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ABSTRACT In this study, the use of the potentiometric method for the determination of the protonation constant of vinyl imidazole (VIM) and the stability constant of the Cu2+ ion complex of VIM used in the immobilized metal ion affinity chromatography (IMAC) was investigated. For this purpose, poly(ethylene glycol dimethacrylate- n-vinyl imidazole) [poly(EGDMA-VIM)] microspheres (average diameter 150-200 μm) were prepared. The microspheres were characterized by elemental analysis, N2 adsorption/desorption isotherms, elemental analysis, energy dispersive spectroscopy (EDS). Protonation constants of vinyl imidazole and the metal-ligand stability constant of vinyl imidazole with Cu2+ ions have been determined potentiometrically in 0.1 M NaCl aqueous solution at 298, 318, and 338 K, respectively. The corresponding thermodynamic parameters of protonation and complexation processes (Δ G, Δ H, and Δ S) were derived and discussed. The formation kinetics of Cu2+-vinyl imidazole complex were also investigated, and the process obeyed the pseudo-second-order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39751. [ABSTRACT FROM AUTHOR]

Poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole) [poly(EGDMA-VTAZ)] beads with an average diameter of 100-200 μm were obtained by the copolymerization of ethylene glycol dimethacrylate (EGDMA) with 1-vinyl-1,2,4-triazole (VTAZ). The copolymer hydrogel bead composition was determined by elemental analysis and was found to contain 5 EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA-VTAZ) beads were characterized by swelling studies and scanning electron microscopy (SEM). The specific surface area of the poly(EGDMA-VTAZ) beads was found 65.8 m/g. Cu ions were chelated on the poly(EGDMA-VTAZ) beads. The Cu loading was 82.6 μmol/g of support. Cu-chelated poly(EGDMA-VTAZ) beads with a swelling ratio of 84% were used in the immobilization of Aspergillus niger glucoamylase in a batch system. The maximum glucoamylase adsorption capacity of the poly(EGDMA-VTAZ)-Cu beads was 104 mg/g at pH 6.5. The adsorption isotherm of the poly(EGDMA-VTAZ)-Cu beads fitted well with the Langmuir model. Adsorption kinetics data were tested with pseudo-first- and second-order models. The kinetic studies showed that the adsorption followed a pseudo-second-order reaction model. The Michaelis constant value for the immobilized glucoamylase (1.15 mg/mL) was higher than that for free glucoamylase (1.00 mg/mL). The maximum initial rate of the reaction values were 42.9 U/mg for the free enzyme and 33.3 U/mg for the immobilized enzyme. The optimum temperature for the immobilized preparation of poly(EGDMA-VTAZ)-Cu-glucoamylase was 65°C; this was 5°C higher than that of the free enzyme at 60°C. The glucoamylase adsorption capacity and adsorbed enzyme activity slightly decreased after 10 batch successive reactions; this demonstrated the usefulness of the enzyme-loaded beads in biocatalytic applications. The storage stability was found to increase with immobilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]