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     

Electrochemical polymerization of poly(o-anisidine) thin films: effect of synthesis temperature studied by cyclic voltammetry

The effect of temperature on the electrochemical synthesis of poly(o-anisidine) (POA) thin films has been investigated. The POA films were synthesized electrochemically under cyclic voltammetric conditions in aqueous solutions of H₂SO₄ at various temperatures between -6°C and 40°C. These films were characterized by cyclic voltammetry (CV), UV–visible spectroscopy and scanning electron microscopy (SEM). It has been found that the rate of polymer formation depends on the synthesis temperature and is highest at 15°C. The optical absorption spectra indicate a major peak at about 800nm and a shoulder at about 440nm independent of the synthesis temperature. The peak at about 800nm corresponds to the presence of the emeraldine salt phase of POA, while the latter may be attributed to the formation of radical cations. The absorbance and width of the peak at about 800nm is observed to increase at low synthesis temperatures. The POA film synthesized at 15°C shows predominant formation of the emeraldine salt phase of POA. The surface morphology as revealed by SEM, is observed to depend on the synthesis temperature, and is caused by different rates of polymer formation at different temperatures. © 1998 SCI.     

Strong effects of counterions on the electrochemistry of poly(N‐methylaniline) thin films

Poly(N‐methylaniline) thin films show different cyclic voltammetric behaviour when cycled in HClO₄, HBF₄, HCl or HNO₃. While in the first two acids the film shows profiles peak potentials similar to those of polyaniline, profiles in HCl and HNO₃ show higher peak potentials for oxidation and a different shape. The free energy for the process, calculated from the oxidation peak potential, shows a linear correlation with the free energy of hydration of the anions present in the test solution. An energy cycle for the oxidation process is proposed to explain the results. The reaction mechanism assumes that anions have to lose their hydration shell to form the polymer salt during electrochemical oxidation of the films. Electropolymerization also depends on the anion present in the solution. While this is possible with low hydration energy anions (ClO₄^?, BF₄^?), it is difficult or impossible when the electrolyte solution contains other anions (Cl^?, NO₃^?) where a higher oxidation potential of the preformed polymer is observed. © 2002 Society of Chemical Industry     

Mediated electron transfer reactions at electrodes coated with poly(viologen)s

Electron and ion transport processes in microdomains of pendant-type poly(viologen)s were analysed by means of rotating disc voltammetry in aqueous media. Stability of poly(viologen)s on the electrode was improved by introducing long alkyl chains. Penetration or the diffusion of ions and the electron-propagation through the polymer layers were greatly affected by the type of supporting electrolyte and chain length of side alkyl groups. Indeed, almost no penetration of large anionic ions was observed in the case of pendant-type poly(viologen) possessing cetyl groups in a perchlorate supporting electrolyte. The electron-propagation through the polymer layers by the self-exchange reactions among redox-active viologen units seemed also to be slow, as the migration of the counter anion of poly(viologen) was limited inside the cationic domain. Similar behaviour was observed in the case of poly(viologen) coatings with ethyl pendant groups, but the electron-propagation was much slower in comparison with the former case. This difference could be attributed to the nature of cationic domains, since the polycations with long alkyl side chains might form a polymer micelle structure with a segregated hydrophobic domain and cationic channel for the electron-propagation.     

Cyclic potential sweep electrolysis for formation of poly(2-vinylpyridine) coatings

A cyclic potential sweep (CPS) technique has been used to form coatings of poly(2-vinylpyridine) on mild steel substrates by electropolymerization of the monomer. This method can produce thick and uniform coatings of much higher quality than can be formed by other electrochemical methods such as galvanostatic electrolysis, constant cell-potential electrolysis and chronoamperometry. The range and rate of the potential sweep during the CPS are important for successful coating formation. Potential sweeps between –1.0 and –2.2 V vs SCE at rates from 10 to 50 mV s^–1 have been found to be most suitable for the formation of poly(2-vinylpyridine) coatings. The essential reason for the successful application of the CPS technique to the electropolymerization process is the compatibility of the nature of the CPS process and the mechanism of 2-vinylpyridine electropolymerization.     

Manifestation of electrolyte ion size effect on electrochemical behavior of poly(ferrocenylsilane) films

The influences of supporting electrolyte ion size on the cyclic voltammetric (CV) behavior of high‐molecular‐weight poly(ferrocenylsilane) films in organic solvents were investigated. Three supporting electrolytes with various ion sizes were tested. Electrolyte anions, as counter ions, take part in charge neutrality in the films, so that the size of anion affects the CV behavior of the films remarkably. The large anions are difficult to penetrate into the films, the resistances of the large ions migrating in films are more, the rates of the electroactive species diffusing in the films are slow, and the CV behavior of the polymer films exhibit irreversible features. The electrolyte cations do not take part in charge neutrality in the films, so that the size of cation does not actually affect the CV behavior of the films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 515–523, 2006     

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.     

Synthesis of poly(ferrocenylsilanes) with different molecular weight and their electrochemical behavior

A series of poly(ferrocenylsilanes) (PFS) with different molecular weight have been prepared via the thermal ring‐opening polymerization of the corresponding monomers. The electrochemical behavior of poly(ferrocenyldimethylsilane) (PFDMS) and poly(ferrocenylmethylphenylsilane) (PFMPS) in solutions were investigated by cyclic voltammetry (CV). It was found that PFS could be adsorbed and electrodeposited on the Pt electrode surface, and the electroactive multilayer films formed on the Pt electrode surface influenced the shape of the voltammogram. The redox potential varied with the molecular weight slightly, and ΔE_1/2 became smaller with the increase in molecular weight. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 473–477, 2006     

Electrochemical behaviors of poly(ferrocenylsilane) solutions

The electrochemical behaviors of two kinds of poly(ferrocenylsilanes) (PFS) with different substituent groups in CH₂Cl₂ solutions were investigated by means of cyclic voltammetry (CV) and electrochemical quartz crystal microbalance. The results demonstrated that the CV processes of the PFS on the glass carbon electrode surface in CH₂Cl₂ solutions are the diffusion‐controlled reversible processes. The oxidative state of PFS forms an adsorption layer on the electrode surface during the oxidation process. The interaction of active ferrocene centers along the main chain induces the stepwise redox process, and makes the CV waves of the PFS solutions present two couples of peaks. The diffusion coefficients of PFS in CH₂Cl₂ solution are much larger than those of PFS in films. The different electrochemical behaviors of the two PFS solutions indicated that the molecular structure of polymer has influence on the electrochemical properties of the PFS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 789–794, 2007     

Orientation microstructure and properties of poly(propylene carbonate)/poly(butylene succinate) blend films

The blends of high molecular weight poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt blended using triphenylmethane triisocyanate (TTI) as a reactive coupling agent. TTI also serves as a compatibilizer for the blends of PPC and PBS. The blend containing 0.36 wt % TTI showed that the optimal mechanical properties were, therefore, calendared into films with different degrees of orientation. The calendering condition, degree of orientation, morphologies, mechanical properties, crystallization, and thermal behaviors of the films were investigated using wide‐angle X‐ray diffraction, scanning electron microscopy, tensile testing, and differential scanning calorimetry (DSC) techniques. The result showed that the as‐made films exhibited obvious orientation in machine direction (MD). Both tensile strength in MD and the tear strength in transverse direction (TD) increased with increasing the degree of orientation. The orientation of the film also increased the crystallinity and improved the thermal properties of the PPC/PBS blend films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(O‐methoxyaniline) thin films: Cyclic voltammetry study

Electrochemical polymerization of poly(O‐methoxyaniline) (POMA) thin films was carried out under cyclic voltammetric conditions. The cyclic voltammograms (CV) of the POMA films in the presence and absence of monomer in the aqueous solution of 1M H₂SO₄ were studied. The electrochemical degradation of the POMA films was investigated by cyclic voltammetry and UV‐visible spectroscopy. It was observed that the rate of degradation is strongly dependent on the applied potential. UV‐visible spectroscopy revealed no significant chemical modification or phase change from the degradation. The temperature dependence of the voltammetric response of the POMA films in the aqueous solution of 1M H₂SO₄ was also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3009–3015, 1999     

聚偏氯乙烯皂化残液在隔膜电槽中的试用

介绍了为解决聚偏氯乙烯皂化残液的浪费和污染问题，将其与精盐水按一定的比例试用于隔膜电槽电解的情况，试用结果表明电槽各项运行指标符合要求，具有较好的经济效益和社会效益。     

Conducting polymer films as model biological membranes: Electrochemical and ion-exchange properties of poly(pyrrole) films doped with asparagine and glutamine

This paper shows the application of conducting polymers (CPs) for constructing model biological membranes in order to study potential formation mechanism. Two amino acids, asparagine and glutamine, were incorporated in the poly(pyrrole) matrix during electrochemical polymerization. The polymer film was characterized by infrared and X-ray photoelectron spectroscopy. The film morphology was studied by atomic force microscopy. The ion-exchange behavior of PPy-Asn and PPy-Gln membranes in dependence on the conditioning solution are characterized using an open circuit potentiometric measurements. Close-to-Nernstian sensitivity was observed for the films under equilibrium. During equilibration provoked by the change in concentration of magnesium and/or calcium ions, the differences in the shape and evolution of the potential response with time were observed. The varying potential-time behavior after a bulk concentration change has been explained by a different participation of the magnesium and calcium ions on the ground diffusion layer model (DLM).     

Calculations of diffusion coefficients of cyclic poly(dimethylsiloxanes)

The Kirkwood equation and a Monte-Carlo technique which employs Metropolis sampling have been used to calculate diffusion coefficients (D) for low molar mass cyclic poly(dimethylsiloxanes). Correlations between calculated and experimental values of D show that the effective segment size is larger for cyclic than for linear PDMS. Thus, free-draining flow is reduced for the cyclic species consistent with its greater segment density. The cyclic molecules also show enhanced diffusion coefficients at very low molar masses which may be associated with the rigid toroidal shapes of these molecules.     

An inelastic electron tunnelling spectroscopy (IETS) study of poly(vinylacetate) poly(methyl methacrylate) and poly(vinylalcohol) adsorbed on aluminium oxide

IETS is used to investigate the adsorption of poly(vinylacetate) (PVA), poly(methylmethacrylate) (PMMA), and poly(vinylalcohol) (PVOH) on aluminium oxide. These polymers are of interest in the field of adhesion science, and until now synthetic macromolecules have not been studied in this way. Both commercially available polymers and those synthesized in our laboratory have been used. On the basis of IET spectra presented here, and existing i.r. spectra it is believed that PMMA and PVA undergo ester cleavage at the oxide surface leading to their subsequent adsorption. For PMMA this is thought to be via carboxylate anions generated on the polymer side groups, while PVA is expected to be adsorbed as PVOH. Bonding of PVOH to the oxide is not fully understood, but may occur by the formation of an AlOC bridge. Another possibility for the above polymers, that of intermolecular hydrogen bonding between polar polymer side groups, and adsorbed hydroxyl species present on the oxide surface, cannot be ruled out.     

Electropolymerization of pyrrole and characterization of the obtained polymer films

Electrochemical oxidative polymerization of pyrrole on platinum electrode in acid medium was carried out. Different reaction parameters were investigated such as current density, acid concentration, monomer concentration, and temperature with duration of time. The orders of the electropolymerization reaction were found to be 1.3, 1.26, and 1.2 with respect to current density, acid concentration, and monomer concentration, respectively. The apparent activation energy was found to be 38.3 kJ mol^?1. The obtained polymer films were characterized by ¹H‐NMR, elemental analysis, thermogravimetric analysis, and cyclic voltammetry. The mechanism of the electrochemical polymerization reaction was also discussed. The surface morphology of the obtained polymer film was characterized by X‐ray diffraction and scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1783–1792, 2003     

The three-phase structure of isotactic poly(1-butene)

A detailed analysis of the three-phase structure of isotactic poly(butene) was conducted by conventional and temperature-modulated calorimetry. The development of the crystalline, mobile amorphous, and rigid amorphous fractions was analyzed as a function of thermal history, upon isothermal and non-isothermal crystallization. It was found that, under the chosen experimental conditions, the amount of rigid amorphous phase (w_RA) in PB-1 ranges from w_RA = 0.14 to 0.23, with higher values formed when the polymer is crystallized at low temperatures or at high cooling rates from the melt. Comparison of total and frequency-dependent reversing heat capacity curves suggested that the rigid amorphous phase of isotactic poly(1-butene) vitrifies after completion of the crystallization process and that its full mobilization takes place at around 50 °C. The exact temperature of complete devitrification is slightly affected by the thermal history of the material. An effort to link the mechanical properties of PB-1 to the three-phase structure was attempted, and a correlation of Young's modulus with the solid fraction at the temperature of analysis, composed of crystalline and rigid amorphous phases, was proposed.     

Blends of poly(ethylene terephthalate) and poly(butylene terephthalate)

Commercial grade poly(ethylene terephthalate), (PET, intrinsic viscosity = 0.80 dL/g) and poly(butylene terephthalate), (PBT, intrinsic viscosity = 1.00 dL/g) were melt blended over the entire composition range using a counterrotating twin‐screw extruder. The mechanical, thermal, electrical, and rheological properties of the blends were studied. All of the blends showed higher impact properties than that of PET or PBT. The 50:50 blend composition exhibited the highest impact value. Other mechanical properties also showed similar trends for blends of this composition. The addition of PBT increased the processability of PET. Differential scanning calorimetry data showed the presence of both phases. For all blends, only a single glass‐transition temperature was observed. The melting characteristics of one phase were influenced by the presence of the other. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 75–82, 2005     

Interpolymer complexes of poly(acrylamide) and poly(N-isopropylacrylamide) with poly(acrylic acid): a comparative study

The interpolymer complexation, through successive hydrogen bonding, between poly(acrylamide) (PAAm) and poly(N-isopropylacrylamide) (PNiPAAm) with poly(acrylic acid) (PAA) in aqueous solution has been viscometrically and potentiometrically investigated. The stoichiometry of the complexes formed was determined. By comparing the strength of the two complexes the very important contribution of the hydrophobic interaction in their formation has been indicated.     

Multiple transitions in poly(allylbenzene): 1. Thermophysical properties

Polyallylbenzene is a semicrystalline material the thermal behaviour and physical properties of which reveal several transitions. Thermal and differential calorimetric analysis have shown the influence of the history of the material about the glass transition and melting. Several techniques such as thermomechanical analysis, dilatometry and inverse gas chromatography give additional information for the unidimensional and volume behaviour of the polymer versus temperature.