Abstract
Poly(p-phenylene) (PPP), polypyrrole (PPY), and poly(p-phenylene-pyrrole) (PPP-PPY) films were electrochemically synthesized in acetronitrile by cyclic voltammetry. For comparison purposes, the films were characterized by cyclic voltammetry in a monomer-free solution, and their optical responses were also obtained in the UV-VIS range of energy after varying the applied potentials. The absorbance spectra of the PPP-PPY film exhibited bands typically seen in the spectra of the homopolymers, PPP and PPY films, but better defined, intense, and related to reversible color transitions. Although it was not possible to confirm by using infrared and Raman spectroscopy that a copolymer was in fact obtained, the presence of both monomers, pyrrole and biphenyl, in the polymerization medium turned easier the process of film formation, yielding darker, more uniform, and rougher films as it was verified by photographic images and AFM (atomic force microscopy) images.
Highlights
Over the last decades, conducting polymers have been studied aiming towards application in electrochromic displays, light-emitting devices, batteries, and sensors[1,2,3,4]
Once the current density increases more effectively for pyrrole, when compared to biphenyl, this type of response can be related to a continuous process of film deposition rather than a surface blocking effect, which will be discussed in more detail later
Our results have shown that it can be possible to obtain PPP-PPY films in acetronitrile under a narrow potential range, and with a response between those obtained for the homopolymers, PPP and PPY
Summary
Over the last decades, conducting polymers have been studied aiming towards application in electrochromic displays, light-emitting devices, batteries, and sensors[1,2,3,4]. The use of electrochemical methods of synthesis for the preparation of polyaniline, poly(p-phenylene), polythiophene, polypyrrole, and derivatives allows one to obtain a variety of conjugated polymers, including copolymers and bi-layers, with improved mechanical, optical, and electrical properties[5]. Poly(p-phenylene) (PPP) has been studied as active layer in light emitting devices in the blue spectral range[6,7]; PPP can be prepared by chemical oxidation of benzene in acidic medium, and exhibits thermal and chemical stabilities, relatively high conductivity ranging from 10–12 to 102 S cm–1 after chemical doping, and relatively high mechanical strength[8]. PPP can be electrochemically prepared yielding adherent and mechanically tough films, which allows one to control parameters such as final potential, potential range, and solvent–salt (electrolyte) combination[9]
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