Development of polymer–dopant interactions during electropolymerization, a key factor in determining the redox behaviour of conducting polymers

Investigation of ionic motion in connection with the redox transformation of conjugated polymers (CP) has always been at the leading edge of research. Motivated by recent proofs for the chemical bond formation between chloride ion and alpha-positioned carbon in poly (3,4-ethylenedioxythiophene) (PEDOT), comprehensive studies have been extended to another strongly electronegative halide (F-) and to another CP, polypyrrole (PPy). As the electrochemical quartz crystal nanobalance (EQCN) results proved, the movement of the bulky Bu4N+ cations has been exclusively experienced during the redox processes of both systems. Moreover, the decisive role of the anions being present in the polymerization solution in determining the redox capacity and, consequently, the maximum doping level of the films was evidenced. On the grounds of the systematic experiments, the strong and permanent chemical interaction of highly electronegative anions and the polymer has been demonstrated as a general phenomenon. Importantly, this observation requires the necessary reconsideration of specific polymer-dopant interactions and calls attention to the necessity of careful design of the polymerization procedure.</p

Corrosion inhibition effect and adsorption behaviour of nicotinamide derivatives on mild steel in hydrochloric acid solution

Background: A new class of nicotinamide derivatives viz., N-((1H-pyrrol-2-yl)methylene)nicotinamide, N-((methyl(phenyl)amino)methylene)nicotinamide, N-nicotinoylbenzimidothioic acid and N-(4-(methylthio)benzylidene)nicotinamide have been synthesized and their corrosion inhibition effect on mild steel in 0.5 M HCl was investigated by mass loss, Tafel polarization technique and AC impedance measurements. Results: The inhibition efficiency of the inhibitors on mild steel in 0.5 M HCl has been studied based on concentration, time interval and temperature. Potentiodynamic polarization studies showed that all the examined inhibitors suppress both anodic and cathodic process and behave as mixed type of corrosion inhibitors. Conclusions: The adsorption of all the inhibitors was found to obey Langmuir isotherm model. Electrochemical impedance data revealed that polarization resistance (RP) increases and double layer capacitance (Cdl) decreases as the concentration of the inhibitors increases. FTIR, EDX and SEM analyses were performed to study the film persistency of the inhibitors

Inhibition of Aluminium Corrosion Using Benzothiazole and Its Phthalocyanine Derivative

Cyclic voltammetry and potentiodynamic polarization techniques were used to study the effects of 4-[4-(1,3-benzothiazol2yl)phenoxy] phthalonitrile (BT) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (ClGaBTPc) as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. The presence of the inhibitors in the concentration range of 2 to 10 μM was found to retard the aluminium corrosion process such that the inhibition efficiency was found to range from 28.2 to 76.1% for BT and from 71.5 to 82.7% for ClGaBTPc. The latter was a better inhibitor. Scanning electron microscopy and energy-dispersive X-ray measurements reveal effective metal surface protection by the inhibitors, most probably by shielding it from the corrosion attacks of Cl− from the acid. The calculated quantum chemical parameters agreed with experimental results