bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nucleation‐controlled growth in polyethylene single crystals: Growth and shape of {100} sectors
Authors: Toda Akihiko 
Published: April 2003

AbstractThe nucleation rate and propagation rate of steps on the {100} faces of polyethylene crystals have been determined. For single crystals, under conditions where the width of the {100} sectors remains constant during growth, it is confirmed that the growth is in regime I or the crossover region between regime I and II. In {110} twinned crystals, the {100} sectors are well developed and the width increases linearly with time; therefore, the growth in the twins must be in regime II. It is shown that the differing growth regimes of {100} faces in single crystals and twins allow the independent determination of the nucleation rate and the propagation rate of steps. The nucleation rate and propagation rate of steps on the {100} faces were determined from measurements of the constant width of the {100} faces in single crystals and the growth rate of the {100} faces in single crystals and twins. The observed rates show abnormal dependence on supercooling and concentration. The results are attributed to a weaker dependence of the constant width of {100} sectors on supercooling and concentration than predicted.
Compatibility of poly(vinyl chloride) with polyalkyleneoxides. II. Poly(propylene oxide) and poly(tetramethylene oxide)
Authors: Margaritis A. G. , Kalfoglou N. K. 
Published: April 2003

AbstractThis study [Part II of a series dealing with the compatibility of polyalkyleneoxides with poly(vinyl chloride)] examines blends of PVC with poly(propylene oxide) (PPrO) and poly(tetra‐methylene oxide) (PTMO), covering the entire composition range. Morphological, dynamic mechanical and thermal properties investigated indicate that PVC/PPrO blends are incompatible, whereas the PVC/PTMO system shows miscibility in the melt. For this polyblend and at high polyether compositions where the Hoffman–Weeks analysis can be applied, Tm equilibrium data allow the determination of the thermodynamic interaction parameter, χ12 = −0.15. Experimental compatibility data of all polyether‐PVC pairs investigated in Parts I and II are also used to test various blend miscibility prediction schemes, using solubility parameter theory and recent theory on copolymer‐copolymer miscibility.
Phase transitions in lattice solutions of semiflexible chains of finite length
Authors: Ronca G. 
Published: April 2003

AbstractLattice solutions of finite chains with reduced flexibility are shown to form phase equilibria characterized by broad phase gaps of width increasing with molecular weight. DiMarzio's treatment of excluded volume also gives predictions on bulk transitions. Both in solution and in the bulk, the orientational order parameter and fraction of straight configurations of the anisotropic phase at the transition increase with chain length. Calculations on infinite chain systems fail to detect phase equilibrium in solution at different concentrations.
Morphology and cation local structure in a blend of copper‐neutralized carboxy‐terminated polybutadiene and poly(styrene‐co‐4‐vinylpyridine)
Authors: Register Richard A. , Sen Ashish , Weiss Robert A. , Li Chi , Cooper Stuart 
Published: April 2003

AbstractCarboxy‐terminated polybutadiene neutralized with Cu2+ (CuPBD) and its blend with poly(styrene‐co‐4‐vinylpyridine) (SVP) were examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), small‐angle x‐ray scattering (SAXS), and extended x‐ray absorption fine structure (EXAFS) spectroscopy. The DSC results indicate that in the blend substantial mixing occurs in the CuPBD‐rich phase, although complete miscibility is not achieved, and the SVP‐rich phase remains relatively pure. The TEM micrographs indicate that the morphology, while irregular, is reasonably described as bicontinuous, with a domain size of order 100 nm. The SAXS patterns show that the ionic aggregates present in CuPBD are destroyed upon blending, which is interpreted as being due to steric hindrances between ionic groups coordinated to vinylpyridine nitrogens. The EXAFS radial structure function of the blend exhibits a marked decrease in the Cu‐Cu peak in comparison with CuPBD, indicating a change in local structure upon blending. The results indicate that some of the SVP is miscible with CuPBD owing to complexation between the pendant pyridine groups and the Cu2+ ions, which disrupts the ionic aggregates. However, the two materials are not fully miscible, leading to a rather coarse two‐phase morphology.
A study of polymer blends by nonradiative energy transfer fluorescence spectroscopy
Authors: Zhao Yue , Lévesque Jocelyne , Roberge Pierre C. , Prud'homme Robert E. 
Published: April 2003

AbstractThe nonradiative energy transfer (NRET) method has been used to study the miscibility of polymer blends in the solid state. This can be done by labeling the polymers with fluorescence donor and acceptor chromophores. The efficiency of energy transfer, which reveals the interpenetration of the chains, is measured by following changes in the fluorescence intensity ratio of the donor and acceptor as a function of the concentration of the polymer mixture and by comparison with reference values corresponding to totally miscible and totally immiscible systems. It is shown that the reference ratio corresponding to the absence of energy transfer must be determined by using donor‐labeled and acceptor‐labeled polymer films, instead of making measurements in chromophore solutions in organic solvents, as has usually been done. It is also shown that fluorescence quenching is important in such studies, since it can lead to variations of the fluorescence intensity ratio by more than an order of magnitude; this factor varies with blend concentration and is particularly sensitive to the presence of halogen atoms. The NRET technique has been applied to several PVC/CPVC binary blends and to PCL/PVC/CPVC ternary blends in which PVC and CPVC were labeled by naphthalene and anthracene, respectively [PCL is poly(ε‐caprolactone), PVC is poly(vinyl chloride), and CPVC is chlorinated PVC]. For binary blends, the measured intensity ratios indicate the immiscibility of PVC with CPVC, although there is nonnegligible energy transfer between the two phases. For ternary blends, the intensity ratios indicate that the addition of up to 40 wt % of PCL to the immiscible PVC/CPVC binary system leads to the formation of two coexisting PCL/PVC and PCL/CPVC phases.
X‐ray diffraction by thermotropic main‐chain polymers with side groups. I. rigid polyesters
Authors: Chin Hui H. , Azároff Leonid V. , Lenz Robert W. 
Published: April 2003

AbstractThermotropic poly(sulfonyl hydroquinone terephthalate) with either H or CH3 in the lateral substituent was aligned by drawing from nematic melts. Virtually identical x‐ray intensity distributions were recorded consisting of “disks” of intensity periodically spaced along the meridian and concentric rings of intensity lying in the equatorial plane of reciprocal space. They correspond to what is expected for the hexagonal packing of parallel periodic chains that are randomly displaced along the chain axes. Using interactive graphics, appropriate molecular models were deduced in conformity with the observed diffraction intensities.
Small‐angle scattering of polarized light. II. experiments with isotropic spheres
Authors: Desbordes M. , Meeten G. H. , Navard P. 
Published: April 2003

AbstractNew experimental measurements are reported of small‐angle polarized and depolarized light scattering from almost monodisperse isotropic, spherical particle, polystyrene latexes. The shape and intensity distribution of the scattering patterns is shown to compare closely with the calculated patterns based on the exact Mie scattering theory from a single sphere.
Crystalline phases of electrically conductive poly(p‐phenylene vinylene)
Authors: Masse Michael A. , Schlenoff Joseph B. , Karasz Frank E. , Thomas Edwin L. 
Published: April 2003

AbstractPoly(p‐phenylene vinylene) (PPV) undergoes a first‐order crystal‐crystal phase transition when chemically doped with AsF5, SbF5, or H2SO4 or electrochemically oxidized with ClO‐4 as the counterion. These structures have been observed using wide‐angle x‐ray diffraction. Doping with these agents does not disrupt the original orientation of the PPV crystallites. The crystalline phases obtained with all dopants employed here are similar in character, indicating a closely related family of electrically conductive structures having orthorhombic symmetry. An electrically conductive phase consisting of layers of polymer chains separated by a layer of the chemical dopant is proposed.
Swelling behavior of an aromatic polyimide
Authors: Gattiglia E. , Russell T. P. 
Published: April 2003

AbstractThe swelling behavior of poly(N, N'‐bisphenoxyphenylpyromellitimide) (PMDA‐ODA) using dimethylsulfoxide DMSO and N‐methylpyrollidinone NMP was investigated by gravimetric means. For PMDA‐ODA samples imidized on a substrate, the weight uptake was found to depend linearly on time over a temperature range from 25 to 150°C. For a given temperature of imidization, the equilibrium swelling concentration was found to be independent of the temperature at which the swelling studies were performed. However, the rate of solvent uptake depended strongly on the swelling temperature, yielding an activation energy of about 50 kJ/mol. In general, increasing the initial imidization temperature caused a decrease in the rate of swelling but did not alter the equilibrium swelling concentration. This swelling behavior resembles Case II diffusion typically seen in glassy polymers with some noteworthy exceptions. In cases, where PMDA‐ODA was imidized in a free‐standing state, no swelling was observed. However, deformation of these isotropic specimens was found to induce substantial swelling.
Modification of transport properties of ion‐exchange membranes VIII. Changes in properties of anion exchange membranes on introduction of hydrophobic groups
Authors: Sata Toshikatsu , Yamamoto Yoshihisa 
Published: April 2003

AbstractA copolymer membrane composed of 4‐vinylpyridine‐styrene‐divinylbenezene was reacted with long chain alkyl bromides (octyl bromide, dodecyl bromide, and hexadecyl bromide) in order to introduce hydrophobic groups into the anion exchange membrane by the quaternization reaction. The resulting membranes show a marked increased in fixed ion concentration as a result of lowered water content. Although the electrical resistance of the membranes increased slightly, the apparent diffusion coefficient of hydrochloric acid through the membranes decreased markedly. Complete quaternization of the membranes by methyl iodide after reaction with the long‐chain alkyl bromides caused an increase in the water content and in the apparent diffusion coefficient of the acid and a decrease in the current efficiency in electrodialysis of the acid. This is explained by the high water content of the anion exchange membranes quaternized by methyl iodide.
Sorption and partial molar volume of gases in polybutadiene
Authors: Kamiya Yoshinori , Naito Yasutoshi , Mizoguchi Keishin 
Published: April 2003

AbstractSorption of He, H2, N2, O2, Ar, CH4, C2H6, and C2H6 in polybutadiene and the dilation of the polymer due to sorption of the gases are investigated over the pressure range 0‐50 atm at 25°C. For CO2 the measurements are made at temperatures ranging from 15 to 80°C. Partial molar volumes of the gases in the polymer are determined. The temperature dependence of partial molar volume is discussed on the basis of the data for CO2. The Flory‐Huggins interaction parameters of CO2, C2H4, and C2H6 are also estimated.
Rheo‐optical properties of polyethylene films in the nonlinear viscoelastic region
Authors: Tanaka Akira , Fukuda Mitsuhiro , Nagai Hiroyuki , Shinohara Masayuki , Onogi Shigeharu 
Published: April 2003

AbstractA new apparatus was designed to investigate the dynamic viscoelastic properties of solid polymer materials in the nonlinear viscoelastic region. The apparatus was combined with a birefringence apparatus in such a way that birefringence could be measured simultaneously with stress under oscillatory deformation. The nonlinear viscoelastic behavior of bulk‐crystallized high‐density polyethylene films was examined. Nonlinearity of mechanical properties became evident around 30°C, while optical properties became markedly nonlinear around 50°C. The nonlinearity of viscoelastic properties changes very little when the films are swollen with tetrachloroethane. It is proposed that disruption of lamellae to crystallites in the drawing process is one of the most important causes of the nonlinear behavior of high‐density polyethylene films.
Annealing effects of phase I poly(vinylidene fluoride)
Authors: Takase Y. , Scheinbeim J. I. , Newman B. A. 
Published: April 2003

AbstractThe effects of annealing temperatures on stretched poly(vinylidene fluoride) film were systematically studied from the “as‐received” condition up to the melting range (180°C). X‐ray diffraction studies indicate that the annealing process brings about better chain packing and increased crystallite perfection. The elastic modulus and piezoelectric strain and stress constants, d3, and e31, decrease as the annealing temperature Ta increases up to 160°C, while the remanent polarization Pr remains almost constant. Some of these characteritics may be interpreted in terms of a morphological transformation of microfibrils. The values of Pr, d31, and e31 increase dramatically as Ta increases from 160 to 180°C; Pr increases from 56 to 85 mC/m2, d31 from 20.2 to 27.7 pC/N, and e31 from 51.4 to 65.2 mC/m2. As a result, the values of Pr and d31 were the largest recorded from any of the samples used in the present study. e31 showed a value close to the largest one; this usually occurs in unannealed samples. Samples annealed in the melting range also exhibit significantly improved ageing characteristics. The large value of Pr and the small relaxation strength of both the dielectric constant and elastic modulus indicates that the largest crystallinity obtained is approximately 70%.
Mechanical relaxations in polypropylene: A new experimental and theoretical approach
Authors: Jourdan C. , Cavaille J. Y. , Perez J. 
Published: April 2003

AbstractAccurate dynamic mechanical measurements have been performed on semicrystalline isotactic polypropylene over wide ranges of temperature and frequency. A mechanical model has been used to analyze experimental results in order to separate the behavior of amorphous and crystalline phases. The two main α and β relaxation processes have been analyzed. The β relaxation, related to the glass‐rubber transition of the amorphous fraction, has been studied with the help of a physical model. The behavior is similar to that of a wholly amorphous polymer, with two characteristics: a high rubbery plateau, indicating a crosslinking effect by the crystalline phase, and a strong effect of interfaces in shear strain. Experimental data suggest the α relaxation originates within the crystalline phase and that it can be attributed to diffusion of defects. The amorphous phase plays an important role in this process, because it has to adapt itself by cooperative movements to respect the compatibility of deformations of the two phases. The formalism developed here rationalizes experimental results obtained with samples having different thermal histories.
Thermal behavior of poly(1,8‐nonadiyne) and its cross‐polymerized product
Authors: Butera R. J. , Lando J. B. 
Published: April 2003

AbstractThe diacetylene macromonomer poly(1,8‐nonadiyne) was investigated using differential scanning calorimetry in an effort to characterize the solid‐state cross‐polymerization reaction which occurs when this material is exposed to high‐energy radiation. Specifically, DSC was used as a means to monitor the degree of conversion in the crystalline regions of partially cross‐polymerized samples. Results from the thermal analysis of the virgin macromonomer indicate that little, if any, thermally induced reaction occurs during the DSC heating scans. Heat of fusion data were used to estimate the degree of conversion in partially cross‐polymerized samples. The apparent maximum degree of conversion in the crystalline regions of this macromonomer system was found to be 78% using this method. The actual maximum conversion for the system is probably somewhat lower.
Crystallization of segmented trans‐1,4‐polyisoprene/epoxidized trans‐1,4‐polyisoprene block copolymers from solution
Authors: S. Zemel Irina , P. Corrigan Joseph , E. Woodward Arthur 
Published: April 2003

AbstractThe crystallization of segmented block copolymers of trans‐1,4‐polyisoprene (TPI)/expoxidized TPI from solution was investigated. One preparation with an average TPI block length of 14.5 and an average epoxidized TPI block length of 10 was crystallized from 2‐pentanol at 20°C, 2‐octanol at 20°C, and 2‐pentanone at 0°C. A second preparation with an average TPI block length of 18 and the same average epoxidized TPI block length was crystallized from 2‐octanol at 20°C and 2‐pentanone at 0°C. The crystallization products were expoxidized in suspension a second time and then characterized by carbon‐13 solution NMR to determine the average noncrystalline traverse length and the average crystalline stem length. The crystallized products were also studied by scanning electron microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry to determine the morphology, the crystal form and crystallinity, and the melting point, respectively. The average noncrystalline traverse length was found to be highly dependent on the crystallization conditions and the crystalline stem length of the parent TPI lamellas; the composition of these traverses is discussed.
Sorption and transport of carbon dioxide in a polyimide from 3,3′4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐diaminodiphenyl sulfone
Authors: Okamoto Ken‐Ichi , Tanaka Kazuhiro , Kita Hidetoshi , Nakamura Asumaru , Kusuki Yoshihiro 
Published: April 2003

AbstractCO2 sorption and transport were investigated for the polyimide prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl sulfone (DDS). The morphology of films did not change on annealing above the glass transition temperature and remained amorphous unlike the polyimide prepared from BPDA and 4,4′‐oxydianilline (ODA). This seems to be due to the strong hindrance to rotation of the sulfonyl linkage. Sorption and transport data were analyzed according to the dual‐mode model. Solubility, diffusion, and permeability coefficients at 20 atm and 80°C for BPDA‐DDS polyimide were substantially equal between as‐cast and annealed films and were 1.7, 2.2, and 3.7 times greater, respectively, than for the as‐cast films of the BPDA‐ODA polyimide. The higher solubility was due to larger values of the Henry's law solubility constant kD, Langmuir capacity constant C, and the Langmuir affinity constant b. The sorption and transport properties were compared with those for amorphous glassy aromatic polymers including other polyimides. The relation of k, C, b, and the diffusion coefficients in the Henry's law population and the Langmuir population (DD and DH) with other properties of the polymers were discussed. Values DD and DH for BPDA‐DDS polyimide were much larger than expected from the estimated free‐volume fraction.
Coefficient seebeck et méanismes de conduction dans les polymères (PPP) electroactifs dopés par implantation ionique
Authors: Moliton A. , Duroux J. L. , Ratier B. 
Published: April 2003

AbstractA study of the Seebeck coefficient has shown that doping of polyparaphenylene by ion implantation makes it possible to obtain an electronically doped semiconductor at low energy: n‐type with alkali metal ions and p‐type with halide ions. At the highest energies (E > 100 keV) the p‐type conductivity is due to the creation of defects by irradiation. Generally the semiconductor obtained is degenerate with a Seebeck coefficient close to that obtained by chemical doping. Study of the mechanisms of conduction suggests plots of log σ = (T−l/n); the greater n is, the better is the agreement between the experimental curve and theory. Representation of the conductivity is proposed according to Mott's theories, which are applicable to amorphous semiconductors and involve several conduction processes in the temperature space. For the variable‐range‐hopping (VRH) mechanism at low temperature, two parameters, α−1 (representing the spatial separation of hopping sites) and N(EF) (the density of states at the Fermi Level) are obtained.
Elastic modulus of poly(ethylene oxide) determined from the Raman longitudinal acoustic mode
Authors: Song Kigook , Krimm Samuel 
Published: April 2003

AbstractThe chain modulus of poly(ethylene oxide) is determined by the Raman longitudinal acoustic mode method with the aid of a normal coordinate analysis and found to be 1.3 × 1011 dyn/cm2. Our normal mode calculations provide a clear basis for explaining the discrepancy between chain moduli determined from Raman and x‐ray experiments. They show that the uncorrected Raman modulus of helical polymers reflects the presence of interchain interactions and therefore should not be taken as the correct elastic modulus of a single chain.
Glass transition temperature versus conversion relationships for thermosetting polymers
Authors: Pascault J. P. , Williams R. J. J. 
Published: April 2003

AbstractOwing to enthalpy relaxation, values of the glass transition temperature (Tg) for partially reacted polymers may depend on the thermal history of samples and the heating rate used for measurements. Use of theoretical relations between Tg and the extent of reaction (x) of a thermoset must take this fact into account. The original DiBenedetto equation has been reevaluated as a convenient constitutive equation for expressing Tg versus x. An extension of Couchman's approach for the expression of the compositional variation of Tg enabled us to derive the same functionality as given by the DiBenedetto equation. Thus, the DiBenedetto equation may be regarded as based on entropic considerations applied to a model of the thermosetting polymer consisting of a random mixture of a fully reacted network with the initial monomers in an amount which depends on the particular conversion level. These two equations have been applied with success to different diepoxy‐diamine copolymers.
Accumulation of monomolecular polystyrene particles from a water surface onto a substrate
Authors: Kumaki Jiro 
Published: April 2003

AbstractMonomolecular particles of polystyrene (Mw/Mn = 1.04, Mw = 3.84 ? 106) formed by spreading of a dilute solution in benzene over a water surface were successfully accumulated onto a hydrophobic substrate by the horizontal lifting method. The accumulation was quantitative (up to 66 layers) to give a multilayer film. The substrates used were silicon single crystals, quartz coated with an iron(III) stearate monolayer, and poly(methylmethacrylate) plates. The film contained voids amounting to 20‐30 vol%. The surface structure observed by transmission electron microscopy clearly showed a multilayer, particle structure. These facts indicate that the molecules exist as monomolecular particles in the film. The film should be a suitable material to study properties of polymeric monomolecules in a very unusual state as compared with the ordinary solid.