Electropolymerization of trimethylsilylphenols to silylated polyphenylene oxides and investigation of their properties. Enhanced conductivity of PPO by silyl group

Polymerization of o-, m-, and p-trimethylsilylphenols (TMS-phenols) was achieved electrochemically. The polymers were prepared as thin films on a platinum electrode and were found to be electroinactive in nonaqueous solutions. The polymers exhibited far higher conductivities than polyphenol or other substituted polyphenols. The conductivity of poly (p-TMS-phenol) was lower than that observed for the polymers of the o- and m-isomers. The polymers were characterized by infrared spectroscopy. The effect of monomer concentration, supporting electrolyte concentration, current densities, and temperature on the poymerization was investigated using microgravimetry. The observed empirical kinetics were as follows. The rates of polymerization of o-, m-, and p-TMS-phenol were found to be of 0.8, 0.8, and 0.7 order dependent on monomer concentation, of 0.5, 0.5 and 0.45 order dependent on electrolyte concentration, and of 0.9, 0.9 and 0.8 order dependent on current densities. By investigating the effect of temperature on electropolymerization, the corresponding activation energies of electropolymerization were calculated to be 0.9, 0.9, and 0.8 kj/mole. The molecular weights of poly(o-TMS-phenol) and poly(m-TMS-phenol) were determined by gel permeation chromotography. © 1997 John Wiley & Sons, Inc

The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol

[EN] Poly(2-amino-4-tert-butylphenol), poly(2A-4TBP), was synthesized from monomer aqueous solution using either electrochemical or chemical oxidation procedures. Several spectroscopic characterization techniques were employed to gain information on the chemical structure and redox behavior of the obtained materials. It was found that the chemical polymerization product could be described as an oligomer mixture containing up to 16 monomer units. In parallel to other polymers derived from o-aminophenol, phenoxazine rings constitute also the basic structure of poly(2A-4TBP). In addition, the occurrence of N-N couplings, which are favored by the presence of the voluminous tert-butyl substituent, seems also relevant. No significant structural differences were found between the chemically or electrochemically synthesized materials. © 2016 Published by Elsevier Ltd.Financial support from the Spanish Ministerio de Economía y Competitividad and FEDER funds (MAT2013-42007-P) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged. M. Abidi thanks the Ministry of Higher Education and Scientific Research of Tunisia for funding her stay at the University of Alicante.Abidi, M.; López-Bernabeu, S.; Huerta, F.; Montilla-Jiménez, F.; Besbes-Hentati, S.; Morallón, E. (2016). The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol. Electrochimica Acta. 212:958-965. https://doi.org/10.1016/j.electacta.2016.07.060S95896521

Inhibitive action of gramine towards corrosion of mild steel in deaerated 1.0 M hydrochloric acid solutions

The effect of addition of gramine on mild steel dissolution in deaerated 1.0 M hydrochloric acid was studied through potentiodynamic polarisation curves, electrochemical impedance spectroscopy and gravimetric measurements in the temperature range from 25 °C to 55 °C. Gramine was found to shift the corrosion potentials towards less noble values and decrease both dissolution of mild steel and hydrogen evolution reaction. Gramine did not affect the corrosion reaction mechanism (blocking effect). Results obtained from the several measurement techniques were in good agreement and revealed good inhibition efficiencies in the concentration range (0.75 mM ÷ 7.5 mM) particularly at higher concentrations

Kinetics and mechanism of electropolymerization of m-aminophenol

The kinetics and mechanism of electropolymerization of m-aminophenol (mAP) has been investigated in acetonitrile (AN) and methanol (MeOH) media. The rate of polymerization is found to be proportional to mAP (current)0.5 at moderate current densities; at higher current densities, the rate of polymerization is independent of current density. A suitable mechanism has been proposed and the rate equation is derived to explain the observed factors. Rotating disc voltametry revealed that at low current densities, the rate of polymerization is charge controlled, while at high current densities it is diffusion controlled. The physicochemical characteristics of AN make it a better solvent than MeOH

Permeability and electrocatalytic properties of film prepared by electropolymerization of m-aminophenol

Permeation of electroactive species, namely hydroquinone (H2Q), potassium ferrocyanide (K4Fe(CN)6) and ferros sulfate (FeSO4) dissolved in solution, through poly(m-aminophenol) coated on Pt electrode and the effect of the polymer layer on the rate of oxidation of these species have been investigated. The film-modified electrode is found to electrocatalyse the oxidation of H2Q while it retards the oxidation of FeSO4 and K4Fe(CN)6. Furthermore, the retardation effect is more pronounced for FeSO4 oxidation than K4Fe(CN)6. Experimental results rule out the possibility of electronic conduction of the film leading to electrolysis at the film/solution interphase; mediation of the redox sites of the polymer and the membrane diffusion through the viscous polymer layer are identified. Chronoamperometric measurements coupled with hydrogen adsorption studies on Pt reveal that the polymer covers only 58 of the electrode surface and contains pinholes of 0.3888 μm radius and also that the transport of the electroactive species takes place through these pinholes. Theoretical studies based on X-ray and IR analyses reveal that pinholes of various size and shape are possible, which explains the discrepany in electrocatalysis towards various species. The results show that high current density prevails on modified electrodes which consequently increases the catalytic rate. However, this advantage is subjected to the transport of species through the polymer coating. The latterphenomenon governs whether the film enhances or decreases the rate of electrochemical reaction. Conclusions drawn from this study indicate that poly(m-aminophenol) may not be a good corrosion protector for long-term applications. © 1993

Dicarboxylic acids as corrosion inhibitors for lead in perchloric acid

The effect of some dicarboxylic acids, e.g., oxalic acid, malonic acid, succinic acid, tartaric acid and phthalic acid, on the corrosion of lead in HClO4 soln. was investigated using wt. loss and polarization studies. The order of effectiveness is as follows: oxalic acid » malonic acid > succinic acid ≈ tartaric acid > phthalic acid. These acids inhibit the corrosion of lead by blocking the anodic reaction sites by getting adsorbed on them. The inhibitive efficiency obsd. is explained on the basis of pKa values and the adsorption bond strength. The max. efficiency obtained was only about 78​

Benzenethiols as inhibitors for the corrosion of copper

The effect of benzenethiol (BT) and some substituted benzenethiols - o-methyl benzenethiol (o-MBT), o-amino benzenethiol (o-ABT), p-amino benzenethiol (p-ABT) and m-methyl benzenethiol (m-MBT) - on the corrosion of copper in H2SO4 and NaOH solutions has been investigated by means of spectrophotometric measurements, potentiostatic polarization studies, cyclic voltammetry and potential stepping experiments. In acid solutions, under ordinary conditions, the thiols are adsorbed onto the metal surface in their molecular forms through their thiol(-SH) moiety and when the potential is made more noble oxidative dimerization of the thiols takes place, and the dimer replaces the thiol. Both thiols and their dimers are not effective as inhibitors. In alkaline solutions in situ polymerization of thiol takes place to yield polythiol which is a very effective inhibitor both in acidic and alkaline media. © 1992 Chapman & Hall

Poly(benzimidazole) and Substituted Poly(benzimidazoles): Novel, Electroactive, and Conducting Polymers Possessing High Catalytic and Coordination Properties

Benzimidazoles and substituted benzimidazoles were electropolymerized on a Pt electrode using acetonitrile containing 0.1 MNaClO4. The polymers are electroactive and conducting. They have a high electrocatalytic effect on the reduction of H+, O2, and CO2 and exhibit high coordination ability. The properties of the polymers depend on the extent of conjugation in the monomer. © 2000 John Wiley & Sons, Inc