A comparative spectroelectrochemistry of homo- and copolymerization of pyrrole and N-methylpyrrole with indole on a gold electrode (original) (raw)
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Journal of Solid State Electrochemistry, 2013
Conducting poly(pyrrole-N-methylpyrrole) (P(Py-NMPy)) was electrochemically synthesized on a gold electrode in a lithium perchlorate-containing acetonitrile electrolyte solution and compared with polypyrrole (PPy) and poly(N-methylpyrrole) (PNMPy) prepared under the same conditions. The obtained polymers were characterized with cyclic voltammetry, in situ resistance measurements, in situ UV-vis spectroscopy, FTIR spectroscopy, and scanning electron microscopy. The onset potentials for pyrrole and N-methylpyrrole monomer oxidation differ by about 0.1 V. Nucleation processes initiated by the radical cations are followed by growth of nuclei into continuous films. The oxidation and reduction peaks for the P(Py-NMPy) copolymer synthesized at 1:1 M concentration ratio of the comonomers are between those of PPy and PNMPy. A decreased [Py]/[NMPy] comonomer concentration ratio yields in the copolymers shifts of peak potentials to more positive values. The in situ resistance of copolymers measured from −0.20 to 0.90 V vs. Ag/AgCl decreased with increasing [Py]/[NMPy] concentration ratio. In situ UV-vis and ex situ FTIR spectra of copolymers show spectroscopic behavior intermediate between those of the homopolymers. Scanning electron microscopy micrographs of the samples show fundamental differences between the morphology of the homo-and copolymers.
In Situ UV-Visible Spectroelectrochemistry and Cyclic
Electrochemical copolymerization of N-methylpyrrole (NMPy) and indole (In) in various monomer ratios were carried out by potentiodynamically methods in acetonitrile electrolyte containing LiClO4 on gold electrode. The obtained homopolymers and copolymers were characterized with cyclic voltammetry (CV), in situ UV-Visible, FT-IR spectroscopy, scanning electron microscopy (SEM) and in situ resistivity measurements. The cyclic voltammetry study shows that the onset potential for the monomers and co monomers curves is located at the different values for N-methylpyrrole, indole and N-methylpyrrole-indole. There is a nucleation process followed by growth of nuclei to continuous films. The oxidation and reduction peaks for copolymer, P(NMPy-In), which synthesized from the 1:1 mole-mole ratio concentration of the relevant monomers, located between those for poly N- methylpyrrole (PNMPy) and polyindole (PIn) films. The observed values were showed a decreased [NMPy]/[In] ratio concentration in the copolymers shifts the peak potential to more positive. The in situ UV-Visible, FT-IR spectroscopy and SEM analysis of homopolymers and copolymers were also studied. The result shows the intermediate spectroscopic properties between homopolymers and copolymers. The in situ resistivity measurements showed that the copolymers have a lower conductivity than the corresponding parent homopolymers.
ELECTROCHEMICAL COPOLYMERIZATION OF N-METHYL PYRROLE WITH CARBAZOLE
International Journal of Polymeric Materials, 2004
Electrocopolymerization of N-methylpyrrole (NMePy) and Carbazole (Cz) was conducted in acetonitrile. Oxidative chemical random copolymerization of NMePy and Cz was also realized by Cerium (IV) ammonium nitrate (CAN) for comparison. The properties of the resulting copolymers were investigated by spectroscopic methods (UV-VIS, FT-IR), cyclic voltammetry and four point probe conductometer, to understand the oligomeric pyrrole ring interaction with carbazole ring where the reactive nitrogen of pyrrole ring was capped (substituted) by methyl group.
The copolymerization of N-Methylpyrrole (N-MPy) and N-ethylcarbazole (ECz) by chemical and electrochemical methods is investigated in detail. Random copolymers of poly[N-Methylpyrrole-N-ethylcarbazole], P[N-MPy-co-ECz], were synthesized in the presence of ceric ammonium nitrate (CAN) in acetonitrile. Electrocopolymerization of N-MPy, and ECz was carried out in various solvents on platinum electrode. Propylene carbonate (PC) was found to be the most suitable solvent for film formation. The effects of sweep rate, supporting electrolyte type, mole ratio, and temperature on the electropolymerization were discussed. The electrochemical properties of Poly(N-ethylcarbazole), (PECz) were improved on copolymerizing it with N-MPy. A copolymerization mechanism has been suggested. The resulting copolymer was characterized by UV-Vis and FT-IR spectroscopic methods, as well as cyclic voltammetric measurements.
2011
C opolymerizations of pyrrole (Py) with N-pentylpyrrole (NPPy) and N-dodecylpyrrole (NDPy) were carried out by chemical and electrochemical oxidation methods. Nanoparticles made of conjugate copolymers with different feed ratios of monomers were prepared by chemical polymerization (conventional and interfacial methods) in presence of iron (III) chloride hexahydrate (FeCl 3 .6H 2 O) as the oxidant. Nanostructure copolymers with higher conductivity were synthesized by simply tuning the preparation conditions in a two-phase medium (toluene-water as solvents). The Npentylpyrrole and N-dodecylpyrrole monomers were synthesized with higher purity from pyrrole. Fourier transform infrared spectroscopy, scanning electron microscopy and four probe conductivity measurement techniques were applied for the characterization of the copolymers. The conductivity of the copolymers obtained by interfacial method using toluene as an organic phase was 5-6 times higher than the copolymer obtained by a conventional method (for molar ratio of Py:NPPy, 30:70). In electrochemical method, copolymer thin films were synthesized with different feed ratios of monomers by cyclic voltammetry in lithium perchlorate-acetonitrile (LiClO 4 /CH 3 CN) electrolyte on the surface of the glassy carbon (GC) as the working electrode. Deposition conditions on the GC, influence of the molar ratio of monomers on the electroactivity and formation of copolymers were studied using cyclic voltammetry.
Substituent Effects on the Electrochemical Properties of Pyrroles and Small Oligopyrroles
Chemistry of Materials, 1997
The electrochemical oxidation of several oligopyrroles, either unprotected, partially blocked, or totally blocked on their R-terminal positions or N-substituted, has been investigated in acetonitrile by cyclic voltammetry. For all the studied oligopyrroles, reversible voltammograms have been obtained at moderate to high scan rates, whereas chemical evolutions of the cation radicals have been observed at lower scan rates. The one-electron redox potentials, E°, of the oligopyrrole/oligopyrrole cation-radical couples have been measured and the lifetimes of the cation radicals have been estimated. The stabilities of the cation radicals have been examined as a function of the chain length and the nature of the substituent.
Oxidative coupling and polymerization of pyrroles
Electrochimica Acta, 2005
The electrochemical oxidation of 2,4-dimethyl-3-ethylpyrrole in acetonitrile has been studied using cyclic voltammetry, constant current coulometry, preparative electrolyses and ab initio calculations. The product analysis after the preparative electrolyses was carried out by HPLC combined with UV-vis and electrospray ionization MS detection. The aim of the work was to address some of the unresolved problems in the oxidative oligomerization and polymerization of alkylpyrroles. The title compound was chosen as a model for studies of pyrroles that are more basic than the solvent-supporting electrolyte system and for that reason are forced to serve as the base accepting the protons released during the coupling steps. The voltammograms obtained by cyclic voltammetry at a substrate concentration of 2 mM and voltage scan rates between 0.02 and 2 V s −1 showed a characteristic trace-crossing phenomenon that could be demonstrated by digital simulation to be related to that fact that the deprotonations of the initially formed dimer dication are slow with second order rate constants in the range 10 3 -10 4 M −1 s −1 . The relative stability of the different tautomers of the protonated pyrrole monomer and the corresponding 2,2 -dimer was determined by ab initio calculations at the RHF 6-31G(d) level. The studies also included investigations of the effects resulting from addition of a non-nucleophilic base, 2,6-di-tertbutylpyridine, to the voltammetry solutions. The major product observed after preparative electrolyses was a trimer the structure of which is proposed to include a central 2H-pyrrole unit. Since 2H-pyrroles are stronger bases than the corresponding 1H-pyrroles, the trimer is effectively protected against further oxidation by protonation. Two other trimers were observed as minor or trace products as well as a 1H,2H-dimer and several tetramers, also in trace amounts. In addition to the dimer, the trimers and the tetramers, a number of other minor products could be detected. These could all be traced back to the nucleophilic attack by residual water on the radical cations or dications of the 2,2 -dimer and the trimers. The results obtained by constant current coulometry are in agreement with the formation of a 2H-pyrrole based trimer as the major product.
The copolymerization of N-Methylpyrrole (N-MPy) and N-ethylcarbazole (ECz) by chemical and electrochemical methods is investigated in detail. Random copolymers of poly[N-Methylpyrrole-N-ethylcarbazole], P[N-MPy-co-ECz], were synthesized in the presence of ceric ammonium nitrate (CAN) in acetonitrile. Electrocopolymerization of N-MPy, and ECz was carried out in various solvents on platinum electrode. Propylene carbonate (PC) was found to be the most suitable solvent for film formation. The effects of sweep rate, supporting electrolyte type, mole ratio, and temperature on the electropolymerization were discussed. The electrochemical properties of Poly(N-ethylcarbazole), (PECz) were improved on copolymerizing it with N-MPy. A copolymerization mechanism has been suggested. The resulting copolymer was characterized by UV-Vis and FT-IR spectroscopic methods, as well as cyclic voltammetric measurements. Ã Given potentials have deviation ¼ AE0.003 V. 1 Polymer oxidation potential, V. 2 Monomer oxidation potential, V. a Initial feed ratio of monomers, n N-MPy =n ECz ¼ 2.
Modification of polyindole by the incorporation of pyrrole unit
Journal of Applied Polymer Science, 2002
Electrochemical copolymerization of pyrrole and indole was performed galvanostatically in a solvent of acetonitrile (AN)/water (vol %: 99/1). The product obtained was characterized by cyclic voltammetry and infrared spectroscopy. The influence of the monomer feed ratio of pyrrole and indole on the synthesis of the copolymer was investigated. The amount of pyrrole units in the copolymer chain increased with increase of the concentration of the pyrrole monomer in the solution. The results showed that the electrochemical activity of the copolymer was improved as the incorporation of pyrrole units increased. Thermogravimetric analysis was carried out to investigate the properties of the copolymer.