bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of the secondary relaxation in isochronal measurement of glasses
Authors: Chung S. H. , Pathmanathan K. , Johari G. P. 
Published: April 2003

AbstractA method by which the occurrence of a secondary relaxation can be deduced from the isochronal dielectric and mechanical loss data of amorphous and crystalline materials is given. The method eliminates the complexity arising from the frequency‐independent, temperature‐dependent background loss in solids.It is shown that the relaxation rate measured at a fixed frequency by varying the temperature substantially differs from that measured at a fixed temperature by varying the frequency when the strength of the relaxation is temperature dependent. This discrepancy leads to a different value of activation energy and of preexponential factor when the strength increases with temperature. The results are discussed in terms of the temperature dependence of the strength of relaxation and its distribution parameter.The method of analysis has been applied to the data for a molecular and a polymeric glass and shows the occurrence of a β process which is otherwise not detected in their tan β isochrones. Experimental data on a wide variety of glasses also show that the activation energies and relaxation rates obtained from isochrones differ from those obtained from the isothermal spectrum.
Direct method of calculating the dynamic scattering spectrum
Authors: Wei Gaoyuan , Cohen Claude 
Published: April 2003

AbstractA method of obtaining the scattering spectrum that bypasses the need to solve for the configurational distribution function of the macromolecules is presented. It involves the direct calculation of averages that appear in the structure factor expression. Application of the method to Rouse coils recovers Pecora's classical results. The method is applied to obtain the coherent spectrum of a solution of “encapsulated” dumbbells for which the configurational distribution is not available.
Synthesis and bulk physical properties of styrene‐alkoxide ionomers. Part I: Sodium salts of polystyrene‐co‐4‐hydroxystyrene
Authors: Clas S.‐D. , Eisenberg A. 
Published: April 2003

AbstractPolystyrene‐co‐4‐hydroxystyrene ionomers (3.0–22 mol%) were synthesized via neutralization of demethylated polystyrene‐co‐4‐methoxystyrene. The physical properties of the ionomers as well as their nonionic precursors were studied by calorimetry, torsion pendulum and small‐angle X‐ray scattering (SAXS). Evidence for ion aggregation was obtained for the styrene‐4‐hydroxystyrene ionomers from SAXS and torsion pendulum studies.
Synthesis and bulk physical properties of styrene‐alkoxide ionomers. Part II: Sodium salts of polystyrene‐co‐4‐hydroxymethylstyrene
Authors: Clas S.‐D. , Eisenberg A. 
Published: April 2003

AbstractPolystyrene‐co‐4‐hydroxymethylstyrene ionomers (2.5–19.4 mol%) were prepared from the partial chloromethylation of polystyrene, followed by esterification, saponification, and finally neutralization. The physical properties of the ionomers as well as their nonionic precursors were studied by calorimetry, torsion pendulum, and small‐angle X‐ray scattering (SAXS). SAXS and torsion pendulum studies show no evidence of extensive clustering.
Styrene‐alkoxide ionomers. Part III: Comparison with other styrene ionomers
Authors: Clas S.‐D. , Eisenberg A. 
Published: April 2003

AbstractThe properties of two novel ionomers, the sodium salts of styrene‐4‐hydroxystyrene and styrene‐4‐hydroxymethylstyrene, obtained from torsion pendulum experiments are compared with those of other styrene ionomers. The glass transition temperature of the matrix, the size of the ionic aggregates, and the strengths of the ionic interactions within these large aggregates were related to the type and position of the ionic group. Attempts were made to explain these results.
The liquid‐crystalline properties of (acetoxypropyl)cellulose: Effect of chain length and degree of acetylation
Authors: Laivins G. V. , Sixou P. , Gray D. G. 
Published: April 2003

AbstractPartially degraded (hydroxypropyl)cellulose methanolysates were acetylated in an acetic anhydride/dioxane mixture with a perchloric acid catalyst, yielding (acetoxypropyl)cellulose (APC) samples with an unit ester content per anhydroglucose unit of three. Eight APC samples of molar masses from 10,000 to 1.8 × 105 g/mol were prepared. On heating, all the samples displayed biphasic behavior prior to isotropization. The isotropization temperature of the samples increased rapidly with molar mass, attaining a limiting value of 174°C. The substitution of hydroxyl groups of HPC by acetyl groups lowered the limiting value. Lyotropic mesophases of APC in dimethyl acetamide (DMAc) showed isotropization temperatures that increase nonlinearly with increasing APC concentration. For chains with contour lengths exceeding 72 nm, the critical concentration for mesophase formation, 0, does not depend on the chain length. However, for short chains the 0 value increases rapidly with decreasing chain length. The cholesteric reflection wavelength, λ0, of a thermotropic APC sample of low molar mass is greater than that of a higher molar mass sample at a given temperature and increases with increasing temperature for all samples. Partially acetylated (hydroxypropyl)cellulose displays reflection colors at lower temperatures than the fully acetylated APC.
Polydispersity effects on diffusion in polymers: Concentration profiles of d‐polystyrene measured by forward recoil spectrometry
Authors: Mills Peter J. , Green Peter F. , Palmstrøm Christopher J. , Mayer James W. , Kramer Edward J. 
Published: April 2003

AbstractForward recoil spectrometry is shown to be a useful technique for measuring diffusion of d‐polymer chains in h‐polymer melts. Concentration profiles of a deuterated diffusing species may be determined with a depth resolution of 80 nm and a sensitivity of 0.1 vol % d‐polymer in h‐polymer. Consequently diffusion coefficients as small as 10−16 cm2/s can be readily measured. If polymer chains diffuse by a reptation mechanism, the concentration profile ø(x) of diffusing polydisperse polymer should be quite different from øm(x), the Fickian solution, which one obtains for monodisperse polymer. This idea was tested by measuring ø(x) of polydisperse d‐polystyrene (d‐PS) diffusing into h‐PS. The results are in excellent agreement with the ø(x) predicted from the reptation model and the experimentally determined molecular weight distribution.
Ionic dissociation of ionene polymers in aqueous solutions
Authors: Fujii Michihiro 
Published: April 2003

AbstractThe degree of ionic dissociation of aliphatic ionene polymers, 3,3‐, 4,4‐, 6,6‐, and 8,8‐ionene bromide in salt‐free aqueous solutions at infinite dilution was obtained by emf measurements with a bromide ion electrode. The results show that the longer the methylene chain between neighboring charges on the polymer backbone, the greater is the degree of dissociation, as Manning's theory predicts. The distance between the neighboring charges on the polymer backbone was calculated by using Manning's equation. The distance was compared with that calculated geometrically on the basis of the contour length of the molecule according to Manning's definition. The former distance was much smaller than the latter. The former distance was then compared with the length calculated from Eyring's equation for the end‐to‐end distance of a freely rotating methylene chain. In this case, good agreement was obtained.
Influence of the rotational mobility of probe molecules on their orientation factors
Authors: Hennecke Manfred H. 
Published: April 2003

AbstractThe influence of a small rotational mobility on the measured orientation factors f2 and f4 (connected with the second and fourth moments of the orientation distribution function), of uniaxial probe molecules in uniaxial polymer systems is calculated with special regard to the fluorescence polarization method. A mean angle of rotation of about 10° within the time scale of the experiment, i.e., the fluorescence lifetime, affects f4 considerably, while it has practically no influence on f2. On the other hand, the knowledge of the true f4 of the sample and some assumptions on the mobility—orientation correlation make it possible to evaluate the mean rotational angle θ from the measured f4. Moreover, the measured f2 value can be precisely corrected. The effect of the assumptions on the reliability of f2 and θ is analyzed. Experimental results on two partially mobile probe molecules in drawn polyethylene are discussed.
Structure of the iodine columns in iodinated nylon‐6
Authors: Burzynski Ryszard , Prasad Paras N. , Murthy N. Sanjeeva 
Published: April 2003

AbstractA study of iodine‐complexed nylon 6 films by polarized resonance Raman spectra shows the presence of both I3− and I5− species, the latter most likely in the form of an I2/I3− complex. Polarization characteristics of the Raman spectra show that the I2/I3 units are orinted along the polymer chain and the I3− ions are perpendicular to the chain axis. The I2/I3− units are in a more stable moiety than the I3− species. These Raman results are consistent with the x‐ray diffraction data.
Diffuse interface between polymers: Structure and kinetics
Authors: Wu Souheng , Chuang Hsiao‐Ken , Han Chang Dae 
Published: April 2003

AbstractThe interfacial structure and diffusion kinetics of two compatible polymers, poly(methyl methacrylate) and poly(vinylidene fluoride) are studied in the melt. The interdiffusion rates of the two components are found to be unequal, giving unequal diffusion coefficients, a net mass flow across the interface, and an asymmetric interfacial composition profile. The structure and kinetics confirm the predictions of the reptation theory. The interfacial thickness d grows with t1/2, and the interdiffusion coefficient is proportional to M−2, where t is the time and M is the molecular weight. The scaling law for the interfacial thickness is therefore d ∝ M−1t1/2. The number of chains per unit area crossing the original interface reaches a constant value independent of diffusion time after a short induction time on the order of the tube disengagement time (about 0.1–10 s in the present cases depending on the molecular weights). The adhesive bond strength σ is scaled by σ ∝ t1/4M−1/2 and σ/σ∞ ∝ t1/4M−1/2 [1‐ (Mc/M)]−1, where σ ∞is the σ at infinite molecular weight and Mc is the entanglement molecular weight.
The relaxation and deformational properties of a carbon‐black filled elastomer in biaxial tension
Authors: Sullivan J. L. 
Published: April 2003

AbstractBiaxial stress relaxation data acquired for a carbon‐black‐filled elastomer are analyzed. Consistent with previously published simple‐tension and pure‐shear results for this elastomer, the biaxial relaxation behavior is also found to be a separable function of time and strain effects. A departure from separability is observed at the larger strain; this might be a manifestation of strain‐induced crystallization. An analysis of the biaxial results together with the earlier reported simple‐tension and pure‐shear data reveals that the deformational dependence of this elastomer obeys the Valanis—Landel hypothesis up to moderate deformations. The Ogden strain energy function is found to be an excellent analytical representation of all of the multiaxial data. Large relative errors found at small tensile strains between the data and the Ogden fit are attributed to carbon black structural effects.
Rheology of hydroxypropylcellulose solutions
Authors: Navard P. , Haudin J. M. 
Published: April 2003

AbstractThe rheology of hydroxypropylcellulose (HPC)—acetic acid solutions was investigated by using a cone‐and‐plate rheometer and a capillary rheometer, for polymer concentrations ranging from 10 to 80%. Isotropic solutions exhibit a Newtonian plateau followed at higher shear rates by a pseudoplastic zone. The apparent viscosity varies as C5.2 if concentration C is less than 27% and as C13 for 27% < C < 30%. A biphasic interval (isotropic and cholesteric phases) exists between 30 and 35%. A maximum in viscosity is observed at C = 30%, the height of the viscosity peak being a decreasing function of shear rate. Anisotropic solutions are strongly viscoelastic. Both isotropic and anisotropic solutions give results (apparent viscosity, first normal‐stress difference, relaxation time, etc.) which are not in good agreement with Doi's theory. This is understandable since the HPC chain cannot be modeled by a rigid rod. Upon heating, anisotropic HPC—acetic acid solutions undergo an anisotropic to isotropic phase transition which is easily detected by a maximum in the temperature dependence of the first normal‐stress difference and of the apparent viscosity.
The solubility and diffusion of water in poly(aryl‐ether‐ether‐ketone) (PEEK)
Authors: Grayson Michael A. , Wolf Clarence J. 
Published: April 2003

AbstractThe transport properties of water in neat poly(aryl‐ether‐ether‐ketone) (PEEK) coupons (2 to 6 mm thick) were investigated by gravimetric and mass spectrometric methods. The solubility of water increases from 0.44 wt.% at 35°C to 0.55 wt.% at 95°C; the temperature coefficient is 8 kJ/mol (1.9 kcal/mol). The diffusion processes for sorption, desorption, and resorption at 35°, 50°, 65°, 80°, and 95°C are, within experimental error, the same. The activation energy for diffusion is 42.7 kJ/mol (10.2 kcal/mol). The diffusion process is classical Case I Fickian in the temperature region investigated.
Microphase structure of interpenetrating polymeric networks based on polyurethane and polyurethane ionomer
Authors: Lipatov Yu. S. , Shilov V. V. , Bogdanovich V. A. , Karabanova L. V. , Sergeeva L. M. 
Published: April 2003

AbstractInterpenetrating polymer networks based on polyurethane and polyurethane ionomer were studied using wide‐angle and small‐angle X‐ray diffraction. The polyurethane network is a multiblock polymer based on the trimethylolpropane adduct with 2,4‐toluene‐diisocyanate and poly(propylene oxide tetrahydrofuran) copolymer. Polyurethane ionomer represents a network formed from poly(propylene glycol) containing three OH side groups, 2,4‐toluene‐diisocyanate, 2,2′‐dimethylethanol‐amine, and 1,5‐dibromopentene. The network polymers are characterized by structure heterogeneity developed during microphase separation as a result of hard and soft block segregation. The interpenetrating networks investigated are amorphous systems over the whole range of compositions. They form a very complicated structure where the phase separation of polyurethane and ionomer takes place. It is important to note that phase separation leads to the appearance of microphase structure periodicity due to regular arrangements of microregions enriched by one of the components. The latter fact is considered to be a sign of spinodal phase separation at the initial stages.
Relaxation properties of some segmented polyurethane‐CaCO3 composites. A Dielectric study
Authors: Báanhegyi Gyöurgy , Rho Man‐Khyun , Chien James C. W. , Karasz Frank E. 
Published: April 2003

AbstractDielectric relaxation in three segmented polyurethane‐CaCO3 composites was investigated between −70°C and +150°C in the 300 Hz to 100 kHz frequency range. Two of the polymers contained a polyacetal‐polyether soft segment, whereas the soft component of the third polymer was polypropylene oxide. The hard segments consisted of 4,4′‐diphenyl methane diisocyanate in two cases and toluene‐2,4‐diisocyanate in the third case.In parallel studies two calorimetric relaxations, designated α and α′, were observed for each sample and were determined to be glass transitions of the soft and hard segments, respectively. In general, the transition temperatures decrease with increasing filler content. High frequency, low temperature permittivities increase while low frequency, high temperature AC conductivities generally decrease with increasing filler content. The shift in the transition temperatures can be explained using the adsorption theory of filler‐polymer interactions and the densities of the samples. The interfacial polarization mechanism becomes important only above the α′ transition temperature and below 1 kHz.
On the percolative behavior of carbon black cross‐linked polyethylene systems
Authors: Benguigui L. , Yacubowicz J. , Narkis M. 
Published: April 2003

AbstractThe dielectric properties of peroxide cross‐linked polyethylene–carbon black composite systems are described in the frequency range between 10 and 107 Hz as a function of frequency and carbon black loading. Very high values for the dielectric constant were obtained when measuring conductive samples. A percolative model gives a suitable explanation, within experimental limits of the properties of the systems studied.
A study of aqueous solutions of dextrans by gel permeation chromatography using a multiple detection system
Authors: Van Dijk J. A. P. P. , Varkevisser F. A. , Smit J. A. M. 
Published: April 2003

AbstractWe studied the elution of dextrans in gel permeation chromatography (GPC) using a low‐angle laser light‐scattering (LALLS) system to monitor the molecular weight and the standard refractive index (RI) detector to measure the concentration. In pure water the dextrans show bimodal chromatograms of the RI response as well as of the LALLS response. The first eluted peak reflects the macroion exclusion due to the repulsion between negatively charged macromolecules and equally charged gel. In spite of the resulting distortion of the chromatograms, correct values of the weight‐average molecular weights (M̄w) are obtained from them. If instead of pure water a salt solution (0.1 M KNO3) is used as eluant, the charge effect is completely suppressed and single‐peak chromatograms are found. Again correct values of M̄w are obtained, but number‐average molecular weights turn out to be too large owing to axial column dispersion in the coupling arrangement. By introducing a spreading factor, values of M̄n could be corrected. Investigations of the charge effect were also carried out by monitoring the electric conductivity of the eluted dextran zone. In this way, the phenomenon of ion inclusion, evidently provoked by charged dextran molecules, was observed.
Hydrostatic compression of the monoclinic form of polyethylene
Authors: Miyaji Hideki , Asahi Takanao , Miyamoto Yoshihisa , Asai Kenjiro 
Published: April 2003

AbstractLattice constants of the monoclinic form of polyethylene under pressures up to 1.8 GPa at 298 K are investigated by x‐ray diffraction. The thermal expansion from 100 K to 300 K at atmospheric pressure is also studied. The equation of state is calculated by Pastine's method, taking into account the zero‐point vibration, and is compared with experimental results. The calculated results depend largely on the interatomic potential used and the limit of the interatomic distance for summation of the potentials. A change in the angle γ between the a and b axes results in an anisotropic change in the unit cell dimension with both pressure and temperature; the a and b axes change at nearly the same rate. The monoclinic form may have a higher density than the orthorhombic form at pressures above 1.0 GPa.
RHEED investigation of thin tin films on polypropylene
Authors: Schultz J. M. , Peneva S. K. 
Published: April 2003

AbstractThin layers of (25–1000 Å) tin were evaporated onto a highly oriented polypropylene sheet. Two rates of deposition were used: 5 and 20 Å/s. For the more rapid deposition rate, a preferred orientation of tin was found in all cases. Here, the Sn a axis lay parallel to the polymer chain (polymer c axis). The same orientation relationship was found for the slower deposition rate, but only at lower Sn film thicknesses; at the higher film thicknesses, a random orientation of crystallites is found. Scanning electron micrographs show an equiaxed tin grain structure for the case of no preferred orientation and a platelet morphology for the case of preferred orientation, the thin dimension of the platelets lying perpendicular to the polymer chain axis. Although no clearcut evidence either for or against crystallographic epitaxy has been found, a plausible case for geometrical epitaxy is presented.
Evolution of structure and properties in fiber formation from a thermoplastic polyester‐polyether segmented copolymer
Authors: Abhiraman A. S. , Kim Y. W. , Wagener K. B. 
Published: April 2003

AbstractProcess‐structure‐property relationships in the formation of an elastic fiber from a melt of segmented polyester‐polyether copolymers are described. The “soft” segment, polyethylene oxide, is modified to prevent its crystallization at use temperatures. Features of the polymer related to phase separation of the soft segments and the crystallizable “hard” segments are discussed. An “ideal” morphology of such a thermoplastic elastomeric fiber that would maximize its recoverable extension is defined, and a path toward its realization in a melt spinning process is described.
Influence of reptation on localized diffusion in crystallizing polymers
Authors: Keith H. D. , Padden F. J. 
Published: April 2003

AbstractCrystalline texture in polymer spherulites appears to be determined in part by interplay during solidification between interface morphology and the diffusion of species segregated at crystal growth fronts; these species are molecules of lower molecular weight (fractionation) or molecules of stereoirregular structure. Early discussions of this behavior were based upon assumption of a single diffusion coefficient in each case. However, it is now known that, because of reptation, each molecule in a polymer melt diffuses with a diffusion coefficient dependent on its individual molecular weight. In this paper, the influence of reptation upon concentration profiles and diffusion ranges is examined. It is shown that such influence is slight when segregated species have relatively narrow distributions of molecular weight, such as are typical when segregation involves fractionation or is mostly confined to fractionated stereoirregular species blended with crystallizable host polymer. With broad distributions, however, concentration profiles are significantly altered and long segregated molecules dominate morphologically important behavior. Meaningful average diffusion ranges can often be derived and related to appropriately averaged molecular weights of participating molecules. Morphological implications of the various results are outlined.
Theoretical prediction of minima in association constants for complex formation between alkylviologens and indole derivatives in the presence of polyelectrolytes
Authors: Ishiwatari Tsutomu , Yoshida Satoshi , Morita Mariko , Seki Ikuko , Mitsuishi Masaru 
Published: April 2003

AbstractAssociation constants K for the complexation between various alkylviologens (methyl, propyl, butyl, pentyl, and hexyl) and indole derivatives (acetate and butyrate) have been determined. The order of K values indicates the important role of hydrophobic interactions in aiding the formation of charge transfer complexes. Influences of two kinds of polyelectrolytes; i.e., potassium polystyrenesulfonate (KPSS, anionic) and 3,3‐ionene (cationic) on the K values were also examined. KPSS decreased the K value but, interestingly, yielded a minimum, and the K value increased at high KPSS concentrations. The influence of the type of alkylviologen on the K versus [KPSS] plots was successfully understood by a theory of substrate partitioning between bulk water and the environment of the polymer.