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    Electrochemical polymerization of 4-allyl-1,2-dimethoxybenzene
    (Elsevier Science Bv, 2004) Testereci, HN; Akin-Oktem, G; Oktem, Z
    Redox behaviour of 4-allyl-1,2-dimethoxybenzene (DMAB) was studied by using cyclic voltammetry and electro-chemical polymerization was conducted at the measured peak potential. Constant potential electrolysis of the monomer was carried out in acetonitrile-tetrabutylammonium-tetrafluoroborate, solvent-electrolyte couple, at room temperature. Electrochemical polymerization of the monomer yielded insoluble polymer film on the electrode surface together with the low molecular weight polymers in bulk of the solution. The effect of temperature on the rate of electro-chemical polymerization was also studied. The structural analyses of the polymers were done by H-1-NMR and FTIR spectroscopy. Molecular weight of the soluble polymer was determined by cryoscopy. (C) 2004 Elsevier B.V. All rights reserved.
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    Functionalization of low molecular weight atactic polypropylene - Part I. Spectroscopic studies
    (Springer Verlag, 1999) Oktem, Z; Cetin, S; Akin-Oktem, G
    Low molecular weight atactic polypropylene (APP) was functionalized with 4-allyl-2-methoxyphenol (eugenol), 4-allyl-1,2-dimethoxybenzene (DMAB), 4-propenylanisole(trans-anethole), cis-2,4,5-trimethoxypropenylbenzene (beta-asarone) and 4-allyl-2,6-dimethoxyphenol (ADMP) in the presence of dicumyl peroxide (DCP) at 170 degrees C. Amount of grafted eugenol, DMAB and anethole on APP and characterization of the products were carried by UV-VIS and FTIR spectroscopies respectively. The effects of the reaction time, concentrations of the functional compounds and DCP on the extent of grafting were examined.
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    Functionalization of low molecular weight atactic polypropylene - Part II. Thermal and molecular weight studies
    (Springer, 2000) Akin-Oktem, G; Cetin, S; Oktem, Z
    Number average molecular weight (M-n), intrinsic viscosity ([eta]) and glass transition temperature (T-g) of low molecular weight atactic polypropylene (APP) grafted with 4-allyl-1,2-dimethoxybenzene (DMAB), 4-allyl-2-methoxyphenol (eugenol) and 4-propenylanisole (trans-anethole) in the presence of dicumyl peroxide (DCP) at 170 degreesC were determined. The influences of reaction time, concentration and extent of grafting on M-n, [eta] and T-g of APP were examined. The data were discussed with the mechanism of grafting reactions.
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    Immobilization of catalase in poly(isopropylacrylamide-co-hydroxyethylmethacrylate) thermally reversible hydrogels
    (John Wiley & Sons Ltd, 1999) Arica, MY; Oktem, HA; Oktem, Z; Tuncel, SA
    Catalase was entrapped in thermally reversible poly (isopropylacrylamide-co-hydroxyethyl-methacrylate) (pNIPAM/HEMA) copolymer hydrogels. The thermoresponsive hydrogels, in cylindIl-rical geometry, were prepared in an aqueous buffer by redox polymerization. It was observed that upon entrapment, the activity retention of catalase was decreased between 47 and 14%, and that increasing the catalase loading of hydrogel adversely affected the activity. The kinetic behaviour of the entrapped enzyme was investigated in a batch reactor. The apparent kinetic constant of the entrapped enzyme was determined by the application of lMichaeiis-Menten model and indicated that the overall reaction rate was controlled by the substrate diffusion rate through the hydrogel matrix. Due to the thermoresponsive character of the hydrogel matrix, the maximum activity was achieved at 25 degrees C with the immobilized enzyme. The K-m value for immobilized catalase (28.6mM) was higher than that of free enzyme (16.5mM). Optimum pH was the same for both free and immobilized enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with immobilization. (C) 1999 Society of Chemical Industry.