bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally stable polyimide isomers for membrane‐based gas separations at elevated temperatures
Authors: Costello L. M. , Koros W. J. 
Published: April 2003

AbstractThe temperature dependence of gas sorption and transport properties is examined for two polyimide isomers. The permeabilities and solubilities of five gases in these materials are reported over an extensive temperature range from 35 to 325°C. Also, the activation energies for permeation, the heats of sorption, and the activation energies for diffusion obtained for both polyimides are compared and correlated with physical properties of the polymers and penetrants. The influence of temperature on the selective properties of these membrane materials is discussed for three gas separations; He/N2, CO2/CH4, and O2/N2. Thorough analysis of these data provides insight into the influence of the subtle difference in chain structure of the two isomers. The performance of the 6FDA‐6Fp DA as a separation membrane at high temperatures suggests that it is an outstanding candidate for use in novel elevated temperature applications. ©1995 John Wiley & Sons, Inc.
Effect of size on the strength of polymeric fibers
Authors: Termonia Yves 
Published: April 2003

AbstractUsing a molecular model introduced previously, we study the effects of chain‐end segregation on the relationship between strength (σ) and diameter (d) in polymeric fibers. For segregated structures with a monodisperse molecular weight distribution, our results show a scaling law σ ∼ d−α, with α in the range [0.4–0.5], in agreement with experimental observation. A weaker dependence is found for polydisperse systems. Further investigation also reveals that macroscopic cracks have little influence on the fiber strength/diameter relationship, unless the crack width shows a faster than linear increase with fiber diameter. Finally, our model results also indicate a very weak dependence of fiber strength on its length, in good agreement with experimental observation. ©1995 John Wiley & Sons, Inc.
Multimodal sorption of nonionic dyes with two amino groups by various polymers from water
Authors: Shibusawa Takao , Nakamura Takashi 
Published: April 2003

AbstractSorption isotherms of nonionic dyes with two amino groups (one anthraquinone dye and two azo dyes) on various polymers from water were measured at 40–90°C (Nylon‐6 and cellulose film) and at 95°C (polyester microfiber). The isotherms were curved, convex to upward, in the range of low dye concentration Cs in water and almost linear in the range of medium to saturated Cs. The isotherms measured at low temperature (40°C for cellulose, 40–60°C for Nylon‐6, and at 95°C for polyester) were satisfactorily described by considering three concurrent modes of sorption. They are Nernst type partitioning and bimodal Langmuir sorption (sorption by the higher affinity sites with a small saturation value and that by the lower affinity sites with a large saturation value). However, for the sorption of the anthraquinone dye and one azo dye by Nylon‐6 film at high temperature (80–90°C), the amount of dye sorbed by the high affinity site decreased to negligibly small. Accordingly, the isotherms were expressed well by simple dual‐sorption model. © 1995 John Wiley & Sons, Inc.
NMR and DSC investigations of the miscibility of blends of cis‐1,4‐polyisoprene with polybutadienes of different microstructures
Authors: Bahani Mustapha , Lauprêtre Franco̧ise , Monnerie Lucien 
Published: April 2003

AbstractDifferential scanning calorimetry and torsional braid analysis investigations of the phase diagram of cis‐1,4‐polyisoprene/polybutadiene blends as a function of the polybutadiene microstructure were reported by several authors. Polybutadienes containing a high vinyl content were shown to be miscible with cis‐1,4‐polyisoprene on the DSC spatial scale, whereas polybutadienes containing a low vinyl content were immiscible. In this article, we used variable‐temperature determinations of 1H NMR free induction decays and low‐temperature, high‐resolution solid‐state 13C NMR measurements of proton spin‐lattice relaxation times in the rotating frame to probe the phase behavior of the cis‐1,4‐polyisoprene/polybutadiene blends at the smaller spatial scale of the NMR technique. Blends of cis‐1,4‐polyisoprene with a polybutadiene having a large number of vinyl 1,2 linkages appeared to be miscible on the molecular scale, in spite of small regions in which the polybutadiene component is not uniformily dispersed in the other polymer. On the contrary, blends in which the polybutadiene has a low content of vinyl 1,2 sequences were phase separated over the whole temperature range considered and no intermixed regions could be detected. The limiting case was observed with the polybutadiene containing 33 wt % vinyl 1,2 units, for which miscibility on a molecular scale is highly dependent on the blend composition. © 1995 John Wiley & Sons, Inc.
Effects of drawing on creep parameters of polyoxymethylene‐drawn fibers
Authors: Komatsu Tamikuni , Aoshima Atsushi 
Published: April 2003

AbstractThe effects of drawing on creep parameters (modulus, viscosity, and retardation time) of polyoxymethylenedrawn fibers were examined on the basis of a series‐parallel, four‐element, mechanical model. These parameters increased with the draw ratio. The change in the modulus was the same between the series and parallel components. This was true also for the viscosity, although the change in the viscosity was much greater than that in the modulus. This means that the series and parallel components are deformed in the same mode by drawing. The parallel viscosity increased with elapsed loading times according to an experimental power function; this was also derived from the usual rate equation for viscosity change in the amorphous component. In contrast, the series viscosity remained unchanged over the short creep range due to an extremely larger value than that of the parallel. © 1995 John Wiley & Sons, Inc.
NMR analysis of interaction between styrene‐divinylbenzene gel beads and small molecules
Authors: Ogino Kenji , Sato Hisaya 
Published: April 2003

AbstractThe interaction of small molecules such as cyclohexane, tetrahydrofuran, and acetonitrile with styrene‐divinylbenzene copolymer gel beads were investigated by 13C‐NMR spectroscopy. When the gel content was 0.1–0.3 g/mL, the 13C‐NMR spectrum of the solvent displayed two peaks. A sharp peak at lower magnetic field was assigned to the free solvent, and a broad one to the solvent affected by the gel. This signal splitting is attributed to the upfield shift caused by aromatic rings of styrene units in the polymer chain. The nitrile carbon of acetonitrile showed the largest upfield shift. The mobility of small molecules in gel beads was also investigated using the nuclear magnetic relaxation method. In the case of good solvents for gel beads, the mobility was affected by the cross‐linking density, whereas poor solvents exhibited little dependence of the cross‐linking density. © 1995 John Wiley & Sons, Inc.
Membrane formation by isothermal precipitation in polyamide‐formic acid‐water systems II. Precipitation dynamics
Authors: Cheng Liao‐Ping , Dwan An‐Hwa , Gryte Carl C. 
Published: April 2003

AbstractAn analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of the aliphatic polyamide membranes such as Nylon‐66 by direct immersion‐precipitation of a polymeric solution in a nonsolvent bath. A material coordinate is employed to derive the mass transfer equations for the membrane solution. The convective mass transfer in the coagulation bath is taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with measured precipitation times and with membrane morphologies observed by scanning electron photomicrographs. © 1995 John Wiley & Sons, Inc.
About the microstructure of PCVD prepared crystal mats of statistical oligo‐vinylidene‐fluoride‐trifluoroethylene in relation to other fluorinated polymers
Authors: Fischer C. , Krüger J. K. , Bohn K.‐P. , Vogt U. , Schreiber J. , Jiménez R. , Wolf D. , Legrand J. F. , Alnot P. , Servet B. 
Published: April 2003

AbstractThe room temperature phase of the physical/chemical vapor‐deposited statistical co‐oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small‐angle x‐ray scattering, wide‐angle x‐ray diffraction, size‐exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high‐performance Brillouin spectroscopy in connection with special scattering geometries. The co‐oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA‐technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA‐prepared n‐alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano‐sized structures giving rise to a marked freezing process below room temperature. © 1995 John wiley & Sons, Inc.
Nanofoam porosity by infrared spectroscopy
Authors: Sanchez M. I. , Hedrick J. L. , Russell T. P. 
Published: April 2003

AbstractInfrared spectroscopy has been used to determine the porosity of polymer nanofoams produced from block copolymers of an aromatic polyimide with either poly(propylene oxide) or poly(α‐methyl styrene). It is shown that, with an independent measurement of the film thickness, both the absorption bands and the interference fringes can yield an accurate measure of the void content. The results obtained are in quantitative agreement with density gradient methods. © 1995 John Wiley & Sons, Inc.
Effect of orientation on the relative dispersion of PMDA‐ODA polyimide and polypropylene
Authors: Cha Cheol Y. , Samuels Robert J. 
Published: April 2003

AbstractThe relative dispersion of birefringence, Db, is determined for isotactic polypropylene and Kapton HA PMDA‐ODA polyimide films. Db is then used to identify the dependence of dispersion on the orientation of polymers and is interpreted in terms of fringe jumping. Optical relationships between the in‐plane birefringence and wavelength are formulated to predict the in‐plane birefringence of oriented Kapton HA PMDA‐ODA polyimide films at any wavelength. These relations can be used for the direct comparison of the in‐plane birefringence of Kapton PMDA‐ODA polyimide films obtained from different optical techniques (i.e., polarized microscopy, polarized refractometry, wave guide coupling, etc.). © 1995 John Wiley & Sons, Inc.
Gas permeability and stability of poly(1‐trimethylsilyl‐1‐propyne‐co‐1‐phenyl‐1‐propyne) membranes
Authors: Nagai Kazukiyo , Higuchi Akon , Nakagawa Tsutomu 
Published: April 2003

AbstractA significant reduction in the gas permeability of the poly(1‐trimethylsilyl‐1‐propyne) (PMSP) membrane was investigated in terms of the membrane thickness and the storage environment. The effects of physical aging were observed with thinner membranes and under vacuum conditions compared with storage in air. The decrease in the permeability coefficient was dependent on the decrease in the hole saturation constant of Langmuir adsorption (C'H), which is related to the volume of the microvoids. Physical aging in the PMSP membrane affected not only the glassy domain but also the rubbery one. To stabilize the permeability of the PMSP membrane, a poly(1‐trimethylsilyl‐1‐propyne‐co‐1‐phenyl‐1‐propyne) [poly(TMSP‐co‐PP)] membrane was prepared. Poly(TMSP‐co‐PP) has the same unit of poly(1‐phenyl‐1‐propyne), which membrane has stable permeability. The poly(TMSP‐co‐PP) with less than 20 mol % PP content was estimated to be a random copolymer based on theoretical gas permeation analysis. In the poly(TMSP‐co‐PP) membrane, the relation between the PP content and C'H was similar to the relation between the PP content and the gas permeability. The stability of the permeability was dependent on the PP content. The poly(TMSP‐co‐PP) membrane containing 10 mol % PP had both high permeability and good stability under some of the aging conditions performed in this work. © 1995 John Wiley & Sons, Inc.
Rotational and translational diffusion of low molecular weight substances in polyblock copolymers with soft and rigid blocks
Authors: Krykin M. A. , Dadaly A. A. , Gasyuk O. V. , Ozerin A. N. , Rebrov A. V. , Shmukler R. A. , Storozhuk I. P. , Wasserman A. M. 
Published: April 2003

AbstractThe rotational diffusion of spin‐probes and the translational diffusion of n‐pentane in a series of random‐block copolymers (BSP) have been studied as a function of composition and block lengths. It was shown that the local diffusion properties of the BCP microphases depend on these two characteristics of BCP. © 1995 John Wiley & Sons, Inc.
The glass temperature of dendritic polymers
Authors: Stutz Herbert 
Published: April 2003

AbstractA theoretical treatment of the glass temperature of dendritic polymers is presented. The influences of polymer backbone, end group, initiator core, branching unit, composition and functionality are discussed. In dendritic polymers the glass temperature is dependent only on the generation number of dendritic growth and thus only on the molecular weight of a dendron, but not on the molecular weight of the whole molecule. It is governed primarily by the backbone glass temperature and depends little on branching functionality. Only minor differences between linear polymer and dendrite are obtained, since the influences of end groups and branching compensate each other to a large extent. © 1995 John Wiley & Sons, Inc.
Composite spectral density functions for the interpretation of the 13C NMR relaxation behavior of polymers containing hydrocarbon side chains. Free and restricted side chain motion
Authors: Spyros A. , Dais Photis 
Published: April 2003

Abstract13C NMR NT1 and NOE have been calculated by using composite spectral density functions describing polymer chain segmental motion and internal rotation of a hydrocarbon side chain attached to the polymer backbone. Numerical results at two magnetic fields are presented as a function of the various motional parameters characterizing the various models. NT1 and NOE relaxation parameters are well behaved and appear to have practical value for describing the dynamics of these systems. The models have been applied to the relaxation data of poly(n‐butyl methacrylate) and poly(n‐hexyl methacrylate) in toluene solutions. The dynamics of the two polymers are characterized by a very localized backbone motion and restricted internal rotation about successive CC bonds of the side chains. © 1995 John Wiley & Sons, Inc.
Molecular images of [M(phthalocyaninato)O]n, where M = Si and Ge: Microphases and structures of crystal domains
Authors: Wu Junhua , Zou Bensan , Pan Ziang , Du Xueli , Zhou Xiao 
Published: April 2003

AbstractThis contribution is a study of the crystal structures and crystal domains in the thin epitaxially growing films of [M(Pc)O]n (M = Si and Ge, Pc = phthalocyaninato) revealed by high‐resolution electron microscopy. Microphases detectable only on the microscopic level were observed: (a) γ‐phase for [Si(Pc)O]n, orthorhombic system, a = 1.38 nm, b = 5.52 nm, c = 0.66 nm; and (b) α‐phase for [Ge(Pc)O]n, base‐centered orthorhombic, a = 1.33 nm, b = 2.66 nm, c = 0.35 nm. Translation and rotation crystal domains were visualized on the nanometeric scale. The high‐resolution images are rich in irregularity and provide direct information on the defects and imperfections in the polymer films. © 1995 John Wiley & Sons, Inc.
Viscoelasticity and birefringence of polyisoprene
Authors: Okamoto Hirotaka , Inoue Tadashi , Osaki Kunihiro 
Published: April 2003

AbstractThe complex Young's modulus, E*(ω), and the complex strain‐optical coefficient, O*(ω), which is the ratio of the birefringence to the strain, were measured for polyisoprene (PIP) over a frequency range of 1 ∼ 130 Hz and a temperature range of 22 ∼ −100°C. The imaginary part of O*, O″, was positive at low frequencies and negative at high frequencies. The real part, O′, was always positive and showed a maximum. The complicated behavior of O* could be understood by the assumption that E* = ER* + EG* and O* = CRER* + CGEG*, where ER* and EG* were complex quantities and CR and CG were constants. The CR value, equal to the ordinary stress‐optical coefficient measured in the rubbery plateau zone, was 2.0 × 10−9 Pa−1. The CG value, defined as the ratio O″/E″ in the glassy zone, was −1.1 × 10−11 Pa−1. The EG*, which was the major component of E* in the glassy zone, showed almost the same frequency dependence as that of polystyrene and polycarbonate. The ER*, which was dominant in the rubbery zone, was described well by the bead‐spring theory. The temperature dependence of the EG* was stronger than that of the ER*. This difference caused the breakdown of the thermorheological simplicity for E* and O* around the glass‐to‐rubber transition zone. © 1995 John Wiley & Sons, Inc.
Mutual diffusion and thermodynamics in the blends of polystyrene and tetramethylbisphenol‐A polycarbonate
Authors: Kim Eugene , Kramer Edward J. , Osby John O. , Walsh David J. 
Published: April 2003

AbstractA study was made of miscible polymer blends of deuterated polystyrene (d‐PS) and tetramethylbisphenol‐A polycarbonate (TMPC). The Flory interaction parameter χ was obtained from the relation between mutual and tracer diffusion coefficients, D̃ and D*, which were measured by forward recoil spectrometry. The temperature dependence of diffusion at PS weight fractions ω of 0.25 and 0.5, and the composition dependence at temperatures 45°C above the glass transition temperature, Tg, were investigated. A stronger dependence of χ on both temperature (at ω = 0.5) and composition was observed in comparison with other miscible binary polymer blends involving PS. Analysis using the generalized lattice‐fluid model of Sanchez and Balazs1 showed that the incorporation of a significant specific interaction is needed to explain the temperature dependence of χ. The diffusion coefficients obtained in the one‐phase region were extrapolated to the two‐phase region, and these were compared with the effective diffusion coefficient extracted from phase separation dynamics measured by light scattering.2 A significant discrepancy between the extrapolated and effective diffusion coefficients was observed. © 1995 John Wiley & Sons, Inc.
Comparison of rheological properties of cross‐linked and thermal‐mechanically degraded HDPE
Authors: Harlin Ali , Heino Eeva‐Leena 
Published: April 2003

AbstractRheological properties of a high‐density polyethylene (HDPE) subjected to thermal‐mechanical degradation were compared with those of the HDPE degraded by the addition of small quantities of peroxides as free radical initiator. The high molecular weight fraction of HDPE changes quantitatively during processing, which has a remarkable effect on the rheological properties of the material, when the MWD narrows and the HMW tail decreases. The molecular weight distribution, especially the highest molecular weight fraction, is concluded to be more important than the long chain for HDPE rheology. © 1995 John Wiley & Sons, Inc.
Dynamic aspects of phase decomposition in reactive blends of polycarbonate and syndiotactic polymethyl methacrylate
Authors: Ko Che‐Chian , Kyu Thein , Smith Steven D. 
Published: April 2003

AbstractDynamics of phase separation in bisphenol‐A polycarbonate (PC)/syndiotactic polymethyl methacrylate (sPMMA) blends has been investigated by means of time‐resolved light scattering. Solvent‐cast films of the PC/sPMMA blends were transparent, suggestive of miscible character. Several temperature jumps were carried out at a 50/50 PC/sPMMA composition from a homogeneous state (room temperature) into a two‐phase regime. The process of phase separation first occurred for some considerable period, then it was followed by phase dissolution driven by chemical reaction. The thermodegradative reaction of sPMMA triggered the dissolution process by probably forming PC/sPMMA graft or random copolymers at the interface, which eventually resulted in a single phase. However, annealing at elevated temperatures for an extended period could lead to cross‐linking, and thus a two‐phase structure could be fixed permanently. The early stage of spinodal decomposition was interpreted in terms of the linearized Cahn‐Hilliard theory. In the late stages of spinodal decomposition, the relationship between scattering peak wavenumber and time was found to obey a power law, but the exponents showed a strong dependence on temperature jumps. The temporal universal scaling failed due to the influence of the chemical reaction. © 1995 John Wiley & Sons, Inc.
Miscibility studies of poly(3‐octylthiophene)/poly(ethylene‐co‐vinylacetate) blends with a solvatochromatic shift in the solid state
Authors: Levon K. , Chu E. , Ho K.‐S. , Kwei T. K. , Mao J. , Zheng W.‐Y. , Laakso J. 
Published: April 2003

AbstractThe mixing of electrically conducting polymers in the undoped state with flexible polymers has been limited due to the stiffness of the delocalized coplanar backbone. The substitution with alkyl side chains has resulted in the distortion of the aromatic rings in the backbone with an increase of the flexibility. The alkyl substituents also prevent the thiophene back‐bones from packing together, thus making blending with other polymers promising. We have investigated the phase behavior of poly(3‐octylthiophene) (P3OT) with a flexible polymer, poly(ethylene‐co‐vinylacetate) (vinylacetate composition 20%, EVA20), and defined a miscibility window based on melting point data, on cloud point measurements, and on analysis by optical microscopy. The miscible region has been studied by UV‐VIS and CPMAS NMR spectroscopies. A UV absorption in the visible region originates from a π‐π * transition in the delocalized structure of P3OT, and a change in the length of the conjugated segment in the backbone results in a shift of this absorption. A gradual solvatochromatic shift of P3OT in the solid state with dilution was observed in the miscible region. T1 relaxation times for the methylene carbons in solid state show a gradual change in the relaxation process as a function of composition. © 1995 John Wiley & Sons, Inc.
A molecular composite approach to the thermal expansion behavior for anisotropic crystalline polymers
Authors: Zahran R. R. , Kardos J. L. 
Published: April 2003

AbstractThe dimensional stability of crystalline polymers such as polyethylene and polypropylene is a critical property in structural applications requiring known dimensional stability. It is essential to evaluate how such structural systems will respond when exposed to thermal fluctuations. Utilizing the molecular composite approach, oriented polyethylene has been modeled as a macroscopic composite of its constituent crystalline and amorphous phases. The molecular composite model, originally developed to describe the isotropic behavior of crystalline polymers, has been refined to account for the anisotropic micromorphological behavior of oriented polyethylene solids. This refinement accounts for the deformation and orientation of both constituent phases; the variation of the amorphous phase mechanical and expansional properties due to the taut tie molecules has likewise been considered. Furthermore, a theoretical expression relating the crystalline orientation descriptors, λ and fc, has been developed. A detailed calculational format for the prediction of the expansivity of oriented polyethylene is outlined. The overall pattern of anisotropic dimensional behavior has been correctly predicted when compared with experimentally measured thermal expansivities of various types of polyethylene. © 1995 John Wiley & Sons, Inc.