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    Immobilization of tyrosinase and alcohol oxidase in conducting copolymers of thiophene functionalized poly(vinyl alcohol) with pyrrole
    (ELSEVIER SCIENCE BV, 2007) Yildiz, Huseyin Bekir; Sahmetlioglu, Ertugrul; Boyukbayram, Ayse Elif; Toppare, Levent; Yagci, Yusuf
    Immobilization of tyrosinase and alcohol oxidase is achieved in the copolymer of pyrrole with vinyl alcohol with thiophene side groups (PVATh-co-PPy) which is a newly synthesized conducting polymer. PVATh-co-PPy/alcohol oxidase and PVATh-co-PPy/tyrosinase electrodes are constructed by the entrapment of enzyme in conducting copolymer matrix during electrochemical copolymerization. For tyrosinase and alcohol oxidase enzymes, catechol and ethanol are used as the substrates, respectively. Kinetic parameters: maximum reaction rates (V-max) and Michaelis-Menten constants (K-m) are obtained. V-max and K-m are found as 2.75 mu mol/(min electrode) and 18 mM, respectively, for PVATh-coPPy/alcohol oxidase electrode and as 0.0091 mu mol/(min electrode) and 40 mM, respectively, for PVATh-co-PPy/tyrosinase electrode. Maximum temperature and pH values are investigated and found that both electrodes have a wide working range with respect to both temperature and pH. Operational and storage stabilities show that although they have limited storage stabilities, the enzyme electrodes are useful with respect to operational stabilities. (c) 2007 Elsevier B.V. All rights reserved.
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    Preparation of conductive polybenzoxazines by oxidative polymerization
    (WILEY-BLACKWELL, 2007) Kiskan, Baris; Yagci, Yusuf; Sahmetlioglu, Ertugrul; Toppare, Levent
    precursors were prepared by oxidative polymerization 3-phenyl-3,4-dihydro-2H-benzo[e][1,3] oxazine (P-a) alone and in the presence of thiophene (Th) with ceric ammonium nitrate in acetonitrile. The structure of the precursors was confirmed by FTIR, H-1 NMR, and DSC measurements, indicating the presence of a cyclic benzoxazine structure, together with small but varying amount of a ring opened phenolic structure. The resulting polymers exhibit conductivities around 10(-2) S cm(-1) and undergo thermal curing at various temperatures. Attempts to copolymerize P-a with another electroactive monomer, pyrrole (Py), by a similar redox process were unsuccessful, which was attributed to the unfavourable oxidation potential of Py. The cured products exhibited high thermal stability but lower conductivity, than those of the precursors. (c) 2006 Wiley Periodicals, Inc.