bluuebunny/crossref_metadata_2025_split huggingface dataset:
A crystallographic study of polymers exhibiting side‐chain crystallization
Authors: Hsieh H. W. S. , Post B. , Morawetz H. 
Published: April 2003

AbstractFibers were drawn from polymers of octadecyl acrylate, octadecyl methacrylate, N‐octadecylacrylamide, and a series of N‐substituted acrylamides with a second amide group in the side chain as well as from copolymers of octadecyl and methyl esters of acrylic and methacrylic acid. Wide‐angle and small‐angle x‐ray diffraction patterns were recorded for these materials. The interpretation of the characteristic difference between the behavior of the polycrylates and polymethacrylates, as proposed by Platé and his collaborators, is found to be inconsistent with a number of features of the experimental evidence. In the case of poly(octadecyl methacrylate) the data allow the estimation of two parameters of the electron density distribution in the side‐chain crystallites. With polyacrylamide derivatives, a second amide group in the side chain is found to destabilize the side chain crystallites. The bahavior of the copolymers is very complex and exhibits, in one case, evidence for a long periodicity parallel to the fiber axis.
Nuclear magnetic relaxation and molecular motion in poly(vinylidine fluoride)
Authors: McBrierty V. J. , Douglass D. C. , Weber T. A. 
Published: April 2003

AbstractPulsed NMR T1, T2, and T1ρ measurements are reported for poly(vinylidine fluoride) (PVF2). The results demonstrate clearly the presence of four relaxation processes, three amorphous and one crystalline. The α relaxation is undoubtedly a crystalline one, while β and γ are both amorphous, in agreement with earlier conclusions from dielectric and dynamic mechanical measurements. The fourth relaxation (β′) observed initially in the mechanical measurements of Kakutani, but undetected in dielectric experiments, has been confirmed in our results and the process is described by an activation energy of 15.1 kcl/mole. Motion of folds on the surface of crystal lamellae is deemed to be the responsible mechanism for the β′ relaxation. Two models have been considered in the interpretation of the α process; rotation of crystalline chains in the vicinity of defects and rotational oscillation of restricted amplitude of all crystalline chains about the main chain axes. Rotation of amorphous chains is a possible mechanism for the γ process while motions of a general nature are responsible for the β relaxation. Our experimental results again indicate that spin diffusion plays an important role in the overall NMR response of the polymer.
Surface properties of styrene–ethylene oxide block copolymers
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami 
Published: April 2003

AbstractHydrophobic–hydrophilic block copolymers were prepared by “living” anionic polymerization. They consist of polystyrene and poly(ethylene oxide) blocks, and are soluble in water. Their interfacial properties were investigated, employing aqueous solutions. The block copolymers lowered the surface tension of water in analogy with the low molecular weight surfactants such as sodium lauryl sulfate and heptaethylene oxide n‐dodecyl ether. Their aqueous solutions exhibited solubilization properties differing from those of polyethylene glycol. Therefore, it is thought that the polystyrene blocks produce solubilization phenomena. In samples of the same styrene content, the precipitation temperature of a high molecular weight copolymer in water was lower than that of a low molecular weight copolymer at the same concentration in the same solvent. The surface tension and precipitation temperature of aqueous solutions seem to be influenced by molecular weight and composition.
Strains induced upon drying thin films solvent‐cast on flexible substrates
Authors: Chow T. S. , Liu C. A. , Penwell R. C. 
Published: April 2003

AbstractSolvent coating is an important commercial technique utilized in fabricating thin films. In certain cases, undesirable strains may be built into the composite as the solvent is removed. The stress field in a two‐layer sample and its distribution along the interface have been analyzed. By considering the shrinkage of the solvent cast film equivalent to applying an axial compressive load, interfacial expressions were derived which are valid for solvent drying of solution cast films. Experimental procedures and measurements are presented for the solvent casting of thin brittle films onto flexible polymeric substrates. Interfacial strains are determined and their dependence on accurate material property measurements is evaluated. The relation between the bulk and interfacial strain is illustrated.
Crystallization of bisphenol‐A polycarbonate. I. Influence of trimellitic acid tridecyloctyl ester on the kinetics of crystallization
Authors: Gallez F. , Legras R. , Mercier J. P. 
Published: April 2003

AbstractThe crystallization of bisphenol‐A polycarbonate plasticized by trimellitic acid tridecyloctyl ester (Morflex 525) has been studied. A half‐crystallization time of 100 min is observed at 170°C with 10% of plasticizer compared with a figure of 18,000 min for the unplasticized material. The kinetic study is limited to the primary crystallization process which can be described by an Avrami equation; however, the Avrami coefficients are much higher than usual. Studies on the effect of the preparation procedure of the samples and of premelting indicate that nucleation is at least partially heterogeneous.
The morphology of polyethylene prepared by γ‐ray‐induced polymerization in various solvents
Authors: Arai Hidehiko , Wada Takeshi , Kuriyama Isamu 
Published: April 2003

AbstractPolyethylenes were prepared by γ‐ray‐induced polymerization in ethyl and n‐butyl alcohols, tert‐butyl alcohol containing 5 vol‐% of water, 2,2,5‐trimethylhexane, 2,2,4‐trimethylpentane, and cyclohexane in the temperature range 25–90°C. The morphology of the polymers as‐polymerized and studied by electron microscopy depends on three factors through the degree of undercooling: the affinity of the solvent, polymerization temperature, and the polymer molecular weight. Large lamellar crystals are formed even in the alcohols when at least two of them are chosen properly.
Small‐angle x‐ray and light scattering studies of the morphology of blends of poly(ϵ‐caprolactone) with poly(vinyl chloride)
Authors: Khambatta F. B. , Warner F. , Russell T. , Stein R. S. 
Published: April 2003

AbstractSolvent‐cast films of blends of poly(ϵ‐caprolactone) (PCL) with poly(vinyl chloride) (PVC) were examined by low‐angle x‐ray scattering and by small‐angle light scattering. X‐ray scattering from crystalline compositions were analyzed using the Tsvankin–Buchanan technique and led to values of the repeat period of the lamellar structure and the thickness of the crystalline and amorphous layers. With increasing content of PVC, the amorphous layer thickness increased sufficiently to accommodate the PVC, leading to values of the linear crystallinity consistent with macroscopic measurements by density and DSC techniques up to about 50% PVC by weight. Above this concentration, the lamellar structure no longer appeared to be volume filling. At high concentration of PCL, the polymer consisted of volume‐filling spherulites containing the lamellar substructure. Spherulite sizes were measured by light scattering and absolute light scattering intensities were consistent with calculations based upon the degree of crystallinity and anisotropy of the spherulites. Compositions containing more than 60% PVC were amorphous. Low‐angle x‐ray scattering was interpreted in terms of the Debye–Bueche theory which leads to values for a correlation distance lc and the mean‐square electron density fluctuation 〈η2〉 (which was also obtained from the invariant). By the method of Porod, the correlation distances were resolved into persistence lengths within the two phases, which were determined as a function of composition. The fluctuation 〈η2〉 was analyzed in terms of a two‐phase model to show that its value was somewhat larger than would be obtained if the phases were composed of the pure components. It was not possible to uniquely determine their compositions. The data were consistent with the existence of a transition zone of the order of 30 Å thick between phases.
Persistence vectors for polypropylene, polystyrene, and poly(methyl methacrylate) chains
Authors: Yoon D. Y. , Flory P. J. 
Published: April 2003

AbstractPersistence vectors a ≡ 〈r〉 are calculated for polypropylene, polystyrene, and poly(methyl methacrylate) chains as functions of chain length and stereochemical constitution. Differences between the progressions of a with chain length for these vinyl polymers are related to their conformational characteristics. The preferences of the syndiotactic chains for the tt dyad conformation are manifested most strikingly in the behavior of this vector.
Molecular orientation in poly(ethylene terephthalate) by means of laser–raman spectroscopy
Authors: Purvis J. , Bower D. I. 
Published: April 2003

AbstractThe intensity of the Raman scattering from uniaxially oriented amorphous poly(ethylene terephthalate) tapes at wave number shifts of 1732, 1616, 1286, 857, and 632 cm−1 has been observed for various combinations of incident and scattered light polarization vectors with respect to the draw direction. An attempt has been made to analyze the data to provide values of 〈P2(ζ)〉 and 〈P4(ζ)〉, where Pn(ζ) is the nth order Legendre polynomial in ζ,ζ is the cosine of the angle between the draw direction and a typtical chain axis in the polymer, and the angle brackets denote the average value over all repeat units. This attempt was successful for the 1616 and 632 cm−1 lines but less successful for the other three, although the data for the 1732 and 1286 cm−1 lines could be analyzed to provide quantities proportional, but not equal, to 〈P2(ζ)〉. In the analysis and discussion two possible models were considered for the conformation of the terephthaloyl residues in the amorphous polymer but it was not possible to reject either model conclusively. The results suggest, in agreement with previous studies by other methods, that the drawing of PET at 80°C takes place essentially as the extension of a rubberlike network which is frozen on subsequent cooling to room temperature.
Changes in light scattering from poly(ethylene terephthalate) and nylon 6 films upon stretching in relation to the deformation mechanism
Authors: Konda Atsuo , Nose Kenkichi , Ishikawa Hiroshi 
Published: April 2003

AbstractUnoriented T‐die flat films of nylon 6 and PET films annealed at 90°C were stretched in water at 80°C. Amorphous PET films were stretched in water at 65–75°C. Changes in the light scattering patterns from these samples upon stretching were investigated. One of the observed LS patterns from the stretched samples is the Hv eight‐leaf pattern consisting of four lobes and streaks. In the nylon 6 and heat‐treated PET showing this pattern, spherulitic patterns can be seen in polarization microscopy. The microscopic spherulitic superstructure may possibly be the factor responsible for producing the lobe‐and‐streak pattern. On the other hand, many microscopic eight‐leaf patterns can be observed in amorphous unannealed PET showing the lobe‐and‐streak pattern. These microscopic patterns are due to retardation at stress concentrations around impurities and nuclei. The superstructure giving these microscopic patterns must be the origin of the lobe‐and‐streak pattern from unannealed PET. Another scattering pattern, the Vv cruciform pattern, was observed in both stretched nylon 6 and unannealed PET. This pattern is due to an orientation change across the slip lines observed under a polarizing microscope. It is noted (1) that the appearance of the slip lines in PET coincides with the occurrence of oriented crystallization on stretching, (2) that the lobe‐and‐streak pattern from PET in which orientation crystallization has taken place is fairly stable to heat treatment and does not disappear until just before melting, and (3) that the superstructures produced at low stretching seem to be deformed on further stretching, in accordance with affine deformation theory.
Thickening of crystals during rapid heating. II. Crosslinked polyethylene and methoxymethylated nylon 6
Authors: Sakurai Kensuke , Oota Teruhisa , Miyasaka Keizo , Ishikawa Kinzo 
Published: April 2003

AbstractThe effect of modification of polymer chains on crystal thickening during heating was investigated with an apparatus devised for rapid measurement of small‐angle x‐ray diffraction. Thickening of crystals still occurred even at a heating rate of 18°C/min in polyethylene irradiated with gamma ray doses of 30–300 Mrad, and the melting point was depressed. These results showed that the melting point depression due to irradiation is not due to a restriction on crystal thickening but rather to crystal lattice distortion. On the other hand, although methoxymethylation of nylon 6 completely inhibits crystal thickening, the melting point increases or decreases depending on the temperature of annealing preceding methoxymethylation. From these results we are led to conclude that irradiation and methoxymethylation are not effective means of obtaining the relation between melting point and crystal thickness.
The scattering of light from thin polymer films: Multiple scattering. II. Effect of depolarization
Authors: Natarajan Raj T. , Prud'Homme Robert E. , Bourland L. , Stein Richard S. 
Published: April 2003

AbstractA procedure is described to include the effect of depolarization of the originally plane‐polarized incident light beam as it passes through a thin polymer sample on the intensity of multiple light scattering. The multiple scattering gives rise to “polarization scrambling” in which, for example, Hv scattering measurements involve multiple scattered rays which may have undergone some Vv scattering. These phenomena reduce the angular dependence of scattering since large intensities originally occurring at small values of θ are rescattered so as to enhance intensities at other angles. Correction factors for both Hv and Vv scattering are presented.
A kinetic effect in the environmental stress cracking of polyethylene due to liquid viscosity
Authors: Shanahan M. E. R. , Schultz J. 
Published: April 2003

AbstractAn Interesting kinetic effect in the environmental stress cracking (E.S.C.) of polyethylene has been observed, in which the liquid viscosity plays an important role. E.S.C. of a low density, high melt index polyethylene due to silicone oils has been studied using constant load creep experiments. For relatively low stresses, it has been found that the time to fracture is independent of the viscosity of the silicone oil, all other factors being approximately equal. However, at high stresses, the time to fracture increases with increasing viscosity for a given stress. This effect has been shown to be due to the relative ease with which the liquid penetrates a growing crack and thus always be at the crack front. Times to fracture for viscous liquids at high stresses are longer since crack propagation continues partially with and partially without liquid contact, fracture rate being much slower when not in the presence of the liquid.
Directional anisotropy of dielectric β‐relaxation in oriented poly(ethylene terephthalate)
Authors: Hsu Bay‐Sung , Kwan Sik‐Hung 
Published: April 2003

AbstractThe dielectric β‐relaxation in oriented poly(ethylene terephthalate) was investigated over wide ranges of frequency and temperature, with the electric field applied at inclinations of 0°, 45°, and 90° to the draw direction. Pronounced directional anisotropy is observed over the entire range of temperature and frequency. With the external field parallel to the draw direction the dielectric loss is considerably smaller than the value obtained with the field normal to the draw direction. The value obtained with the electric field at 45° to the draw direction is intermediate between the other two. On the other hand, the activation energy is largest for 0° inclination and smallest for 90° inclination. It is suggested that motions of the dipoles involve localized rocking of the molecular chain backbone, particularly when the external electric field is parallel to the chain direction.
Mechanical relaxations in γ‐ray‐polymerized polyethylene
Authors: Arai Hidehiko , Kuriyama Isamu 
Published: April 2003

AbstractDynamic mechanical properties of cold‐compacted films of polyethylene prepared by γ‐ray‐induced polymerization in bulk at 30°C are discussed in connection with the fine structure. The cold‐compacted films show a broad α‐relaxation at a lower temperature than do single‐crystal mats or melt‐crystallized polymer. From the effects of annealing and swelling by carbon tetrachloride on the relaxation, it is concluded that the α‐relaxation, like the α‐relaxation in the single‐crystal mats, originates from molecular motions within lamellar crystals. This is consistent with the finding that these films are composed of stacked small irregular lamellar crystals. The γ‐relaxation is also similar to that in crystal mats.
Light scattering from spherulitic materials
Authors: Blum L. , Frisch H. L. 
Published: April 2003

AbstractThe azimuthal angular dependence of the depolarized component of the light scattered from spherulitic materials is derived by an algebraic method that avoids the difficult angular integrations of the usual approach. The result appears as a sum of products of two factors, a molecular factor, that depends only on the structure and the scattering angle θ, and a geometrical factor that depends only on the azimuthal angle ϕ and the scattering angle θ. The molecular factors are evaluated for models of spherulitic structure that assume a constant tilt of the optical polarizability tensor. The radial distribution, in principle, is arbitrary, and an evaluation for the layered spherulite is made. If the tilt angle is ω when the azimuthal patterns depend only on a linear combination of P2(cos ω) and P4(cos ω), where Pn(x) is the Legendre polynomial of order n. In our theory the VH scattering pattern is a four‐leaf clover whose axes are restricted by the theory to be at either 0 or 45° to the polarization directions.
Poly(styrene sulfonic acid)–poly(vinylidene fluoride) interpolymer ion‐exchange membranes. II. Ultrafiltration properties
Authors: Gryte Carl C. , Gregor Harry P. 
Published: April 2003

AbstractHighly porous interpolymer ion‐exchange membranes of poly(styrene sulfonic acid) and poly(vinylidene fluoride) have been investigated under pressure filtration with KCI, Na2SO4, erythrosin, and bovine serum albumin as solutes in the feed solution. The rejection of the ionic solutes is governed by a Donnan exclusion of electrolyte from the membrane phase. A model for the transport behavior is proposed that includes both diffusive and convective salt transport. The calculated rejections agree adequately with the observed data.
The effect of sorbed oxygen on the γ and δ dielectric relaxations in polystyrene
Authors: Pochan J. M. , Hinman D. F. 
Published: April 2003

AbstractThe γ and δ relaxations of polystyrene (PS) are rendered more active dielectrically by sorbed oxygen. This effect, coupled with comparative work on molecularly similar systems has led to the assignment of the γ relaxation to a rotational libration of the phenyl ring in PS. Specific interactions of the pendant phenyl ring with molecular oxygen to induce off‐axis dipole moments in the phenyl moiety is proposed. It is concluded that this interaction is strong enough to influence the dielectric relaxation strength of other relaxations in PS. It is further concluded that because of the interactions occuring in aromatic polymers containing sorbed oxygen, care must be taken to exclude oxygen or to vary its content, in order that intrinsic motions in the polymer system can be studied.
Studies of molecular relaxation of poly(propylene oxide) solutions by dielectric relaxation and brillouin scattering
Authors: Yano S. , Rahalkar R. R. , Hunter S. P. , Wang C. H. , Boyd R. H. 
Published: April 2003

AbstractDielectric relaxation and Brillouin scattering are jointly used in studying molecular relaxation in poly(propylene oxide) (PPO) and its solutions in methylcyclohexane. The dielectric method was applied to the more concentrated (100%, 80%, 60%, by volume) solutions over a wide temperature and frequency range (30 Hz to 8 GHz) in order that the variation in activation energy characteristic of a glass‐forming substance could be delineated. The present work extends previous work on the undiluted polymer to higher frequencies so that range of 12 decades in the dielectric loss maximum fmax as a function of temperature is now available. The “Antoine” equation is found to represent the behavior of log fmax, of the bulk concentrated solutions very well. The more dilute (40%, 20%) solutions were studied only in the high‐frequency (GHz) region since phase separation occurred at low temperatures. Both the temperature and dilution effects were interpreted in terms of free‐volume theory. Brillouin scattering spectra were obtained at several scattering angles and a wide range of temperatures. A maximum in the curve of hypersonic attenuation versus temperature was observed in each polymer solution. The attenuation maximum shifts toward lower temperature upon dilution, in agreement with the dielectric relaxation result. The Brillouin scattering follows different activation parameters and evidences a more rapid process than does the dielectric relaxation. It is speculated that it monitors a secondary or subglass relaxation, due perhaps, to damped torsional oscillations.
Isothermal and nonisothermal creep of lightly crosslinked cis‐1,4 polybutadiene
Authors: Caruthers J. M. , Cohen R. E. 
Published: April 2003

AbstractA nonisothermal creep experiment has been analyzed to ascertain its suitability for determining the temperature dependence of low activation energy viscoelastic processes in elastomers far above Tg. The nonisothermal method was employed to determine the activation energy for creep near 35°C in a lightly crosslinked cis‐1,4 polybutadiene elastomer at small strains within the linear viscoelastic region, and at various large deformations up to rupture. The observed activation energy was essentially independent of the level of strain, and the value of ΔHa (∼11 kcal/mole) determined via the nonisothermal creep method was in good agreement with the result (∼12 kcal/mole) obtained via time‐temperature superposition of isothermal linear viscoelastic creep data. The nonisothermal data allowed for an estimate of the volume of the “flow unit” associated with the controlling viscoelastic creep mechanism, attributed here to slippage of entanglements within the lightly crosslinked network.
Extensional infrared orientation
Authors: Wool Richard P. 
Published: April 2003

AbstractIn evaluating molecular orientation by dynamic infrared techniques, it is shown, subject to certain restrictions, that an extensional mechanism plays an important role in the measured orientation. Dichroic measurements can indicate a change in segmental orientation without any change occurring in the chain axis orientation. Extensional orientation was evaluated for a general helical molecule in terms of singular and coupled vibrational modes. Significant orientation changes can occur by the extensional mechanism, the sign and magnitude of which depend on the components of the transition moment vector.
Incompatibility of polymer solutions. I. Binodals and spinodals in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Vrij A. 
Published: April 2003

AbstractThe incompatibility of polystyrene (PS) and polyisobutylene (PIB) in toluene is characterized by binodals obtained from phase separation and spinodals obtained from light scattering at zero scattering angle. From these the interaction parameter χ23, between unlike polymer segments was calculated. It appears to be dependent on molecular weight and composition. The nature of χ23, especially its low value, is discussed.