bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of lanthanum cyanurate as novel organic thermal stabilizers for polyvinyl chloride
Authors: Li Mei , Jiang Zaiyong , Liu Zhaogang , Hu Yanhong , Wang Mitang , Wang Haiou 
Published: December 2012

AbstractLanthanum cyanurate was synthesized by reacting cyanuric acid and lanthanum nitrate at basic condition and was characterized by elemental analysis and Fourier transform infrared spectroscopy. Its application as thermal stabilizer for poly(vinyl chloride) (PVC) was investigated by Congo red test and discoloration test. In comparison with other heat stabilizers, including lanthanum stearate, calcium stearate, and zinc stearate, lanthanum cyanurate exhibits high stabilizing effect with excellent initial color of PVC. The stability time reaches the maximum (80 min) when the percentage of lanthanum cyanurate in PVC is 2.5%. The combination stabilizers (LaC3N3O3/Zn(St)2 obviously increase the complete discoloration time of PVC in comparison with the stabilizer of Zn(St)2. The stability time of PVC increases from 14 min (stabilized by zinc stearate) to 26 min (stabilized by LaC3N3O3/Zn(St)2). LaC3N3O3 also shows a slightly stronger effect on tensile strength of PVC than La(St)3. Therefore, the LaC3N3O3 can be used to replace La(St)3 and serve as a costabilizer to improve stabilization efficiency of calcium/zinc stabilizers for PVC. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Plastisol foaming process. Decomposition of the foaming agent, polymer behavior in the corresponding temperature range and resulting foam properties
Authors: Verdu J. , Zoller A. , Marcilla A. 
Published: December 2012

AbstractThe decomposition of azodicarbonamide, used as foaming agent in PVC—plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min−1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g−1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol−1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Synthesis, swelling capacity, and texture of polymers from monomers of sulfonic acid and acrylamide
Authors: Rosa Fátima , Bordado João , Casquilho Miguel 
Published: December 2012

AbstractThe monomers 2‐acrylamido‐2‐methyl‐propanosulfonic acid and acrylamide, and methyleno‐bisacrylamide (BA) whenever a crosslinker was added, were selected for the synthesis of superabsorbent polymers. Texture was observed by scanning electronic microscopy, and specific gravity and swelling were measured. The influence of synthesis conditions—polymerization technique, reaction medium pH, and BA addition—on the texture of the synthesized polymer and its influence on polymer characteristics were assessed. The tests showed that the pores' sizes and distribution in the polymer depend on the polymerization conditions. Swelling rate of the polymers, namely from inverse emulsion technique, with BA and at pH 9, is remarkably high, suiting applications. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Mixed monolayers of pmas with poly(styrene‐b‐methyl methacrylate) at the air/water interface
Authors: Su Hsin‐Kai , Hsu Wen‐Ping 
Published: December 2012

AbstractPoly(methyl methacrylate) (PMMA) is known to be immiscible with poly(styrene) (PS) in the bulk state. Poly(ethyl methacrylate) (PEMA), poly(propyl methacrylate) (PPMA), and poly(n‐butyl methacrylate) (PBMA) are also known to be immiscible with PMMA (or PS). Therefore, PMAs (PMMA, PEMA, PPMA, and PBMA) are predicted by the mean field theory to be immiscible with poly(styrene‐b‐methyl methacrylate) (PS‐b‐PMMA) in the bulk state. However, the miscibility of PMAs with PS‐b‐PMMA may be different in the two‐dimensional state. Therefore, the mixed monolayer behavior of PMAs and PS‐b‐PMMA was investigated from the measurements of surface pressure‐area per molecule (π‐A) isotherms at three different temperatures (10°C, 25°C, and 40°C). Calculation of compressibility from isotherms provided the inflection data from maximum and minimum peaks. The miscibility and nonideality of the mixed monolayers were examined by calculating the excess area as a function of composition. Mostly, negative deviations from ideality were observed in the mixed monolayers. This is likely because of favorable interaction between PMMA and PMAs in the monolayer state. The positive deviations occurred at 40°C with PBMA at a high surface pressure. Therefore, with confinement in the two‐dimensional state, the miscibility between PMAs and PS‐b‐PMMA was greatly improved in comparison with the bulk state. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Efficient zinc initiators supported by NNO‐tridentate ketiminate ligands for cyclic esters polymerization
Authors: Chuang Hui‐Ju , Chen Hsiao‐Li , Huang Bor‐Hunn , Tsai Tsung‐En , Huang Pei‐Ling , Liao Tzu‐Ting , Lin Chu‐Chieh 
Published: December 2012

AbstractA series of zinc benzylalkoxide complexes, [LnZn(μ‐OBn)]2 (L = L1H–L5H), supported by NNO‐tridentate ketiminate ligands with various electron withdrawing‐donating subsituents have been synthesized and characterized. X‐ray crystal structural studies revealed that complexes 2b and 4b are dinuclear bridging through the benzylalkoxy oxygen atoms with penta‐coordinated metal centers. All the metal complexes have acted as efficient initiators for the ring‐opening polymerization of L‐lactide (within 12 min, 0 °C). Remarkably, a molecular weight of PLLA up to 580,000 can be achieved using [(L5Zn(μ‐OBn)]2 (5b) as an initiator. The kinetic studies for the polymerization of L‐lactide with complex 3b at −10 °C corresponded to first‐order reactions in the monomer. The ring‐opening polymerization (ROP) of ε‐caprolactone, ε‐decalactone, β‐butyrolactone and their copolymer with complex 3b was investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Formation of linear and cyclic polyoxetanes in the cationic ring‐opening polymerization of 3‐allyloxymethyl‐3‐ethyloxetane and subsequent postpolymerization modification of poly(3‐allyloxymethyl‐3‐ethyloxetane)
Authors: Schulte Bjoern , Dannenberg Carl A. , Keul Helmut , Möller Martin 
Published: December 2012

AbstractThe synthesis of 3‐allyloxymethyl‐3‐ethyloxetane (AllylEHO) and its polymerization with BF3 × Et2O is described in this study. Size exclusion chromatography (SEC) and membrane osmometry are used for the determination of molecular weights of the obtained products, ranging from Mn,SEC = 41,500‐131,500 g/mol. 1H NMR spectroscopy, SEC, as well as MALDI‐TOF MS reveal the formation of cyclic tetramer beside low, but detectable concentrations of larger cyclic oligomers as by‐products during the polymerization process. These results help to understand mechanistically why attempts for a controlled homopolymerization of AllylEHO fail and why a controlled homopolymerization of oxetanes has not been described so far in the literature. Additionally, the high versatility of allyl‐functional polyoxetane for postpolymerization modification is proven by thiol–ene reactions with 3‐mercaptopropionic acid and N‐acetyl‐L‐cysteine methyl ester. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
H‐transfer reaction during decomposition of N‐(2‐methylpropyl)‐ N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines
Authors: Edeleva Mariya , Marque Sylvain R. A. , Kabytaev Kuanish , Guillaneuf Yohann , Gigmes Didier , Bagryanskaya Elena 
Published: December 2012

AbstractThermal decomposition of four tertiary N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines (SG1‐C(Me)2‐C(O)‐OR, R = Me, tBu, Et, H) has been studied at different experimental conditions using 1H and 31P NMR spectroscopies. This experiment represents the initiating step of methyl methacrylate polymerization. It has been shown that H‐transfer reaction occurs during the decomposition of three alkoxyamines in highly degassed solution, whereas no products of H‐transfer are detected during decomposition of SG1‐MAMA alkoxyamine. The value of the rate constant of H‐transfer for alkoxyamines 1 (SG1‐C(Me)2‐C(O)‐OMe) and 2 (SG1‐C(Me)2‐C(O)‐OtBu) has been estimated as 1.7 × 103 M−1s−1. The high influence of oxygen on decomposition mechanism is found. In particular, in poorly degassed solutions, nearly quantitative formation of oxidation product has been observed, whereas at residual pressure of 10−5 mbar, the main products originate from H‐atom transfer reaction. The acidity of the reaction medium affects the decomposition mechanism suppressing the H‐atom transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Ionic networks derived from the protonation of dendritic amines with carboxylic acid end‐functionalized PEGs
Authors: González Lidia , Ladegaard Skov Anne , Hvilsted Søren 
Published: December 2012

AbstractThe synthesis and characterization of novel ionic networks linked by the ammonium salts of poly(propylene imine) (PPI) dendrimers of the first (PPI G1) and second (PPI G2) generation and two short bis carboxymethyl ether terminated poly(ethylene glycol)s (DiCOOH‐PEG) with different molecular weights (Mn ∼ 250 and Mn ∼ 600) are reported. Likewise, an ionic network based on PPI G1 and a long αω‐dicarboxylic acid functionalized PEG (Mn ∼ 4800) were evaluated. Simpler ionic structures based on tris(2‐aminoethyl)amine or hexamethylene diamine and the short DiCOOH‐PEGs are also investigated. The ionic structures formed were confirmed by differential scanning calorimetry, Fourier Transform Infrared spectroscopy in the attenuated‐total‐reflection mode, and 1H‐13C NMR spectroscopy. A comprehensive 1H NMR analysis revealed that only the primary amines of the PPI G1 dendrimer residing at the periphery take part in the ionic network formation. In the case of PPI G2, the picture is less clear. A thorough investigation of the thermal degradation of the utilized precursors and all the ionic materials prepared was additionally performed by thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Thermosensitive water‐soluble poly(ethylene glycol)‐based polythiophene graft copolymers
Authors: Das Sandip , Samanta Sanjoy , Chatterjee Dhruba P. , Nandi Arun K. 
Published: December 2012

AbstractDiethyleneglycol methylethermethacrylate(MeO2MA) and oligoethylene glycol methylethermethacrylate(OEGMA) are polymerized on polythiophene(PT) backbone to produce water‐soluble PT‐g‐PMeO2MA(PTD) and PT‐g‐P(MeO2MA‐co‐OEGMA)(PTDO) using atom transfer radical polymerization. They are characterized by 1H NMR and GPC techniques. TEM micrographs indicate that PT‐chains self‐organize as nanospheres, and atomic force micrographs suggest that aggregated PT‐chains are present at the centre surrounded by dispersed PMeO2MA fibers producing miceller‐type aggregates. Dynamic light scattering study indicates an initial decrease followed by sharp increase of Z‐average particle size of PTD with temperature for attaining lower critical solution temperature (LCST) at 20 °C. The LCST increases with OEGMA concentration in PTDO. The temperature dependent PL emission of PTD shows a minimum at 19 °C, followed by a sharp increase till 21 °C, and in the cooling cycle, it shows a complete reversibility. In the PTDO copolymers, the PL intensity shows the hike at progressively higher temperatures due to the increase of LCST with increasing OEGMA concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Feeding‐Gas Effects of Plasma Jets on Escherichia coli in Physiological Solutions
Authors: Baik Ku Youn , Kim Yong Hee , Ryu Young Hyo , Kwon Hye Seon , Park Gyungsoon , Uhm Han S. , Choi Eun H. 
Published: December 2012

AbstractThe effects of air and N2 plasma jets on Escherichia coli inside four different physiological solutions and deionized water are reported here. The feeding gases are found to influence the plasma compositions, the interactions with the liquids, and the subsequent bactericidal effects depending on the aqueous solutions to which they are exposed. Air plasma enhances the bactericidal effects of deionized water and saline by acidification. On the other hand, N2 plasma induces higher toxicity in phosphate buffered saline by generating more electrons. Little bactericidal effects of cell culture media and blood plasma may be due to the slight change in the pH and due to electron scavenging by organic components. Taken together, our study provides additional insight into the basic interactions between plasma and cells in physiological solutions. magnified image
Chemical and Physical Sputtering of Polyethylene Terephthalate (PET)
Authors: Große‐Kreul Simon , Corbella Carles , von Keudell Achim 
Published: December 2012

AbstractThe polymer polyethylene terephthalate (PET) has been exposed to quantified beams of argon ions and oxygen atoms and molecules. The etch rate (ER) and the surface composition of PET thin films have been analyzed by real time in situ Fourier transform infrared spectroscopy (FTIR). After the onset of the exposure of PET to the ion beam, the ER decreases rapidly by one order of magnitude irrespective of the ion energy. This slowing down of the ER is caused by cross‐linking of the polymer surface. The steady state etch yields are generally orders of magnitude higher than predicted by computer calculations. The addition of oxygen to the particle flux is only changing the surface composition. At low ion energies, chemical sputtering dominates causing very high sputter yields. In addition, no threshold ion energy is observed. magnified image
Antimicrobial Activity and Cyto‐Compatibility of Plasma Polymerized Zinc Acetylacetonate Thin Films
Authors: Malzahn Kerstin , Duque Luis , Ciernak Peter , Wiesenmüller Steffi , Bender Katja , Förch Renate 
Published: December 2012

AbstractPlasma polymerized thin films deposited from zinc acetylacetonate in a low pressure RF capacitively coupled plasma reactor have been studied to correlate the zinc content to the metal ion release properties, antimicrobial activity and cytocompatibility. Zinc content and zinc release properties were studied using inductively coupled plasma optical emission spectroscopy (ICP‐OES) and results were correlated to those from different standard methods of surface analysis. The coatings were shown to act as a zinc reservoir, allowing for a fast release of zinc within a few hours of being in contact with aqueous solution. For all films studied a log 106 reduction in the growth of Staphylococcus aureus was observed. The results show the films to be cyto‐compatible towards NIH 3T3 mammalian cells up to a zinc content of about 5 µg/cm2. magnified image
Optical properties of Eu‐doped NaYP2O7 under UV and X‐ray excitation
Authors: Novais Suellen Maria Valeriano , Macedo Zélia Soares 
Published: December 2012

AbstractEu‐doped NaYP2O7 polycrystalline samples were produced via sol‐gel method based on PVA. Structural investigation of calcined powders was made by X‐ray diffraction analysis. High crystalline purity was achieved when using molar ratio Na:Y:P of 1.15:1:2 and the presence of dopant caused no noticeable change on the structure. The influence of secondary phases on the optical properties of NaY0.99Eu0.01P2O7 was investigated by photoluminescence (PL) and X‐ray excited optical luminescence (XEOL). In general, each XEOL emission spectrum was similar to that obtained from PL. The spectroscopic properties measured indicate that the dopant occupies two sites of high symmetry on the host matrix and that the spurious phases significantly affect the luminescence yield. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural evolution of AlN buffer and crystal quality of GaN films on a‐ and c‐sapphire grown by metalorganic vapor phase epitaxy
Authors: Okuno Koji , Oshio Takahide , Shibata Naoki , Honda Yoshio , Yamaguchi Masahito , Tanaka Shigeyasu , Amano Hiroshi 
Published: December 2012

AbstractLow‐temperature‐deposited (LT‐) AlN layers and the initial growth of GaN on a‐ and c‐sapphire have been investigated and compared. The as‐deposited LT‐AlN layers on both a‐ and c‐sapphire are composed of high‐density islands. By annealing, the islands become large. The density of islands on a‐ and c‐sapphire are 5.6 × 1010 and 7.9 × 1010 cm‐2, respectively, indicating that the evolution of the solid phase epitaxy of AlN islands induced by annealing is different on a‐ and c‐sapphire. The moiré spacings obtained by plan‐view electron microscopy reveal that the strain of the AlN islands on a‐sapphire is larger than that of islands on c‐sapphire. These results imply that development of the solid phase epitaxy is influenced by the strain. The coalescence of GaN islands grown on a‐sapphire, which has larger AlN islands, is advanced compared with that of islands on c‐sapphire. The relationship between the annealed AlN island density and the threading dislocation (TD) density in the GaN films is investigated on a‐ and c‐sapphire. The TD density of the GaN films is small when the density of annealed AlN islands is low. These results indicate that decreasing the island density of the annealed AlN layers is essential for improving the crystalline quality of GaN films. It is therefore important to control the solid phase epitaxy of LT‐AlN layers by annealing. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of extended defects in the transformation of InGaN/GaN multiple quantum well structure optical properties under low energy electron beam irradiation
Authors: Vergeles P. S. , Shmidt N. M. , Yakimov E. B. 
Published: December 2012

AbstractIt is shown that threading extended defects can enhance the excess carrier transport through the InGaN/GaN multiple quantum well (MQW) region. The enhanced excess carrier transport through a GaN film is also revealed that was explained by a carrier transport along extended defects. A possible role of threading extended defects in the low energy electron beam irradiation induced modification of electrical and optical properties in InGaN/GaN MQW structures are discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN photodetectors for the UV‐C spectral region on planar and epitaxial laterally overgrown AlN/sapphire templates
Authors: Knigge A. , Brendel M. , Brunner F. , Einfeldt S. , Knauer A. , Kueller V. , Weyers M. 
Published: December 2012

AbstractWe present Schottky type metal semiconductor metal (MSM) AlGaN photodetectors (PDs) suited for the ultraviolet C (UV‐C) spectral region grown on conventional planar AlN templates in comparison with epitaxial laterally overgrown (ELO) AlN templates. On planar templates solar blind MSM PDs with state‐of‐the‐art dark current in the pA range and a power independent responsivity are obtained. Using ELO templates with sapphire substrates tilted to the m direction the defect density in the absorber material is reduced compared to that for planar templates. The MSM PDs on this ELO templates exhibit photoconductive gain leading to external quantum efficiencies of up to 77 at 30 V applied bias surpassing that of the planar grown PDs by a factor of 100. In spite of the high gain these PDs also show low dark currents in the pA range up to 100 V applied bias, short switching times and two operating regimes with power independent responsivity. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and optical properties of bulk GaN substrates studied by Kelvin probe and photoluminescence
Authors: McNamara J. D. , Foussekis M. A. , Baski A. A. , Li X. , Avrutin V. , Morkoç H. , Leach J. H. , Paskova T. , Udwary K. , Preble E. , Reshchikov M. A. 
Published: December 2012

AbstractWe have investigated the N‐ and Ga‐polar faces of bulk GaN substrates with photoluminescence (PL) and the surface photovoltage (SPV) technique using a Kelvin probe attached to an optical cryostat. Experiments were conducted in vacuum. Some of the surfaces were mechanically polished (MP), while others were epi‐ready after a chemical‐mechanical polish (CMP). From the SPV measurements, the band bending in a sample having both surfaces treated with the CMP method was calculated to be about 0.83 and 0.70 eV for the Ga‐ and N‐polar surfaces, respectively. The restoration of the SPV after ceasing the UV illumination showed that the SPV from CMP‐treated surfaces behaved as predicted by a thermionic model, whereas the SPV from MP‐treated surfaces restored with a much faster‐than‐predicted rate. This result can be interpreted by the hopping of charge carriers in the highly‐defective near‐surface layer of the MP‐treated samples. Remarkably, removing the top 700 nm defective layer by dry etching restored the quality of the electrical and optical properties of GaN. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructure of Mg doped GaNAs alloys
Authors: Liliental‐Weber Z. , Reis R. dos , Novikov S. V. , Yu K. M. , Levander A. X. , Dubon O. D. , Wu J. , Walukiewicz W. , Foxon C. T. 
Published: December 2012

AbstractTransmission Electron Microscopy of Mg doped GaN1‐xAsx samples, grown by MBE at low temperatures, show substantial structural changes for samples that are semi‐insulating and those with high or low conductivity. The conductive samples show p‐type conductivity as evidence from the positive thermopower values. All the Mg doped samples show phase segregation: cubic GaAs and GaN grains (a mixture of cubic and some hexagonal) phases within an amorphous matrix. The best conductive samples show cubic GaAs grains with high density of stacking faults embedded into an amorphous matrix. The samples that are less conductive have lower ratio of the amorphous to the crystalline phase of the samples and much lower density of stacking faults. Higher Mg concentration is expected in the amorphous parts of the samples The semi‐insulating samples that have either low Mg concentration or low As show grains of GaAs and GaN attached to each other with no evidence of the amorphous phase between them. There are no SFs in these grains. It is possible that the presence of the GaN between the GaAs grains lead to semi‐insulating material properties since p‐type doping of GaN is more difficult. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suppression of twin formation for the growth of InN(10‐1‐3) on GaAs(110) by metalorganic vapor phase epitaxy
Authors: Murakami Hisashi , Takenaka Sae , Hotta Tetsuro , Kumagai Yoshinao , Koukitu Akinori 
Published: December 2012

AbstractThe influence of hydrogen (H2) in the carrier gas on the crystalline quality as well as twin‐crystal formation were investigated in the metalorganic vapor phase epitaxy (MOVPE) of InN on GaAs(110). The inclusion of twin crystals of InN(10‐13) was suppressed by the introduction of a small amount of H2 during crystal growth. The surface morphology of the InN layer was also significantly influenced by the input partial pressure of H2 in the carrier gas. The suppression of twin‐crystal formation and improvements in the surface morphology can be explained by the differences in the stability of the In‐ and N‐polar InN{0001} asymmetric planes in the presence of H2. Both electronic and optical properties were improved by the introduction of H2, which was probably due to the reduction of impurities such as oxygen and carbon in the InN grown layer. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)