bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscopic study of dendritic growths on the anode during prebreakdown conditions in an organic residual gas
Authors: Moretti Paul , Mesnard Guy 
Published: April 2003

AbstractAnodic growths on tungsten electrodes as a result of an applied electrostatic field with an atmosphere of benzonitrile (from about 5 × 10−4 to 10−5 torr) are studied as a function of many parameters. In order to observe the growth phenomena at high resolution in situ, the experiments were performed in an electron microscope. The growth rate of the dendrites is found to be irregular; an expression for dependence on the electric field is proposed to explain the evolution of needle length versus time t:

The mechanism of branching is also discussed.
Conformational behavior of styrene–p‐chlorostyrene triblock copolymers in dilute solutions. I. Composition dependence of conformational behavior
Authors: Shima Mikiko , Ogawa Etsuyo , Ban Seiko , Sato Mari 
Published: April 2003

AbstractDilute solution properties of (styrene‐p‐chlorostyrene) triblock copolymers in various solvents were studied over a wide range of molecular weight and composition. Viscosity and osmotic pressure results indicate that the conformational behavior of the BmAnBm and AmBnAm copolymers (A = styrene; B = p‐chlorostyrene; m and n denote the number of units) are similar in nonselective solvents such as toluene and 2‐butanone, but different in selective solvents such as carbon tetrachloride and cumene. Short‐range and long‐range interaction parameters of the block copolymers were determined by applying the Stockmayer–Fixman method to viscosity data and also by application of the equation relating the osmotic virial coefficient and the excluded volume. The results show that the unperturbed dimensions of the block copolymers vary linearly with composition, and long‐range interaction parameters in nonselective solvents can be expressed by those of the parent homopolymers, the chemical composition, and values of the interaction parameter βAB between styrene and p‐chlorostyrene monomeric units.
Interaction between styrene–ethylene oxide block copolymers and sodium lauryl sulfate in aqueous solution
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami 
Published: April 2003

AbstractInteractions of water‐soluble AB block copolymers of polystyrene and poly(ethylene oxide) with sodium lauryl sulfate (SLS) in aqueous solution were investigated by high‐resolution proton magnetic resonance (NMR). The viscosity in aqueous SLS solution was also measured. From the NMR results in D2O, it appears that molecular motions of the polystyrene blocks of the copolymer in aqueous solution are activated by interaction between the polystyrene blocks and the added SLS. From solution viscosity, on the other hand, it is apparent that a complex is formed between the copolymer and SLS and that it exhibits typical polyelectrolyte properties. The polyelectrolyte character is attributable largely to intrachain repulsions between like charges of the SLS anions adsorbed on the poly(ethylene oxide) blocks of the copolymers since the polystyrene blocks are insoluble in water and the styrene content is less than 10%.
Study of molecular motion of block copolymers in solution by high‐resolution proton magnetic resonance
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami 
Published: April 2003

AbstractMolecular motions of hydrophobic–hydrophilic water‐soluble block copolymers in solution were investigated by high‐resolution proton magnetic resonance (NMR). Samples studied include block copolymers of polystyrene–poly(ethylene oxide), polybutadiene–poly(ethylene oxide), and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide). NMR measurements were carried out varying molecular weight, temperature, and solvent composition. For AB copolymers of polystyrene and poly(ethylene oxide), two peaks caused by the phenyl protons of low‐molecular‐weight (M̄n = 3,300) copolymer were clearly resolved in D2O at 100°C, but the phenyl proton peaks of high‐molecular‐weight (M̄n = 13,500 and 36,000) copolymers were too broad to observe in the same solvent, even at 100°C. It is concluded that polystyrene blocks are more mobile in low‐molecular‐weight copolymer in water than in high‐molecular‐weight copolymer in the same solvent because the molecular weight of the polystyrene block of the low‐molecular‐weight copolymer is itself small. In the mixed solvent D2O and deuterated tetrahydrofuran (THF‐d8), two peaks caused by the phenyl protons of the high‐molecular‐weight (M̄n = 36,000) copolymer were clearly resolved at 67°C. It is thought that the molecular motions of the polystyrene blocks are activated by the interaction between these blocks and THF in the mixed solvent.
A small‐angle x‐ray scattering study of blends of isotactic and atactic polystyrene
Authors: Warner Frank P. , MacKnight William J. , Stein Richard S. 
Published: April 2003

AbstractSmall‐angle x‐ray scattering (SAXS) from blends of isotactic and atactic polystyrene has been studied. Results have been interpreted and compared using the Tsvankin, Vonk, and Hosemann techniques. The studies suggest that segregation of the atactic component occurs during crystallization within the growing spherulite of the isotactic component. However, since the interlamellar distance does not increase with atactic content, segregation is believed to occur with the formation of domains larger than interlamellar but smaller than spherulite size.
Dynamics of macromolecular chains. VII. Nuclear magnetic relaxation of monosubstituted polystyrenes in solution
Authors: Lauprêtre F. , Noël C. , Monnerie L. 
Published: April 2003

AbstractThe 1H spin‐echo and 13C spin–lattice relaxation times have been measured for solutions of polystyrene derivatives: ortho, meta, and para‐halo (F, Cl, Br) and ortho, meta, para, and α‐methyl. Results obtained from these two techniques permit comparison of the intramolecular mobility of these polymers with that of polystyrene. Poly(α‐methylstyrene) does not differ from polystyrene except for a slight slowing of both segmental reorientation and internal phenyl‐group motions and apparent hindrance of the methyl‐group rotation. Segmental reorientation of poly(m‐methylstyrene) is similar to that of polystyrene; rotation of the methyl group is free, while the internal phenyl‐ring process is slower. Poly(p‐methylstyrene) and poly(o‐methylstyrene) also contain freely rotating methyl groups; the intramolecular mobility decreases from the para to the ortho position of the substituent. Finally, in poly(o‐bromostyrene) and poly(o‐chlorostyrene), the internal motion of the phenyl ring is completely overshadowed by the segemental reorientation, which is itself quite reduced.
Strain energy function of styrene butadiene rubber and the effect of temperature
Authors: Glucklich Joseph , Landel Robert F. 
Published: April 2003

AbstractBiaxial and uniaxial tensile stress relaxation tests were made on square sheet specimens of styrene butadiene rubber (SBR), mounted in a universal biaxial tester within a temperature‐controlled box, with the object of studying the effect of temperature on the strain energy function. The stress relaxation responses, usually for times up to 10 min, were obtained for various degrees of biaxiality, various extension ratios, and various temperatures within the limits of +25 to −45°C. The results indicated that if the Valanis–Landel representation of the strain energy function \documentclass{article}\pagestyle{empty}\begin{document}$ W = \sum\nolimits_{i = 1}^3 {w\left( {\lambda _i } \right)} $\end{document}
is adopted, then time and strain are factorizable over the indicated temperature range, with time and temperature being related in the usual fashion. That is, changing the temperature does not affect the form of w(λi) but only that of G(t/αT), the temperature‐dependent relaxation modulus, aT being the regular Williams–Landel–Ferry (WLF) shift factor. The results verify the Valanis–Landel theory for various combinations of biaxiality
Spectroscopic analysis of electrically polarized polyacrylonitrile
Authors: Stupp S. I. , Carr S. H. 
Published: April 2003

AbstractElectrically polarized and unpolarized films of polyacrylonitrile (PAN) have been investigated by both infrared attenuated total reflection (ATR) and thermally stimulated discharge (TSD). ATR analysis of PAN films has been aimed at explaining the molecular origin of thermally stimulated currents, and consequently that of phenomena contributing to electrical polarization in this material. Preferred orientation of nitrile dipoles along the thickness direction (applied electric field direction) has been detected by ATR in both polarized and unpolarized films. It is suggested that dipolar alignment in unpolarized solvent‐cast films could result from internal electric fields associated with space charges. The observed orientational anisotropy is found to disappear gradually as films (both polarized and unpolarized) are heated from ambient temperature to 100°C and rotational motion in the backbone is thermally activated. TSD currents observed in this thermal range are thus associated with randomization of molecular dipoles. TSD currents observed above 100°C are suggested to originate from drift of space charges, since both an isotropic orientation of dipoles and onset of considerable diffusion are detected by ATR in this temperature range. PAN films polarized by high‐intensity electric fields (5 × 105Vcm−1, as opposed to 5 × 104Vcm−1) are found to retain orientational anisotropy above 100°C, and this is believed to be associated with a structural rearrangement induced by electrical polarization.
Polarized Raman studies of crystalline and amorphous orientation in polyethylene
Authors: Maxfield J. , Stein R. S. , Chen M. C. 
Published: April 2003

AbstractPolarized Raman intensities have been obtained from thin films of oriented low‐density polyethylene (PE) immersed in silicone oil to minimize surface scattering. Studies were made using the 1170 cm−1 crystalline band and the 1081 cm−1 amorphous band, and from these the orientation averages 〈cos2 θ〉 and 〈cos4 θ〉 were calculated. These were found to compare favorably with the values of 〈cos2 θ〉 for the polymer chain in the crystalline and amorphous phases obtained from measurements of infrared dichroism. Both orientation averages could be theoretically fitted by using reasonable parameters.
Structure of the quenched form of polypropylene
Authors: McAllister P. B. , Carter T. J. , Hinde R. M. 
Published: April 2003

AbstractX‐ray diffraction has been used to further investigate the quenched form of polypropylene. The diffractometer traces were analyzed by a mathematical peak separation procedure which assumed a combined Cauchy and Gaussian shape for the peaks. The results confirmed that the quenched form contains about 60% of amorphous polypropylene. In the remainder, the x‐ray diffraction peak positions indicate that the chain helices are arranged in a square array and a cubic or tetragonal symmetry is proposed for this phase. The shape of the x‐ray diffractometer peaks indicates a degree of strain in the structure. Crystallite sizes, determined from peak breadths, have been estimated as approximately 30 Å.
Dynamic mechanical and dielectric properties of phosphonylated polypentenamers and their hydrogenated derivatives
Authors: Rahrig D. , Azuma C. , MacKnight W. J. 
Published: April 2003

AbstractDynamic mechanical and dielectric properties of substituted polypentenamers with phosphonate side groups and their hydrogenated derivatives have been studied. Methyl esters, acids, and salts were investigated at two concentrations, 6.5 and 11.1 mole percent. In the unhydrogenated derivatives, one principal relaxation, labeled β, is observed mechanically in the temperature range from −160 to 100°C. This β relaxation arises from micro‐Brownian segmental motion accompanying the glass transition. Its temperature is substantially affected by the substituent concentration while its breadth is affected by the chemical nature of the substituent. An extended “rubbery plateau” region exists in the acid and salt derivatives. The dielectric results generally reinforce the mechanical assignments. In the hydrogenated derivatives, three relaxations labeled α, β, and γ in order of decreasing temperature occur mechanically in this temperature range. The temperatures at which the α and β relaxations occur depend greatly on the chemical nature of the substituents, the substituent concentration, and the thermal history of the sample; while the γ relaxation appears to be independent of these variables. Suggested assignments for the relaxations observed in these polymers, based on the dual glass transition theory of Boyer for semicrystalline polymers, have been proposed. The dielectric results are consistent with the proposed assignments.
On a nonexponential transformation equation for spherulitic crystallization
Authors: Hay J. N. , Przekop Z. J. 
Published: April 2003

AbstractAn equation has been derived for the development of crystallinity from heterogeneously nucleated spherulites which impinge with a small number of neighboring but randomly centered spherulites. The crystallization‐time dependence calculated from the equation conforms to an Avrami equation with initial fractional values for the n exponent, and the equation appears to be a better fit of the initial time dependence of the crystallization of polyethylene than the Avrami equation itself. It appears to account satisfactorily for the observation of fractional n values in the analysis of the crystallization curves of this polymer. The derivation of the equation only accounts for the impingement of spherulites in pairs and does not allow for multiple impingements. This limits its fit to less than the total primary crystallization. The effect on nonrandom centering of spherulites is discussed.
Vapor sorption isotherms for benzene and n‐hepatane with poly(styrene‐co‐butadiene)
Authors: Yen L. Y. , Eichinger B. E. 
Published: April 2003

AbstractVapor sorption measurements of Flory–Huggins interaction parameters χ for three poly(styrene‐co‐butadiene) + solvent systems at 25°C are reported. For Philprene 1502 + benzene: χ = 0.379–0.297 v22; for Philprene 1502 + n‐heptane: χ = 0.595 + 0.030 v2 for Solprene 1204 + benzene: χ = 0.516–0.026 v2. The volume for fractions of polymer v2 range from ca. 0.4 to 0.9.
Observation of preferred (epitaxial) orientation relationships between polyethylene crystals
Authors: Miles M. , Gleiter H. 
Published: April 2003

AbstractPreferred orientations have been observed for polyethylene single crystals deposited at room temperature on a clean polyethlene substrate crystal or a polyethylene substrate crystal coated with silicone oil (but not with a carbon layer). The observed angular relationships can be explained in terms of a network of interfacial dislocations, the cores of which lie in the fold regions between the crystals, and the long‐range strain fields extend into the lattices of both crystals. The interfacial dislocations seem likely to result from the plugging of cilia from one crystal into another.
Epitaxial growth of low molecular weight polypropylene from vapor phase
Authors: Ashida Michio , Ueda Yasukiyo , Watanabe Teizo 
Published: April 2003

AbstractPolypropylene was evaporated on the (001) cleavage faces of alkali halide single crystals, NaCl, KCl, KBr, and KI, under a vacuum of 10−5 torr. Films evaporated on the substrate were found to be composed of low molecular weight polypropylene with a narrow molecular weight distribution. The polypropylene film evaporated on the substrate maintained at 100°C, was composed of rod‐like crystals of α form, the (010) plane of which was parallel to the (001) plane of alkali halide and their long axes were oriented in the (110) direction of the substrate. When the substrate was kept above 150°C, the film included three crystalline forms, α, γ, and δ forms. Fiber‐like crystals of the α form lay parallel to the (110) direction of NaCl. In the initial stage of growth, lamellar crystals were observed in the film. The lamellar (001) plane lay flat in the film and branching occurred on the (010) lateral faces. Both the γ‐form and the (predominately) new δ‐form crystals were observed in the same area of the film prepared at temperatures above 150°C.
Selective degradation of nylon 6,6. II. Application of the degradation technique to commercially drawn fibers
Authors: Bell James P. , Hughes Alfred J. 
Published: April 2003

AbstractTreatement with hydrazine was used to investigate the crystalline morophology of commercially drawn nylon 6,6 fibers. Electron microscopic investigation revealed a stacked lamellar structure for the debris of a highly oriented, rapidly drawn fiber. However, the high molecular weight range of the gel permeation chromatogram of this same oriented fiber indicated the presence of high molecular weight material. This is thought to be due to the production of rod‐like, partially extended regions during drawing.
Crystal and amorphous orientation behavior of poly(chlorotrifluoroethylene) films in relation to crystalline superstructure
Authors: Hashimoto Takeji , Kawasaki Hiroshi , Kawai Hiromichi 
Published: April 2003

AbstractThe relationship between the crystalline superstructure of polymer films and molecular orientation was studied in cold‐drawn poly(chlorotrifluoroethylene) films by wide‐angle x‐ray diffraction, birefringence, and depolarized light scattering. By changing crystallization conditions, specimens with almost identical crystallinity but different crystalline superstructures were obtained; i.e., (1) a structure having a random array of crystallites, (2) a superstructure having a rod‐like orientation correlation of the chains (a prespherulitic and sheaf‐like superstructure), and (3) spherulitic superstructure. Upon stretching of specimens, crystallites initially randomly arranged orient with their chain axes along the stretching direction in accord with simple affine deformation. The amorphous chains also orient along the stretching direction. The orientation behavior of the specimens having the rod‐like superstructure is similar to that of the specimens with a random array of crystallites, indicating that the interaction between the crystallites in the superstructure is relatively weak. The molecular orientation behavior of the spherulitic specimens, however, strongly deviates from simple affine deformation owing to strong interaction of the crystallites in the spherulites. The deviation can be interpreted in terms of spherulite deformation and of internal reorientation of chains within deformed spherulites.
Equilibrium melting parameters of poly(ethylene terephthalate)
Authors: Mehta Aspy , Gaur Umesh , Wunderlich Bernhard 
Published: April 2003

AbstractThe equilibrium melting temperature, volume, and enthalpy and entropy changes on melting of poly(ethylene terephthalate) have been analyzed and heats of fusion have been newly measured with an automated scanning calorimeter to yield the following data: 553°K, 16.9 cm3/mole, 2.69 kJ/mole, and 48.6 J/deg/mole, respectively. A more detailed discussion of annealed samples obtained from etched starting materials shows that the density of the noncrystalline regions may be variable.
Nonstationary diffusion of polystyrenes through a cellophane membrane
Authors: Hoogervorst C. J. P. , Smit J. A. M. , Staverman A. J. 
Published: April 2003

AbstractDiffusion of five polystyrene fractions at various concentrations in toluene through cellophane membranes has been observed. The results have been used to calculate friction coefficients between solvent and solute, and between solute and membrane. The calculation requires measurement of the diffusion coefficient and the reflection coefficient of the solute, of the permeability for the solvent, of the pore volume of the membrane, and of the partition coefficient of the solute between membrane and solvent. By comparing the friction coefficient between solvent and solute in the membrane with this coefficient in free solution, the tortuosity factor and the pore diameter of the membrane can be estimated. The dependence of the friction coefficients on molecular weight M2 of the solute is determined. For large values of M2, the friction between solute and solvent is the determining factor. The friction coefficient between solute and solvent increases more strongly with M2 in the membrane than in free solution owing to an entrance effect for the permeating solute at the interface.
Collapse of pyramidal polyethylene crystals
Authors: White J. R. 
Published: April 2003

AbstractAn assessment of the possible collapse mechanisms for solution‐grown pyramidal polymer crystals is made, taking into account electron microscope observations and the mechanics of the loading situation. That comprehensive collapse always occurs is shown not to be as self‐evident as is normally assumed, even though the more exacting criteria for its establishment are indeed usually met. Bending of lamellar crystals is found to account for many observations, although an alternative means of tilting molecular chains, the “differential shear tilt model” is also considered.
Analysis of the effect of interfacial slippage on the elastic moduli of a particle‐filled polymer
Authors: Takahashi Kiyohisa , Ikeda Masahiko , Harakawa Kazuhisa , Tanaka Kenji , Sakai Tetsuya 
Published: April 2003

AbstractAn attempt was made to study the effect of interfacial slippage on the filler reinforcement based on the boundary condition that the constituents of a particle‐filled composite can slip relative to each other, but no cavities are formed at the interfaces. The elastic field satisfying these conditions is derived using the linear theory of elasticity and the effective elastic moduli of the composite are calculated. The following assumptions are made: (1) Filler particles are spherical, (2) fillers are completely dispersed, and (3) the volume fraction of fillers is sufficiently small that the interaction among fillers may be neglected. The expression for the shear modulus of the composite μ**, which is derived here, is consistent with the viscosity of a suspension which has been derived by Oldroyd. Experiments who that the increase of Young's modulus by glass beads (GB) is lower in polystyrene (PS) than in epoxy resin (Ep). The reinforcement in Ep‐GB systems can be estimated by the well known formula derived assuming perfect adhesion. However, the reinforcement in PS‐GB systems is in rather good agreement with the formula derived here assuming interfacial slippage.
Study of latex film structure by radiothermoluminescence
Authors: Zlatkevich L. , Shepelev M. 
Published: April 2003

AbstractRadiothermoluminescence has been used to show that the surface of latex globules in nonvulcanized latex films contain segments which become mobile at a temperature 20°K below that observed in bulk polymer. Vulcanization in latex films takes place mainly on the surfaces of the latex globules; vulcanized latex films are microheterogeneous systems.
Association of stereoregular poly(methyl methacrylates) in dilute solution. Proton NMR study
Authors: Spéváček J. 
Published: April 2003

AbstractBy measurement of integrated intensities of high‐resolution proton nuclear magnetic resonance (NMR) bands, associated structures of isotactic (i) and syndiotactic (s) poly(methyl methacrylate) (PMMA) in dilute toluene‐d8 and dimethylformamide‐d7 solutions were detected and characterized. In 1% (w/v) solutions of highly stereoregular s‐PMMA in toluene‐d8 at 27°C, 76% of the monomer units are present in the form of compact aggregates. Consequences of this finding for the polymerization of methyl methacrylate in toluene in the presence of s‐PMMA are discussed.