A comparative study of the effect of organic dopant ions on the electrochemical and chemical synthesis of the conducting polymers polyaniline, poly(o-toluidine) and poly(o-methoxyaniline)

Abstract

Electroactive polymers such as polyaniline and its derivatives have many potential applications, but the nature of the dopants can have an adverse effect on their properties. Polyaniline (PANI), poly(o-methoxyaniline) (POMA) and poly(o-toluidine) (POT) have been synthesised using appropriate organic acid dopants (2-naphthalenesulfonic acid and 1,5-naphthalenedisulfonic acid) via electrochemical and chemical polymerisation methods, where the later was achieved at pH (1-2) in the presence of ammonium persulfate as an oxidant. The effects of the monomers and organic dopants on the physiochemical properties and morphological surface of the polymers were studied by means of Fourier transform infrared spectroscopy, electrical conductivity measurements, thermogravimetric analysis, and scanning electron microscopy (SEM). The above films were also synthesised electrochemically whilst varying conditions such as scan rate, scan number, and in aqueous solution of organic acids using cyclic voltammetry techniques. Cyclic voltammetry experiments have been employed to analyse the growth behaviour and electrochemical stability of films in the background electrolytes (monomer-free). It was found that PANI salts displayed higher doping levels and conductivity while POMA and POT salts were found to show lower conductivity and doping levels, respectively. Furthermore the electrochemical response of films was different in the stability and this may be because of the methoxy (-OCH3) and methyl (-CH 3 ) groups located at the ortho position of the aromatic ring structure of the monomers (o-methoxyaniline and o-toluidine). The -OCH 3 and-CH 3 groups have significant steric effects and can reduce to form long chains of polymers, and also decrease conductivity. The SEM showed that the morphologies of the prepared conducting polymers were different, which was associated with the nature and size of the dopant and monomer present in the bath solution.

Conducting Polymer-Coated Carbon Cloth Captures and Releases Extracellular Vesicles by a Rapid and Controlled Redox Process

“…The voltammograms of PEDOT on the carbon cloth substrate show broad oxidation and reduction processes, with peaks at approximately +0.8 V and +0.5 V (vs Ag/AgCl), respectively, and an onset polymerization potential at ca. +0.9 V. In these homopolymerizations, the current during the first cycle can be attributed to the monomer oxidation, while the continuous increase in the redox currents displayed with further potential sweeps indicates chain propagations and formation of electroactive high-molecular-weight oligomers and polymers deposited on the electrode surface …”

Voltammetric Determination of Hg2+, Zn2+, and Pb2+Ions Using a PEDOT/NTA-Modified Electrode

“…Electroactive polymers such as polythiophene, polypyrrole, poly­(3,4-ethylenedioxythiophene), polyaniline, , polyfuorene, poly­(5-aminoquinoline), poly­( o -toluidine), and their derivatives have attracted considerable interest . The optical, chemical, electronic, and mechanical features of these polymer films render them suitable candidates for possible applications in chemical sensors, corrosion protection, electrochromic devices, supercapacitors, energy storage, and artificial muscles .…”

Effect of Graphene Oxide and Temperature on Electrochemical Polymerization of Pyrrole and Its Stability Performance in a Novel Eutectic Solvent (Choline Chloride–Phenol) for Supercapacitor Applications

“… 32 , 33 Several researchers have synthesized various conducting polymers in DESs and studied different associated parameters, including the growth mechanism and cycling stability of polymers in DESs as well as ion and solvent transport. 34 − 36 Indeed, the type of solvent and, thus, the size of the dopant counteranions have a significant effect on all the films’ properties including structure, morphology, and cycling stability, 37 , 38 where the positive charges are produced in the backbone of polymer during oxidation. Thereafter, solvated anions ingress into the oxidized polymer matrix to counterbalance the positive charge.…”

“…DESs have been applied in many areas including electrodeposition of metals and alloys, , conducting polymers, , metal finishing, desulfurization, pharmaceuticals, , and energy storage . This is due to the fact that they are cheap, are easy to prepare, are non-volatile, are biodegradable, are insensitive to water, and typically have low toxicity, all of which make their use in large-scale applications highly favorable. , Several researchers have synthesized various conducting polymers in DESs and studied different associated parameters, including the growth mechanism and cycling stability of polymers in DESs as well as ion and solvent transport. − Indeed, the type of solvent and, thus, the size of the dopant counteranions have a significant effect on all the films’ properties including structure, morphology, and cycling stability, , where the positive charges are produced in the backbone of polymer during oxidation. Thereafter, solvated anions ingress into the oxidized polymer matrix to counterbalance the positive charge.…”