bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperbranched polyethyleneimine architecture onto poly(allylamine) by simple synthetic approach and the chelating characters
Authors: Kuo Ping‐Lin , Ghosh Swapan K. , Liang Wuu‐Jyh , Hsieh Yun‐Tsung 
Published: August 2002

AbstractIn resemblance to the ethoxylation of alkylamine or polymeric amines to introduce the nonionic hydrophiles by incorporation of ethylene oxide groups to make surfactants, ethyleneimine (EI) groups were introduced into poly(allylamine) by a simple in situ reaction of this polymer with 2‐chloroethylamine hydrochloride. The resultant polymers were allylic and chain‐pendant with hyperbranched polyethyleneimine. The EI number (n) of the polymers was determined by 1H NMR. The percentages of primary, secondary, and tertiary amine present were estimated by potentiometric titration. The chelating abilities of the polymers that were applied growth conditions once (G1, n ≈ 2) and twice (G2, n ≈ 6) were also examined by potentiometric titration and ultraviolet–visible spectoscopy in the presence of metal ions (Cu+2). Continuous‐variation analysis revealed that each repeat unit of G1 and G2 behaves as a multident chelate and forms a stable complex with Cu+2 ions utilizing an average of three EI dents per ion. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3018–3023, 2001
Microemulsion polymerization of acrylamide and styrene: Effect of the structures of reaction media
Authors: Hao Jingcheng 
Published: August 2002

AbstractIsothermal phase diagrams of the system cetyltrimethylammonium bromide (CTAB)/n‐butanol/n‐octane/water were constructed, and the effect of the oil (n‐octane) contents on the microemulsions was studied at 40 °C. We determined the microemulsion structures of two systems, CTAB/n‐butanol/10% n‐octane/water and sodium dodecyl sulfonate (As)/n‐butanol/20% styrene/water, by conductivity measurements to investigate the polymerization of acrylamide and styrene in the two microemulsion systems. The polymerization kinetics of the water‐soluble monomer acrylamide in CTAB micelles and the different CTAB/n‐butanol/10% n‐octane/water microemulsion media [water‐in‐oil (W/O), bicontinuous (BC), and oil‐in‐water (O/W)] were studied with water‐soluble sodium bisulfite as the initiator. The maximum polymerization rate in CTAB micelles was found at the second critical micelle concentration. A mechanism of polyacrylamide formation and growth was proposed. A connection between the structures of the microemulsions and the polymerization rates was observed; the maximum polymerization rate occurred at two transition points, from W/O to BC and from BC to O/W, and the polyacrylamide molecular weights, which depended on the structures of the microemulsions, were also found. A square‐root dependence of the polymerization rates on the initiator concentrations was obtained in CTAB micelles and O/W microemulsion media. The polymerization of the oil‐soluble monomer styrene in different As/n‐butanol/20% styrene/water microemulsion media (W/O, BC, and O/W) was also investigated with different initiators: water‐soluble potassium persulfate and oil‐soluble azobisisobutyronitrile. A similar connection between the structures of the microemulsions and the conversions of styrene in CTAB/n‐butanol/10% n‐octane/water for the polymerization of acrylamide was observed again. The structures of the microemulsions had an important role in the molecular weights and sizes of polystyrene. The polystyrene particles were 10–20 nm in diameter in BC microemulsion media and 30–60 nm in diameter in O/W microemulsion media according to transmission electron microscopy. We determined the solubilization site of styrene in O/W microemulsion drops by 1H NMR spectra to analyze the results of the microemulsion polymerization of styrene. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3320–3334, 2001
Relationship of deformation behavior to thermal transitions of ethylene/styrene and ethylene/octene copolymers
Authors: Chang A. , Cheung Y. W. , Hiltner A. , Baer E. 
Published: August 2002

AbstractThe stress‐strain response of low‐crystallinity ethylene‐octene (EO) and ethylene‐styrene (ES) copolymers with 7–20 mol % comonomer was compared over a temperature range that spanned the glass‐transition and crystal melting regions. Above the onset temperature of the glass transition, the copolymers exhibited elastomeric behavior with low initial modulus, uniform deformation to high strains, and high recovery after the stress was released. In the glass‐transition range, an initial low‐stress elastomeric response was followed by a distinct “bump” in the stress‐strain curve. On the basis of the temperature and rate dependence of the stress‐strain curve, local strain‐rate measurements, local temperature changes, and recovery characteristics, the “bump” was identified as high strain yielding. Hence, the stress‐strain curve sequentially exhibited the features of elastomeric and plastic deformation. Following high strain yielding, strain hardening dramatically increased the fracture strength. This behavior was defined as elastomeric‐plastic. Elastomeric‐plastic behavior in the broad glass‐transition range constituted a gradual transition from elastomeric behavior at higher temperatures to low‐temperature plastic behavior with high modulus and macroscopic necking. Because of the lower glass‐transition temperature of EO, −40 °C as compared with −10 °C for ES, the onset of elastomeric‐plastic behavior occurred at a significantly lower temperature. The concept of a network of flexible chains with fringed micellar crystals serving as the multifunctional junctions that provides the structural basis for elastomeric behavior of low‐crystallinity ethylene copolymers was extended to elastomeric‐plastic behavior by considering a network with a fraction of rigid, glassy chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 142–152, 2002
Effect of coagulation conditions on the microfibrillar network of a rigid polymer
Authors: Tsabba Yizhak , Rein Dmitry M. , Cohen Yachin 
Published: August 2002

AbstractAn important element in the microstructure of high performance fibers and films fabricated from rigid polymers is an interconnected network of oriented microfibrils, the lateral size of which is about 10 nm. This study is an attempt to elucidate the mechanism by which the microfibrils are formed so that larger lateral dimensions can be achieved by suitable processing. Because this morphology emerges in the coagulation stage of the spinning process, we compared the microfibrillar network formed by drastically different coagulation conditions. Ribbons, spun from solution of poly(p‐phenylene benzobisthiazole) in polyphosphoric acid through a slit die, were coagulated either in the ordinary rapid process with water (timescale of seconds) or in a slow process with phosphoric acid (timescale of hours). The coagulated microfibrillar network was dried with supercritical CO2 for X‐ray scattering measurements and impregnated with epoxy resin for sectioning and imaging by TEM. Slow coagulation yields better‐aligned microfibrils of enhanced chain packing, but the lateral size of the microfibrils formed in both cases is similar, about 10 nm. Heat treatment increases the width of water‐coagulated microfibrils but not the acid‐coagulated ones. The observations do not support spinodal decomposition as the mechanism of microfibril formation during coagulation, as was previously suggested. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1087–1094, 2002
Molecular composites made of ionic poly(p‐phenylene terephthalamide) and poly(4‐vinylpyridine): Relaxation behavior
Authors: Chen W. C. , Sauer J. A. , Hara M. 
Published: August 2002

AbstractMolecular composites were prepared from several types of ionically modified, poly(p‐phenylene terephthalamide) (PPTA) dispersed in a poly(4‐vinylpyridine) matrix. Optical clarity tests indicated that the component polymers of the composite were miscible, at least at low concentrations of the rodlike reinforcement. In composites containing ionic PPTA, where ionic sulfonate groups were attached as side groups either to PPTA chains or to PPTA anion chains, the glass‐transition temperature (Tg) was increased by l0 °C or more, at 5 wt % reinforcement. At concentrations of 10–15 wt % of the ionic polymer, Tg values leveled off or decreased slightly. This suggested that some aggregation of the rigid‐rod molecules occurred. In composites containing ionic PPTA, where the ionic sulfonate groups were directly attached to the phenylene rings of PPTA chains, not only was Tg shifted significantly to higher temperatures, but the rubbery plateau modulus retained high values up to temperatures of 250 °C or above. Observed effects were considered to be the result of strong ionic interactions between the ionic reinforcement polymer and the polar matrix polymer. The possible effects of the counterion on Tg and the storage modulus are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1110–1117, 2002
ESR studies in γ‐irradiated and PS‐radiation‐grafted poly(vinylidene fluoride)
Authors: Aymes‐Chodur C. , Esnouf S. , Le Moël A. 
Published: August 2002

AbstractThe fluoropolymer poly(vinylidene fluoride) was irradiated with γ rays to induce a polystyrene (PS) radiation grafting via an indirect method. Electron spin resonance and Fourier transform infrared studies were performed to identify the species that initiated the PS grafting. Specific experiments were performed to prove separately the importance of each kind of radical. A localization of the radicals in this irradiated polymer is proposed, and a kinetic model of the grafting is given. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1437–1448, 2001
Polytetrahydrofuran amphiphilic networks. IV. Swelling behavior of poly(acrylic acid)‐l‐polytetrahydrofuran and poly(methacrylic acid)‐l‐polytetrahydrofuran networks
Authors: Guan Ying , Jiang Weiwen , Zhang Wenchuan , Wan Guoxiang , Peng Yuxing 
Published: August 2002

AbstractPoly(acrylic acid)‐l‐polytetrahydrofuran (PAA‐l‐PTHF) and poly(methacrylic acid)‐l‐polytetrahydrofuran (PMAA‐l‐PTHF) networks were synthesized by the free‐radical copolymerization of hydrophobic polytetrahydrofuran diacrylates with hydrophilic acrylic acid and methacrylic acid. Their swelling behavior was studied. Both PAA‐l‐PTHF and PMAA‐l‐PTHF networks had four solubility parameters, which indicated that they exhibited not only the properties of both hydrophobic and hydrophilic segments but also the combined properties of these two segments. The swell of these two series of networks was composition‐dependent in organic solvents and water. The relationship between the equilibrium swelling ratio (SRe) in nonpolar solvents and the composition of the networks [the weight fraction of the PTHF segment (PTHF%)] may be expressed with a linear equation: SRe = A × PTHF% + B. A and B are parameters that relate to the interaction of hydrophilic and hydrophobic segments with nonpolar solvents and to the properties of the networks, respectively. Because of the presence of a COOH group, these two network series were pH‐sensitive when the content of hydrophilic segments was higher. The pH sensitivity of networks could be controlled not only by the composition of the networks but also by the hydrophobic degree of the hydrophilic segments. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1784–1790, 2001
Characterization of polyolefin melts using the polymer reference interaction site model integral equation theory with a single‐site united atom model
Authors: Freischmidt Helen M. , Shanks Robert A. , Moad Graeme , Uhlherr Alfred 
Published: August 2002

AbstractA general approach, based on the polymer reference interaction site model (PRISM) integral equation theory, suitable for characterizing arbitrarily complex polyolefin melts is described. We tested the method by calculating the melt structures of linear polyethylene (PE) and isotactic polypropylene (iPP) and the spinodal decomposition temperatures for PE/iPP blends. The computational expense of the PRISM calculation was reduced with a single‐site united atom model in which the polyolefin CH, CH2, and CH3 groups were approximated as chemically equivalent sites with spherically symmetric energetic interactions. The site–site interactions were defined by a potential function comprising a hard core with an attractive Lennard–Jones term. These energetic parameters were optimized with a central composite design strategy that enabled a simultaneous fit of experimental melt density and structure factor data. Values were obtained for PE and iPP individually and for common universal parameters that could potentially be used for all polyolefins. The rotational isomeric state–metropolis Monte Carlo (RMMC) technique was used to generate sets of conformers at specified temperatures covering the melt‐temperature range of the polymers. The characteristic ratio was used to assess the quality of the conformers and the RMMC method. Values of 9.68 for PE and 9.27 for iPP were obtained. The single‐chain structure factors calculated by the RMMC method were used to calculate the total structure factor for each melt. These were validated against published X‐ray diffraction results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1803–1814, 2001
Phase behavior of ternary poly‐(2‐vinylpyridine)/poly‐(N‐vinyl‐2‐pyrrolidone)/bis‐(4‐hydroxyphenyl)methane blends
Authors: Li Xue‐Dong , Goh S. H. 
Published: August 2002

AbstractThe phase behavior of ternary poly‐(2‐vinylpyridine) (P2VPy)/poly‐(N‐vinyl‐2‐pyrrolidone) (PVP)/bis‐(4‐hydroxyphenyl)methane (BHPM) blends was studied. Fourier transform infrared spectroscopic examinations demonstrated that BHPM interacts with P2VPy and PVP through hydrogen‐bonding interactions. The addition of a sufficiently large amount of BHPM transformed an opaque blend with two glass‐transition temperatures (Tg's) to a transparent single‐Tg blend. Scanning electron microscopic studies showed that the transparent single‐Tg blend is micro‐phase‐separated at a scale of about 30 nm. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1815–1823, 2001
Oxygen‐barrier properties of polyethylene terephthalate modified with a small amount of aromatic comonomer
Authors: Polyakova A. , Connor D. M. , Collard D. M. , Schiraldi D. A. , Hiltner A. , Baer E. 
Published: August 2002

AbstractThe oxygen‐barrier properties of amorphous copolyesters based on ethylene terephthalate with 10%, or less, of an acid comonomer were examined. Comonomer units were isophthalate, phthalate, 1,5‐naphthalate, 1,8‐naphthalate, 2,6‐naphthalate, 1,8‐anthracenate, 2,6‐anthracenate, and 2,7‐pyrenate. Even 2.5 mol % comonomer significantly affected the permeability. Linear comonomers decreased the permeability. In contrast, small amounts of a kinked comonomer increased the permeability. However, increasing the amount of kinked comonomer further (gradually) decreased permeability P below that of polyethylene terephthalate. Generally, comonomer affected solubility S less than diffusivity D; therefore, changes in P reflected primarily changes in D. The solubility and diffusivity depended on copolymer composition in accordance with static and dynamic free‐volume concepts of gas permeability in glassy polymers. The solubility correlated with the amount of free volume, as determined by the glass‐transition temperature. This study also explored the relationship of dynamic free volume, which determines D, to thermally accessible segmental motions of the polymer chain. The effect of comonomer on D correlated with the intensity of the gauche component of the subambient γ relaxation. Changes in the fraction of gauche‐glycol conformations resulting from copolymerization were confirmed by Fourier transform infrared spectroscopy. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1900–1910, 2001
Small‐angle x‐ray scattering study of thermoreversible poly(vinyl chloride) gels
Authors: Seki Motohiro , Yamamoto Satoru , Aoki Yuji , Takagi Katsuhiro , Izumi Yoshinobu , Nojima Shuichi 
Published: August 2002

AbstractPoly(vinyl chloride) (PVC)/bis(2‐ethylhexyl)phthalate (DOP) gels were prepared at room temperature from tetrahydrofuran solutions of PVC and DOP. PVC/DOP gels of different molecular weights at various PVC concentrations (c) were investigated with small‐angle X‐ray scattering (SAXS). The mean distance between two neighboring inhomogeneities (D) and two characteristic lengths, the intrainhomogeneity distance (d1) and interinhomogeneity distance (d2), were evaluated from Bragg's law and the distance distribution function, respectively. Both D and d2 can be expressed by a power‐law relation (e.g., D and d2 ∝ c−0.5). After a period of rapid cooling to 25 °C from the sol state, the structural evolution was examined with time‐resolved SAXS measurements. An Avrami analysis with the SAXS invariant data revealed that the growth kinetics of PVC/DOP gels was one‐dimensional growth from predetermined nuclei, regardless of c. These results suggest that the PVC/DOP gels are constructed from a fibrillar structure that forms gel structures at high concentrations or low temperatures. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2340–2350, 2001
Crystallization kinetics for low‐ether‐content polyether–polyester block copolymers with amide linkages
Authors: Ho Rong‐Ming , Hseih Ping‐Yen , Yang Ching‐Cheng , Lin Jiang‐Jen 
Published: August 2002

AbstractA series of low‐ether‐content polyether–polyester block copolymers with amide linkages were synthesized. Their crystallization kinetics and mechanisms were investigated. The crystallization kinetics were analyzed via Avrami treatment; an average value of 1.8 for the Avrami index was thus obtained. Athermal nucleation was evidenced by observations of a linear boundary between impinged spherulites under polarized light microscopy and transmission electron microscopy. The development of spherulitic morphology with a hedgehog texture was attributed to the mechanism of lamellar branching. On the basis of the morphological observations and Avrami analysis, a crystallization mechanism through a heterogeneous nucleation process with homogeneous lamellar branching was proposed. No regime transition was found for polyether–polyesters in the examined temperature ranges, and the crystallization was identified as regime I kinetics on the basis of a Lauritzen Z test. The copolymerization of poly(ether amide)s with polyesters led to a significant suppression of the crystallization rate of polyester crystals. The suppression was explained as the result of a dilution effect in nucleation combined with an increasing nucleation barrier. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2469–2480, 2001
Some morphometric measurements on ploughing blocks in the McGregor Mountains, Canadian Rockies
Authors: Hall K. , Boelhouwers J. , Driscoll K. 
Published: August 2002

AbstractMorphology and site characteristics are described for ploughing blocks in a sub‐alpine zone of the Canadian Rockies. The ploughing block features (blocks, troughs, levees, etc.) are generally larger than those described for other parts of the world. Good correlations were found between block size and both depression size and mound height. A number of ancillary observations and measurements suggest active block movement in the study area. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉLa morphologie et les caractéristiques des sites où se trouvent des blocs labourant sont décrites dans une zone sub‐alpine des Rocheuses canadiennes. Les caractéristiques de ces blocs labourant (taille des blocs, importance des sillons, levées, etc.) sont généralement plus grandes que celles décrites dans d'autres régions du monde. De bonnes corrélations sont trouvées entre la taille des blocs et, à la fois, la dimension des sillons et la hauteur des levées. De nombreuses observations accessoires et des mesures suggèrent que des mouvements de blocs se produisent actuellement dans le secteur étudié. Copyright © 2001 John Wiley & Sons, Ltd.
Location of permafrost in marginal regions: Corral del Veleta, Sierra Nevada, Spain
Authors: Gómez Antonio , Palacios David , Ramos Miguel , Tanarro Luis M. , Schulte Lothar , Salvador Ferran 
Published: August 2002

AbstractThis article discusses the methodology and techniques used in observations of permafrost, which is confined to a small enclave in south‐east Spain (Corral del Veleta, Sierra Nevada, 3398 m altitude, 37°03′ N, and 3°22′ W). Several geophysical, geothermal and geomorphologic prospecting techniques were used to locate the permafrost at Corral del Veleta, an area highly sensitive to slight climatic variations, and to study its evolution under marginal conditions. The results from the application of this methodology confirm the location of Europe's southernmost permafrost remnant. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉLe présent article discute la méthodologie et les techniques utilisées pour observer le pergélisol qui se trouve dans un petit territoire du sud‐est de I'Espagne (Corral del Veleta, Sierra Nevada, 3.398 m d'altitude, 37° 03′ N, 3°22′ W). Différentes techniques de prospection géophysiques, géothermiques et géomorphologiques ont été utilisées pour localiser le pergélisol dans le site de Corral del Veleta, un endroit hautement sensible aux variations climatiques et favorables à l'étude de son évolution sous des conditions marginales. Les résultats de l'application de cette méthodologie confirment qu'il s'agit du lambeau le plus méridional de pergélisol européen. Copyright © 2001 John Wiley & Sons, Ltd.
Bronchial trifurcation in a congenital pulmonary venolobar syndrome*
Authors: de Lagausie Pascal , Van Den Abbeele T. , Elmaleh M. , Ferkadji L. , Maintenant J. , Aigrain Y. 
Published: August 2002

AbstractCongenital malformations of the tracheobronchal tree and the related arterial blood supply are a complex group of lesions in which there are abnormalities of the venous drainage and lung parenchyma. These malformations are examples of congenital pulmonary venolobar syndrome (CPVS). Tracheal trifurcation is an extremely rare anomaly associated with CPVS. We report on an unusual case of lower right extralobar sequestration connected to the trachea, plus a type I posterior laryngeal cleft, an aberrant systemic artery, and an anomalous route of the phrenic nerve. This paper discusses the place of this unusual abnormality in the spectrum of congenital bronchopulmonary vascular malformations. Pediatr Pulmonol. 2001; 31:303–305. © 2001 Wiley‐Liss, Inc.
Cystic fibrosis and down's syndrome: Not always a poor prognosis
Authors: Saglani Sejal , Bush Andrew 
Published: August 2002

AbstractA child developed a bronchiolitis‐like illness and was found to have mosaic Down's syndrome (diagnosed on karyotype) and also cystic fibrosis, diagnosed on the basis of a high sweat osmolality (247 mosmoles/kg sweat; normal, 62–137) and a homozygous delta F508 genotype. Despite two potentially life‐threatening conditions, the child is doing well at the age of 7 years, despite pancreatic insufficiency. Pediatr Pulmonol. 2001; 31:321–322. © 2001 Wiley‐Liss, Inc.