bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer functionalization by free radical addition to alkynes
Authors: Wu Wei , Parent J. Scott 
Published: October 2008

AbstractA new chemical modification of saturated polymers involving free radical addition to mono‐substituted alkynes is presented and examined in terms of reaction yield, graft structure, and changes to molecular weight. Solvent‐free, peroxide‐initiated reactions of ethyl propiolate and poly(ethylene oxide) provide good yields of ethyl (2‐E,Z)‐3‐alkylacrylates, whereas less efficient hydrogen atom donation by polyethylene impacts negatively on reaction yields and encourages alkyne oligomerization. Model compounds are used to characterize alkyne grafting products, and to probe the relationship between reagent properties, reaction yields, and product structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7386–7394, 2008
A new approach for controlling birefringent property of cyclic olefin copolymers
Authors: Ban Hoang The , Hagihara Hideaki , Nishii Kei , Tsunogae Yasuo , Nojima Shuichi , Shiono Takeshi 
Published: October 2008

AbstractThis article reports an original method to control the birefringent property of the cyclic olefin copolymer, which has been recently commercialized as a new type of optical resins, via introduction of a third monomer that possesses a negative birefringence into the cyclic olefin copolymer that exhibits an inherently positive birefringence. The mutual compensation between these opposite‐sign birefringences effectively reduced the birefringent magnitude of the corresponding terpolymer. In fact, terpolymerization of norbornene (N), ethylene (E), and styrene (S), in which S exhibits a negative birefringence regarding to the positive birefringence of the NE copolymer was successfully prepared using fluorenylamidodimethyltitanium‐based catalyst, yielding NES terpolymers with controllable birefringent property. Especially, when the S content in the NES terpolymer was controlled at optimum values, it is possible to synthesize a new type of the cyclic olefin copolymer that exhibits an extremely low birefringent magnitude close to zero regardless of high degrees of chain orientation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7395–7400, 2008
Efficient tuning nonlinear optical properties: Synthesis and characterization of a series of novel poly(aryleneethynylene)s co‐containing BODIPY
Authors: Zhu Mei , Jiang Li , Yuan Mingjian , Liu Xiaofeng , Ouyang Canbin , Zheng Haiyan , Yin Xiaodong , Zuo Zicheng , Liu Huibiao , Li Yuliang 
Published: October 2008

AbstractA series of novel conjugated poly(aryleneethynylene)s (PAEs) co‐containing BODIPY have been synthesized and characterized, and their third‐order nonlinear optical properties were studied using the Z‐scan technique. Interestingly, by introducing the BODIPY skeleton into the PAE backbone, the polymers showed that their nonlinear optical properties were dependent on the BODIPY component. From poly‐4 to poly‐1, the third‐order nonlinear optical properties of the polymers enhanced regularly with the increase of the BODIPY component of the copolymers, indicating that the BODIPY component played decisive roles in enhancing the nonlinear optical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7401–7410, 2008
Copolymerization of ethylene and norbornene using cyclopentadienylzirconium trichloride activated by isobutyl‐modified methylaluminoxane
Authors: Nishizawa Osamu , Misaka Hideki , Sakai Ryosuke , Kakuchi Toyoji , Satoh Toshifumi 
Published: October 2008

AbstractThe copolymerization of ethylene (E) and norbornene (NB) was investigated using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl3)/isobutyl‐modified methylaluminoxane (MMAO), at a moderate polymerization temperature in toluene. For the CpZrCl3 catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO), the quantities of the charged NB and the polymerization temperature significantly affected the molecular weights, polydispersities, and NB contents of the obtained copolymers and the copolymerization activities in all the experiments. As the charged NB increased and thereby the NB/E molar ratio increased, the NB content in the copolymer increased and reached a maximum value of 71 mol %. The CpZrCl3/MMAO ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.77 mol L−1 and ethylene of 0.70 MPa at 50 °C showed the highest activity of 1690 kg molZr−1 h−1 and molecular weight of 21,100 g mol−1. The 13C NMR analysis showed that the CpZrCl3/MMAO catalyst system produced the E‐NB random copolymer with a number of NB homosequences such as the NN dyad and NNN triad. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7411–7418, 2008
Highly soluble green‐emitting Ir(III) complexes with 9‐(6‐phenyl‐pyridin‐3‐ylmethyl)‐9H‐carbazole ligands and their application to polymer light‐emitting diodes
Authors: Cho Min Ju , Kim Jae Il , Hong Chang Seop , Kim Young Min , Park Young Wook , Ju Byeong‐Kwon , Choi Dong Hoon 
Published: October 2008

AbstractHighly organic soluble Ir(III) complexes with 9‐(6‐phenyl‐pyridin‐3‐ylmethyl)‐9H‐carbazole were simply synthesized, and the solubility of the new complex was significantly improved when compared with the conventional green‐emitting Ir(ppy)3. Since a carbazole group is tethered through a nonconjugated methylene spacer, the photophysical properties of new complexes are almost identical with those of conventional Ir(ppy)3. The pure complexes were utilized to prepare electrophosphorescent polymer light‐emitting diodes (PLEDs). The device performances were observed to be relatively better or comparable with those of Ir(ppy)3 based poly(N‐vinylcarbazole) systems. The integration of rigid hole‐transporting carbazole and phosphorescent complex provides a new route to design highly efficient solution‐processable complex for electrophosphorescent PLED applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7419–7428, 2008
Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one‐pot route for the preparation of controlled delivery systems
Authors: Galia Alessandro , Scialdone Onofrio , Ferraro Gianpiero , Filardo Giuseppe 
Published: October 2008

AbstractThe polymerization of 1‐vinyl‐2‐pyrrolidone in supercritical carbon dioxide in the presence of ibuprofen as a model drug was investigated as a new one‐pot process for the preparation of polymer‐based drug delivery systems (DDSs). The composites were prepared at 65 °C and P = 31–42 MPa by changing the initial concentration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure compound. Copolymerization with methyl methacrylate was the most effective route to obtain a DDS with sustained temporal release of the drug molecule. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7429–7446, 2008
Epoxy/amine‐functionalized short‐length vapor‐grown carbon nanofiber composites
Authors: Ahn Soo‐Na , Lee Hwa‐Jeong , Kim Bang‐Jun , Tan Loon‐Seng , Baek Jong‐Beom 
Published: October 2008

AbstractShort length vapor‐grown carbon nanofibers (VGCNFs) were functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous phentoxide medium via “direct” Friedel‐Crafts acylation reaction to afford aminobenzoyl‐functionalized VGCNFs (AF‐VGCNFs). The AF‐VGCNFs as a cocuring agent were mixed with epoxy resin by simple mechanical stirring in methanol which was added to help efficient mixing. After evaporation of methanol, 4,4′‐methylenedianiline as a curing agent was added to the mixture, which was then cured at elevated temperatures. The resultant composites displayed uniform dispersion of AF‐VGCNFs into cured epoxy matrix. During curing process, the amine functionalities on AF‐VGCNF together with 4,4′‐methylenedianiline were expected to be involved in covalent attachment to the epoxy resin. As a result, both tensile modulus and strength of the composites were improved when compared with those of pure epoxy resin. Thus, the AF‐VGCNFs play a role as an outstanding functional additive, which could resolve both dispersion and interfacial adhesion issues at the same time by functionalization of VGCNFs and covalent bonding between the additive and matrix, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7473–7482, 2008
Micelle‐to‐vesicle transition induced by oligonucleotide in SDS/DEAB mixed system with a net negative charge
Authors: Guo Xia , Li Hua , Gong Zhiyun , Zhang Fengmin , Zheng Songyun , Guo Rong 
Published: October 2008

AbstractSodium dodecyl sulfate (SDS)/dodecyl triethyl ammonium bromide (DEAB) mixed micelles (with SDS in excess) can transform to vesicles only when the temperature is higher than a critical value. In this study, we report for the first time that oligonucleotide can decrease the critical temperature to a much lower value and, hence, induce micelle‐to‐vesicle transition. The facilitation efficiency of oligonucleotide on vesicle formation is closely dependent on its size and base composition. Moreover, the SDS/DEAB/oligonucleotide vesicles are negatively charged and the hydrophobic interaction between oligonucleotide and SDS/DEAB mixed micelles is the driving force. As, so far, the report about the facilitation effect of oligonucleotide and DNA on vesicle formation is very limited, this study may provide some helpful information for the application of DNA/amphiphile system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7491–7504, 2008
Photodegradation‐induced photoluminescence behaviors of π‐conjugated polymers upon the doping of organometallic triplet emitters
Authors: Chang Jungyun , Yu Young‐Jun , Na Jung Hoon , An Jongdeok , Im Chan , Choi Dong‐Hoon , Jin Jung‐Il , Lee Seung Hee , Kim Young Kwan 
Published: October 2008

AbstractThe different effects on the photodegradation‐induced photoluminescence (PL) of π‐conjugated polymeric thin films upon the doping of Ir(III) containing triplet emitters in ambient conditions at room temperature were investigated. In this study, we prepared spin‐coated thin films using three different polymer matrices including poly(9‐vinylcarbazole) (PVK), poly[9,9‐bis(2‐ethylhexyl)fluorene‐2,7‐diyl] (PF2/6), and poly[2‐(5′‐cyano‐5′‐methyl‐hexyloxy)‐1,4‐phenylene] (CNPPP) derivatives doped with Ir(III) containing triplet emitters: Ir(III) bis[(4,6‐fluorophenyl)‐pyridinato‐N,C2′] picolinate (FIrpic), or Ir(III)fac‐tris(2‐phenylpyridine) (Ir(ppy)3), or Ir(III)bis(2‐(2′‐benzothienyl) pyridinato‐N‐acetylacetonate) (Ir(btp)2acac). Using the doped films, and their neat films, on quartz substrates, the UV‐Visible absorption (UV‐Vis) and PL spectra were recorded under continuous illumination with the excitation wavelengths at the absorption maxima of the corresponding matrix polymers. The dopant effects on the photodegradation‐induced PL were extracted from the kinetic data obtained from the doped films by subtracting the mutual degradation kinetics of their corresponding neat films. The obtained dopant effects show a strong correlation between the photo‐induced PL degradation and the exciton migration behaviors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2395–2403, 2008
Micromechanics model based on the nanostructure of PFSA membranes
Authors: Kusoglu Ahmet , Santare Michael H. , Karlsson Anette M. , Cleghorn Simon , Johnson William B. 
Published: October 2008

AbstractA micromechanics model is developed to predict Young's modulus of perfluorosulfonic acid (PFSA) membranes at various temperatures and water contents. The morphology of PFSA membranes is characterized by a two‐phase structure, where hydrophilic clusters expand to hold water molecules during swelling, whereas the hydrophobic polymer network maintains the structural stability. A representative volume element (RVE) is proposed based on the descriptions for the nanostructure of PFSA membranes available in the literature. On the basis of mechanics model, we estimate Young's modulus in tension of PFSA membranes as a function of water volume fraction for various temperatures. The results show that inclusion of water‐filled cylindrical channels connecting the spherical clusters yields significantly better prediction than considering spherical clusters alone. Comparison of these results with the existing experimental data shows good agreement over a range of temperatures. This study takes into account current understanding of the nanostructure of these materials and incorporates it into a micromechanics model that agrees well with the experimental results. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2404–2417, 2008
Synthesis and characterization of magnetoelectric polymer nanocomposites
Authors: Prabhakaran T. , Hemalatha J. 
Published: October 2008

AbstractMagnetoelectric polymer nanocomposite structures are synthesized using conducting polyaniline and nanosized BFO particles through in situ sol–gel polymerization. The effect of nanosized BFO in polyaniline matrix is studied. The SEM, XRD, VSM, FTIR, and UV–Vis studies were made to understand the morphology, crystalline structure, magnetic, and optical properties of PANI/BFO composites with various concentrations of nanofiller. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2418–2422, 2008
Structures and photoactive properties of poly(styrene‐co‐vinylbenzophenone)
Authors: Hong Kyung Hwa , Sun Gang 
Published: October 2008

AbstractPoly(styrene‐co‐vinylbenzophenone) prepared by a graft reaction on polystyrene revealed photoactive properties under irradiation of UVA. The photoactive structural features of the polymer were examined via electron paramagnetic resonance (EPR) under irradiation of UVA and fluorescent light. The photoactive functions of the polymer such as antimicrobial performance and dye decolorization ability were investigated. The results revealed that the poly(styrene‐co‐vinylbenzophenone) could generate radicals under fluorescent and UVA irradiation, and some radicals could stay alive for about 30 min in a dark chamber. The photoexcited polymer showed excellent antibacterial ability and decolorization effect on methylene blue and methyl orange dye under both daylight and UVA light. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2423–2430, 2008
From quantum dots and nanocrystals to organic systems and biomolecules: Excitons and excitonic processes on their way from fundamental research to applications. 8th International Conference on Excitonic Processes in Condensed Matter (EXCON '08), Kyoto, Japan, 22–27 June 2008
Authors: Petelenz Piotr , Schreiber Michael 
Published: October 2008

AbstractThis conference report is meant to offer a selective overview on a recently held scientific meeting rather than a comprehensive list of the conference presentations. We tried to describe what we feel were the most interesting contributions at EXCON'08. This conference maintained the focus of the EXCON series on both, experimental and theoretical topics of current research in excitonic processes in organic and inorganic condensed matter, considering also other subjects re‐ lated to excitonic processes. It provided an interdisciplinary forum for photo‐physicists, photo‐chemists and material scientists who discussed novel and new results in the field of excitons.The full Proceedings of the 8th International Conference on Excitonic Processes in Condensed Matter (EXCON'08) shall be published in phys. stat. sol. (b) and phys. stat. sol. (c) in December 2008. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of MnGeO3 polycrystalline and single‐crystal samples and comparative analysis of their magnetic properties
Authors: Sapronova N. V. , Volkov N. V. , Sablina K. A. , Petrakovskii G. A. , Bayukov O. A. , Vorotynov A. M. , Velikanov D. A. , Bovina A. F. , Vasilyev A. D. , Bondarenko G. V. 
Published: October 2008

AbstractMnGeO3 single crystals have been grown by a flux method. The obtained MnGeO3 is orthorhombic; a Pbca space group does not undergo any structural phase transitions in the range from room temperature to 900 °C. Magnetic measurements carried out for the first time on the MnGeO3 single crystal have revealed higher values (TN = 38 K and θ = –100 K) as compared to the data for polycrystalline samples reported in the literature (TN = 10 K and 14 K, θ = –54 K and –46 K). These magnetic parameters for polycrystalline samples synthesized by us are close to the literature data. A Mössbauer spectrum taken at T = 300 K for a sample containing 5% Fe257O3 shows that manganese ions, Mn2+, occupy two nonequivalent positions and iron is included in a sublattice as Fe2+ and distributed among two positions substituting Mn2+. In this study, the magnetic characteristics are shown to be sensitive even to minor impurity amounts. The MnGeO3 magnetic structure and one of possible reasons causing the effect of impurities on the MnGeO3 magnetic properties are considered in the framework of a simple indirect coupling model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of Fe4Si4–xGex (x = 0–4) compounds: ab initio calculation
Authors: Ameereh G. I. , Hamad B. A. , Khalifeh J. M. 
Published: October 2008

AbstractThe structural and electronic properties of Fe4Si4–x Gex (x = 0–4) with a cubic B20‐type structure are investigated by density functional theory using an ab initio method. The calculations are based on a plane‐wave expansion of the electronic wave functions and performed using the local density approximation. It is found that these compounds are narrow‐gap semiconductors in the non‐magnetic state. The band gap is found to decrease with increasing x, and the B20 FeSi is a small‐gap semiconductor with sharp density of states features near the top of the valence band. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrasonic study on RuSr2GdCu2O8
Authors: Li H. L. , Zhang H. , Wang W. , Xiang X. Q. , Zhang Y. Q. , Li X. G. 
Published: October 2008

AbstractThe physical properties of RuSr2GdCu2O8 have been investigated by ultrasonic measurements. The huge stiffening of the velocity and the sharp elastic energy loss peak with the asymmetric shape near 220 K both indicate a phase transformation in the sample, which is induced by the disorder to order transformation of the orientation of RuO6 octahedra. The softening of the velocity and the elastic energy loss peak near 132 K may give further evidence to the strong spin–phonon interaction in the compound, and suggest a complex interplay of spin and lattice degrees of freedom in RuSr2GdCu2O8. A velocity jump and a decrease of the elastic energy loss are observed around the onset of the superconducting transition temperature TC,onset ∼ 50 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and luminescence property of Sm‐doped ZnWO4 powders and films with wet chemical methods
Authors: He H. Y. 
Published: October 2008

AbstractSm‐doped ZnWO4 powders and films have been prepared with wet chemical methods. XRD analysis indicated that single‐phase Sm‐doped ZnWO4 were formed above a calcining temperature of 400 °C, and the particle size and intensity of XRD peak of the powders were varied with calcining schedules. SEM micrographs indicated that powders and films had uniform morphology and a grain size of about 10–150 nm, which increased with increasing calcining temperature. Compared with the ZnWO4 powders synthesized with the same method, Sm‐doped ZnWO4 powders showed obviously less crystallinity and smaller grain size and more dispersive morphology. The Sm‐doped ZnWO4 and undoped materials showed broad emissions in the blue‐green bands. The Sm‐doped ZnWO4 materials showed red emissions near 567 nm, 603 nm, and 641 nm. The intensities of the blue‐green emission and the red emission were increased with the crystallinity and the grain size of the powders. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the large temperature variation of the dielectric constant of Na0.4K0.6Br
Authors: Katsika‐Tsigourakou V. , Bekris P. 
Published: October 2008

AbstractSince polycrystals of alkali halides are highly useful as components in optical devices, a number of mixed crystals of NaBr and KBr have been recently prepared from melts by other workers. Among these crystals, it was reported that the polycrystal Na0.4K0.6Br exhibits the strongest temperature variation of the dielectric constant. Here, we show quantitatively that this is due to the temperature variation of the ionic polarizability. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emergence of optical magnetism in stratified metal–dielectric metamaterials
Authors: Iwanaga Masanobu 
Published: October 2008

AbstractOptical magnetism in stratified metal–dielectric metamaterials (SMDM) has been explored numerically. Effective permeability and permittivity in the semi‐infinite SMDM have been extracted by two‐complex reflectivity method. Huge negative permeability has been achieved and found that the real part reaches about –200 at 1.585 eV. The origin of the huge optical magnetism is ascribed to the exotic magnetic field distributions in SMDM. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneous emission rate of a single‐impurity molecule depending on a crystalline host
Authors: Rebane Inna , Koch Rein 
Published: October 2008

AbstractThe influence of the anisotropy of the host crystal on the spontaneous emission rate of the single‐impurity molecule and thus also on the radiative line width has taken into account. The anisotropy reveals itself in the dependence of the spontaneous emission rate on the orientation of the radiative transition dipole moment in the crystal. In this paper calculations of the relative spontaneous emission rate (the spontaneous emission rate divided by the spontaneous emission rate in the case when the transition dipole moment is parallel to the optical axis) of the quadrupole transition in a uniaxial host crystal are presented in the form which is convenient for experimenters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Picosecond transient absorption and excitonic luminescence at low temperature in undoped ZnO
Authors: Ucer K. Burak , Wall R. Andrew , Lipke Kyle C. , Williams R. T. 
Published: October 2008

AbstractTransient optical absorption is observed upon band‐gap excitation of undoped single‐crystal ZnO. Using 2‐photon excitation by 300 fs pulses of 410 nm light to create electron–hole pairs and an infrared continuum pulse to probe absorption, the evolution of induced absorption has been measured in the time range 2–100 ps at 17 K. Approximately 38% of the induced absorption decays with a time constant of 50 ps. Based on measurements of 50 ps lifetime for neutral donor‐bound exciton luminescence (D0X) in the same samples in our laboratory and the known dominance of D0X luminescence at low temperature in many studies of undoped ZnO, we assign the 50 ps infrared absorption to photoionization of the bound excitons. The observed spectral shape of the absorption band rises monotonically with increasing wavelength from 950 nm to 1600 nm, very similar to expectation of the shape of free‐carrier absorption. Since both the internal electron–hole binding energy and the binding of center‐of‐mass motion to the neutral donor are much less than the transition energies of 0.8–1.3 eV observed in absorption, it can be argued that the broad infrared absorption signal is a measure of the combined population of free carriers, shallow trapped carriers, and bound or free excitons. Based on this hypothesis, we deduce from the time‐dependent infrared absorption that the quantum efficiency of D0X luminescence in this sample is approximately 38%. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)