bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nachweis maximaler Spinpolarisation in Chromdimerkationen durch zirkularen magnetischen Röntgendichroismus
Authors: Zamudio‐Bayer Vicente , Hirsch Konstantin , Langenberg Andreas , Niemeyer Markus , Vogel Marlene , Ławicki Arkadiusz , Terasaki Akira , Lau J. Tobias , von Issendorff Bernd 
Published: February 2015

AbstractMithilfe des magnetischen zirkularen Röntgendichroismus wurden die elektronische Struktur und das magnetische Moment von Cr2+ bestimmt. Unsere Ergebnisse zeigen, dass sich die bevorzugte Kopplung der 3d‐Spins durch das Entfernen eines einzelnen Elektrons aus dem bindenden 4sσg‐Orbital des Cr2 dramatisch umkehrt. Im Unterschied zum neutralen Molekül, das einen Grundzustand mit verschwindendem Spin bei kurzer Bindungslänge besitzt, zeigt das Molekülkation einen ferromagnetisch gekoppelten Grundzustand mit dem höchstmöglichen Spin von S=11/2 bei nahezu der doppelten Bindungslänge des neutralen Moleküls. Diese besondere Spinkonfiguration ist das Resultat einer indirekten Austauschkopplung der an den Ionenrümpfen lokalisierten 3d‐Elektronen durch das delokalisierte 4sσ‐Elektron über den starken intraatomaren 3d‐4s‐Austausch. Unsere Ergebnisse ermöglichen erstmals eine Abschätzung der relativen Energien des ferromagnetisch gekoppelten 12Σ‐Grundzustands und des angeregten 2Σ‐Zustands.
Formation of a ZnO Overlayer in Industrial Cu/ZnO/Al2O3 Catalysts Induced by Strong Metal–Support Interactions
Authors: Lunkenbein Thomas , Schumann Julia , Behrens Malte , Schlögl Robert , Willinger Marc G. 
Published: February 2015

AbstractIn industrially relevant Cu/ZnO/Al2O3 catalysts for methanol synthesis, the strong metal support interaction between Cu and ZnO is known to play a key role. Here we report a detailed chemical transmission electron microscopy study on the nanostructural consequences of the strong metal support interaction in an activated high‐performance catalyst. For the first time, clear evidence for the formation of metastable “graphite‐like” ZnO layers during reductive activation is provided. The description of this metastable layer might contribute to the understanding of synergistic effects between the components of the Cu/ZnO/Al2O3 catalysts.
Cation‐Triggered Switchable Asymmetric Catalysis with Chiral Aza‐CrownPhos
Authors: Ouyang Guang‐Hui , He Yan‐Mei , Li Yong , Xiang Jun‐Feng , Fan Qing‐Hua 
Published: February 2015

AbstractAn aza‐crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host–guest interactions. In the OFF state, the catalyst is almost inactive (less than 1 % conversion) because of the formation of an intermolecular sandwich complex by two aza‐crown ether moities and the cationic rhodium metal center. In using alkali‐metal‐cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98 % ee).
Impact of Hydrogenolysis on the Selectivity of the Fischer–Tropsch Synthesis: Diesel Fuel Production over Mesoporous Zeolite‐Y‐Supported Cobalt Nanoparticles
Authors: Peng Xiaobo , Cheng Kang , Kang Jincan , Gu Bang , Yu Xiang , Zhang Qinghong , Wang Ye 
Published: February 2015

AbstractSelectivity control is a challenging goal in Fischer–Tropsch (FT) synthesis. Hydrogenolysis is known to occur during FT synthesis, but its impact on product selectivity has been overlooked. Demonstrated herein is that effective control of hydrogenolysis by using mesoporous zeolite Y‐supported cobalt nanoparticles can enhance the diesel fuel selectivity while keeping methane selectivity low. The sizes of the cobalt particles and mesopores are key factors which determine the selectivity both in FT synthesis and in hydrogenolysis of n‐hexadecane, a model compound of heavier hydrocarbons. The diesel fuel selectivity in FT synthesis can reach 60 % with a CH4 selectivity of 5 % over a Na‐type mesoporous Y‐supported cobalt catalyst with medium mean sizes of 8.4 nm (Co particles) and 15 nm (mesopores). These findings offer a new strategy to tune the product selectivity and possible interpretations of the effect of cobalt particle size and the effect of support pore size in FT synthesis.
Caterpillar Track Complexes in Template‐Directed Synthesis and Correlated Molecular Motion
Authors: Liu Shiqi , Kondratuk Dmitry V. , Rousseaux Sophie A. L. , Gil‐Ramírez Guzmán , O'Sullivan Melanie C. , Cremers Jonathan , Claridge Tim D. W. , Anderson Harry L. 
Published: February 2015

AbstractSmall alterations to the structure of a star‐shaped template totally change its mode of operation. The hexapyridyl template directs the conversion of a porphyrin dimer to the cyclic hexamer, but deleting one pyridine site changes the product to the cyclic decamer, while deleting two binding sites changes the product to the cyclic octamer. This surprising switch in selectivity is explained by the formation of 2:1 caterpillar track complexes, in which two template wheels bind inside the nanoring. Caterpillar track complexes can also be prepared by binding the hexapyridyl template inside the 8‐ and 10‐porphyrin nanorings. NMR exchange spectroscopy (EXSY) experiments show that these complexes exhibit correlated motion, in which the conrotatory rotation of the two template wheels is coupled to rotation of the nanoring track. In the case of the 10‐porphyrin system, the correlated motion can be locked by binding palladium(II) dichloride between the two templates.
Hypercrosslinked Phenolic Polymers with Well‐Developed Mesoporous Frameworks
Authors: Zhang Jinshui , Qiao Zhen‐An , Mahurin Shannon M. , Jiang Xueguang , Chai Song‐Hai , Lu Hanfeng , Nelson Kimberly , Dai Sheng 
Published: February 2015

AbstractA soft chemistry synthetic strategy based on a Friedel–Crafts alkylation reaction is developed for the textural engineering of phenolic resin (PR) with a robust mesoporous framework to avoid serious framework shrinkage and maximize retention of organic functional moieties. By taking advantage of the structural benefits of molecular bridges, the resultant sample maintains a bimodal micro‐mesoporous architecture with well‐preserved organic functional groups, which is effective for carbon capture. Moreover, this soft chemistry synthetic protocol can be further extended to nanotexture other arene‐based polymers with robust frameworks.
The Yin and Yang in the Development of Catalytic Processes: Catalysis Research and Reaction Engineering
Authors: Prieto Gonzalo , Schüth Ferdi 
Published: February 2015

AbstractFor the implementation of commercial catalytic processes, catalyst development and reactor design and engineering need to go hand‐in‐hand. As both fields are mutually interdependent, a co‐evolution of catalysts and chemical reactors has historically been the right path towards successful, large‐scale technologies. Over the 150 years of its existence, the contributions of BASF to the development of several commercial catalytic processes constitute perfect illustrations of this necessary and synergetic interplay between catalyst science and reactor engineering.
The σ‐Aromatic Clusters [Zn3]+ and [Zn2Cu]: Embryonic Brass
Authors: Freitag Kerstin , Gemel Christian , Jerabek Paul , Oppel Iris M. , Seidel Rüdiger W. , Frenking Gernot , Banh Hung , Dilchert Katharina , Fischer Roland A. 
Published: February 2015

AbstractThe triangular clusters [Zn3Cp*3]+ and [Zn2CuCp*3] were obtained by addition of the in situ generated, electrophilic, and isolobal species [ZnCp*]+ and [CuCp*] to Carmona’s compound, [Cp*ZnZnCp*], without splitting the ZnZn bond. The choice of non‐coordinating fluoroaromatic solvents was crucial. The bonding situations of the all‐hydrocarbon‐ligand‐protected clusters were investigated by quantum chemical calculations revealing a high degree of σ‐aromaticity similar to the triatomic hydrogen ion [H3]+. The new species serve as molecular building units of CunZnm nanobrass clusters as indicated by LIFDI mass spectrometry.
Single‐Shell Carbon‐Encapsulated Iron Nanoparticles: Synthesis and High Electrocatalytic Activity for Hydrogen Evolution Reaction
Authors: Tavakkoli Mohammad , Kallio Tanja , Reynaud Olivier , Nasibulin Albert G. , Johans Christoffer , Sainio Jani , Jiang Hua , Kauppinen Esko I. , Laasonen Kari 
Published: February 2015

AbstractEfficient hydrogen evolution reaction (HER) through effective and inexpensive electrocatalysts is a valuable approach for clean and renewable energy systems. Here, single‐shell carbon‐encapsulated iron nanoparticles (SCEINs) decorated on single‐walled carbon nanotubes (SWNTs) are introduced as a novel highly active and durable non‐noble‐metal catalyst for the HER. This catalyst exhibits catalytic properties superior to previously studied nonprecious materials and comparable to those of platinum. The SCEIN/SWNT is synthesized by a novel fast and low‐cost aerosol chemical vapor deposition method in a one‐step synthesis. In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation. This finding opens new avenues for utilizing active transition metals such as iron in a wide range of applications.
Fixation and Release of Intact E4 Tetrahedra (E=P, As)
Authors: Spitzer Fabian , Sierka Marek , Latronico Mario , Mastrorilli Piero , Virovets Alexander V. , Scheer Manfred 
Published: February 2015

AbstractBy the reaction of [NacnacCuCH3CN] with white phosphorus (P4) and yellow arsenic (As4), the stabilization and enclosure of the intact E4 tetrahedra are realized and the disubstituted complexes [(NacnacCu)2(μ,η2:2‐E4)] (1 a: E=P, 1 b: E=As) are formed. The mono‐substituted complex [NacnacCu(η2‐P4)] (2), was detected by the exchange reaction of 1 a with P4 and was only isolated using low‐temperature work‐up. All products were comprehensively spectroscopically and crystallographically characterized. The bonding situation in the products as intact E4 units (E=P, As) was confirmed by theory and was experimentally proven by the pyridine promoted release of the bridging E4 tetrahedra in 1.
Siloxane‐Based Hybrid Semiconducting Polymers Prepared by Fluoride‐Mediated Suzuki Polymerization
Authors: Lee Junghoon , Han A‐Reum , Lee Sang Myeon , Yoo Dohyuk , Oh Joon Hak , Yang Changduk 
Published: February 2015

AbstractSiloxane‐containing materials are a large and important class of organic‐inorganic hybrids. In this report, a practical variation of the Suzuki polymerization to generate semiconducting polymeric hybrids based on siloxane units, which proceeds under essentially nonbasic conditions, is presented. This method generates solution‐processable poly(diketopyrrolopyrrole‐alt‐benzothiadiazole) (PDPPBT‐Si) consisting of the hybrid siloxane substituents, which could not be made using conventional methods. PDPPBT‐Si exhibits excellent ambipolar transistor performance with well‐balanced hole and electron FET mobilities. The siloxane‐containing DPP‐thiophene polymer classes (PDPP3T‐Si and PDPP4T‐Si), synthesized by this method, exhibit high hole mobility of up to 1.29 cm2 V−1 s−1. This synthetic approach should provide access to a variety of novel siloxane‐containing conjugated semiconductor classes by using a variety of aryldihalides and aryldiboronic acids/esters.
Electrocatalytic Water Oxidation by a Dinuclear Copper Complex in a Neutral Aqueous Solution
Authors: Su Xiao‐Jun , Gao Meng , Jiao Lei , Liao Rong‐Zhen , Siegbahn Per E. M. , Cheng Jin‐Pei , Zhang Ming‐Tian 
Published: February 2015

AbstractElectrocatalytic water oxidation using the oxidatively robust 2,7‐[bis(2‐pyridylmethyl)aminomethyl]‐1,8‐naphthyridine ligand (BPMAN)‐based dinuclear copper(II) complex, [Cu2(BPMAN)(μ‐OH)]3+, has been investigated. This catalyst exhibits high reactivity and stability towards water oxidation in neutral aqueous solutions. DFT calculations suggest that the OO bond formation takes place by an intramolecular direct coupling mechanism rather than by a nucleophilic attack of water on the high‐oxidation‐state CuIVO moiety.
Theoretical and experimental investigations of the inverse emulsion polymerization of acrylamide
Authors: Abdi Ardeshir , Shahrokhi Mohammad , Ramazani S. A Ahmad , Vafa Ehsan 
Published: February 2015

ABSTRACTIn this study, the inverse emulsion polymerization modeling of polyacrylamide with population balance equations (PBEs) was performed. The PBEs were derived on the basis of the zero–one kinetic model. The effects of the surfactant steric barrier and surfactant reaction with radicals, including monomeric radicals, on the radical entry rate into the particle were taken into account. In the modified model, the coagulation phenomenon was included through consideration of the effects of forces not included in the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory; these include hydration and steric forces in addition to DLVO forces. The effects of the surfactant and initiator concentrations on the conversion, particle size, and average molecular weight (MW) were investigated by simulation and experimental studies. Increasing the surfactant concentration initially increased the conversion and decreased MW. A further increase in the surfactant concentration resulted in a decrease in the conversion and an increase in MW. The average particle size decreased with an increase in the surfactant concentration. An increase in the initiator concentration led to an increase in the monomer conversion and a decrease in the average MW. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41916.
Differences in regenerated silk fibroin prepared with different solvent systems: From structures to conformational changes
Authors: Cheng Guotao , Wang Xin , Tao Sijie , Xia Ju , Xu Shui 
Published: February 2015

ABSTRACTDissolution is an important part of silk fibroin (SF) reprocessing, and it is the only way to process it into films, gels, porous scaffold materials, and electrostatic spinning silk fibers. There are a variety of dissolution systems used to dissolve SF. However, few studies have focused on the differences between these different solvent systems. The dissolution of SF with different solvent systems was investigated in this study. Regenerated silk fibroin (RSF) solutions and films were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy. The results show that the RSF film structures changed with the solvent system, especially LiBr–H2O. The characterization proved that the random coil did not change into a β‐sheet structure during film formation, and this indicated that its crystal structure and thermal stability was different from others. Interestingly, the differences in the morphologies of all of the RSF films prepared with different solvents were outstanding. Because the mechanism and force of the ion in the solvent systems were different, the SF molecule was hydrolyzed differently in individual solvent systems and produced different hydrolyzed SF molecular chains. These chains had different self‐assembly processes and would lead to RSF products with different microstructures and properties. This suggests that a suitable solvent should be chosen for different uses. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41959.
Tailoring block‐copolyesters by reactive blending of polyethylene terephthalate and polyethylene naphthalate using statistical design of experiments
Authors: Röhner Stefan , Geyer Björn , Gad'on Sina , Kandelbauer Andreas , Chassé Thomas , Lorenz Günter 
Published: February 2015

ABSTRACTBlock‐copolyesters of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) were synthesized via reactive extrusion. The influence of processing parameters on the material properties on a molecular scale like degree of trans‐esterification, block length, and degree of randomness were investigated. The varied process factors were extrusion temperature and rotational speed. The effects of process parameter variation were investigated by 1H‐NMR‐spectroscopy. The experimental results show a clear dependence of the molecular properties on the processing conditions. By using statistical experimental design (DoE), it was possible to prepare defined copolyesters from PET and PEN without addition of further chemicals. With a degree of randomness between 0.05 and 0.5, the presence of an actual copolyester was confirmed when appropriate extrusion conditions were applied. The reactive extrusion process was confirmed to be suitable to produce defined block‐copolyesters in a predictable and reproducible way. It was possible to produce designed sequence lengths, which could be adjusted within a range of 11–136 repeating units in the case of PET and, in the case of PEN, of 2.5–26. The produced materials can be used as barrier materials or barrier coatings to protect substrates against molecular oxygen and water vapour, e.g., in organic photovoltaic applications or food packaging. The described method is a one‐pot alternative method to the previously described chemical recycling pathway. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41997.
High‐performance copoly(benzimidazole‐benzoxazole‐imide) fibers: Fabrication, structure, and properties
Authors: Luo Longbo , Zheng Yaxin , Huang Jieyang , Li Ke , Wang Huina , Feng Yan , Wang Xu , Liu Xiangyang 
Published: February 2015

ABSTRACTNovel high‐performance copolyimide (co‐PI) fibers containing benzimidazole and benzoxazole ring in the main chain were prepared by a two‐step spinning via the poly(amic acid)s. Effects of the incorporated benzimidazole and benzoxazole units on the micro‐structure and properties of co‐PI fibers were investigated. Fourier transform infrared (FTIR) results indicated that hydrogen bonding is formed in the co‐PI fibers. The co‐PI fibers exhibited discernible crystallization peaks at 14°∼15° and 23°∼26° (2θ), showing crystalline‐like structure. Moreover, the packing type of benzimidazole‐imide units determined the macromolecules packing of co‐PIs. It was amazedly found that the co‐PI fibers exhibited higher tensile strength and initial modulus than those of corresponding homo‐PI fibers, reaching tensile strength of 2.2–2.6 GPa, initial modulus of 99.1–113.2 GPa. The results of dynamic mechanical analysis (DMA) indicated co‐PI2 fiber had a positive Tg deviation due to the presence of strong intermolecular hydrogen bonding between benzimidazole‐imide and benzoxazole‐imide units, which maybe lead to the effective stress transfer between benzimidazole‐imide units and benzoxazole‐imide units. In addition, the obtained PI fibers exhibited excellent thermal properties with the 10% weight loss temperatures under N2 in the range of 574–585°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42001.
The effect of octamethylcyclotetrasiloxane (D4) addition on the structure and properties of film‐forming polyacrylate/silica core–shell composite particles
Authors: Yuan Junjie , Qian He 
Published: February 2015

ABSTRACTThe film‐forming polyacrylate/silica core–shell nanocomposite particles with octamethylcyclotetrasiloxane (D4) were successfully synthesized via aqueous emulsion polymerization in the presence of a glycerol‐functionalized nano silica sol. The ring‐opening polymerization of D4 and the reaction with the glycerol‐functionalized nano silica particles before emulsion polymerization was the key procedure in this process. Transmission electron microscopy results showed that more nano silica particles tended to coat on the polyacrylate particles surface after the nano silica sols were modified with D4. The silica aggregation efficiency was increased from 90.9 to 98.6% when the amount of D4 used in the system was varied from 0 to 8.0 wt %. The transparency of the nanocomposite films was not compromised after D4 was incorporated into the system. The films of the nanocomposite particles with or without D4 both exhibited superior abrasive resistance. Furthermore, the water resistance and hydrophobicity of the films of these particles with D4 were also improved significantly. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42003.
Autonomic self‐healing of poly(vinyl butyral)
Authors: Arayachukiat Sunatda , Doan Vu Anh , Murakami Tatsuya , Nobukawa Shogo , Yamaguchi Masayuki 
Published: February 2015

ABSTRACTThe self‐healing behavior of poly(vinyl butyral) (PVB) is evaluated below the glass transition temperature Tg. It is found that PVB shows autonomic self‐healing even at room temperature, although Tg is around at 76°C. Furthermore, a large amount of water is found to be adsorbed on the surface of the film. This is attributed to the surface localization of hydroxyl group in PVB, which is confirmed by X‐ray photoelectron spectroscopy. Since the surface is plasticized by water, the scar applied by a razor blade is healed even in the glassy state of the bulk. Moreover, the healing efficiency is enhanced at high humidity condition, owing to the pronounced plasticizing effect by water. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42008.
Partial replacement of EPR by GTR in highly flowable PP/EPR blends: Effects on morphology and mechanical properties
Authors: Lima Paulo Silva , Oliveira José Martinho , Costa Vítor António Ferreira 
Published: February 2015

ABSTRACTThis research analyzes the effect of ground tire rubber (GTR) and a novel metallocene‐based ethylene–propylene copolymer (EPR), with high propylene content, on the morphology and mechanical behavior of ternary polymer blends based on a highly flowable polypropylene homopolymer (PP). The PP/EPR blends morphology, with very small domains of EPR dispersed in the PP matrix, indicates a good compatibility among these materials, which leads to a significant improvement on elongation at break and impact strength. The incorporation of EPR on the rubber phase of thermoplastic elastomeric blends (TPE) based on GTR and PP (TPEGTR) has a positive effect on their mechanical performance, attributed to the toughness enhancement of the PP matrix and to the establishment of shell‐core morphology between the rubber phases. The mechanical properties of the ternary blends reveal that TPEGTR blends allow the upcycling of this GTR material by injection molding technologies. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42011.
Design and verification of a single slab RAS through mass production of glass/MWNT added epoxy composite prepreg
Authors: Shin Jae‐Hwan , Jang Hong‐Kyu , Choi Won‐Ho , Song Tae‐Hoon , Kim Chun‐Gon , Lee Woo‐Yong 
Published: February 2015

ABSTRACTIn this study, glass fiber composite prepreg is manufactured with multi‐walled carbon nanotube (MWNT) added epoxy using two different methods. Because MWNT agglomeration occurs, the calendering dispersion method is used to resolve this problem. The tensile and shear tests of glass/MWNT 1.8wt % added epoxy composite (CNT18) are conducted and the results are compared with the properties of a commercial glass/epoxy composite (GEP 118). The complex permittivity is measured using a network analyzer and a waveguide in the Ku‐band. A single slab radar absorbing structure (RAS) is also designed and verified. It is found that the tensile and shear properties of CNT18 are sufficient to replace GEP 118 as a structural material. Furthermore, the—10 dB bandwidth and reflection loss of the RAS using CNT18 is 12.87 to 17.78 GHz (4.91 GHz) and—29.2 dB at 14.95 GHz, respectively. The measurement results align well with the simulation results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42019.