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Marijana Ponjavic,Marija S. Nikolic,Sanja Jevtic,Jelena Rogan,Sanja Stevanovic,Jasna Djonlagic 한국고분자학회 2016 Macromolecular Research Vol.24 No.4
Two series, one of triblock (PCL/PEO/PCL) and the other of diblock (PCL/PEO) copolymers were prepared by ring-opening polymerization of ε-caprolactone catalized with tin(II) octoate and by using dihydroxy or monohydroxy poly(ethylene oxide) as the macroinitiator. The PEO block length was fixed (Mn 1,000 g/mol) and the PCL block lengths (Mn 10,000-40,000 g/mol) were tailored by changing weight ratio of ε-CL/PEO. The copolymers’ structure was confirmed by 1H and quantitative 13C NMR spectroscopy while their molecular weights were determined by GPC analysis. The thermal properties and the degree of crystallinity of the copolymers were investigated and compared by using DSC and WAXS. Both types of copolymers were semicrystalline with the orthorhombic PCL crystal lattice. The surface morphology of the copolymer films was investigated by using optical microscopy and AFM analysis, which confirmed the spherulitic lamellar structure with spherulites of different diameters. Data indicated that a low content of PEO segment had an influence on thermal degradation behavior, crystallinity and morphology of copolymers. Roughness of copolymer films was affected by the content of PEO and correlated with the spherulites’ diameter. The small changes in water and moisture absorption properties of copolymers compared to homopolymer PCL were observed.
Adsorption of lipase from Candida rugosa on multi walled carbon nanotubes
Nevena Z. Prlainovic,Dejan I. Bezbradica,Zorica D. Knezevic-Jugovic,Sanja I. Stevanovic,Milka L. Avramov Ivic,Petar S. Uskokovic,Dusan Z. Mijin 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.1
In this work lipase from Candida rugosa was adsorbed on unmodified surface of multi walled carbon nanotubes (raw-MWCNT). The effects of immobilization time, initial enzyme concentration and buffer ionic strength on enzyme loading and activity of immobilized preparations were tested. High loadings are attained. The immobilized enzyme obtained at lowest initial enzyme concentration and high ionic strength retained 85% of initial enzyme activity. It is assumed that immobilization on hydrophobic surface led to conformational changes that resulted in the adsorption of lipase in active conformation. Immobilized preparations were characterized, with FT-IR spectroscopy, AFM, and cyclic voltammetry.