bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas transport properties of polycarbonates and polysulfones with aromatic substitutions on the bisphenol connector group
Authors: Aguilar‐Vega M. , Paul D. R. 
Published: April 2003

AbstractThe effect that substitution of aromatic groups on the bisphenol connector unit of bisphenol‐A based polycarbonate and polysulfone materials has on their gas transport properties was assessed. Replacement of a methyl group by a phenyl ring (bisphenol acetophenone polycarbonate, PC‐AP, and bisphenol acetophenone polysulfone, PSF‐AP) gives a small increase in permeability coefficients with similar or slightly higher selectivity for all gases compared to bisphenol‐A polycarbonate, PC, or polysulfone, PSF. Substitution of two locked phenyl rings (fluorene bisophenol polycarbonate, FBPC, and fluorene bisphenol polysulfone, FBPSF) in place of the methyl groups in the connector unit leads to permeability and solubility coeffcients that are about twice those observed for PC or PSF. Increases in permeability for the polycarbonate and polycarbonate and polysulfone materials with aromatic substitutions are related to their larger fractional free volume. FBPC and FBPSF have the largest fractional free volume and the largest permeability coefficients. Thermal measurements show that the fluorene based polycarbonate and polysulfone materials have the highest thermal and oxidative stability. Such aromatic substitutions can be useful for developing gas separation membranes to be used in harsh thermal or oxidative environments. © 1993 John Wiley & Sons, Inc.
Statistical approach to light scattering from deformed textured heterogeneous polymer materials
Authors: Patlazhan S. A. 
Published: April 2003

AbstractA statistical theory of light scattering from deformed isotropic and textured heterogeneous polymer materials is formulated. Two types of textured structures are analyzed: assemblies of optically isotropic and anisotropic rods and a spatially anisotropic distribution of isotropic spherical inclusion centers. The small‐angle Hv light‐scattering patterns are calculated. The appearance of scattering from isotropic rods and spheres in deformed materials has been demonstrated. The changes of the Hv scattering patterns as a function of elongation and strucuture parameters are discussed. © 1993 John Wiley & Sons, Inc.
Computer simulation of crystallization kinetics and morphology in fiber‐reinforced thermoplastic composites. I. Two‐dimensional case
Authors: Mehl Nathan A. , Rebenfeld Ludwig 
Published: April 2003

AbstractA body of experimental evidence suggests that reinforcing fibers influence both the crystallization kinetics and morphology of those composite materials that are based on crystallizable thermoplastics. The absence of an analytical model to predict the effect of fibers on crystallization has hindered data analysis. A new approach, using computer simulation of polymer crystallization, makes it possible to study the influence that reinforcing fibers have on the crystallization kinetics and morphology of semicrystalline polymers. Fibers depress the crystallization rate relative to an unreinforced polymer since they constrain spherulitic growth by an impingement mechanism. On the other hand, reinforcing fibers can also enhance crystallization rate by providing added surface nucleation sites. This work describes a two‐dimensional simplification of the crystallization process that occurs in bulk materials. It is demonstrated that the relative bulk and fiber nucleation densities, in addition to the fiber fraction, fiber diameter, and spherulitic growth rate control the crystallization kinetics and also the spherulitic and transcrystalline morphologies that develop in reinforced thermoplastic composites. © 1993 John Wiley & Sons, Inc.
Light scattering from swollen textured polymer network composites
Authors: Patlazhan S. A. 
Published: April 2003

AbstractLight scattering from a swollen textured heterogeneous polymer network is discussed using example of a network composite filled by spherical inclusions anisotropically distributed in the matrix. The dependence of the scattering intensity on the Fourier transform of the correlation function dry‐state shear moduli fluctuations has been established. Hv scattering patterns from uniaxial textures and their ratio with the composite anisotropy parameter are analyzed. The sensitivity of the Hv scattering pattern on restrictions during the swelling is emphasized. © 1993 John Wiley & Sons, Inc.
Study of structure and polymerization of epitaxially grown SiPc(OH)2 thin films by high‐resolution electron microscopy
Authors: Kawase Noboru , Kurata Hiroki , Kubono Koji , Isoda Seiji , Kobayashi Takashi 
Published: April 2003

AbstractThin films of SiPc(OH)2 (Pc = phthalocyanine) were formed epitaxially on the (001) surface of mica by vacuum deposition and were then polymerized by heat treatment. The molecular packing of the SiPc(OH)2 was determined by electron diffraction and high‐resolution electron microscopy as triclinic\documentclass{article}\pagestyle{empty}\begin{document}${\rm P\bar 1} $\end{document} having dimensions a = 0.727, b = 1.307, c = 0.688 nm, α = 102.5, β = 104.2, and γ = 97.4°. This monomer crystal grows with its c‐axis parallel to the a‐axis of the substrate mica and its bc‐plane parallel to the (001) surface of mica. By heat treatment at 320°C, the SiPc(OH)2 polymerized with the c‐axis of the polymer parallel to the c‐axis of the monomer. At 420°C, the c‐axis of the polymer became parallel to the a*‐axis of the monomer (i.e., perpendicular to the film surface). From high‐resolution electron microscopy of partially polymerized specimens, the polymerization was shown to start at the edges of small monomer crystals. This may be considered to be due to the volume expansion during the polymerization. © 1993 John Wiley & Sons, Inc.
On the flexibility of cyclochain polymers
Authors: Pavlova S. S. A. , Ronova I. A. , Timofeeva G. I. , Dubrovina L. V. 
Published: April 2003

AbstractConformational parameters for a wide variety of aromatic cyclochain polymers have been computed assuming free rotation about virtual bonds. The flexibility with free rotation is shown to be determined by the geometry of the repeat unit and can vary over a wide range (15–1500 Å). Experimental values of the Kuhn segment length A are calculated from literature data on the hydrodynamic behavior of polymeric macromolecules of this class in solution. For most polymers Afr for free rotation is equal to the experimental Aexp, and hindered rotation is mainly due to bulky substituents. © 1993 John Wiley & Sons, Inc.
The microstructure and macrostructure of sulfonated poly(ethylene terethphalate) fibers
Authors: Timm Debra A. , Hsieh You‐Lo 
Published: April 2003

AbstractThe effects of fiber‐forming processes on the microstructure and macrostructure and overall orientation in sulfonated poly(ethylene terephthalate) (SPET) fibers are reported. The processing parameters examined include drawing, crimping, relaxing, and annealing. Drawing and annealing cause changes in both the crystalline structure and molecular packing in the noncrystalline regions, while crimping and relaxing appear to affect only the noncrystalline regions. A bimodal melting endotherm was observed for the SPET fibers. Experimental data suggest the low‐temperature endotherm of the SPET fibers originates from melting of the crystalline structure formed on drawing, and that the high‐temperature endotherm results from melting the heat‐induced crystals formed during fiber processing and/or thermal analysis. Compared to the PET fibers, the SPET chains in the undrawn fibers appear to have higher mobility, are easier to crystallize, and form smaller crystals upon drawing as well as DTA heating. At the crimped stage, the SPET fibers have higher overall molecular packing but lower overall orientation than the PET fibers. The differences in physical and thermal properties between the analogous SPET and PET fibers are related to their different responses to processing variations because of molecular weight and sidegroup effects. © 1993 John Wiley & Sons, Inc.
Ionic conductivity of conjugated water‐soluble rigid‐rod polymers
Authors: Dang T. D. , Bai S. J. , Heberer D. P. , Arnold F. E. , Spry R. J. 
Published: April 2003

AbstractPoly[(1,7‐dihydrobenzo[1,2‐d:4,5‐d′] diimidazole‐2,6‐diyl)‐2‐(2‐sulfo)‐p‐phenylene], a conjugated rigid‐rod polymer, was derivatized with pendants of propane‐sulfonated ionomers. The derivatized rigid‐rod polymer was soluble in aprotic solvents as well as in water for isotropic solutions that were processed into isotropic films. Direct‐current electrical conductivity σ of the films was measured using the four‐probe technique. Room‐temperature σ as high as 2.9 × 10−4S/cm was achieved on pristine isotropic films without using dopants. When the rigid‐rod polymer concentration exceeded 25 wt %, the isotropic solution could be transformed into a liquid‐crystalline solution that allowed deformations to be applied to produce anisotropic films. Significant increase in σ was obtained in a sheared film along both the parallel direction (∥) and the transverse direction (⊥) with a σ∥/σ⊥ = 5. Additionally, enhanced σ was realized in films heat‐treated at about 100°C, in the derivatized polymer with higher molecular weight from dialysis, and in substituting the sulfonated ion Na+ by H+ in the pendants of the polymers. Constant‐voltage measurements were applied to the polymers to monitor the σ stability for ascertaining the nature of the conductivity. No electronic contribution in σ was detected. Instead, a monotonically decreasing σ was consistently observed indicative of ionic conductivity. © 1993 John Wiley & Sons, Inc.
Quantitative characterization of optical anisotropy in high refractive index films
Authors: Hardaker S. S. , Moghazy S. , Cha C. Y. , Samuels R. J. 
Published: April 2003

AbstractWaveguide coupling measurements of polymers have largely concentrated on the application of mode analysis to the study of thin supported films (such as spin coatings). The use of prism coupling to study thick, freestanding polymer films, however, has not been reported. In this paper, the ability of prism coupling to characterize the three‐dimensional optical properties of thick, freestanding polymer films and sheets is demonstrated. A modified prism coupling procedure is described that allows the determination of all three principal refractive indices in thick, three‐dimensionally anisotropic freestanding films. A Metricon prism coupler is used in a manner similar to an Abbé refractometer for the measurement of isotactic polypropylene, poly(ethylene terephthalate), PMDA‐ODA polyimide, and poly(phenylene sulfide). Three series of PMDA‐ODA films are also investigated in this study. The first series has been drawn to different extensions from three‐dimensionally random films. The second series has random orientation in the plane of the film but different degrees of planarity with respect to the through direction. The third series are commercial films of varying thickness. These three series of films are compared as to the optical an‐isotropy that is developed from the three different fabrication processes. © 1993 John Wiley & Sons, Inc.
Fifty years of light scattering: A perspective
Authors: Stein Richard S. , Srinivasarao Mohan 
Published: April 2003

AbstractIt is 50 years since Debye first described the use of light scattering for the characterization of polymer solution. Ben Chu has been a leader in its subsequent development. Significant advances in theory, experimental techniques, their interpretation, and application during this period are described. © 1993 John Wiley & Sons, Inc.
Irreversible formation of a network during melting/dissolution of nascent PE
Authors: Delmas Geneviève 
Published: April 2003

AbstractA high temperature endotherm has been reported recently for PE samples during a slow T ramp which has been associated with a phase change in strained chains. From comparison of NMR and calorimetric data on nascent and melt/recrystallized samples, the following origin of the strain is now proposed. Nascent PE is a homogeneous material which contains a sizeable proportion of short‐range ordered chains interrupted by loose knots. Due to expansion during melting, the knots become tighter and a physical network which encompasses a fraction of the chains is produced. The network so formed interrupts the melting process in the ordered chains. In PE and other polyolefins, melting resumes at higher T. The high T endotherms of physical and chemical networks are compared. The consequences of this network for polymer properties as well as its general occurrence are discussed briefly. © 1993 John Wiley & Sons, Inc.
Matched ring diblock and linear triblock copolymers in dilute solution
Authors: Amis Eric J. , Hodgson Donald F. , Wu Wenjun 
Published: April 2003

AbstractA unique diblock copolymer ring and its linear triblock copolymer precursor composed of polystyrene and polydimethylsiloxane have been characterized by static and dynamic light scattering in dilute solution. The measurements were carried out with cyclohexane as the solvent over a temperature range of 12–35°C. Cyclohexane has the useful property that it is nearly isorefractive with the PDMS so that the PDMS block segments are invisible to the light‐scattering technique and it is a theta solvent for polystyrene at 34.5°C. The block polymers in this work contain 35.1 wt % of styrene as determined by proton NMR. In the linear triblock polymer, the polystyrene is the center block with PDMS blocks on each side. Static light scattering measurements give 4.31 × 104 for the average molecular weight of the whole polymer. Light scattering also shows that the apparent theta temperature for the linear triblock is shifted by 15°C to a value of 20°C at which point the second virial coefficient drops sharply and phase separation begins to induce aggregation. The diblock ring, however, shows a strongly positive second virial coefficient and no aggregation even at 12°C which is the limit of these experiments. The diffusion coefficients of cyclic diblock (Dc) and linear triblock copolymer (D1) are measured by dynamic light scattering. The ratio of diffusion coefficients of cyclic and linear copolymers at 14.9°C and 30°C are Dc/Dl = 1.13 and 1.107 respectively. These compare well with prediction of 1.18 for this ratio from consideration of the hydrodynamics of matched linear and cyclic polymer chains. Dynamic light scattering quantitatively confirms that the linear copolymer experiences a solvent quality change near 20°C but the cyclic polymer remains in good solvent over the entire experimental temperature range. © 1993 John Wiley & Sons, Inc.
Sorption and partial molar volumes of gases in poly(ethylene‐co‐vinyl acetate)
Authors: Kamiya Yoshinori , Naito Yasutoshi , Bourbon Dominique 
Published: April 2003

AbstractSorption and dilation properties of polymer‐gas systems involving poly(ethylene‐co‐vinyl acetate) and N2, CH4, or CO2, have been investigated at pressures up to 50 atm at temperatures of 10–40°C. Sorption isotherms for low‐solubility gases (i.e., CH4 and N2) can be described by Henry's law, and those for high‐solubility gas (i.e., CO2) by Flory‐Huggins dissolution equation. Dilation isotherms are similar in contour to the corresponding sorption isotherms. From the obtained sorption and dilation data, partial molar volumes of the gases in the polymer were determined as a function of temperature. Thermal expansivity of dissolved CO2 molecules was estimated at ca. 2.4 × 10−3°C−1 from the temperature dependence of partial molar volume. The expansivity is smaller than that of liquid CO2 and larger than those of the polymer and organic liquids. © 1994 John Wiley & Sons, Inc.
Effect of network heterogeneity on tensile and tear strengths of radiation, peroxide, efficient and conventional cured polyisoprene
Authors: Grobler J. H. A. , McGill W. J. 
Published: April 2003

AbstractAt any given crosslink density, the ultimate tensile and tear strengths of vulcanizates depend on the curing system and decrease in the order: conventional (CV) > efficient (EV) > peroxide > radiation cured. Measurements on three network parameters were interpreted as indicating that crosslinks were not uniformly distributed throughout the networks and that network heterogeneity decreased in parallel with a decrease in physical properties. (1) Plots of the freezing point of the gel‐solvent in a network, swollen to equilibrium, versus the volume fraction of rubber in the swollen gel, showed a straight line relationship for radiation cured networks and an increasingly large deviation from linearity on passing from radiation cured networks through peroxide and EV to CV cured networks. (2) The glass transition temperature of CV cured networks was higher than that of radiation cured networks of the same crosslink density. (3) Scanning electron micrographs of cryofracture surfaces showed a more uneven surface in CV than in radiation cured networks. The development of heterogeneity in the four networks studied is discussed in terms of the reactions that lead to crosslinking with the different curing systems. © 1994 John Wiley & Sons, Inc.
Novel rolltruded films. II. Effect of draw ratio on the gas transport properties of rolltruded isotactic poly (propylene)
Authors: Ciora R. J. , Magill J. H. 
Published: April 2003

AbstractModification of the gas transport properties of rolltruded isotactic poly(propylene) films have been studied. Changes in the amorphous solubility, diffusivity, and the activation energies of CO2, N2, and CH4 in iPP rolltruded at 150°C for draw ratios to ca. 20 are recorded. At this processing temperature variations in the transport coefficients have been found to be weakly dependent upon draw ratio and do not suffer the dramatic reductions often reported in uniaxially drawn polymers. In general, the morphological differences between uniaxially drawn and rolltruded films are subtle and are responsible for the significant difference in the measured transport properties. © 1994 John Wiley & Sons, Inc.
The influence of pressure‐induced structural changes on the ionic conductivity of zwitterionic polymers
Authors: Cardoso J. , Montiel R. , González L. , Huanosta A. , Manero O. 
Published: April 2003

AbstractIn this investigation, ionic conductivity measurements are performed on N‐oxide polymers neutralized with NaOH. The polymer samples were conformed in disk shapes using an Instron machine considering various values of the pressure required to compact the samples. The dielectric properties of these systems were obtained by the a.c. spectroscopy technique. Results indicate a substantial variation in the ionic conductivity due to the pressure‐induced structural changes on the morphology of these samples, as confirmed by WAXS studies. © 1994 John Wiley & Sons, Inc.
Complexation of poly(ethylene oxide) and urea
Authors: Bogdanov Bogdan G. , Michailov Marin , Uzov Christo V. , Gavrailova Girka G. 
Published: April 2003

AbstractThe complexation of ultrahigh‐molecular‐weight poly(ethylene oxide) (PEO) with urea in both the solid and molten states was studied by infrared spectroscopy. Information about the temperature dependences of the absorption bands in the 3600–2600 and 1300–600 cm−1 region on heating and cooling was obtained. Some conclusions concerning the interaction between PEO and urea were also made. The formation of a high temperature, metastable molecular complex between PEO and urea, which is susceptible to undercooling, was confirmed spectroscopically. Heating to 85–90°C resulted in a molecular complex stable at room temperature.© 1994 John Wiley & Sons, Inc.
Environment‐induced morphological changes of polyethylene lamellae during crystallization in solution
Authors: Kawaguchi Akiyoshi , Ohara Masayoshi , Tsuji Masaki 
Published: April 2003

AbstractPolyethylene (PE) lamellar crystals were grown by two dual‐staged crystallization methods: (1) Fractionated PE was first crystallized from n‐octane by the self‐seeding method, the solvent of the resulting suspension of crystals was exchanged for p‐xylene, and thereafter, the suspension was mixed with a solution in p‐xylene at various temperatures so that PE grew from p‐xylene onto the lamellae pregrown from n‐octane, and (2) according to the similar procedure, PE lamellae were first grown from p‐xylene and subsequently, PE was deposited from n‐octane onto the lamellae pre‐grown from p‐xylene. In the crystallization procedure (1), triangular lamellae with the 〈010〉 chain folding developed randomly on the {100} lateral surfaces of truncated parent lamellae so that the surfaces were serrated, and otherwise, thin daughter lamellae bordered the parent lamellae along the {110} surfaces, retaining the flat growth fronts with the 〈110〉 folding. In the procedure (2), the {100} sectors with the 〈010〉 folding developed at the apexes of the long diagonal of lozengeshaped parent lamellae, and consequently, their morphology was transfigured into a truncated crystal. These morphological transformations are discussed on the basis of the change in the interfacial free energy between the parent crystal and the surrounding phase due to the substitution of solvent. © 1994 John Wiley & Sons, Inc.
In situ measurement of the glass transition temperature of polymers with compressed fluid diluents
Authors: Condo P. D. , Johnston K. P. 
Published: April 2003

AbstractIn situ measurement of the creep compliance of poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA), equilibrated with a pressurized CO2 phase, is used to determine the glass transition temperature. Corrections due to dilation of the polymer by CO2 as well as the buoyancy are assessed. Both polymer systems exhibit a recently discovered phenomenon, retrograde vitrification, in which a liquid polymer becomes a glass with an increase in temperature. The experimental results are predicted semi‐quantitatively in terms of the temperature and pressure effects on the solubility of the compressed fluid in the polymer. © 1994 John Wiley & Sons, Inc.
Morphologies and electro‐optic properties of polystyrene/liquid crystal composite films
Authors: Kim Byung Kyu , Ok Young Sook 
Published: April 2003

AbstractMorphology and electro‐optic properties of composite films composed of polystyrene (PS) and nematic liquid crystal (LC) have been studied for a wide range (30‐70 wt% of liquid crystal) of film composition. At two specific levels of LC loadings (50 and 60 wt%), effects of temperature, frequency and voltage of applied ac electric field on the transmittance of the films were intensively measured, and the results were interpreted in terms of aggregation structure of the film, the geometry of LC domains, LC loading, dielectric constant, conductivity, birefringence, and the solubility of LC in polymer. © 1994 John Wiley & Sons, Inc.
The mechanical anisotropy of stratified polyvinyl chloride
Authors: Sinan Özkan H. , Oskay Taner , Yüksel Güney H. , Dirim Hüseyin 
Published: April 2003

AbstractThe mechanical anisotropy of a material obtained by stratification of oriented polyvinyl chloride (PVC) layers in different ways has been studied. PVC layers, uniaxially oriented by drawing each with a different draw ratio, were stratified in such a way that their draw axes were either parallel or perpendicular. The propagation velocities of ultrasonic pulses were measured in three principal planes defined by draw axes of the stratified material. With an immersion technique, measurements were performed at 2 MHz and 22°C. Experimentally, it was shown that while stratification of layers with draw axes parallel preserves hexagonal symmetry, the stratified material with layers' draw axes perpendicular possesses orthorhombic symmetry. © 1994 John Wiley & Sons, Inc.