bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the structure of glassy polymers. I. Small‐angle X‐ray scattering from polycarbonate
Authors: Renninger A. L. , Wicks G. G. , Uhlmann D. R. 
Published: April 2003

AbstractThe small‐angle x‐ray scattering (SAXS) from glassy bisphenol‐A polycarbonate has been measured using a Bonse–Hart system. The data cover the angular range (2θ) between 20 sec and 2 deg. After correcting for absorption, background, and vertical beam divergence, they have been placed on an absolute basis by comparison with the scattering from a standard silica suspension. The corrected absolute intensity decreases strongly with increasing angle over the range between 20 sec and 30 min, and is nearly constant between 30 min and 2 deg. The magnitude of the scattering in the constant range, 0.44 (electrons)2 Å−3, is well represented by the thermodynamic theory for fluids applied at the glass‐transition temperature. The increase in intensity at smaller angles cannot be described by structures on the scale of the nodules reported in this material (50–200 Å), but can be well represented by a small concentration of heterogeneities (0.04% by volume or less), several thousand angstrom units in size, superimposed on the thermal density fluctuations frozen in at the glass transition.It is suggested that the nodular features reported for this material are not representative of bulk material but should be associated with surface effects. The bulk structure can—as far as the SAXS is concerned—be well described as a random amorphous solid, containing simple thermal fluctuations and a small concentration of relatively large heterogeneities.
Photoinduced charge transfer at the poly(N‐vinylcarbazole)—tin oxide interface
Authors: Reucroft P. J. , Ghosh S. K. , Takahashi K. 
Published: April 2003

AbstractAn investigation of steady state and transient photoconductivity in films of poly‐(N‐vinylcarbazole) equipped with SnO2 and metal electrodes is described. The studies have shown that photoinduced charge transfer, leading to hole injection into the polymer film, takes place with photons of energy greater than 1.8–1.9 eV. Dark conductivity studies on samples equipped with grounded guard rings have shown that carriers originating in the bulk of the polymer film dominate the dark current when the metal electrode is at negative bias. Thermionic hole emission from the SnO2 electrode is not observed.
Effect of interfacial bonding on the strength of adhesion
Authors: Ahagon A. , Gent A. N. 
Published: April 2003

AbstractThe strength of adhesion has been determined experimentally for an elastomer layer coupled to a rigid substrate by interfacial chemical bonds of varying surface density. Sites for interfacial bonding were obtained by treating glass plates with mixtures of vinyl‐and ethylsilanes in varying proportions. A layer of polybutadiene was then applied and cross‐linked in situ by a free‐radical process. Formation of interfacial bonds to vinyl groups (when present) on the glass substrate is inferred from the proportional increase in strength of adhesion under near‐equilibrium conditions, i.e., at low rates of detachment and at high temperatures. A 35‐fold increase in strength was found for vinylsilane, relative to ethylsilane, in rough agreement with the relative magnitudes of the strengths of covalent and dispersion bonds. However, the absolute magnitudes were much greater than predicted, by a factor of about 25 in both cases. This is attributed to the polymeric character of the elastomer: many molecular bonds must be stressed in order to detach or rupture one.4 In agreement with this hypothesis, the strength of adhesion decreased with increasing crosslinking. Anomalously high adhesion was found with clean glass. It presumably reflects a specific bonding mechanism of unknown type.
NMR measurements on cis‐1,4‐polybutadiene as a function of pressure
Authors: Geissler E. 
Published: April 2003

AbstractMeasurements are reported of the nuclear spin—lattice relaxation time T1 in cis‐1,4‐polybutadiene at room temperature up to a pressure of 3,500 bar. Up to 2,000 bar the relaxation curves are described by a single T1, the pressure variation of which indicates, in the Arrhenius model, an activation volume of 14.5 cm3 mole−1. Above 2,000 bar the effects of strain due to partial crystallization become evident, and multiple relaxation is observed. By measuring the compressibility of this material up to 10 kbar an estimate of the free volume is made, giving

with P in kbar. This measurement is applied in turn to two models of the glassy state, that of Cohen and Turnbull1 which yields an activation volume of 84 cm3 mole−1, and that of Adam and Gibbs,2 which leads to a critical configurational entropy of 7.7 kB.In the liquid state the transverse nuclear relaxation, measured by the spin‐echo technique, appears to be governed by the same process as T1.
Electrical properties of dry and wet polyglycine
Authors: Michel R. , Seytre G. , Maitrot M. 
Published: April 2003

AbstractReal and imaginary parts of the dielectric constant of wet and dry polyglycine have been measured for several temperatures over a wide range of frequencies. A simple, rather crude model, proposed earlier for nylon 66, fits the experimental data rather well, but the blocking coefficient p is larger and adsorption effects are more important.
Physical properties and structure of silk. II. Dynamic mechanical and dielectric properties of silk fibroin
Authors: Magoshi Jun , Magoshi Yoshiko 
Published: April 2003

AbstractDynamic mechanical and dielectric properties of amorphous regenerated films of silk fibroin were studied as a function of temperature. A mechanical loss tangent peak at about 175°C may be due to the segmental motion of the main chains in the amorphous silk fibroin film. The dynamic modulus of the amorphous silk fibroin increased at 185°C due to the crystallization of the silk fibroin. Dielectric loss tangent peaks were observed at about −40°C and 175°C at 1 kHz. The former is ascribed to the local motion of the amorphous silk fibroin with absorbed water, while the latter seems to originate from the segmental motion of the main chains and the crystallization of silk fibroin.
Dielectric relaxation in concentrated solutions of poly(methyl methacrylate)
Authors: Phillips P. J. , Singh G. 
Published: April 2003

AbstractMeasurements of dielectric relaxation have been made for a series of solutions of poly(methyl methacrylate) in toluene. A range of concentrations between 2% and 20% was used for a number of polymers of differing molecular weights. The dispersion was studied over the frequency range 103‐106 Hz for temperatures between −90°C and +20°C. It has been found that both the distribution of relaxation times and the activation energy increase with increasing concentration. The magnitudes of the effects vary with molecular weight. A significant observation is that the increase in dielectric constant with concentration is not linear.
The nature of multiple melting transitions in cis‐polyisoprene
Authors: Edwards B. C. 
Published: April 2003

AbstractThe multiple melting transitions previously reported for cis‐polyisoprene have been related to different morphological species observed in thin films using transmission electron microscopy. Two distinct types of spherulitic lamellar crystal have been identified which have characteristic growth rates, lamellar thicknesses, and fold planes.In addition to the α‐lamellar crystals, which grow in prestrained films with the a axis perpendicular to the stretch direction, a second type of lamellar crystal was identified with the b axis perpendicular to the stretch direction: β‐lamellae. From an analysis of the kinetics of growth and the variation of lamellar thicknesses with crystallization temperature, values of the side and surface free energies of the two types of lamellar crystal have been calculated.
A method for experimental determination of the temperature dependence of relaxation times in dielectrics
Authors: Ponevski Ch. , Solunov Ch. 
Published: April 2003

AbstractA new method is suggested for the experimental determination of the dependence of the relaxation times on the temperature in dielectrics for which the time–temperature superposition principle is valid. The method makes possible the determination of this dependence for a separate relaxation process (for instance, for the β‐relaxation process) over a wide temperature range by means of comparatively simple mathematical operations which are only slightly sensitive to experimental errors. Two or more discharge‐current curves, measured with temperatures increasing in an arbitrary way with time, are used for this purpose.
On the structure of glassy polymers. II. Small‐angle x‐ray scattering from poly(methyl methacrylate)
Authors: Renninger A. L. , Uhlmann D. R. 
Published: April 2003

AbstractThe small‐angle x‐ray scattering (SAXS) from glassy poly(methyl methacrylate) has been measured using a Bonse–Hart system. The data cover the angular range (2θ) between 20 sec and 2 deg. After correcting for absorption, background, and beam divergence, the data have been placed on an absolute basis by comparison with the scattering from a standard silica suspension. The corrected absolute intensity decreases strongly with increasing angle over the range between 20 sec and 30 min, and is nearly constant between 30 min and 2 deg. The magnitude of the scattering in the constant range, 0.6 (electrons)2 Å−3, is within a factor of 1.5 of the value predicted by the thermodynamic fluctuation theory for fluids applied at the glass transition temperature. The increase in intensity at smaller angles cannot be described by structures on the scale of the nodules reported in highly isotactic PMMA (150–200 Å), but can be well represented by small concentrations of heterogeneities, several thousand angstrom units in size, superimposed on the thermal density fluctuations frozen‐in at the glass transition. The bulk structure of this material is well described as a random amorphous solid, containing simple thermal fluctuations and a small concentration of relatively large heterogeneities.
Phase transition in dilute solution of poly(γ‐benzyl‐L‐glutamate) in dichloromethane at a low temperature
Authors: Adachi Keiichiro , Hirose Yumiko , Ishida Yoichi 
Published: April 2003

AbstractThe dielectric constant of solutions of poly(γ‐benzyl‐L‐glutamate) (PBLG) in dichloromethane shows a jump near 195°K, irrespective of frequency. Therefore, the discontinuity is not a dispersion phenomenon but a phase transition in the thermodynamic sense. The transition temperature is independent of the concentration in the range from 0.01 to 10% by weight, but it increases linearly with the logarithm of the molecular weight of PBLG. The height of the jump depends strongly on frequency, concentration, and molecular weight. The viscosity also changes abruptly at 195°K. These results suggest that the PBLG molecule forms a cluster like a liquid crystal or is in a random coil state below the transition point.
The fusion of highly crystalline poly(vinyl chloride)
Authors: Gouinlock E. V. 
Published: April 2003

AbstractLow molecular weight PVC polymers of known degree of crystallinity (44% by x‐ray diffraction), prepared in the presence of the chain‐transfer agents n‐butyraldehyde and n‐butyl mercaptan, are examined by differential scanning calorimetry in order to ascertain temperatures and heats of fusion. Initial thermal scans are accompanied by large endotherms and appreciable weight losses due to the lability of the terminal groups originating from the chain‐transfer agents. However, further successive scans result in approximately invariant endotherms attributable to crystalline fusion. The maximum melting point, about 265°C, exceeds the value for commercial PVC, about 210°C, but is lower than a value deduced for a hypothetical completely syndiotactic polymer, about 400°C. The average heat of fusion ΔHu is 1180 ± 90 cal/mole, and the resultant entropy of fusion is 1.1 cal/deg/bond. The present ΔHu value differs significantly from previously reported values of 660–785 and 2700 cal/mole, based on melting point depression theory, but appears to be concordant with known heats for a series of vinyl polymers.
Nonlinear viscoelasticity of polystyrene solutions. II. Non‐Newtonian viscosity
Authors: Osaki Kunihiro , Fukuda Mitsutoshi , Ohta Shin‐Ichi , Kim Bong Shik , Kurata Michio 
Published: April 2003

AbstractThe steady shear viscosity η(k) and the stress decay function \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \eta \left({t,k} \right)$\end{document} (the shear stress divided by the rate of shear k after cessation of steady shear flow) were measured for concentrated solutions of polystyrene in diethyl phthalate. Ranges of molecular weight M and concentration c were 7.10 × 105 to 7.62 × 106 and 0.112–0.329 g/cm3, respectively. Measurements were performed with a rheometer of the cone‐and‐plate type in the range 10−4 < k < 1 sec−1. The Cox–Merz relation η(k) = |η*(ω)|ω=k was tested with the experimental result (|*(ω)| is the magnitude of the complex viscosity). It was found to be applicable to solutions of relatively low M or c but not to those of high M and c. For the latter η(k) began to decrease at a lower rate of shear than |η*(ω)|ω=k did; the Cox–Merz law underestimated the effect of rate of shear. The stress decay function was assumed to have a functional form \documentclass{article}\pagestyle{empty}\begin{document}$\tilde \eta \left( {t,k} \right) = \sum {\eta _p \left( k \right)e^{ - t/\tau p\left( k \right)} } $\end{document} where τ1 > τ2 > …, and the values of τ1, τ2 η1 and η2 were determined for some solutions. The relaxation times τ1 and τ2 were found to be independent of k and equal to the relaxation times of linear viscoelasticity. At the limit of k → 0, η1 and η2 were approximately 60 and 20–30%, respectively, of η and the non‐Newtonian behavior was due to large decreases of η1 and η2 with increasing k. It was shown that η1(k) may be evaluated from the relaxation strength G1(s) for the longest relaxation time of the strain‐dependent relaxation modulus with a constitutive model for relatively high c–M systems as well as for low c–M systems.
Mechanical properties of composite heterogeneous gels
Authors: Janáček J. , Raab M. , Boček B. 
Published: April 2003

AbstractComposites with a matrix of poly(2‐hydroxyethyl methacrylate) (PHEMA) and 10% by volume of various crosslinked PHEMA polymer fillers (prepared by copolymerization with 0.1, 0.4, 1.0, and 20.0% by weight of ethylenedimethacrylate) of particle size about 1 μm were prepared. Some polymer matrixes were prepared from soluble branched PHEMA (Hydron S), and others by copolymerization, in the presence of the filler with 0.4 and 1.0% of ethylenedimethacrylate as a crosslinking agent. In the case of the uncrosslinked matrix, a linear polymer–crosslinked polymer system, resulted; in the case of the crosslinked matrix, a composite heterogeneous network was formed (in the latter case, the particles of the filler were swollen with monomer during the crosslinking polymerization).Stress–strain, equilibrium, and ultimate characteristics were measured at 3, 10, 25, 40, 60, and 80°C on samples swollen to equilibrium in water (Tg ≈ −50°C) and at 80, 110, and 140°C on dry samples (Tg ≈ 100°C). Depending on experimental conditions, above all on the distance from the main transition region and on whether the polymer is dry or swollen, it was found that the measured hydrophilic composite systems behaves as a filled system (with the polymer filler acting mostly as solid particles, irrespective of the crosslink density) or as a system with crosslink density fluctuations (where both networks, the matrix and the filler, contribute roughly additively to the properties of the system), or finally as defect heterogeneous systems (where the properties depend primarily on the character of the polymer–filler interface).
Light scattering from polymer films having optically anisotropic rodlike texture. A quantitative test of theories
Authors: Hashimoto Takeji , Murakami Yukinobu , Kawai Hiromichi 
Published: April 2003

AbstractThe light scattering intensity distribution from rodlike crystalline superstructures is quantitatively investigated theoretically and experimentally. The arithmetic average of theoretical Hv scattered intensities at azimuthal angle μ = 0° and μ = 45° is shown to decrease with increasing scattering angle θ in proportion to W−1 at high scattering angles for a system composed of a random assembly of rodlike superstructure having very small lateral dimensions relative to the length. The quantity W is defined as 2π(L/λ) sin θ where L is the length of the rod, and λ is the wavelength of light in the medium. A method is proposed to estimate the length L by using the W−1 dependence. Effects of internal heterogenity, polydispersity in rod length, and finite lateral dimensions of the rodlike superstructure are considered to account for experimental deviation of the scattered intensity distributions from the W−1 dependence. The effect of finite lateral dimensions turns out to be the most important.
Investigation of the dual mode sorption of ammonia in polystyrene by NMR
Authors: Assink R. A. 
Published: April 2003

AbstractThe sorption of ammonia by polystyrene was investigated by pulsed nuclear magnetic resonance (NMR) relaxation techniques. The concentration of sorbed gas was determined from the intensity of the gas signal and analyzed by the dual mode sorption model. The relaxation data were used to examine the validity of assuming that the molecules exchange rapidly between sites and that the adsorbed species is relatively immobile. Both assumptions were found to be substantially correct although the possibility that the adsorbed species may have some small mobility (no more than 5% that of the faster moving molecules) could not be eliminated.
Rubber networks containing unattached macromolecules. II. Viscoelastic properties in small strains of the system ethylene–propylene terpolymer with ethylene–propylene copolymer
Authors: Kramer Ole , Greco Roberto , Ferry John D. , McDonel E. T. 
Published: April 2003

AbstractMixtures of crosslinkable ethylene–propylene terpolymer with saturated ethylene–propylene copolymer (molecular weights 3.6, 16.7, and 45 × 104) containing up to 50% by weight of copolymer were crosslinked by sulfur, leaving the saturated copolymer unattached and free to reptate in the terpolymer network. Stress relaxation in small simple elongations (stretch ratio about 1.15) and dynamic Young's modulus at frequencies from 3.5 to 110 Hz were measured at temperatures from 10 to 50°C. Comparison with the properties of the terpolymer crosslinked without added copolymer showed contributions to stress relaxation and mechanical loss attributable to the unattached species. The time required in stress relaxation for the portion of the modulus attributable to the unattached species to decay to half its plateau value, t1/2, is approximately proportional to the 3.5 power of the molecular weight; t1/2 appears to be slightly smaller for networks containing 50% than for those containing 25% unattached component.
Rubber networks containing unattached macromolecules. III. Nonlinear stress relaxation in the system ethylene–propylene terpolymer with ethylene–propylene copolymer and behavior of extracted networks
Authors: Greco Roberto , Taylor Carl R. , Kramer Ole , Ferry John D. 
Published: April 2003

AbstractFurther stress relaxation experiments, mostly at 50°C, are reported on mixtures of crosslinkable ethylene–propylene terpolymer with saturated ethylene–propylene copolymer (molecular weights 3.6 and 45 × 104) containing up to 50% by weight of copolymer, crosslinked by sulfur to leave the saturated copolymer unattached and free to reptate in the copolymer network. Stress relaxation was measured in small simple elongations (stretch ratio about 1.15) on samples which had been extracted to remove a large part of the unattached copolymer and dried. The relative increase in modulus at long times (104 sec) increased with the proportion extracted; at short times (1 sec), extraction of the lower molecular weight copolymer increased the modulus to about the same extent but extraction of the higher molecular weight copolymer affected it very little. The relaxation modulus of the copolymer extracted from sample 50H (50% copolymer of high molecular weight), obtained by difference, agreed with that for the total copolymer except for a small difference probably attributable to molecular weight selectivity in the extraction. Stress relaxation was measured on sample 50H at six higher elongations up to a stretch ratio of 3. The dependence of stress on time and strain was consistent with an analysis based on the following assumptions: (a) linear additivity of the network and unattached copolymer contributions, (b) strain–time factorization of the stress contributions from the individual components, (c) a strain dependence for the unattached component corresponding to the presence of a Mooney–Rivlin C2 term only, (d) a strain dependence for the network component which does not follow the Mooney–Rivlin equation but is dominated by a simple neo‐Hookean term.
Flow, high‐elastic (recoverable) deformation, and rupture of uncured high molecular weight linear polymers in uniaxial extension
Authors: Vinogradov G. V. , Ya. Malkin A. , Volosevitch V. V. , Shatalov V. P. , Yudin V. P. 
Published: April 2003

AbstractThe behavior of narrow molecular weight distribution polymers has been investigated under uniaxial extension at constant deformation rate and at constant stress. It has been established that up to rupture these polymers behave as linear viscoelastic bodies. A detailed investigation of the rupture phenomenon has shown that the rupture of fluid polymers is due to their transition to the rubbery state at critical deformation rates, with the result that they disintegrate like quasi‐cured rubbers. The effect of the temperature and the molecular weight on the critical conditions of rupture has been described in terms of viscoelastic relaxation.
Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. I. α relaxation and shift factors
Authors: Naoki Motosuke , Motomura Masatoshi , Nose Takuhei , Hata Toshio 
Published: April 2003

AbstractThe complex dielectric constant was measured under elevated pressure for the α relaxation of vulcanized chlorinated polyethylene. Both temperature and pressure effects on the static dielectric constants, the activation enthalpy, and volume, and the pressure dependence of the glass‐transition temperature were obtained. The dependence of shift factors on temperature was expressed by the Vogel–Fulcher–Tamman–Hesse (VFTH) equation: −log aT = A − B/(T − T0). The parameters A, B, and T0 for each pressure applied were calculated by minimizing the standard deviation between log aT and experiments. The values of the parameters in the Williams–Landel–Ferry (WLF) equation: −log aT = C1(T − Tg)/[C2 + (T − Tg)], were also estimated from the resulting values of the VFTH parameters. All these parameters depended on pressure. The activation volume plotted against T − Tg decreased with increasing pressure.