Nurettin Şahiner

Radiation synthesis, characterization and amidoximation of N-vinyl-2-pyrrolidone/acrylonitrile interpenetrating polymer networks

Abstract Interpenetrating polymer networks (IPNs) were synthesized by irradiating acrylonitrile solutions of poly(N-vinyl-2-pyrrolidone) with 60Co-γ rays. The conversion to insoluble IPN structure was characterized using FT-IR and thermal analysis methods. The amidoximation of polyacrylonitrile moieties of IPN was carried out in aqueous solutions of NH2OH·HCl–NaOH at 50°C. The conversion of amidoximation was followed by using FT-IR spectrophotometer and conversion of nitrile groups to amidoxime was determined as percentage. The structure of amidoximated IPN was characterized by FT-IR and thermal methods as well.

Biosynthesis and Characterization of Laccase Catalyzed Poly(Catechol)

Enzymatic polymerization of catechol was conducted batch-wise using laccase enzyme produced by the culture Trametes versicolor (ATCC 200801). The polymerization reaction was carried out in 1:1 (v/v) aqueous-acetone solution, buffered at pH 5.0 with sodium acetate (50 mM) in a sealed, temperature-controlled reactor at 25°C. The molecular weight of the produced polymer was determined with GPC. FT-IR, DSC, and TGA were employed to investigate the structure and thermal behavior of synthesized poly(catechol). It was found that catechol units were linked together with ether bonds and thermal stability of the catechol increased in the poly(catechol) polymeric structure effectively. The number average molecular weight of poly(catechol) was found as 813 ± 3 Da with a very narrow polydispersity value of 1.17 showing selective polymerization of catechol by the enzyme.

Synthesis and characterization of N-vinylimidazole–ethyl methacrylate copolymers and determination of monomer reactivity ratios

Abstract Radical-initiated copolymerization of N-vinylimidazole (VIM) and ethyl methacrylate (EMA) was carried out with 2,2′-azobisisobutyronitrile (AIBN) as an initiator in benzene at 70°C in nitrogen atmosphere. Structure and composition of copolymers for a wide range of monomer feed were determined by elemental analysis (content of N for VIM-units) and by Fourier transform infrared spectroscopy through recorded analytical absorption bands for VIM (667 cm−1 for C–N of imidazole ring) and EMA (1729 cm−1 for CO of ester group) units, respectively. Monomer reactivity ratios for VIM (M1)–EMA (M2) pair were determined by Fineman–Ross and Kelen–Tudos (KT) methods. They are r1=0.35±0.02 and r2=3.47±0.2 as determined by KT method. Parameters of Q1=0.14 and e1=−0.61 for VIM monomer were calculated by using the Alfrey–Price scheme. Observed relatively high activity of EMA growing radical was explained by effect of complex formation between carbonyl group and imidazole fragments in chain growth reactions. Thermal behaviors of copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. It was observed that glass transition temperature and thermal stability of copolymers increased with increasing of VIM content in copolymers.

Development of new chelating hydrogels based on N-vinyl imidazole and acrylonitrile

Copolymers derived from the binary mixture of N-vinyl imidazole (VIm) and Acrylonitrile (AN) monomers have been synthesized by the irradiation of their solution with 60 Co-g rays. Gelation percent‐dose graphs were formed, and 80% of gelation (maximum percentage) has been reached at around 14kGy dose. To impart metal ion adsorption properties, the hydrogels were amidoximated by the reaction of cyano groups on AN with hydroxylamine in aqueous media. Swelling behaviors of hydrogels were investigated before and after amidoximation. Hydrogels had 54% of swelling originally, this ratio reached 220% of swelling after amidoximation. The degree of amidoximation was followed by FT-IR spectroscopy. The structures of copolymers were analyzed spectroscopically and thermally before and after the amidoximation reaction. # 2000 Elsevier Science Ltd. All rights reserved.