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81.
Ozcan Altintas A. Levent Demirel Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5916-5928
Two samples of dendrimer‐like miktoarm star terpolymers: (poly(tert‐butyl acrylate))3‐(polystyrene‐poly(ε‐caprolactone))3 (PtBA)3‐(PS‐PCL)3, and (PS)3‐(PtBA‐poly(ethylene glycol)3 were prepared using efficient Cu catalyzed Huisgen cycloaddition (click reaction). As a first step, azido‐terminated 3‐arm star polymers PtBA and PS as core (A) were synthesized by atom transfer radical polymerization (ATRP) of tBA and St, respectively, followed by the conversion of bromide end group to azide. Secondly, PS‐PCL and PtBA‐PEG block copolymers with alkyne group at the junction as peripheral arms (B‐C) were obtained via multiple living polymerization mechanisms such as nitroxide mediated radical polymerization (NMP) of St, ring opening polymerization (ROP) of ε‐CL, ATRP of tBA. Thus obtained core and peripheral arms were linked via click reaction to give target (A)3‐(B‐C)3 dendrimer‐like miktoarm star terpolymers. (PtBA)3‐(PS‐PCL)3 and (PS)3‐(PEG‐PtBA)3 have been characterized by GPC, DSC, AFM, and SAXS measurements. (PtBA)3‐(PS‐PCL)3 did not show any self‐organization with annealing due to the miscibility of the peripheral arm segments. In contrast, the micro‐phase separation of the peripheral arm segments in (PS)3‐(PtBA‐PEG)3 resulted in self‐organized phase‐separated morphology with a long period of ~ 13 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5916–5928, 2008 相似文献
82.
Ozcan Altintas Burcu Yankul Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3588-3598
The preparation of 3‐miktoarm star terpolymers using nitroxide mediated radical polymerization (NMP), ring opening polymerization (ROP), and click reaction [3 + 2] are carried out by applying two types of one‐pot technique. In the first one‐pot technique, NMP of styrene (St), ROP of ε‐caprolactone (ε‐CL), and [3 + 2] click reaction (between azide end‐functionalized poly(ethylene glycol) (PEG‐N3)/or azide end‐functionalized poly(methyl methacrylate) (PMMA‐N3) and alkyne) are carried out in the presence of 2‐(hydroxymethyl)‐2‐methyl‐3‐oxo‐3‐(2‐phenyl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethoxy) propyl pent‐4‐ynoate, 2 , as an initiator for 48 h at 125 °C (one‐pot/one‐step). As a second technique, NMP of St and ROP of ε‐CL were conducted using 2 as an initiator for 20 h at 125 °C, and subsequently PEG‐N3 or azide end‐functionalized poly(tert‐butyl acrylate (PtBA‐N3) was added to the polymerization mixture, followed by a click reaction [3 + 2] for 24 h at room temperature (one‐pot/two‐step). The 3‐miktoarm star terpolymers, PEG‐poly(ε‐caprolactone)(PCL)‐PS, PtBA‐PCL‐PS and PMMA‐PCL‐PS, were recovered by a simple precipitation in methanol without further purification. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3588–3598, 2007 相似文献
83.
Ozcan Altintas Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(4):1218-1228
Two samples of ABCD 4‐miktoarm star quarterpolymer with A = polystyrene (PS), B = poly(ε‐caprolactone) (PCL), C = poly(methyl methacrylate) (PMMA) or poly(tert‐butyl acrylate) (PtBA), and D = poly(ethylene glycol) (PEG) were prepared using click reaction strategy (Cu(I)‐catalyzed Huisgen [3 + 2] reaction). Thus, first, predefined block copolymers of different polymerization routes, PS‐b‐PCL with azide and PMMA‐b‐PEG and PtBA‐b‐PEG copolymers with alkyne functionality, were synthesized and then these blocks were combined together in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst in DMF at room temperature to give the target 4‐miktoarm star quarterpolymers. The obtained miktoarm star quarter polymers were characterized by GPC, NMR, and DSC measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1218–1228, 2008 相似文献
84.
Determination of tocopherol contents of some olive varieties harvested at different ripening periods
The tocopherol contents of oils obtained from Ayval?k, Domat and Gemlik olive varieties harvested at different ripening periods were evaluated by high-performance liquid chromatography. α-Tocopherol was the major tocol detected in all the studied olive oil samples. The oils extracted from olive fruits composed of 130.54-180.43?mg?kg?1 α-tocopherol, 0.73-1.61?mg?kg?1 β-tocopherol and 0.53-2.28?mg?kg?1 γ-tocopherol for Ayval?k oil. The α-, β- and γ-tocopherol contents of Domat oil are in the ranges 95.60-125.56, 0.71-2.70 and 0.49-1.25?mg?kg?1 at different harvesting periods. The α-, β- and γ-tocopherol contents of Gemlik olive oil are in the ranges 112.59-168.19, 0.94-1.21 and 0.85-2.40?mg?kg?1, respectively. There were significant differences between the oils from cultivars grown in different environments. 相似文献
85.
We report a cell-phone based Escherichia coli (E. coli) detection platform for screening of liquid samples. In this compact and cost-effective design attached to a cell-phone, we utilize anti-E. coli O157:H7 antibody functionalized glass capillaries as solid substrates to perform a quantum dot based sandwich assay for specific detection of E. coli O157:H7 in liquid samples. Using battery-powered inexpensive light-emitting-diodes (LEDs) we excite/pump these labelled E. coli particles captured on the capillary surface, where the emission from the quantum dots is then imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. By quantifying the fluorescent light emission from each capillary tube, the concentration of E. coli in the sample is determined. We experimentally confirmed the detection limit of this cell-phone based fluorescent imaging and sensing platform as ~5 to 10 cfu mL(-1) in buffer solution. We also tested the specificity of this E. coli detection platform by spiking samples with different species (e.g., Salmonella) to confirm that non-specific binding/detection is negligible. We further demonstrated the proof-of-concept of our approach in a complex food matrix, e.g., fat-free milk, where a similar detection limit of ~5 to 10 cfu mL(-1) was achieved despite challenges associated with the density of proteins that exist in milk. Our results reveal the promising potential of this cell-phone enabled field-portable and cost-effective E. coli detection platform for e.g., screening of water and food samples even in resource limited environments. The presented platform can also be applicable to other pathogens of interest through the use of different antibodies. 相似文献
86.
Yates BJ Temsamani KR Ceylan O Oztemiz S Gbatu TP Larue RA Tamer U Mark HB 《Talanta》2002,58(4):739-745
Exploitation of the physical, chemical and electrically conductive properties of poly(3-dodecylthiophene) (P3DDT) for the preconcentration and release in solid phase microextraction (SPME) of organometallic arsenobetaine (AsB) from aqueous media was investigated. Hydrophobic interactions between this neutral arsenic species and an undoped polythiophene (no applied potential) with n-substituted alkyl groups (n=12) in the three position were used for the diffusion-controlled preconcentration. After absorption into the polymer matrix, the chemical properties of this conductive polymer were changed by applying an external potential. This potential provides a sufficient driving force for desorption of the analyte from the extraction phase into an aqueous solution for subsequent analysis. The applied positive potential oxidizes the polymer to its charged hydrophilic state, which releases the neutral analyte. The concentration and speciation of the analyte from the sample matrix was analyzed by HPLC coupled to an ICP-MS. The diffusion-controlled uptake was fast (equilibrium attained within minutes) and did not require pretreatment of the analyte. The electrochemically-controlled release of the analyte is also very rapid (within minutes). This conducting polymer film system, therefore, can offer analytical applications for the convenient preconcentration and subsequent analysis of neutral environmental species. 相似文献
87.
In this study, the use of syringe filled with sorbent for the separation and enrichment of bismuth, lead and nickel prior to their analysis by graphite furnace atomic absorption spectrometry was described to substitute for batch and column techniques. The method proposed in this paper was compared with column technique with respect to easiness, fastness, simplicity, recovery and risk of contamination. The syringe was filled with 0.5 g of sorbent and in order to retain the analyte elements, 5 ml of sample solution (pH≥5) was drawn into the syringe to 15 s and discharged again in 15 s. Then, 2.0 M of HCl, as the eluent, was drawn into the syringe and ejected back to desorb the analyte elements. At optimum conditions, the recoveries of Bi, Pb and Ni were 95-99% with relative standard deviations (RSDs) of around ±2%. Detection limit (δ) was 0.5 μg l−1 for Bi, Pb and Ni, respectively. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only one time. Bi, Pb and Ni added to a seawater sample were quantitatively recovered (>95%) with low RSD values of around ±2-3%. The risk of contamination is less than that with the column technique. In addition, it is much faster, simpler, easier, more practical and handy compared with column technique. 相似文献
88.
Ufuk Sancar Vural Fatih Durmaz Ozcan Kocyigit Hasan Kocyigit V. Muradoglu Beril Akin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2260-2268
Excess molar volumes (V
E), viscosities, refractive index, and Gibbs energies were evaluated for binary biodiesel + benzene and toluene mixtures at
298.15 and 303.15 K. The excess molar volumes V
E were determined from density, while the excess Gibbs free energy of activation G*E was calculated from viscosity deviation Δη. The excess molar volume (V
E), viscosity deviation (Δη), and excess Gibbs energy of activation (G*E) were fitted to the Redlich-Kister polynomial equation to derive binary coefficients and estimate the standard deviations
between the experimental data and calculation results. All mixtures showed positive V
E values obviously caused by increased physical interactions between biodiesel and the organic solvents. 相似文献
89.
Ni-ferrite (NiFe2O4) nanoparticles have been synthesized via a solid state reaction process. Ni and Fe bi-metallic nanoparticles in the form of Ni33Fe67 alloy nanopowder are first synthesized by simultaneous evaporation of the required amounts of pure Ni and Fe metals followed by rapid condensation of the evaporated metal flux into solid state by means of an inert gas, helium, using the process of inert gas condensation (IGC). In order to form the NiFe2O4 structure, as-synthesized samples (Ni33Fe67) are annealed for 12 h in ambient conditions at different annealing temperatures. Structural analyses show that NiFe2O4 starts to form at around 450 °C and gets progressively well defined with increasing annealing temperatures yielding particle with size ranging between 15 and 50 nm. Besides successfully forming NiFe2O4, NiO/Fe3O4 core/shell nanoparticles have also been synthesized by adjusting the annealing conditions. Three different structures, Ni33Fe67, NiO/Fe3O4, and NiFe2O4, obtained in this study are compared with respect to their structural and magnetic properties. 相似文献
90.
Canturk Ozcan Pınar Zorlutuna Vasıf Hasirci Nesrin Hasirci 《Macromolecular Symposia》2008,269(1):128-137
For any biomaterial placed into a biological medium, the surface properties of the material, such as porosity, crystallinity, presence and distribution of electrical charge and functional groups are very critical parameters that determine the acceptance or rejection of the material. Applications, especially tissue engineering require some surface modifications at the molecular level without disturbing the bulk properties of the implants in order to enhance the cell attachment on the material. An appropriate technique is the application of glow discharge plasma which employs no solvents, takes place at ambient temperatures, and alterations take place only at the surface by changing the surface chemistry along with surface free energy (SFE) and efficiency for cell-material interaction. In this study, poly(methyl methacrylate) (PMMA) film surfaces were modified with oxygen plasma. SFE and its dispersive and polar (acidic-basic) components of the modified surfaces were calculated by means of several theoretical approaches including geometric mean, harmonic mean and acid-base equations. The relation between SFE and its dispersive and polar components and cell attachment on surfaces were studied. The highest 3T3 cell attachment was obtained for the surface with the total SFE of 61.77 mJ/m2 and polar component of 50.91 mJ/m2 according to Geometric mean. The total SFE of this surface was calculated to be 61.06 mJ/m2 and the polar component as 40.96 mJ/m2 using the Harmonic mean method. 相似文献