polymers ∗ Corresponding author. Tel.: +54-358-4676233; fax: +54-358-4676233. E-mail address: cbarbero@exa.unrc.edu.ar (C. Barbero). 1 Present address: INQUIMAE, Departamento de Qu´ ımica Inorg´ anica, Anal´ ıtica y Qu´ ımica F´ ısica, Facultad de Ciencias Exactas y Naturales, Pabell´ on 2, Ciudad Universitaria, AR-1428 Buenos Aires, Argentina. 2 Present address: Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA. [6,7], due to its conductivity, environmental stability and inexpensive monomer. It has been shown that function- alization, adding sulphonate groups to the polymer back- bone, alters the ion exchange properties of the polymer (“self-doping” effect) making it suitable to be used in pH sensor/actuators [8]. The same functionalization makes the modified polyaniline a good material for battery applications [9]. To obtain materials for specific tasks it is important to develop the ability to introduce a wide variety of functional groups. A simple way to do that is to polymerise substituted anilines bearing functional groups of interest. However, inductive and/or steric effects could make such monomers difficult to polymerise [10]. Two simple ways to overcome such limitation could be devised: one involves the copoly- merisation of the less reactive (or altogether unreactive) monomer with aniline, the other consists of the controlled modification of the polymer backbone by synthetic reac- tions on the whole polymer. Indeed, it has been shown that is possible to modify polyaniline by different modification reactions. Wrighton and coworkers described the nucle- ophilic reaction of PANI with trifluoracetic anhydride [11] where the reaction rate could be controlled by varying the electrochemical potential of the polymer. Similarly, Liu and 0013-4686/$ – see front matter © 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2003.11.035