Ural Akbulut

Immobilization of invertase in conducting polymer matrices

This paper reports a novel approach in the electrode immobilization of an enzyme, invertase, by electrochemical polymerization of pyrrole in the presence of enzyme. The polypyrrole/invertase and polyamide/polypyrrole/invertase electrodes were constructed by the entrapment of enzyme in conducting matrices during electrochemical polymerization of pyrrole. This study involves the preparation and characterization of polypyrrole/invertase and polyamide/polypyrrole/invertase electrodes under conditions compatible with the enzyme. It demonstrates the effects of pH and temperature on the properties of enzyme electrode. Enzyme leakage tests were carried out during reuse number studies. The preparation of enzyme electrodes was done in two different electrolyte/solvent systems. The enzyme serves as a sucrose electrode and retains its activity for several months.

Conducting polymers of aniline. II: A composite as a gas sensor

Abstract The gas sensing ability of electrochemically prepared pure polyaniline and polyaniline-poly(bisphenol-A carbonate) films is investigated. The responses of the composite films to several vapours are more well defined and reproducible compared to the pure conducting polymer. The changes in resistance as determined via the two-probe technique are well defined down to a level of 0.025% vol./vol. ammonia. The possible reason for such a difference is discussed. The structure of the composite is examined through pyrolysis FT-IR studies.

Immobilization of invertase in conducting polypyrrole/polytetrahydrofuran graft polymer matrices

Abstract Four different polypyrrole/polytetrahydrofuran/invertase electrodes were constructed by the entrapment of invertase in conducting polymer matrices via electropolymerization. Immobilization of the enzyme was achieved by the application of a 1.1 V constant potential to a platinum electrode for 30 min in a solution containing 0.01 M pyrrole, 0.4 mg/ml invertase and 0.4 mg/ml sodium dodecyl sulphate. Performance of each electrode was optimized by examining the effects of pH and temperature on the properties of the electrodes. The changes in the maximum velocity of the reaction and variation of Michaelis–Menten constant upon immobilization were investigated. The enzyme immobilized in those matrices retained its activity for several months.

Synthesis of a novel poly(arylene ether ketone) and its conducting composites with polypyrrole

Abstract The synthesis of a 1,3-bis(4-fluorobenzoyl)-5-tert-butyl benzene and hexafluoro bisphenol A based poly(arylene ether ketone) (PEK) was described. The electrically conductive composites of polypyrrole (PPy) and PEK were formed by electropolymerization of pyrrole on a PEK coated platinum electrode in a medium containing water and p -toluenesulfonic acid as the solvent and the electrolyte, respectively. The electrical conductivity of the composites was found to be between 1 and 4 S/cm. The polypyrrole/poly (ether ketone) composites were characterized by scanning electron microscopy, FT-IR and thermal analyses (TGA, DSC).

A conducting composite of polypyrrole I. Synthesis and characterization

Abstract A conducting composite of polypyrrole was prepared via electrochemical methods. A polyamide was used as the insulating matrix polymer. The characterization of the composite was done by FT-IR, SEM, TGA, DSC and pyrolysis studies. Conductivity and solubility studies together with spectroscopic methods reveal that H bonding exists between the two polymers and a possible grafting to a certain extent.

Conducting polymers of aniline I. Electrochemical synthesis of a conducting composite

Abstract We describe an electrochemical synthesis of a conducting composite of polyaniline. Poly(bisphenol A carbonate) was used as the insulating polymer matrix. Composite characterization was made using FT-IR, SEM and DSC data. The conductivities of the composites seemed to be in the order of pure polyaniline as prepared by the same method. Moreover, the above-mentioned methods reveal that the resultant composites have different properties compared to a simple mechanical mixture of the two polymers.

Studies on immobilization of urease in gelatin by cross-linking

Urease enzyme was immobilized in photographic gelatin by chemical cross-linking using formaldehyde, glutaraldehyde and chromium (III) acetate. The effects of enzyme and cross-linker concentrations, temperature, incubation time and pH on urea hydrolysis were investigated. Effect of reuse on the activity of immobilized enzyme was also studied. Glutaraldehyde (0.004 M) was the most suitable cross-linker; relative activities within 2.5 months after 24 reuses were stable (about 78%).

Conductive polyaniline/poly(methyl methacrylate) films obtained by electropolymerization

Electrochemical polymerization of aniline, on a Pt foil electrode coated with poly(methyl methacrylate) (PMMA), produces a homogeneous, free-standing, flexible, and conductive polymer film. The conductivity of the films depends on the aniline content and reaches 0.1–0.2 S/cm for films having aniline content of 15% or more. The optimum thickness of precoated PMMA to obtain durable conducting films was found to be in the range of 10–15 μm. Cyclic voltammetric investigation revealed that aniline exhibits a similar electrochemical behavior on a PMMA coated platinum electrode similar to a bare Pt surface. The film gives a fast and reproducible response against ammonia gas within a concentration range of 1.0–0.01%. Scanning electron micrographs indicate that the films have a rough structure consisting of globular regions.

Electroinitiated copolymerization of indene with β-methoxystyrene

Abstract Electroinitiated copolymerization of indene with β-methoxystyrene was carried out at 0°C and five different potentials. Monomer consumption was studied by cyclic voltammetry. It is known that, when the difference between oxidation potentials of two monomers is large, polymerization potential affects copolymer composition. In the present study indene and β-methoxystyrene were selected because their oxidation potentials are almost equal, ca . + 1.40 V. The effect of polymerization potential on copolymer composition was studied. The copolymer composition did not change with polymerization potential, a novel result, for these monomers with almost equal oxidation peak potentials. The total reacted monomer concentration did not change with polymerization potential either. The amount of precipitated polymer, however, increased with polymerization potential.

Conducting polymer composites of polythiophene with natural and synthetic rubbers

Electrochemical synthesis of conducting polymer composites of polythiophene was achieved. Synthetic and natural rubbers were used as the insulating polymer matrices. FT-IR, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and mass spectrometry (MS) were utilized to characterize the composite blends. The conductivity measurements were done by using a standard four-probe technique. The above-mentioned methods show that the resultant composites have different properties compared to polythiophene due to interaction of the rubbers with electrochemical polymerization of thiophene, whereas the same argument is not valid for the polypyrrole synthesis via the same procedure.