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排序方式: 共有253条查询结果,搜索用时 31 毫秒
51.
Tuba Erdogan Eda Gungor Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1396-1403
We prepared a novel miktoarm star copolymer with an azobenzene unit at the core via combination of atom transfer radical polymerization (ATRP) and nitroxide‐mediated free radical polymerization (NMP) routes. For this purpose, first, mikto‐functional initiator, 3 , with tertiary bromide (for ATRP) and 2,2,6,6‐tetramethylpiperidin‐1‐yloxy (TEMPO) (for NMP) functionalities and an azobenzene moiety at the core was synthesized. The initiator 3 thus obtained was used in the subsequent living radical polymerization routes such as ATRP of MMA and NMP of St, respectively, to give A2B2 type miktoarm star copolymer, (PMMA)2‐(PSt)2 with an azobenzene unit at the core with controlled molecular weight and low polydispersity (Mw/Mn < 1.15). The photoresponsive properties of 3 and (PMMA)2‐(PSt)2 miktoarm star copolymer were investigated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1396–1403, 2006 相似文献
52.
Humeyra Mert Umit Tunca Gurkan Hizal 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5923-5932
The copper‐catalyzed living radical polymerization (LRP) of styrene (St) was carried out in the presence of thiophenol derivative such as sodium thiophenolate (PhSNa) or p‐methoxythiophenol as a reducing agent for Cu(II) by using either 1‐chloro‐1‐phenyl ethane or ethyl‐2‐bromoisobutyrate as an initiator and N,N,N′,N″,N″‐pentamethyldiethylenetriamine as ligand at 110 °C. Kinetic experiments were carried out to reveal the effect of PhSNa concentration on copper‐catalyzed LRP of St. This technique was successfully applied for the preparation of both chain‐extended polymer and block copolymer polystyrene‐b‐poly(methyl methacrylate). The obtained polymers were characterized using GPC, 1H‐NMR, and MALDI‐TOF measurements. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5923–5932, 2006 相似文献
53.
Ozturk Ozum Farouk Fathima Manaal Ooi Luyi Law Christine Shing Wei Muhammed Muhammed Tilahun Aki-Yalcin Esin Yeong Keng Yoon 《Molecular diversity》2022,26(5):2863-2876
Molecular Diversity - Selectively inhibiting butyrylcholinesterase (BChE) is hypothesized to help in the management of Alzheimer’s disease (AD). Several studies have determined a correlation... 相似文献
54.
Aydan Dag Mehtap Aydin Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2012,50(21):4476-4483
In this work, we used Diels–Alder click reaction for the preparation of various types of aliphatic polycarbonates (PCs). We first prepared a novel anthracene‐functionalized cyclic carbonate monomer, anthracen‐9‐ylmethyl 5‐methyl‐2‐oxo‐1,3‐dioxane‐5‐carboxylate (2), followed by ring‐opening polymerization of this monomer to prepare PC with pendant anthracene groups (PC‐anthracene) using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)/1‐(3,5‐bis(trifloromethyl)phenyl)‐3‐cyclohexylthiourea (TU) as the catalyst and benzyl alcohol as the initiator in CH2Cl2 at room temperature. Subsequently, the resulting PC‐anthracene (Mn,TDGPC = 6000 g/mol, Mw/Mn = 1.22) was grafted with a linear α‐furan protected‐maleimide terminated‐poly(methyl methacrylate) (PMMA‐MI) (Mn,GPC = 3100 g/mol, Mw/Mn = 1.31), or poly(ethylene glycol) (PEG‐MI) (Mn,GPC = 550 g/mol, Mw/Mn = 1.09), or a mixture of PMMA‐MI and PEG‐MI to yield well‐defined PC graft or hetero graft copolymers, PC‐g‐PMMA (Mn,TDGPC = 59000 g/mol, Mw/Mn = 1.22) or PC‐g‐PEG, or PC‐g‐(PMMA)‐co‐PC‐g‐(PEG) (Mn,TDGPC = 39900 g/mol, Mw/Mn = 1.16), respectively, using Diels–Alder click reaction in toluene at 110°C. The Diels–Alder grafting efficiencies were found to be over 97% using UV spectroscopy. Moreover, the structural analyses and the molecular weights of resulting graft copolymers were determined via 1H NMR and triple detection GPC (TD‐GPC), respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
55.
Oznülüer T Erdogan I Demir U 《Langmuir : the ACS journal of surfaces and colloids》2006,22(9):4415-4419
Ultrathin films of ZnS were grown on Au (111) substrates using a novel, simple co-deposition method and characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy. Cyclic voltammograms were used to determine approximate deposition potentials for co-deposition. XRD shows that the material growth is highly preferential with (111) orientation. Both AFM and XRD data indicate that the ZnS growth mechanism starts by the formation of rounded nanoparticles at the surface and then continues by lateral and vertical growth to form flat square crystallites of ZnS. UV-vis spectra taken for the ZnS thin films with various thicknesses, which is related to deposition time, shows that the band gap of the ZnS decreases as the film thickness increases. 相似文献
56.
Jensen MR Hansen DF Ayna U Dagil R Hass MA Christensen HE Led JJ 《Magnetic resonance in chemistry : MRC》2006,44(3):294-301
The utility of pseudocontact shifts in the structure refinement of metalloproteins has been evaluated using a native, paramagnetic Cu(2+) metalloprotein, plastocyanin from Anabaena variabilis (A.v.), as a model protein. First, the possibility of detecting signals of nuclei spatially close to the paramagnetic metal ion is investigated using the WEFT pulse sequence in combination with the conventional TOCSY and (1)H-(15)N HSQC sequences. Second, the importance of the electrical charge of the metal ion for the determination of correct pseudocontact shifts from the obtained chemical shifts is evaluated. Thus, using both the Cu(+) plastocyanin and Cd(2+)-substituted plastocyanin as the diamagnetic references, it is found that the Cd(2+)-substituted protein with the same electrical charge of the metal ion as the paramagnetic Cu(2+) plastocyanin provides the most appropriate diamagnetic reference signals. Third, it is found that reliable pseudocontact shifts cannot be obtained from the chemical shifts of the (15)N nuclei in plastocyanin, most likely because these shifts are highly dependent on even minor differences in the structure of the paramagnetic and diamagnetic proteins. Finally, the quality of the obtained (1)H pseudocontact shifts, as well as the possibility of improving the accuracy of the obtained structure, is demonstrated by incorporating the shifts as restraints in a refinement of the solution structure of A.v. plastocyanin. It is found that incorporation of the pseudocontact shifts enhances the precision of the structure in regions with only few NOE restraints and improves the accuracy of the overall structure. 相似文献
57.
H. Ibrahim Ugras Ismet Basaran Turgut Kilic Umit Cakir 《Journal of heterocyclic chemistry》2006,43(6):1679-1684
58.
[reaction: see text] Highly functionalized pyrrolidines are obtained in a single chemical step via a mild, efficient, and selective Ag(I)-catalyzed asymmetric [C+NC+CC] coupling process. Oppolzer's camphorsultam enables the desired reaction cascade and provides a reliable means to control the developing stereochemistry and purify the products. This three-component reaction provides unprecedented access to structurally diverse pyrrolidines for both target- and diversity-oriented syntheses. 相似文献
59.
We obtained, what is to our knowledge, record tuning from an intracavity-pumped gain-switched Cr2+:ZnSe laser. In the experiments, a polycrystalline Cr2+:ZnSe sample with an absorption of about 43% at 1570 nm was used to minimize reabsorption losses at the lasing wavelengths below 2000 nm. By placing the gain medium inside the cavity of a pulsed KTP optical parametric oscillator (OPO) operating at 1570 nm, smooth, continuous tuning was achieved in the 1880-3100 nm range with four different sets of cavity optics. As high as 145 mW of average laser output power was obtained at 2365 nm with 1.2 W of intracavity OPO power. 相似文献
60.
Within the framework of a piecewise homogeneous body model, with the use of the three-dimensional linearized theory of elastic
waves in initially stressed bodies, the propagation of torsional waves in prestressed multilayered circular cylinders is investigated.
The elasticity relations for cylinder components are given through the Murnaghan potential. The influence of variations in
the geometric and mechanical parameters of the cylinders on the dispersion curves is analyzed. 相似文献