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Volkan Kseli Zakir M. O. Rzaev Erhan Pikin 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1580-1593
Stimuli‐responsive poly[(N‐isopropylacrylamide‐co‐maleic anhydride)‐g‐poly(ethylene oxide)]/poly(ethylene imine) macrobranched macrocomplexes were synthesized by (1) the radical copolymerization of N‐isopropylacrylamide and maleic anhydride with α,α′‐azobisisobutyronitrile as an initiator in 1,4‐dioxane at 65 °C under a nitrogen atmosphere, (2) the polyesterification (grafting) of prepared poly(N‐isopropylacrylamide‐co‐maleic anhydride) containing less than 20 mol % anhydride units with α‐hydroxy‐ω‐methoxy‐poly(ethylene oxide)s having different number‐average molecular weights (Mn = 4000, 10,000, or 20,000), and (3) the incorporation of macrobranched copolymers with poly(ethylene imine) (Mn = 60,000). The composition and structure of the synthesized copolymer systems were determined by Fourier transform infrared, 1H and 13C NMR spectroscopy, and chemical and elemental analyses. The important properties of the copolymer systems (e.g., the viscosity, thermal and pH sensitivities, and lower critical solution temperature behavior) changed with increases in the molecular weight, composition, and length of the macrobranched hydrophobic domains. These copolymers with reactive anhydride and carboxylic groups were used for the stabilization of penicillin G acylase (PGA). The conjugation of the enzyme with the copolymers significantly increased the thermal stability of PGA (three times at 45 °C and two times at 65 °C). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1580–1593, 2003 相似文献
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S. G. Mamedova N. Sh. Rasulov Z. M. Rzaev 《Journal of polymer science. Part A, Polymer chemistry》1987,25(2):711-717
Some regularities of radical alternating copolymerization of maleic anhydride with allyl chloroacetate are studied. The formation of donor–acceptor complexes between comonomers with complexing constant Kc = 0.052 L/mol is found using 1H NMR spectroscopy. The kinetic parameters for this copolymerization reaction are found and the quantitative contribution of monomer complexes to chain-growth radical reactions is calculated. It is shown that either a “free-monomer” mechanism (dilute solutions) or a “mixed” mechanism (concentrated solutions) prevails for chain growth during radical copolymerization depending on total monomer concentration. It is found that inhibition of degradative chain transfer in the course of the reaction studied takes place owing to the presence of α-chlorine atom in the allyl chloracetate molecule and formation of charge transfer complex. 相似文献
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T. M. Burbaev E. A. Bobrik V. A. Kurbatov M. M. Rzaev N. N. Sibel’din V. A. Tsvetkov F. Schäffler 《JETP Letters》2007,85(7):331-334
The electron-hole liquid has been found in strained SiGe thin films of Si/Si1?x Gex/Si heterostructures. The density and binding energy of the electron-hole liquid have been determined. Owing to the presence of internal strains in the SiGe layer, the density and binding energy are significantly smaller than the respective quantities for the electron-hole liquid in a bulk single crystal of the solid solution of the same composition. The critical temperature of the transition from the exciton gas to the electron-hole liquid is estimated using the experimental data. The Mott transition (from the exciton gas to electron-hole plasma) occurs above the critical temperatures for high excitation intensities. 相似文献
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A. M. Afanas’ev M. A. Chuev R. M. Imamov É. Kh. Mukhamedzhanov M. M. Rzaev F. Schäffler M. Müehlberger 《Crystallography Reports》2002,47(6):1058-1062
The structural characteristics of silicon samples containing one and two Si1 ? x Gex/Si quantum wells 1.8 to 15 nm thick were determined by high-resolution X-ray diffraction. A detailed analysis of X-ray rocking curves made it possible to reproduce the Ge-concentration profiles in the quantum wells. The diffusion of germanium (up to 20%) into interface layers was observed, with a consequent broadening of the quantum well interfaces. 相似文献
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The scattering of spin-oriented electrons, moving in a constant homogeneous magnetic field, by a short-range potential is analyzed. The change in the electron spin orientation is calculated using the Born approximation. 相似文献
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Z. M. O. Rzaev S. G. Mamedova G. A. Jusifov F. B. Rustamov 《Journal of polymer science. Part A, Polymer chemistry》1988,26(3):849-857
Mechanisms of radical copolymerization of di-n-butylstannyl dimethacrylate with maleic anhydride in the presence of 2,2-asobisisobutyronitrile are discussed. Complexing (Keq) and copolymerization (r1 and r2) constants have been determined. Quantitative contributions of cyclization and complexing to reactivity ratios of the monomers under study and to propagation reactions have been estimated. The copolymerization has been found to proceed predominantly at the complex radical cyclocopolymerization step, leading to cyclized and linear unsaturated units in the macromolecule chain. 相似文献