A comparative study on protective properties of electrosynthesized poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), poly(pyrrole)/poly(N-methoxyphenylpyrrole) composite coatings

In this study, three sets of different bilayered composite coatings of pyrrole and N-substituted pyrroles were synthesized by a layer-by-layer approach on copper surface and corrosion performances of the synthesized materials were compared. Electrodepositions of poly(N-methylpyrrole), poly(N-phenylpyrrole), and poly(N-methoxyphenylpyrrole) were performed in nonaqueous medium on a poly(pryrrole)-coated copper surface using cyclic voltammetry. The morphologies of the resulting bilayered composite coatings of poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), and poly(pyrrole)/poly(N-methoxyphenylpyrrole) were investigated by scanning electron microscopy. Stabilities of a doping-dedoping process of the composites were determined from the cyclic voltammetric study of the bilayer-coated electrodes in a monomer-free solution. Corrosion performances of the bilayer composite-coated and uncoated copper electrodes were investigated in 0.1 M H₂SO₄ solution using open circuit potential–time (E _ocp–t) curves, anodic polarization, and electrochemical impedance spectroscopy. All the investigated bilayered coatings gave significant enhancement in the corrosion resistance of copper, compared to the single poly(pyrrole) coating. Stability and corrosion tests revealed that the composite material poly(pyrrole)/poly(N-methoxyphenylpyrrole) exhibited higher electrochemical stability and corrosion resistant behavior than the other bilayered composite coatings.     

Role of substituent in electrooxidation of poly(1-substituted pyrrole) films

Poly(1-substituted pyrrole)s were prepared on a platinum electrode with different electrolysis times, and their properties were studied by cyclic voltammetry. The oxidation potential for most of the poly(1-alkylpyrrole)s were almost 0.3 V versus the Ag/Ag⁺ reference electrode, except for poly(1-butylpyrrole). The electron transfer rate in polymer films depends on the electrolysis time and the size of the substituent. The difference of the redox peak potential of poly(1-phenylpyrrole) was smaller than that of poly(1-anisylpyrrole) films. The role of a substituent in the electrochemical behavior of the polymer main chain is discussed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 471–475, 1998     

Electrochemical behaviour of poly(pyrrole) coatings on steel

The electrochemical and corrosion protective properties of electrochemically deposited thin films of polypyrrole (PPy) have been studied. Two systems have been investigated: (1) Oxalate-doped PPy; and (2) a dual layer system consisting of PPy-oxalate and PPy-poly(styrene sulfonate). Large anions like PSS are interesting, because they possibly prevent ingress into the layer by halide ions like chloride. Open circuit potential measurements and impedance spectra of both systems are compared. For intact coating systems the impedance spectra of the four systems investigated can be described by an equivalent circuit model consisting of an R _f Q _f circuit, due to the polypyrrole film itself, and a modified Randles circuit in series, to account for the double layer at the polypyrrole/electrolyte interface and the polypyrrole reaction. In 0.1 m NaCl the time to failure for the dual layer is almost 6-fold that of the single layer. This indicates that PSS is indeed capable of preventing the ingress of chloride ions. In 0.1 m Na₂SO₄ the time to failure for the dual layer is less than double that of the single layer.     

Influence of electrochemically prepared poly(pyrrole-co-N-methyl pyrrole) and poly(pyrrole)/poly(N-methyl pyrrole) composites on corrosion behavior of copper in acidic medium

Poly(pyrrole-co-N-methyl pyrrole) copolymer and poly(pyrrole)/poly(N-methyl pyrrole) bilayer composites were electrochemically synthesized on copper by cyclic voltammetry from aqueous solution of 0.3 M oxalic acid and 0.1 M monomer. Synthesis of copolymers were performed with different monomer feed ratios (pyrrole:N-methyl pyrrole, 8:2, 6:4, 5:5, 4:6 and 2:8) and in order to determine the copolymer, which has the best corrosion performance, anodic polarization was applied to copolymer coated samples. It was found that the performance of coatings was strongly dependent to the monomer feed ratio and the copolymer synthesized with 8:2 concentration ratio showed the most protective property compared to others. Bilayer of poly(pyrrole)/poly(N-methyl pyrrole) was also synthesized to compare the anticorrosive properties. Polymer films were characterized by ATR-FTIR spectroscopy and SEM techniques. Corrosion behavior of polymer composites was investigated in 0.1 M H₂SO₄ solution by anodic polarization and electrochemical impedance spectroscopy. Different approaches such as phase angle at high frequency and areas under Bode plots were used to evaluate corrosion performances of the coatings. Copolymer and bilayer coatings were found to have higher protection effect than single polypyrrole coatings. Moreover, bilayer coating exhibited better protection efficiency than copolymer coating against corrosion of copper when the obtained results were compared.     

Physicochemical properties of electrochemically prepared poly(pyrrole hexafluorophosphate)

Poly(pyrrole hexafluorophosphate) (PPPF₆) was prepared with the potentiostatic method to supply a constant potential of 1.21 V for 5 h in water/acetonitrile (1/99 vol %) solution of 0.2M pyrrole containing 0.1M tetraethylammonium hexafluorophosphate as a supporting electrolyte. The result of elemental analysis and Fourier transform infrared spectrum showed that it was a PPPF₆ that was doped with ∼28 wt % 6 was irreversible. Scanning electron microscopy was performed to know the morphology of PPPF₆. The result of the differential scanning calorimetry did not show any special peak in temperature range of 25–800°C. From the temperature dependence of the electrical conductivity and electron spin resonance measurement, it was suggested that a possible conduction mechanism for the PPPF₆ polymer should be a small polaron hopping conduction. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 605–612, 1998     

Formation of honeycomb‐patterned microporous films based on a fluorinated poly(siloxane imide) segmented copolymer

The preparation of honeycomb‐patterned microporous films from a soluble fluorinated poly(siloxane imide) segmented copolymer (PSI) by means of water‐droplet templating is reported first in this article. The fluorinated PSI was synthesized from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and diamine‐terminated poly(dimethyl siloxane) by condensation polymerization. The obtained copolymer had good solubility in chlorinated solvents (chloroform, dichloromethane, and 1,2‐dichloroethane), good thermal stability, and a microphase‐separated amorphous structure. The effects of the copolymer concentration, atmospheric humidity, and solvent properties on the pattern formation were investigated. The results show that the film fabricated from the copolymer solution with chloroform as the solvent at a humidity of 90% and a concentration of 0.5 g/L had the most regular honeycomb‐patterned micropores. We could tailor the pore shape and size by changing the copolymer concentration or the atmospheric humidity. The prepared regular honeycomb‐patterned microporous PSI films have potential applications in cell culture and tissue engineering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Constant voltage electrodeposition of poly(vinylidene chloride) emulsions

In the field of organic coatings, electrodeposition is a technique that holds many advantages over traditional methods of immersion and dispersion, such as low levels of contamination, ease of control and automatization, and high penetration capacity. In this article, the results of the electrodeposition of poly(vinylidene chloride) emulsions on galvanized steel are presented. The operating conditions to form thin, uniform, and adherent films were established. A mathematical model was also developed to predict film growth with time as a function of the process parameters. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2479–2486, 1998     

Morphology,structure, and properties of poly(lactic acid) microporous films containing poly(butylene terephthalate) fine fibers fabricated by biaxial stretching

The effects of size and shape, i.e., sphere and fiber, of dispersed poly(butylene terephthalate) (PBT) in poly(lactic acid) (PLA) matrix on the morphology and porous structure of the biaxially stretched films are comparatively investigated. Scanning electron microscope results confirm that the PBT fine fibers can be produced by melt‐stretching following by fast quenching. Rheological characterization reveals the random network structure of PBT fibers. Further, the stretched films composed of spherical PBT particles show the ellipsoidal microvoids due to the interfacial debonding, and the void size relates to the particle size of PBT. However, size of PBT droplets does not influence the void content of the stretched films. The void content considerably increases for equibiaxial deformation as compared with planar deformation, particularly at high draw ratio. Additionally, the stretched films containing fibrous dispersion exhibit the nonaffine behavior and the highest void content of 8%, which is probably due to the localized deformation between fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41415.     

Direct electrodeposition of thin-layer (phenylene–carbazolylene) copolymers

Thin (phenylene–carbazolylene) copolymer films of controlled composition can be directly deposited onto solid cathodes such as indium tin oxide (ITO) glass or glassy carbon through a dehalogenative polycondensation of 4,4′-dibromobiphenyl and 3,6-dibromo-N-alkylcarbazole mixtures in the presence of an electrogenerated zero-valent nickel catalyst. The electrochemical and optical properties of the resulting thin films have been studied. The electrochemical behavior reveals two distinct electronic states that depend on the copolymer composition and structure. The first electronic state is characterized by either only one redox process, attributed to the presence of phenylene-disubstituted carbazolic units in the case of copolymers with the highest proportion of phenylene, or two successive redox processes, attributed to the occurrence of a radical cation and dication of carbazolic diades, in the case of copolymers with the lowest proportion of phenylene. The second electronic state shows in all cases a single redox system occurring at a higher potential than the first state and due to phenylene moieties in the copolymer. All the electrodeposited copolymer films were found to be reducible in the same manner as pure poly(p-phenylene). © 1994 John Wiley & Sons, Inc.     

Electrodeposition of membrane-oriented conducting poly(pyrrole, thiophene) on stainless steel meshes

Absract Dense membrane preparation was attempted by electrochemical deposition of polypyrrole and polythiophene on stainless steel meshes. The effect of modifying experimental factors such as supporting electrolyte, electrochemical parameters and water addition were investigated. Compact polypyrrole deposits spreading over the meshes could be obtained, but preparative deposition of polythiophene on the same substrate was hindered by competitive anodic corrosion.     

Integration of vanadium-mixed addenda Dawson heteropolytungstate within poly(3,4-ethylenedioxythiophene) and poly(2,2′-bithiophene) films by electrodeposition from the nonionic micellar aqueous medium

A comparative study describing immobilization of the Dawson type mixed addenda heteropolyanion, [P₂W₁₇VO₆₂]⁸⁻ into conducting polymer films of poly(3,4-ethylenedioxythiophene), PEDOT, and poly(2,2′-bithiophene), PBT, is reported. Electrosynthesis of these hybrid films was performed using a micellar aqueous solution of the nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-100). Deposited composite films were characterised electrochemically and, on the whole, they exhibited fast electron transfer (ET) properties and relatively high stability towards continuous potential cycling in acidic media. In particular, PEDOT composite showed relatively faster ET properties in comparison to PBT composite. Their permeability was investigated in the presence of cationic and anionic redox probes. Our results implied good mediating capabilities of the [P₂W₁₇V⁴⁺O₆₂]⁸⁻ anion (within the [P₂W₁₇V⁴⁺O₆₂]⁸⁻–PEDOT hybrid film) towards the iron (III) reduction. The specific electrocatalytic (reductive) capabilities of hybrid films were also studied by probing the reduction of bromate. The films were further characterised by X-ray photoelectron spectroscopy to establish their interfacial elemental composition. Moreover, their surface morphology was imaged by atomic force microscopy and scanning electron microscopy. Results have shown that physicochemical properties of the investigated hybrid films were affected by polymer hydrophobicity.     

Investigations of electrochemical polymerization processes of thin poly(pyrrole) films and its application to anion sensor based on surface plasmon resonance

A study of the response behavior of anion to surface plasmon resonance (SPR) based sensor, in which a Poly(pyrrole) (Ppy) modified thin gold film was used as a sensor chip is described. In situ surface plasmon resonance and electrochemical methods were used to investigate the electropolymerization and doping/dedoping processes of thin Ppy film. The electropolymerization of pyrrole was carried out under cyclic voltammetric conditions, and simultaneously monitored by in situ SPR. It has revealed that the transition between the reduced state and oxidized state of the Ppy, corresponding to the doping/dedoping of anions, can lead to very distinct changes in SPR signal at a fixed angle of incident laser beam. Furthermore, it has demonstrated that the concentration, the charge and size of anions, as well as the film thickness play important roles in the ingress/egress process of anions. Based on this, this combination of experimental approaches can be used to detect Cl⁻. SPR signal exhibited a good linear relationship with the concentration of Cl⁻.     

Palladium electrodeposition on polyaniline films

The electrochemical nucleation and growth of palladium particles onto polyaniline (PAni) films have been investigated by chronoamperometry and topographic and phase-mode atomic force microscopy (AFM). The films were synthesized under different potentiodynamic conditions in order to obtain polymer layers with comparable electroactivity but distinctly different morphology/porosity. The analysis of the current transients obtained for the initial stages of the Pd deposition indicates a 3D nucleative formation regime. A detailed Pd electrodeposition study onto the polymer matrix, using different deposition times, suggests that a constant number of critical nuclei is formed in the superficial part of the polymer porous matrix in the time scale between ca. 5 and 15 s.     

Electropolymerization of poly(2-vinylpyridine) films on zinc

The electroreductive polymerization on a zinc substrate of 2-vinylpyridine in aqueous solution produces thin films. Various electropolymerization conditions have been studied. The deposits have been characterized structurally and compositionally. The best films were obtained at 50°C by potentiostatic polymerization at –1.26 V vs NHE for 15 min.     

Thermoluminescence of poly(ethylene terephthalate) films

Thermoluminescence of γ-ray-irradiated poly(ethylene terephthalate) (PET) films in the temperature range from 77K to 300 K is studied. Three glow peaks were observed in this temperature range, at 102 K, 257 K, and 277 K, which preferentially emit at 365, 326, and 304 nm, corresponding to usual fluorescence peaks of normal PET films. The cause may be seen in the self-trapping mechanism which is involved during irradiation of the PET films by γ-rays. A simultaneous observation of the effect of thermal release and photobleaching on thermoluminescence glow intensity supports this mechanism. Energy required to release the electrons from trapping centres also supports this observation.     

Wet poly(vinyl chloride) membrane

Wet, porous, and semipermeable poly(vinyl chloride) (PVC) membrane prepared from a binary system, PVC and dimethylformamide, by immersing in alcohols or ethers was studied. The pore dimensions of the wet PVC membrane were from 0.01 to 0.05 μm, calculated from hydrodynamic permeability by using experimental values such as water flux and water content. They agreed reasonably well with the dimension of the pores which prevented the protein passing through the membrane, observed by SEM photographs. Formation of the wet PVC membrane can be explained by slow phase separation and slow leaching of the casting solution immersed in alcohols and ethers such as methanol and ethylene glycol monomethyl ether.     

Structural characterization of Celgard® microporous membrane precursors: Melt-extruded polyethylene films

“Row nucleated lamellar” structures are formed when highly crystalline polymers are melt-extruded and recrystallized under high stress. Polyethylene (PE) and polypropylene (PP) films with row lamellar structures have been utilized to produce microporous membranes. Birefringence measurements of melt-extruded PE films show that improved film orientation can be achieved by annealing, extruding at higher speed, and using higher molecular weight polymers. Images from scanning tunneling, atomic force, and field emission scanning electron microscopy (STM, AFM, and FESEM) clearly show the lamellar structures in the melt-extruded PE and PP films. Microscopy results also show that surface lamellar textures are more pronounced with thicker lamellae and are better aligned along the extrusion direction after annealing. X-ray diffraction results show that the increase in film orientation can be attributed to increased lamellar perfection and orientation during annealing and also to better crystallite alignment along the machine direction with higher extrusion speed or with higher molecular weight. High-resolution capabilities of STM, AFM, and FESEM prove to be very effective tools in elucidating lamellar structures in polymeric membrane precursors and can be used as an aid in establishing structure–process–property relationships in making microporous membranes. © 1994 John Wiley & Sons, Inc.     

Comparative studies of electrochemically deposited poly(o-toluidine) and poly(m-toluidine) films

Under galvanostatic deposition conditions poly(o-toluidine) exhibits a higher rate of polymerization than poly(m-toluidine). This observation is supported by results obtained by different characterization techniques such as spectrophotometry, scanning electron microscopy and thermogravimetric analysis. The monomer concentration was found to be the predominant parameter in obtaining selectively a conducting salt phase in both cases. However, the morphology of these polymeric films does not reveal any particular relationship with monomer concentration; instead a mixed morphology, i.e. a combination of granules and fibres, is observed. Finally, the thermal stability of poly(m-toluidine) is lower than that of poly(o-toluidine) with a shift of 190°C in the final decomposition temperature.     

Thermal crosslinking of collagen immobilized on poly(acrylic acid) grafted poly(ethylene terephthalate) films

Graft polymerization of acrylic acid onto plasma‐treated poly(ethylene terephthalate) (PET) films was used to prepare surfaces suitable for collagen immobilization by dip‐coating. Such surfaces could be used as matrices for smooth muscle cell cultures in tissue engineering. Contact angle measurements showed that plasma‐treated and grafted PET films undergo considerable surface reorganization during storage under ambient conditions. However, after collagen immobilization the contact angle remained relatively stable. The amount of collagen initially attached to the film surface increased with increasing poly(acrylic acid) graft density, but subsequent washing in water led to significant collagen loss. This loss could nevertheless be substantially reduced by thermal crosslinking of the collagen in the range 110–130 °C. Atomic force microscopy (AFM) observations suggested that the washed crosslinked collagen has a very similar structure to that of the un‐crosslinked collagen. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1874–1880, 2002