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ABSTRACT:The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65-90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 ϫ 10 Ϫ2 mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate-grafted gelatin as density, moisture regain, and water uptake were also determined.

Summary: The effects of polymerization temperature and time, initiator and monomer concentrations, ratio of water and solvent employed on the grafting of methacrylamide onto poly(ethylene terephthalate) fibers by the use of benzoyl peroxide initiator were studied. The graft yield was observed to increase with temperature and monomer concentration. The highest graft yield was obtained with an initiator concentration of 1 × 10−2 mol/L. The rate of grafting was proportional to the power 0.48 and 1.6 of the methacrylamide and benzoyl peroxide concentrations, respectively. The overall activation energy for grafting calculated was 42.8 kcal/mol. The thermogravimetric data revealed that the thermal stability of poly(ethylene terephthalate) fibers decreased with grafting.SEM micrographs of ungrafted PET fiber (a) and 44.9% MAAm‐grafted fiber (b).magnified imageSEM micrographs of ungrafted PET fiber (a) and 44.9% MAAm‐grafted fiber (b).

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10−2 mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999

The electrochemistry of the tetranuclear copper-nickel heteropolymetallic complexes [(µ 4 -O)L 4 Cu 4Ϫx {Ni-(H 2 O)} x Cl 6 ] [x = 0-4, L = N,N-diethylnicotinamide (denc)] were studied at a platinum electrode in dimethyl sulfoxide with 0.20 M tetrabutylammonium hexafluorophosphate as supporting electrolyte. At potentials more cathodic than Ϫ1.0 V the complexes are electrodeposited as Cu-Ni alloy and metal oxide films and display a complicated set of cyclic voltammographs. The voltammographs of all the Cu-containing complexes show a quasi-reversible redox couple in the potential range 0.250 to Ϫ0.450 V vs. Ag-AgPF 6 (0.01 M)-CH 3 CN. As the number of Cu atoms decreases in the complex, the peak currents i pa and i pc decrease proportionally and the peak potential shifts anodically. The cyclovoltammetric (CV) results indicate that electron transfer initially occurs only to the Cu II centres and that the electron-transfer reaction appears to be quasi-reversible. Using steady-state voltammetry at an ultramicroelectrode in combination with chronoamperometry at a microelectrode and exhaustive electrolysis at a Hg-pool electrode, the number of electrons (n) transferred for this initial reduction of the Cu 4 , Cu 3 Ni, Cu 2 Ni 2 and CuNi 3 complexes were 3.1, 2.1, 1.8 and 0.57, respectively. The diffusion coefficient for all the complexes was 2.2(±0.1) × 10 Ϫ6 cm 2 s Ϫ1 . The electronic spectrum of the Cu 4 complex taken after exhaustive electrolysis shows that one quarter of the Cu atoms remain in the Cu II form and that the Cu I complex remains stable. Since only a single CV peak results for all of the complexes, the electron transfer is most likely consecutive with very closely spaced EЊ potentials. A model based on statistically determined electron transfer to Cu II in particular faces is also proposed.

In this study, two‐component free‐standing films were obtained by coating a polycarbonate (PC)‐coated Pt electrode first with polypyrrole (PPy) in an organic medium and then polyaniline (PAn) in an aqueous medium using an electrochemical technique. The amount of PPy and PAn contained in the films was controlled by varying the electrolysis time. The PC/PPy/PAn films were characterized by cyclic voltammetry, conductivity, FTIR and UV–visible spectrophotometry, and thermogravimetric analysis. The resistance change of the films was determined in the temperature range of −15 to 120 °C and their temperature sensor properties were investigated. © 2002 Society of Chemical Industry

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negatif bir ilişki mevcuttur. İllegal para ile kayıtdışı ekonomi arasında çift yönlü ve pozitif ilişki saptanmıştır. İllegal para ile GSMH arasında çift yönlü ve pozitif bir ilişki bulunmuştur.