Langmuir–Blodgett films of different ionomeric polymers deposited on electrode surfaces

Abstract

This paper shows the possibility to apply the Langmuir-Blodgett (LB) techniques for the preparation of ultrathin films of various ionomeric polymers, namely Nafion ® (perfluorinated cation-exchanger), Tosflex ® (perfluorinated anion-exchanger) and Eastman AQ55 ® (polyestersulfonated cation-exchanger). The pressure-area isotherms and the condensation degree of the interfacial films depend on the chemical structure of the ionomer and on the nature of the electrolyte dissolved in the subphase. The addition of a strong electrolyte to the subphase is, in fact, a compulsory requirement in order to allow the formation of a stable ionomer layer at the air-water interface. The interfacial film can be transferred by LB deposition technique onto substrates such as glassy carbon, gold or indium-tin oxide electrodes. Quartz crystal microbalance data indicate the uniformity of such LB-coatings and ion-exchange voltammetric measurements confirm their ion-exchange preconcentration capabilities. Films based on perfluorinated ionomers such as Nafion ® and Tosflex ® are characterized by higher condensation degrees and are closer to reach a monolayer packing than films based on the polyestersulfonated Eastman AQ55 ® .

Electrochemiluminescence of loaded in Nafion Langmuir–Blodgett films: Role of the interfacial ultrathin film

“…Moreover, it was shown that Nafion LB or Nafion LS films present other peculiar characteristics different from those of recasted Nafion, as recently outlined by electrochemical studies [20,21] also in combination with epifluorescence microscopy [22]. Nafion LB films are indeed very homogeneous and compact [18] and being very thin, they present very short response time to electrochemical switching [22].…”

“…First of all, the deposition of Langmuir monolayers on electrodes allows one to build continuous permselective coatings as thin as few nanometers [17][18][19]. Moreover, it was shown that Nafion LB or Nafion LS films present other peculiar characteristics different from those of recasted Nafion, as recently outlined by electrochemical studies [20,21] also in combination with epifluorescence microscopy [22].…”

“…In order to overcome these limitations, the deposition of Nafion using the Langmuir-Schaefer (LS) [17] and Langmuir-Blodgett (LB) [18] techniques received recently great attention. First of all, the deposition of Langmuir monolayers on electrodes allows one to build continuous permselective coatings as thin as few nanometers [17][18][19].…”

Composite films of poly-(ester-sulphonated) and poly-(3-methylthiophene) for ion-exchange voltammetry in acetonitrile solutions

“…This could be obtained by preparing ultrathin bi-layers, by resorting, for instance, to Langmuir-Blodgett techniques which can be employed for preparing ionomer permselective films as thin as few nanometers [44,45]. Further studies on such a possibility are presently in progress.…”

Electrochemical and photoelectrochemical response of electrodes coated with LB films of an azopolymer

“…From a practical point of view, the arrangement of polymers in films is more attractive than the use of low molecular weight materials because of their widely demonstrated device applications [12]. In the case of electrochemical applications, three kinds of polymers can be distinguished in terms of the redox group position in the polymer: (i) electroactive polymers, the redox group is in the lateral chain [13]; (ii) conducting polymers, the redox group is in the main chain [14,15]; (iii) ionomeric polymers, the electroactive specie is an ion [16,17].…”