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101.
Hyperfine Interactions - Nuclear forward scattering (NFS) of synchrotron radiation was applied to investigate the electronic and magnetic properties of (i) the diamagnetic... 相似文献
102.
Hakan Durmaz Aydan Dag Alp Hizal Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(21):7091-7100
3‐Arm star‐block copolymers, (polystyrene‐b‐poly(methyl methacrylate))3, (PS‐b‐PMMA)3, and (polystyrene‐b‐poly(ethylene glycol))3, (PS‐b‐PEG)3, are prepared using double‐click reactions: Huisgen and Diels–Alder, with a one‐pot technique. PS and PMMA blocks with α‐anthracene‐ω‐azide‐ and α‐maleimide‐end‐groups, respectively, are achieved using suitable initiators in ATRP of styrene and MMA, respectively. However, PEG obtained from a commercial source is reacted with 3‐acetyl‐N‐(2‐hydroxyethyl)‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2‐carboxamide (7) to give furan‐protected maleimide‐end‐functionalized PEG. Finally, PS/PMMA and PS/PEG blocks are linked efficiently with trialkyne functional linking agent 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane 2 in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at 120 °C for 48 h to give two samples of 3‐arm star‐block copolymers. The results of the peak splitting using a Gaussian deconvolution of the obtained GPC traces for (PS‐b‐PMMA)3 and (PS‐b‐PEG)3 displayed that the yields of target 3‐arm star‐block copolymers were found to be 88 and 82%, respectively. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7091–7100, 2008 相似文献
103.
Aydan Dag Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):302-313
Diels–Alder click reaction was successfully applied for the preparation of 3‐arm star polymers (A3) using furan protected maleimide end‐functionalized polymers and trianthracene functional linking agent (2) at reflux temperature of toluene for 48 h. Well‐defined furan protected maleimide end‐functionalized polymers, poly (ethylene glycol), poly(methyl methacrylate), and poly(tert‐butyl acrylate) were obtained by esterification or atom transfer radical polymerization. Obtained star polymers were characterized via NMR and GPC (refractive index and triple detector detection). Splitting of GPC traces of the resulting polymer mixture notably displayed that Diels–Alder click reaction was a versatile and a reliable route for the preparation of A3 star polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 302–313, 2008 相似文献
104.
105.
Andr Studer Xiaojun Han Fritz K. Winkler Louis X. Tiefenauer 《Colloids and surfaces. B, Biointerfaces》2009,73(2):325-331
Free-standing lipid bilayers are formed in regularly arranged nanopores of 200, 400 and 800 nm in a 300 nm thin hydrophobic silicon nitride membrane separating two fluid compartments. The extraordinary stability of the lipid bilayers allows us to monitor channel formation of the model peptide melittin and α-hemolysin from Staphylococcus aureus using electrochemical impedance spectroscopy and chronoamperometry. We observed that melittin channel formation is voltage-dependent and transient, whereas transmembrane heptameric α-hemolysin channels in nano-BLMs persist for hours. The onset of α-hemolysin-mediated conduction depends on the applied protein concentration and strongly on the diameter of the nanopores. Heptameric channel formation from adsorbed α-hemolysin monomers needs more time in bilayers suspended in 200 nm pores compared to bilayers in pores of 400 and 800 nm diameters. Diffusion of sodium ions across α-hemolysin channels present in a sufficiently high number in the bilayers was quantitatively and specifically determined using ion selective electrodes. The results demonstrate that relatively small variations of nano-dimensions have a tremendous effect on observable dynamic biomolecular processes. Such nanopore chips are potentially useful as supports for stable lipid bilayers to establish functional assays of membrane proteins needed in basic research and drug discovery. 相似文献
106.
Aziz Gozgen Aydan Dag Hakan Durmaz Okan Sirkecioglu Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2009,47(2):497-504
A combination of ring opening metathesis polymerization (ROMP) and click chemistry approach is first time utilized in the preparation of 3‐miktoarm star terpolymer. The bromide end‐functionality of monotelechelic poly(N‐butyl oxanorbornene imide) (PNBONI‐Br) is first transformed to azide and then reacted with polystyrene‐b‐poly(methyl methacrylate) copolymer with alkyne at the junction point (PS‐b‐PMMA‐alkyne) via click chemistry strategy, producing PS‐PMMA‐PNBONI 3‐miktoarm star terpolymer. PNBONI‐Br was prepared by ROMP of N‐butyl oxanorbornene imide (NBONI) 1 in the presence of (Z)‐but‐2‐ene‐1,4‐diyl bis(2‐bromopropanoate) 2 as terminating agent. PS‐b‐PMMA‐alkyne copolymer was prepared successively via nitroxide‐mediated radical polymerization (NMP) of St and atom transfer radical polymerization (ATRP) of MMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 497–504, 2009 相似文献
107.
Aydan Dag Hakan Durmaz Umit Tunca Gurkan Hizal 《Journal of polymer science. Part A, Polymer chemistry》2009,47(1):178-187
Two types of multiarm star block copolymers: (polystyrene)m‐poly(divinylbenzene)‐poly(methyl methacrylate)n, (PS)m‐polyDVB‐(PMMA)n and (polystyrene)m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)k, (PS)m‐polyDVB‐(PtBA)k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using 1H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009 相似文献
108.
109.
Aydan Dag Hakan Durmaz Emrah Demir Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6969-6977
The double click reactions (Cu catalyzed Huisgen and Diels–Alder reactions) were used as a new strategy for the preparation of well‐defined heterograft copolymers in one‐pot technique. The synthetic strategy to the various stages of this work is outlined: (i) preparing random copolymers of styrene (St) and p‐chloromethylstyrene (CMS) (which is a functionalizable monomer) via nitroxide mediated radical polymerization (NMP); (ii) attachment of anthracene functionality to the preformed copolymer by the o‐etherification procedure and then conversion of the remaining ? CH2Cl into azide functionality; (iii) by using double click reactions in one‐pot technique, maleimide end‐functionalized poly(methyl methacrylate) (PMMA‐MI) via atom transfer radical polymerization (ATRP) of MMA and alkyne end‐functionalized poly (ethylene glycol) (PEG‐alkyne) were introduced onto the copolymer bearing pendant anthryl and azide moieties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6969–6977, 2008 相似文献
110.
Rainer Cremer Mirjam Witthaut Dieter Neuschütz Cyril Trappe Martin Laurenzis Olaf Winkler Heinrich Kurz 《Mikrochimica acta》2000,133(1-4):299-302
Cu3N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at
a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For
basic investigations concerning the composition and structure of Cu3N, Si wafers were used as substrate material. To study the suitability of Cu3N as an optical data storage medium under technical conditions, Cu3N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray
photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).
The decomposition of Cu3N into metallic copper and nitrogen was induced and characterized with a dynamic tester consisting of an optical microscope
with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity
photo detector. Optimized Cu3N films could be decomposed into metallic copper at pulse lengths of 200 ns. The reflectivity change from 3.2% to 33.2% for
completely transformed areas and to 12% for single bits as well as the maximum write data rate of 3.3 Mbit/s demonstrated
the suitability of Cu3N for write once optical data storage. Especially the carrier to noise ratio of 41 dB shows an increase of a factor of 3 for
this novel material as compared to conventional optical data storage media. 相似文献