bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of ethylene oxide sequences of the acetal copolymer from trioxane and ethylene oxide
Authors: Yamasaki Naoaki , Kanaori Kenji , Masamoto Junzo 
Published: August 2002

AbstractAn NMR method for the analysis of the ethylene oxide sequence of the acetal copolymer from trioxane and ethylene oxide has not yet been established. We found three novel cyclic compounds composed of 1 mol of ethyelene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different 1H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that have one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the 1H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequence by the 1H NMR method for the copolymer from trioxane and ethylene oxide. Good agreement was observed between the 1H NMR method and the hydrolysis method for the analysis of the ethylene oxide sequences. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3239–3245, 2001
Lamellar‐level morphology induced by combined crystallization and liquid–liquid demixing in a poly(ethylene terephthalate)/poly(ethylene‐2,6‐naphthalate) blend
Authors: Lee Jong Kwan , Bang Hyo Jae , Lee Kwang Hee 
Published: August 2002

AbstractThe lamellar‐level morphology of an extruded poly(ethylene terephthalate) (PET)/poly(ethylene‐2,6‐naphthalate) (PEN) blend was investigated with small‐angle X‐ray scattering (SAXS). Measurements were made as a function of the annealing time in the melt and the crystallization temperature. The characteristic morphological parameters at the lamellar level were determined by correlation function analysis of the SAXS data. At a low crystallization temperature of 120 °C, the increased amorphous layer thickness was identified in the blend, indicating that some PEN was incorporated into the interlamellar regions of PET during crystallization. The blend also showed a larger lamellar thickness than pure PET. A reason for the increase in the lamellar thickness might be that the formation of thinner lamellar stacks by secondary crystallization was significantly restricted because of the increased glass‐transition temperature. At high crystallization temperatures above 200 °C, the diffusion rates of noncrystallizable components were faster than the growth rates of crystals, with most of the noncrystallizable components escaping from the lamellar stacks. As a result, the blend showed an interfibrillar or interspherulitic morphology. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 317–324, 2002
Structure and properties of the mesophase of syndiotactic polystyrene. I. Effect of casting conditions on the preparation of the mesophase
Authors: Rani D. Amutha , Yamamoto Y. , Saito A. , Sivakumar M. , Tsujita Y. , Yoshimizu H. , Kinoshita T. 
Published: August 2002

AbstractA syndiotactic polystyrene–toluene solution was cast under two different casting conditions to obtain the δ form. A systematic study of its conformational transition, thermal behavior, and structural transformation as functions of the annealing temperature and time was performed. Spectroscopic studies revealed the content of its helical conformations and its retention up to 190 °C. Thermal analyses showed a significant difference in the transformation from the γ form to the α form. The retention of the intermediate emptied clathrate form (mesophase) of the conformational order for a longer duration (from 120 to 180 °C) in a syndiotactic polystyrene membrane cast at room temperature was confirmed by X‐ray diffraction analysis. On the basis of the experimental results in this work, the transition mechanism is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 530–536, 2002; DOI 10.1002/polb.10120
Binary versus ternary interactions in a completely miscible three‐polymer blend system: Poly(ϵ‐caprolactone) with two different methacrylic polymers
Authors: Lee Su‐Chiu , Woo E. M. 
Published: August 2002

AbstractA truly miscible ternary miscible blend consisting of poly(ϵ‐caprolactone) (PCL), poly(phenyl methacrylate), and poly(benzyl methacrylate) (PBzMA) was discovered. The three‐polymer blend system was completely miscible within the entire composition range at ambient temperature up to about 150 °C, and ternary phase diagrams at increasing temperatures were characterized and interpreted. A ternary‐interaction model based on the modified Flory–Huggins expression was used to describe the phase diagrams with the individual binary interaction strengths. The model fitted well with the experimental‐phase diagram for the ternary blend system at T = 250 °C, where the binary PCL‐PBzMA blend system is on the critical points of phase separation. Interpretation of discrepancy between the model and experimental at other temperatures was handled with an empirical approach. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 747–754, 2002
Development of a methodology to predict material properties from environmental exposure. II. Structural features
Authors: Robertson J. E. , Ward T. C. 
Published: August 2002

AbstractA general scheme is presented in the first part of this series in which degradation‐induced changes in a polymer that are produced by exposure to an aggressive environment are linked to measurable kinetic parameters and molecular weight distribution variations. Although general in nature for all polymers and environments, the data were collected on bisphenol A polycarbonate that was degraded by elevated temperatures. A parameter, τ, the product of a kinetic rate constant, k, and the environmental exposure time, provided a metric that was suitable for superposition methods to reduce the data. τ was directly related to the molecular weight distribution shifting during environmentally induced changes. This article extends the methodology to structure–property correlations such as the relationship of the glass‐transition temperature, rheology, and the tensile strength of polycarbonate after the environmental treatment. Again, in a universal fashion, the τ value (the degree of degradation) was sufficient to model the observed physical property changes with the amount of exposure to the hostile environment. As long as the kinetics of the process of change are amenable to a mathematical model and a quantitative measure of the change in a fundamental polymer parameter is available, this methodology should be applicable to any polymer in any environment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 802–812, 2002
Excited‐state energy dynamics of conjugated polycarbogermane oligomers: Introduction effects of germanium atom into π‐conjugated molecular system
Authors: Choi Sang Ho , Hwang In‐Wook , Kim Sung Hee , Park Young Tae , Kim Yong‐Rok 
Published: August 2002

AbstractExcited‐state energy dynamics of the conjugated polycarbogermane oligomers, poly{[1,4‐bis(thiophenyl)buta‐1,3‐diyne]‐alt‐(dimethylgermane)} (PBTBD‐DMG; n = 33), poly{[1,4‐bis‐(thiophenyl)buta‐1,3‐diyne]‐alt‐(diphethylgermane)} (PBTBD‐DPG; n = 12), poly{[1,4‐bis(phenyl)buta‐1,3‐diyne]‐alt‐(dimethylgermane)} (PBPBD‐DMG; n = 36), and poly{[1,4‐bis(phenyl)buta‐1,3‐diyne]‐alt‐(diphenylgermane)} (PBPBD‐DPG; n = 2), were investigated by steady‐state and picosecond time‐resolved fluorescence spectroscopies in liquid solution. The introduction effect of a germanium atom into π‐conjugated oligomer backbones and the substitution effect of a methyl or phenyl group on the germanium atom are discussed from solvent polarity‐dependent studies. Steady‐state and time‐resolved fluorescence studies on the thiophene‐containing polycarbogermane (PBTBD‐DMG and PBTBD‐DPG) oligomers revealed considerable solvent polarity‐dependent characteristics, whereas those of the phenylene‐containing polycarbogermane (PBPBD‐DMG and PBPBD‐DPG) oligomers do not significantly show such characteristics. As the solvent polarity increased from n‐hexane to tetrahydrofuran, the steady‐state fluorescence spectra of PBTBD‐DMG and PBTBD‐DPG oligomers were significantly redshifted, and their fluorescence lifetimes seemed to change from ∼624 to ∼46 ps. These results suggest that the excited‐state dynamics of PBTBD‐DMG and PBTBD‐DPG oligomers are related to an intramolecular charge transfer (ICT) emission process through (d‐p) π conjugation between the π‐conjugated system and unoccupied 4d orbitals of the germanium atom. These results are supported by quantum chemical (AM1 and CNDO/2) calculations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1298–1306, 2002
Synthesis, structural characterization, and properties of polyurethane elastomers containing various degrees of unsaturation in the chain extenders
Authors: Auten Kenneth L. , Petrović Zoran S. 
Published: August 2002

AbstractWe prepared polyurethane block copolymers with both 50 and 70% soft segment concentrations, using 4,4′‐diphenylmethane diisocyanate–poly(propylene glycol) prepolymer and 1,4‐butanediol, cis‐2‐butene‐1,4‐diol, and 2‐butyne‐1,4‐diol as chain extenders. The effects of the different chain extenders were observed during synthesis and in the final products. A comparison of spectroscopic, mechanical, and thermal data reveals that polymer properties can be significantly altered by differences in chemical bonding within the chain extender backbone. Although all data support the expected differences in phase morphology between the two series of samples, they also suggest that increasing chain extender unsaturation reduced reactivity with isocyanate, adversely affected hydrogen bonding, lowered the degree of crystallinity of the hard segments, and decreased phase separation. The tensile strength, elongation, modulus, and elastic recovery decreased and the electrical conductivity of iodine‐doped samples increased with increasing chain extender unsaturation. The thermal stability of the urethane group was also lower in samples with increased unsaturation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1316–1333, 2002
Melting behavior, crystallization kinetics, and crystal structure of poly(2‐hydroxyethoxybenzoate)
Authors: Finelli L. , Siracusa V. , Lotti N. , Munari A. , Gazzano M. 
Published: August 2002

AbstractThe melting behavior and crystallization kinetics of poly(2‐hydroxyethoxybenzoate) (PHEBA) were investigated with differential scanning calorimetry and hot‐stage optical microscopy. The observed multiple endotherms, commonly displayed by polyesters, were influenced by the crystallization temperature. By the application of the Hoffman–Weeks method to the melting temperatures of isothermally crystallized samples, a value of 232 °C was obtained for the equilibrium melting temperature. Isothermal crystallization kinetics were analyzed according to Avrami's treatment. Values of Avrami's exponent n close to 3 were obtained, independently of the crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three‐dimensional spherulitic growth. In fact, space‐filling banded spherulites were observed by hot‐stage optical microscopy at all crystallization temperatures explored, with the band spacing increasing with increasing crystallization temperature. The rate of crystallization became lower as the crystallization temperature increased as usual at low undercooling, with the crystallization process controlled by nucleation. The equilibrium heat of fusion was determined by differential scanning calorimetry and wide‐angle X‐ray scattering measurements. Finally, the crystal phase of PHEBA was investigated with wide‐angle X‐ray scattering, and a triclinic unit cell was hypothesized. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1354–1362, 2002
A model for structural relaxation in amorphous glassy polymers based on the aggregation–fragmentation theory
Authors: Drozdov Aleksey D. 
Published: August 2002

AbstractGoverning equations are derived for the kinetics of physical aging in polymeric glasses. An amorphous polymer is treated as an ensemble of cooperatively rearranged regions (CRRs). Any CRR is thought of as a string of elementary clusters (ECs). Fragmentation of the string occurs at random times at any border between ECs. Two strings aggregate at random instants to produce a new string. Aggregation and fragmentation are treated as thermally activated processes, and the rate of fragmentation is assumed to grow with temperature more rapidly than the rate of coalescence. A nonlinear differential equation is developed for the distribution of CRRs with various numbers of ECs. Adjustable parameters of the model are found by the fitting of experimental data for polycarbonate, poly(methyl methacrylate), polystyrene, and poly(vinyl acetate) (PVA). Fair agreement is established between observations and results of numerical simulation. For PVAc, the relaxation spectrum found by matching data in a calorimetric test is successfully employed to predict experimental data in a shear relaxation test. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1312–1325, 2001
Morphology development during isothermal crystallization. II. Isotactic and syndiotactic polypropylene blends
Authors: Wang Zhi‐Gang , Phillips Roger A. , Hsiao Benjamin S. 
Published: August 2002

AbstractMorphology development during isothermal crystallization in equal molecular weight isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and iPP/sPP blends was studied with time‐resolved simultaneous small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray diffraction (WAXD) with synchrotron radiation. The sPP melting point is 15–20 °C below that of the iPP component, and sPP multiple melting is not affected by blending for 50–100 wt % sPP compositions. SAXS and WAXD (at 115 and 137.5 °C) show that sPP crystallizes more slowly than iPP. The sPP long spacing is larger than that of iPP at both crystallization temperatures, exhibits a broader distribution, and changes to a greater extent during crystallization. Differential scanning calorimetry (DSC) cooling and SAXS/WAXD measurements show iPP crystallizing first and nearly to completion before sPP in a 50:50 iPP/sPP blend. At 115 °C, iPP crystals nucleate sPP in a 50:50 blend and modify the sPP lamellar spacing. The nucleation does not overcome the large difference in the iPP and sPP rates at 137.5 °C. Before sPP crystallization in a 50:50 blend (115 °C), the iPP long spacing is not affected by molten sPP. The iPP long spacing is slightly expanded by molten sPP, and the WAXD induction time is delayed at 137.5 °C. The observed iPP long spacing in the presence of molten sPP is consistent with previously reported results for iPP/atactic polypropylene (aPP) blends of similar molecular weight. Quantitative differences between the two types of blends are consistent with previously reported thermodynamic rankings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1876–1888, 2001
Swelling behaviors of sub‐micron‐sized copolymer gel particles: The effect of physical crosslinking
Authors: Choi Hyun Seok , Kim In Ha , Bae Young Chan 
Published: August 2002

AbstractThe swelling equilibria model of copolymer gel particles is proposed. It accounts for physical crosslinking as a result of hydrogen bonding. The modified Flory–Erman model is used to describe the elastic contribution to swelling. The model considers hydrogen bonding as a physical crosslinker. A free‐energy‐of‐mixing term is represented using the extended Flory–Huggins theory. The interaction parameter χ in the model is a function of both composition and temperature. We then compare the proposed model with the swelling behaviors of copolymer gel particles. Our model offers fairly good agreement with the experimental data for given systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1928–1934, 2001
Orientation of cellulose triacetate films cast from solution in high magnetic field
Authors: Kimura T. , Yamato M. , Endo S. , Kimura F. , Sata H. , Kawasaki H. , Shinagawa Y. 
Published: August 2002

AbstractCellulose triacetate solutions with various solvents, including methylene chloride, methyl acetate, and their mixture with ethanol, were cast in high magnetic fields, and the obtained films were subjected to the optical and infrared measurements. The film cast from a solution with a methyl acetate/ethanol mixed solvent exhibited birefringence as well as infrared dichroism, whereas the films cast from the other solutions did not. The aligned structure was discussed by comparison with a mechanically stretched sample. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1942–1947, 2001
High‐throughput characterization of pattern formation in symmetric diblock copolymer films
Authors: Smith Archie P. , Douglas Jack F. , Meredith J. Carson , Amis Eric J. , Karim Alamgir 
Published: August 2002

AbstractSurface‐pattern formation in thin block copolymer films was investigated by utilizing a high‐throughput methodology to validate the combinatorial measurement approach and to demonstrate the value of the combinatorial method for scientific investigation. We constructed measurement libraries from images of subregions of block copolymer films having gradients in film thickness and a range of molecular mass,M.A single gradient film covers a wide range of film morphologies and contains information equivalent to a large number of measurements of films having a fixed thickness,h.Notably, the scale of the surface patterns is generally much larger than the molecular dimensions so that the interpretation of the patterns is more subtle than ordering in bulk block copolymer materials, and there is no predictive theory of this type of surface‐pattern formation. We observed a succession of surface patterns that repeat across the film with increasingh[extended smooth regions, regions containing circular islands, labyrinthine (“spinodal”) patterns, holes, and smooth regions again]. The extended smooth regions and the labyrinthine patterns appear to be novel features revealed by our combinatorial study, and these patterns occurred as bands ofhthat were quantized by integral multiples of the bulk lamellar period,Lo.The magnitude of the height gradient influenced the width of the bands, and the smooth regions occupied an increasing fraction of the film‐surface area with an increasing film gradient. The average size of the spinodal patterns, λ, was found to scale asλ ∼ Lorλ ∼ M−1.65and reached a limiting size at long annealing times. The hole and island features had a size comparable to λ, and their size likewise decreased with increasingM.The smooth regions were attributed to an increase in the surface‐chain density in the outer brushlike block copolymer layer with increasingh,and the scaling of λ withMwas interpreted in terms of the increasing surface elasticity withM.© 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2141–2158, 2001
Molecular dimensions and melt rheology of an all‐aromatic liquid crystalline polymer
Authors: Seo K. S. , Caflisch G. B. 
Published: August 2002

AbstractThe molecular dimensions and melt rheology of a thermotropic all‐aromatic liquid crystalline polyester (TLCP) composed of p‐hydroxy benzoic acid, hydroquinone, terephthalic acid, and 2,4‐naphthalenedicarboxylic acid is examined. The Mark–Houwink exponent (α) of 0.95 is estimated for the TLCP. The persistence length estimated from molecular weight (M) and intrinsic viscosity ([η]) data using the Bohdanecky–Bushin equation is about 95 Å, whereas that estimated from light scattering data is 117 Å. These persistence lengths and the observed α value, both higher than those for flexible polymers, suggest that the present TLCP is a semirigid polymer. The zero shear melt viscosity (η0) varies with approximately M6 for molecular weight M > 3 × 104 g/mol; below this molecular weight, η0 varies almost linearly with M. Widely different entanglement molecular weights (Me) are predicted, depending on the method used; the plateau modulus estimates Me of about 8 × 105 g/mol, whereas the ratio of mean square end‐to‐end distance and molecular weight (〈R2〉0/M) predicts Me's either too small (0.33 g/mol) or too large (2.5 × 106 g/mol), depending on the theory used. Although the change in the molecular weight dependency of melt viscosity appears to be associated with the onset of entanglement coupling of the semirigid molecules, its origin needs further investigation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2378–2389, 2001
Slow ester side‐group flips in glassy poly(alkyl methacrylate)s characterized by centerband‐only detection of exchange nuclear magnetic resonance
Authors: Bonagamba T. J. , Becker‐Guedes F. , DeAzevedo E. R. , Schmidt‐Rohr K. 
Published: August 2002

AbstractSlow side‐group dynamics in a series of five poly(alkyl methacrylate)s with various side‐group sizes [poly(methacrylic acid) (PMAA), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(isobutyl methacrylate) (PiBMA), and poly(cyclohexyl methacrylate), with H, CH3, CH2CH3, CH2CH(CH3)2, and cyclohexyl alkyl substituents (CODEX), respectively] were studied quantitatively by centerband‐only detection of exchange nuclear magnetic resonance (NMR). Flips and small‐angle motions of the ester groups associated with the β relaxation were observed distinctly in the CODEX NMR data, and the fraction of slowly flipping groups was measured with a precision of 3%. In PMMA, 34% of the side groups flipped on a 1‐s timescale, whereas the fraction was 31% in PEMA at 25 °C. Even the large isobutylether and cyclohexylester side groups flipped in the glassy state, although the flipping fraction was reduced to 22 and about 10%, respectively. In PMAA, no slow side‐group flips were detected on the 1‐s timescale. A striking difference in the temperature dependence of the flipping fraction in PMMA versus PEMA and PiBMA was observed. In PMMA, the flipping fraction was temperature‐independent between 25 and 80 °C, whereas in PEMA, it increased continuously from 31 to 60% between 25 and 60 °C. A similar doubling was also observed in PiBMA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2444–2453, 2001
Internal Structure of a relict rock glacier, Ślęża Massif, Southwest Poland
Authors: Żurawek Roman 
Published: August 2002

AbstractThe sediments of a large accumulation landform, interpreted as one of six Pleistocene rock glaciers occurring in the Ślęża Massif, southwest Poland, are described. The sediments have been subject to strong compression and the main deformation mechanism is that of shearing. The similar angle of shear in sediments of extremely different lithology is inferred from the geometry of failure surfaces and indicates that ice was necessary for the debris transport. Because the geomorphological setting excludes a glacigenic origin, the sediments are interpreted to result from the creep of permafrost, i.e. the landform is a relict rock glacier. The movement of the rock glacier, at least in its terminal stage, is associated with a dense pattern of shear planes and would have occurred even in the presence of a small amount of interstitial ice. Copyright © 2002 John Wiley & Sons, Ltd.