Showing papers in "Journal of Polymer Science Part A in 1992"

Synthesis and characterization of thermally reversible macroporous poly(N‐isopropylacrylamide) hydrogels

Abstract: Thermally reversible poly(N-isopropylacrylamide) (PNIPAAm) hydrogels having macroporous structures were prepared by a new method These gels have large pore volumes, large average pore sizes and faster macromolecule permeation rates in comparison to conventional PNIPAAm conventional hydrogels Compared with conventional PNIPAA hydrogels, the macroporous PNIPAAm gels have higher swelling ratios at temperatures below the LCST and exhibit faster deswelling and reswelling rates The deswelling rates are especially rapid

Gamma‐, photo‐, and thermally‐initiated oxidation of linear low density polyethylene: A quantitative comparison of oxidation products

Abstract: It was found that all types of initiation gave very similar products but in varying quantities. In photooxidation, hydroperoxide was clearly shown to approach a photostationary concentration either from below for fresh film or from above for samples that had been pre-oxidized by γ-irradiation, prior to UV exposure. Carboxylic acid groups, the main backbone scission product, dominated in photooxidations, possibly as the result of the further oxidation of sec-hydroperoxide sites.

Synthesis of thermally‐induced phase separating polymer with well‐defined polymer structure by living cationic polymerization. I. Synthesis of poly(vinyl ether)s with oxyethylene units in the pendant and its phase separation behavior in aqueous solution

Abstract: Living cationic polymerization of alkoxyethyl vinyl ether [CH2CHOCH2CH2OR; R: CH3 (MOVE), C2H5 (EOVE)] and related vinyl ethers with oxyethylene units in the pendant was achieved by 1-(isobutoxy)ethyl acetate (1)/Et1.5AlCl1.5 initiating system in the presence of an added base (ethyl acetate or THF) in toluene at 0°C. The polymers had a very narrow molecular weight distribution (Mw/Mn = 1.1–1.2) and the Mn proportionally increased with the progress of the polymerization reaction. On the other hand, the polymerization by 1/EtAlCl2 initiating system in the presence of ethyl acetate, which produces living polymer of isobutyl vinyl ether, yielded the nonliving polymer. When an aqueous solution of the polymers thus obtained was heated, the phase separation phenomenon was clearly observed in each polymer at a definite critical temperature (Tps). For example, Tps was 70°C for poly(MOVE), and 20°C for poly(EOVE) (1 wt % aqueous solution, Mn ∼ 2 × 104). The phase separation for each case was quite sensitive (ΔTps = 0.3–0.5°C) and reversible on heating and cooling. The Tps or ΔTps was clearly dependent not only on the structure of polymer side chains (oxyethylene chain length and ω-alkyl group), but also on the molecular weight (Mn = 5 × 103-7 × 104) and its distribution. © 1992 John Wiley & Sons, Inc.

The crosslinking of chitosan fibers

Abstract: A need exists for the development of totally biodegradable packaging materials. Chitosan is an under-utilized polymer which possesses many of the desired characteristics for this application. This article describes the crosslinking of chitosan fibers. Epichlorohydrin (ECH) was selected as a convenient base catalyzed crosslinking agent. The strength of chitosan fibers, especially wet tenacity, is improved by crosslinking. © 1992 John Wiley & Sons, Inc.

Accelerated imidization reactions using microwave radiation

Abstract: Microwave radiation has been clearly shown to result in enhancement of the rate of reaction for an imidization reaction. Analysis of the kinetic parameters showed that the apparent activation energy for the reaction was reduced from 105 to 55 kJ/mol, under the conditions of this experiment. The mechanism which has been proposed to explain this enhancement is based on the concept of a nonuniform temperature on a molecular scale, rather than a true reduction in the activation energy. © 1992 John Wiley & Sons, Inc.

Preparation and properties of novel soluble aromatic polyimides from 4,4′‐diaminotriphenylamine and aromatic tetracarboxylic dianhydrides

Abstract: New aromatic polyimides containing triphenylamine unit were prepared by two different methods, i.e., a conventional two-step method starting from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides and the one-step thioanhydride method starting from the aromatic diamine and aromatic tetracarboxylic dithioanhydrides. Both procedures yielded high-molecular-weight polyimides with inherent viscosities of 0.47–1.17 dL/g. Some of these polymers were soluble in organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, and pyridine. All the polyimides afforded transparent, flexible, and tough films, and the color varied from pale yellow to dark red, depending markedly on the tetracarboxylic acid components. The glass transition temperatures (Tgs) of these polyimides were in the range of 287–331°C and the 10% weight loss temperatures were above 520°C in air. The polyimides prepared by the one-step method exhibited better solubility in organic solvents and had somewhat lower Tgs than the polymers prepared by a conventional two-step method.

An improved method for the diimide hydrogenation of butadiene and isoprene containing polymers

Abstract: The hydrogenation of unsaturated polymers with diimide generated in-situ by thermolysis of p-toluenesulfonyl hydrazide (TSH) is a commonly used method for preparing laboratory scale quantities of saturated diene based polymers. The by-products from TSH, particularly p-toluenesulfinic acid, can attack at olefinic sites, adding p-tolylsulfone functionality and degrading polymer molecular weight. The addition of tri-n-propyl amine has been found to eliminate these side reactions in butadiene containing polymers and copolymers, enabling the preparation of polymers devoid of backbone unsaturation. No detectable sulfur-containing impurities were indicated by IR, NMR, or elemental analysis, and no chain degradation was observed via GPC analysis of the hydrogenated polymers. cis-Polybutadiene and butadiene containing random and block copolymers with styrene were hydrogenated cleanly using this technique. A ratio of 2 mol TSH and 2 mol amine/mol of olefin was necessary to assure > 99% hydrogenation, and a w/v ratio of 2 parts butadiene/100 parts o-xylene gave the most efficient hydrogenation. Polymers prepared from isoprene were only partially hydrogenated when treated with TSH in the presence of tri-n-propyl amine, and gave evidence of slight degradation of the polymer structure.

Consistent values of rate parameters in free radical polymerization systems. II. Outstanding dilemmas and recommendations

Abstract: The problems of determining reliable, well-characterized values of kinetic parameters in free-radical polymerizations are discussed. The origins of the fact that experimental determinations of rate coefficients of ostensibly identical systems often result in quite different values being reported can be ascribed to subtle mechanistic assumptions made in data interpretation, which are considered in detail. A series of recommendations to assist in overcoming these problems, and to highlight their origins, are presented, with emphasis placed on new techniques including those employing laser photolysis and EPR.

Thermally reversible crosslinking of polystyrene via the furan-maleimide diels-alder reaction

Abstract: Mixtures of maleimidomethylated polystyrene with difurfuryl adipate or with furfuryl alcohol-esterified poly[styrene-co-(maleic anhydride)] underwent thermally reversible Diels–Alder crosslinking. Reversal of crosslinking occurred rapidly at 150°C. The instability of the furfuryl group, however, limits the practicability of the reaction. © 1992 John Wiley & Sons, Inc.

Particle nucleation and monomer partitioning in styrene O/W microemulsion polymerization

Abstract: Particle nucleation in the polymerization of styrene microemulsions was found to take place throughout the polymerization as indicated by measurements of the particle number as a function of conversion. A mechanism based on the nucleation in the microemulsion droplets was proposed to explain the experimental findings although homogeneous nucleation and coagulation during polymerization were not completely ruled out. A thermodynamic model was developed to simulate the partitioning of monomer in the different phases during polymerization. The model predicts that the oil cores of the microemulsion droplets were depleted early in the polymerization (4% conversion). Due to the high monomer/polymer swelling ratio of the polymer particles, most of the monomer resides in the polymer particles during polymerization. The termination of chain growth inside the polymer particles was attributed to the chain transfer reaction to monomer. The low n (less than 0.5) of the microemulsion system was attributed to the fast exit of monomeric radicals.

Synthesis and characterization of monodisperse porous polymer particles

Abstract: Monodisperse porous polymer particles in the size range of 10 μm in diameter were prepared via seeded emulsion polymerization. Linear polymer (polystyrene seed) or a mixture of linear polymer and solvent or nonsolvent were used as inert diluents. The pore diameters of these porous polymer particles were on the order of 1000 A with pore volumes up to 0.9 mL/g and specific surface areas up to 200 m2/g. The physical features of the porous polymer particles depended on the diluent type and the crosslinker content, as well as the molecular weight of polymer seed particles. By varying the molecular weight of the linear polymer, monodisperse porous polymer particles with different pore size distribution could be synthesized. Polymer seed with a low degree of crosslinking instead of linear polymer could also be used to prepare monodisperse porous polymer particles with smaller pore volume and pore size.

Thermal redistribution reactions in crosslinked polysiloxanes

Abstract: The thermolysis under argon of various polysiloxane resins containing D, T, DH, or TH units was investigated using thermogravimetric analysis combined with mass spectroscopy (TG/MS analysis) and solid-state 29Si-NMR Redistribution reactions involving the exchange of SiC/SiO bonds or SiH/SiO bonds were evidenced in addition to the exchange of SiO/SiO bonds reported to date These reactions significantly modify the initial siloxane units and lead to an escape of volatile silanes or siloxanes The exchange of SiH/SiO bonds takes place at lower temperatures (300°C) than the exchange of SiC/SiO bonds (500°C)

Model filled polymers. V. Synthesis of crosslinked monodisperse polymethacrylate beads

Abstract: Monodisperse polymethacrylate beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylate and divinyl monomers in the absence of emulsifiers. The sizes of polybutyl and polyethyl methacrylate beads decreased with increasing polymerization temperature, while polymethyl methacrylate beads were largely unchanged in size. The molar mass of polymer in polymethyl metnacrylate beads markedly exceeded that in polystyrene beads. The rate of polymerization increased, and bead size decreased, with increasing initiator concentration or decreasing monomer concentration. The polymethacrylate beads are used as filler particles in polymer composites.

Surface modification of Kapton film by plasma treatments

Abstract: Kapton films were treated with seven plasmas: Ar-, N2-, O2-, CO-, CO2-, NO-, and NO2- plasmas. Surface properties and chemical composition of the plasma-treated Kapton films were investigated from the contact angle measurement, and the IR and XPS spectra. The plasmas, especially NO- and NO2-plasma, made the Kapton film surface hydrophilic. The XPS and IR spectra showed that the plasma led to the modification of the imide groups in the Kapton film to secondary amide and carboxylate groups.

Absorption spectra of thin film of polyaniline

Abstract: The absorption spectra of thin film of polyaniline (PANI) were measured as a function of the protonation state of the polymer, the concentration of PANI in NMP, drying temperature and atmosphere. The absorbance value of the 950 nm peak and the ratio of the absorbance value at 950 nm to that of the 630 nm peak increases with increasing the protonation state of PANI. This is consistent with the observation of varying the conductivity with the protonation state. A modified molecular structure of PANI is proposed [(PhNHPhNH)] y [(PhN=Ph=N) x (PhNHPhNH .+ ) 1-x ] 1-y (0≤y andx≤1) where y and x are defined as the oxidation and the protonation states of PANI, respectively

Fatty acid terminated polyanhydrides.

Abstract: Fatty acid terminated polyanhydrides suitable for use as controlled release matrices in biodegradable sustained release drug delivery systems and methods for making thereof as described. The polymers are more soluble in organic solvents, and have a lower melting point than the corresponding non-fatty acid terminated polyanhydrides. The fatty acid terminated polyanhydrides are also more hydrophobic than the corresponding polyanhydrides that are not terminated with a fatty acid, and combine the properties of thermodynamic and hydrolytic stability, and easy storage. The polymers can be produced with a controlled and low molecular weight. The polyanhydrides are useful in a number of applications, including as a matrix in biodegradable drug delivery systems.

Liquid crystalline epoxy thermosets based on dihydroxymethylstilbene: Synthesis and characterization

Abstract: This article describes the synthesis and characterization of a new series of liquid crystalline thermosets. Nematic epoxy-terminated oligoethers based on dihydroxy-α-methylstilbene were synthesized for this study. These prepolymers were crosslinked within the nematic mesophase using methylenedianiline. Depending upon the molecular weight and polydispersity of the oligoether, the crosslinking reaction resulted in networks with either a smectic or nematic molecular organization in contrast to the simple nematic phase of the oligoether. The formation of a smectic-like structure on curing was found to be related to the breadth of the prepolymer molecular weight. In those networks with a low crosslink density a clearing transition could be observed, whereas in the more highly crosslinked networks the molecular organization was frozen in until decomposition. The glass transition temperature of these LC networks rose as the crosslink density was increased, ranging from 35 to 152°C. In agreement with theory, the clearing transition of the networks was found to be dependent on the phase state during curing © 1992 John Wiley & Sons, Inc.

A fluorine-containing hydrophobically associating polymer. I. Synthesis and solution properties of copolymers of acrylamide and fluorine-containing acrylates or methacrylates

Abstract: Fluorine-containing hydrophobically associating polymers have been synthesized by copolymerization of acrylamide with a small amount of an acrylate or methacrylate having a fluorocarbon containing ester group. It was found that hydrophobic associations occurring between these fluorocarbon chains was stronger than the interactions of the corresponding hydrocarbon comonomers and depend on the length of the fluorocarbon chain. The polymer solutions were found to be highly pseudoplastic but the viscosity loss was completely reversible upon removal of shear

Kinetic study of light‐induced polymerization by real‐time UV and IR spectroscopy

Abstract: Real time ultraviolet (RTUV) spectroscopy was used to study the photolysis kinetics of a radical-type morpholino initiator, during the polymerization of a multiacrylate monomer exposed to UV radiation in bulk, in solution, in a polyurethane-acrylate resin, and in a poly(methyl methacrylate) matrix. The photolysis rate constant k was determined from the exponential loss profile recorded; it was found to vary between 0.1 and 3s−1, depending on the light intensity and on the monomer concentration. The quenching of the photoinitiator excited states by the acrylate monomer was shown to be an important deactivation pathway which substantially reduces the rate of initiation. The observed influence of the film thickness and photoinitiator concentration on the k value were accounted for by the internal filter effect. Conversion versus time curves were recorded by real time infrared (RTIR) spectroscopy for the various systems examined, thus allowing a direct comparison of both the actual polymerization rate and the residual unsaturation content of the cured polymer. Various factors were shown to be responsible for the early stop of the polymerization, such as depletion of the photoinitiator, O2 inhibition, or vitrification of the polymer. The photoinitiated cationic ring-opening polymerization of a cycloaliphatic diepoxy monomer was also studied in real time by RTUV and RTIR spectroscopy. Despite a very fast photolysis of the triarylsulphonium initiator, the polymerization of the epoxy monomer developed less rapidly than for the acrylic monomer, with shorter kinetic chain lengths. A linear relationship was found to exist between the decay rate constant and the light intensity, for both the radical and the cationic photoinitiators, as expected for a direct photolysis process.

Emulsifier‐free emulsion copolymerization of styrene and sodium styrene sulfonate

Abstract: The kinetics of the emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate have been examined over a range of comonomer compositions. The rate of polymerization was found to increase dramatically in the presence of small amounts of sodium styrene sulfonate. This increase is attributed to the increased number of particles formed when sodium styrene sulfonate was present and to a gel effect enhanced by ion association. At low concentrations of functional comonomer, where a monodisperse product was obtained, a homogeneous nucleation mechanism of particle generation is proposed. At higher concentrations, broader and then bimodal size distributions were obtained, and this is ascribed to significant aqueous phase polymerization of sodium styrene sulfonate. The water-soluble homopolymer is supposed to act as a locus of polymerization. The occurrence of this aqueous phase side reaction and the generation of secondary particles makes impossible the preparation of highly sulfonated polystyrene latexes by batch or seeded batch emulsion copolymerization.

Synthesis and characterization of bismaleimides from epoxy resins

Abstract: Novel bismaleimides (BMIs) were prepared from functional monomaleimides and diglycidyl ether of bisphenol A (DGEBA) and some of them were shown to have good processibility and improved water resistance while retaining characteristic thermal stability of polyimide. Functional monomaleimides were synthesized via the condensation reaction of maleic anhydride with either aminobenzoic acid or aminophenol. Crosslinking reaction of thus obtained BMIs was carried out with or without catalyst at the temperature range of 100–250°C. The type of the functional group species and their position in monomaleimides significantly affected the crosslinking behavior of the resulting BMIs and the thermal property of their crosslinked products. BMIs with meta linkage, obtained from meta monomaleimides, exhibited much faster thermal crosslinking behavior than corresponding para BMIs. When the molecular weight of BMI was larger, the crosslinking density became smaller and Tg was lower as expected, while the viscosity started to increase at a higher temperature. Glass transition temperatures of the crosslinked resins were in the range of 160–250°C and these resins showed excellent thermal stability up to 370°C.

N-alkoxy-pyridinium and N-alkoxy-quinolinium salts as initiators for cationic photopolymerizations

Abstract: The polymerization of n-butyl vinyl ether (BVE), cyclohexene oxide (CHO) and 3,4-epoxycyclohexyl(methyl)-3′,4′-epoxycyclohexane carboxylate (EEC) was initiated upon UV irradiation (λinc > 300 nm) of dichloromethane solutions containing N-ethoxy-2-methylpyridinium (V), N-ethoxy-4-phenyl-pyridinium (VI) or N-ethoxy-isoquinolinium hexafluorophosphate (VII). Whereas the bifunctional EEC was converted into an insoluble gel, BVE and CHO formed polymers of molar mass: Mw = 2 X 104−2 X 105 (PCHO) and Mw ≈ 2 X 104 (PBVE). Protons are formed with a rather high quantum yield [o(H+) = 0.48 on irradiating VII in dichloromethane; titration with sodium p-nitrophenolate] and it is, therefore, assumed that the polymerization is initiated by photochemically generated protons. © 1992 John Wiley & Sons, Inc.

The mechanical and magnetic alignment of liquid crystalline epoxy thermosets

Abstract: The processing of a new series of liquid crystalline (LC) epoxy networks was evaluated. Above the glass transition temperature, the low crosslink density networks could be mechanically aligned. The mechanically oriented networks readily lost orientation upon heating. Highly anisotropic liquid crystalline (LC) epoxy networks were also prepared by aligning the mesophase of the prepolymer during the curing process under the influence of a magnetic field. Orientation parameters (f) of 0.13 to 0.57 were achieved by these processes as determined by x-ray diffraction analysis. The ability of the magnetically aligned networks to retain their orientation above the glass transition temperature was determined by time-resolved x-ray diffraction. The stability of the alignment of these networks was found to depend on crosslink density. The effect of the anisotropy of these networks was investigated by measuring the coefficient of thermal expansion (CTE). In the aligned networks, there was a substantial reduction in CTE parallel to the direction of the applied field compared to the randomly oriented networks. © 1992 John Wiley & Sons, Inc.

Monodisperse porous polymer particles: Formation of the porous structure

Abstract: Monodisperse porous styrene-divinylbenzene copolymer particles were prepared via seeded emulsion polymerization using a mixture of linear polymer (polystyrene seed) and non-solvent as inert diluent. Experimental evidence was presented to describe the mechanism of formation of porous polymer particles during the copolymerization and solvent extraction stages, in which porosity was a consequence of phase separation in the presence of diluents. Pore structure formation was investigated by changes in copolymerization kinetics, gel content, crosslinking density, particle morphology, surface area, pore volume, and pore size distribution. The process of copolymerization was presented, based on the concepts of production, agglomeration, and fixation of the interior gel microspheres of polymer particles. A portion of linear polymer used as diluent was found to participate in the network structure while the porous matrix was built-up. The influence of the removal of the linear polymer from the matrix pores during the solvent extraction process on the porous structure was also discussed.

Amphiphilic comb‐shaped polymers from poly(ethylene glycol) macromonomers

Abstract: Comb-shaped amphiphilic graft copolymers composed of hydrophobic backbones and hydrophilic side chains were prepared by radical copolymerization of poly(ethylene glycol) monomethacrylate macromonomers, and methacrylate and acrylate comonomers in toluene. The copolymerizations were very sensitive to the reaction conditions, and insoluble cross-linked gels were easily formed. The yields of soluble copolymers were affected by the initiator concentration, the macromonomer concentration, and the choice of chain transfer agents and comonomers. Solubilities of the copolymers in water or methanol were found to depend on the sizes and the numbers of the PEG side chains. The copolymers showed surface activity with CMC:s in the order of 0.1–1.5 g/L and surface tensions of 36–56 dyn/cm. When tested as emulsifiers most of the copolymers gave oil-in-water type emulsions at room temperature. Polymers carrying MPEG 2000 side chains were crystalline with melting points of 38–44°C, while those based on PEG 400 and 1000 were mostly amorphous with glass transition temperatures between -55 and -60°C. © 1992 John Wiley & Sons, Inc.

Thermal degradation of polymethacrylic acid

Abstract: The thermal degradation of polymethacrylic acid was found to have two separate decomposition regions. The first decomposition region, due to anhydride formation primarily, was caused by the conversion of polymethacrylic acid to polymethacrylic anhydride. This reaction followed first-order kinetics and had an activation energy of 40.5 kcal/mol. The second decomposition region was the thermal degradation for the corresponding polymethacrylic anhydride. In this region, the fragmentation of anhydride rings structure in polymethacrylic anhydride constitutes the major decomposition reaction with an activation energy of 37.4 kcal/mol

Modeling of the styrene microemulsion polymerization

Abstract: A mathematical model was developed to simulate the polymerization kinetics of styrene oil-in-water microemulsions. Nucleation of particles in microemulsion droplets was assumed to account for the number of particles generated. It was found that the entry rate coefficient of radicals into microemulsion droplets is much smaller than the entry rate coefficient into monomer-swollen particles. All particles contain at most one growing radical. Various radical entry mechanisms were evaluated using the simulation. The possibility of flocculation between particles during the later stages of the polymerization and the high desorption rate of monomeric radicals was suggested by the simulation results. The likelihood of re-entry of desorbed radicals was den onstrated.

Synthesis and polymerization of N‐[4‐N′‐ (α‐methylbenzyl)aminocarbonylphenyl]maleimide

Abstract: A novel type of optically active N-[4-N′-(α-methylbenzyl)aminocarbonylphenyl]maleimide [(R)-MBCP] was synthesized from maleic anhydride, p-aminobenzoic acid, and (R)-methylbenzylamine. Radical homopolymerization of (R)-MBCP was performed in tetrahydrofuran (THF) at 50 and 70°C for 24 h to give optically active polymers having [α]25D = -141° and -129°, respectively. Anionic polymerization of (R)-MBCP with n-butyllithium in THF and N,N-dimethylformamide gave an optically active polymer having −78 to −81° of [α]25D. Radical copolymerizations of (R)-MBCP (M1) were performed with styrene (ST, M2) and methyl methacrylate (MMA, M2) in THF at 50°C. The monomer reactivity ratios (r1, r2) and the Alfrey-Price Q-e values were determined as follows: r1 = 0.009, r2 = 0.091, Q1 = 1.30, e1 = 1.87 in the (R)-MBCP-ST; r1 = 0.27, r2 = 1.21, Q1 = 0.93, e1 = 1.46 in the (R)-MBCP-MMA system. Chiroptical properties of the polymers were also investigated. © 1992 John Wiley & Sons, Inc.

Electrochemically initiated chain polymerization of pyrrole in aqueous media

Abstract: The electrochemical quartz crystal microbalance has been employed to investigate the electropolymerization of pyrrole in a variety of aqueous electrolytes. In contrast to the generally accepted cation–radical coupling process for the electropolymerization of pyrrole, an electrochemically initiated chain polymerization, featuring a high polymerization rate and involving little charge transport, was found under specific conditions in the presence of ClO−4, BF−4, and PF−6 electrolytes. The more typical cation-radical coupling mechanism, characterized by a constant polymerization charge to mass deposited ratio, is observed in the presence of Cl−, NO−3, dodecyl sulfate, copper phthalocyanine tetrasulfonate, β-cyclodextrin tetradecasulfate, and poly(styrene sulfonate). Electrochemical characterizations of polypyrrole films prepared in aqueous ClO−4 electrolytes reveal that the polymer formed via chain polymerization exhibits the ability to transport both cations and anions during electrochemical switching between redox states, while the polymer synthesized through cation-radical coupling is only capable of transporting a single ionic species.

Chemical and electrochemical characterization of chemically synthesized conducting polypyrrole

Abstract: The conducting polypyrrole chemically synthesized in water, using the variable concentrations of FeCl3 and CuCl2 as oxidizing agents, was chemically and electrochemically characterized and compared with electrochemically generated polypyrrole. According to the results of elemental analysis and counter ion determinations, it can be concluded that a mixture of dimer and trimer was obtained using CuCl2, i.e., a dimer composition using FeCl3 as an oxidant. Cyclic voltammetric studies of polypyrrole obtained by using FeCl3 as an oxidant showed no evidence of polypyrrole decomposition after repetitive cycling. The voltammograms showed also that after the oxidation reaction a high capacitive current remained, confirming the assumption that the capacitive current is intrinsically associated with polypyrrole, irrespective of the way of its preparation. Cyclic voltammogram of the polypyrrole synthesized by oxidation with CuCl2 showed different shape, probably influenced by the presence of copper ions incorporated in polymers. © 1992 John Wiley & Sons, Inc.