bluuebunny/crossref_metadata_2025_split huggingface dataset:
P‐V‐T properties of alternating poly(ethylene‐propylene) liquids
Authors: Chen S.‐j. , Chiew Y. C. , Gardecki J. A. , Nilsen S. , Radosz M. 
Published: April 2003

AbstractThe pressure‐volume‐temperature (P‐V‐T) properties of monodisperse alternating poly(ethylene‐propylene) (hydrogenated polyisoprene) melts of varying molecular weights are measured at 0.1 MPa < P < 200.1 MPa, and 290 K < T < 510 K in a dilatometer‐type apparatus. The Flory‐Orwoll‐Vrij (FOV), Modified Cell Model (MCM), Sanchez‐Lacombe (SL), and the Statistical Associating Fluid Theory (SAFT) equations of state are found to correlate the experimental data with excellent accuracy, except either at low pressures and high temperatures, or at high pressures and low temperatures. On average, MCM and SAFT fit the data slightly better than FOV and SL. The equation‐of‐state parameters are found to be independent of molecular weight, especially for SAFT, as required by the theory. © 1994 John Wiley & Sons, Inc.
Mechanical properties of unsaturated polyester resins in relation to their chemical structure: 2. Plastic deformation behavior
Authors: Melot D. , Escaig B. , Lefebvre J. M. , Eustache R. P. , Lauprêtre F. 
Published: April 2003

AbstractThe plastic deformation behavior of unsaturated polyester (UP) networks has been investigated in compression at constant strain‐rate over a wide temperature range. The temperature evolution of the activation parameters is directly related to the local molecular dynamics of the different networks previously characterized by dynamic mechanical spectroscopy and high resolution 13C solid‐state NMR. © 1994 John Wiley & sons, Inc.
TEM evidence for the existence of conducting islands in highly conductive polyaniline
Authors: Lux F. , Hinrichsen G. , Pohl M. M. 
Published: April 2003

AbstractThis article deals with the microlevel structure of the electronically conductive polymer, polyaniline, on the basis of the conducting islands model of Epstein et al. The paper presents, for the first time, TEM pictures of the microlevel structure of heavily doped polyaniline, possibly showing the conducting islands in the material. © 1994 John Wiley & Sons, Inc.
Compatibilization of polypropylene/poly (ethylene oxide) blends and crystallization behavior of the blends
Authors: Tang Tao , Huang Baotong 
Published: April 2003

AbstractThe compatibilization of incompatible polypropylene (PP)/poly(ethylene oxide) (PEO) blends was studied. The experimental results showed that the graft copolymer [(PP‐MA)‐g‐PEO] of maleated PP(PP‐MA) and mono‐hydroxyl PEO (PEO‐OH) was a good compatibilizer for the PP/PEO blends in which PP‐MA also had some compatibilization. The crystallization of the blends was affected by the compatibility between PP and PEO. The interfacial behavior of the compatibilizers had an important effect on crystallization behavior of the PP/PEO blends. PEO showed fractionated crystallization in the PP/PEO blends. This behavior was studied from the view point of the theory of fractionated crystallization. © 1994 John Wiley & Sons, Inc.
Specific heat capacity and melting/crystallization characteristics of polytridecanolactone
Authors: Skoglund Peter , Fransson Åke 
Published: April 2003

AbstractAn investigation of the thermodynamical properties of polytridecanolactone (PTDL) was made with the aid of a differential scanning calorimeter (DSC). PTDL is a linear polyester and belongs to the polylactones, which have been poorly investigated. In this paper we contribute with specific heat capacity in the range 180‐400 K, and melting and glass transition characteristics. Further, we present unique results corresponding to the effect of different cooling rates on crystallization temperatures and crystallization energies. PTDL has a melting temperature of 350 K, and a glass transition at about 237 K. The crystallization results show that PTDL crystallizes easily, with a crystallization degree of about 80%. In addition, the crystallization energy decreases with increasing cooling rate, and levels out at a constant value at higher cooling rates. The crystallization temperature, on the other hand, shows an increasing sensitivity of cooling rate, where the supercooling is increasing more rapidly at higher cooling rates. © 1994 John Wiley & Sons, Inc.
Polyimide‐polysiloxane‐segmented copolymers as high‐temperature polymer electrolytes
Authors: Tian S. B. , Pak Y. S. , Xu G. 
Published: April 2003

AbstractBased on the fact that the flexibility of the polymer backbone will affect the ion transport and sometimes enhance the ionic conductivity, copolymer electrolytes of 1,2,4,5‐benzene‐tetracarboxylic dianhydride (PMDA), 4‐aminophenyl ether (ODA), and aminopropyldimethyl‐terminated polydimethylsiloxane (PSX), with or without doping of lithium triflate, have been prepared and investigated by infrared spectroscopy and electrical conductivity measurements. The PSX was found to be incorporated into PMDA‐ODA polyimide to form block copolymers, and the best conductivity (10‐7 s/cm at 300°C) is observed in the lithium triflate‐doped PMDA‐ODA‐PSX copolymer with a composition of 4PMDA: 3DA: 0.6PSX: 2LiCF3SO3. This conductivity is about 100 times better than the result of the lithium‐doped PMDA, ODA, and 2,5‐diaminobenzene sulfonic acid (DABSA) copolymer (4PMDA: 3DA:1DABSA:1LiCF3SO3) recently reported by this group. © 1994 John Wiley & Sons, Inc.
A study of tensile yielding of isotactic polypropylene
Authors: Liu Yan , Truss Rowan W. 
Published: April 2003

AbstractThe yielding behavior of isotactic polypropylene (iPP) sheets prepared by hot pressing was studied by tensile testing. The corresponding microstructural changes in the specimens after testing were investigated by image analysis, optical microscopy (OM), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The yielding of iPP was found to follow a two‐process Eyring yielding model. In the necked regions, stress‐whitening occurred only in specimens tested over a certain range of strain rates and temperatures. The occurrence of the stress‐whitening was correlated well with the activation of Process II in the two‐process Eyring model. SEM revealed that the stress‐whitening in the necked regions was associated with the formation of craze‐like structures that were parallel to the loading direction. Furthermore, DSC analysis showed that the necked regions of the unwhitened tensile specimens had an additional low‐temperature melting peak. However, no additional melting peaks were found in the stress‐whitened specimens. © 1994 John Wiley & Sons, Inc.
FTIR‐ATR studies of drawing and poling in polymer bilaminate films
Authors: Chen Gang Chi , Su Ji , Fina Leslie J. 
Published: April 2003

AbstractA large increase in the remnant polarization of drawn and poled poly(vinylidene fluoride) (PVF2)/nylon 11 bilaminates compared with the individual films observed in other studies provides the motivation for the examination of dipole orientation in variously treated single and bilaminate films with FTIR‐ATR spectroscopy. Four ATR spectra are collected from each surface using two sample orientations and two light polarizations for each incident light angle. The incident light angle is varied to obtain information about the change in structure with depth. Computer simulations of the experimental optics using anisotropic optical constants aides in the interpretation of experimental results. As the result of simple one‐way drawing in PVF2 and nylon 11, anisotropy in dipole orientation is observed in the plane transverse to the draw direction. In both single and bilaminate films, the average direction of the amide plane in nylon 11 and the CF2 dipoles in PVF2 resides in the plane of the film, perpendicular to the subsequent poling field direction as a result of one‐way drawing. The transverse plane orientation is depth dependent in nylon 11 in both single and bilaminate films and is attributed to a surface‐induced effect. Poling fields of 1.6 MV/cm produce large differences between the surfaces of single films and the bilaminates. At the interior interface of the drawn and poled bilaminates, the PVF2 and nylon 11 dipoles important in polarization appear to be random. The structural implications of this as well as other observations from the spectra are interpreted in terms of the large remnant bulk polarization in the poled bilaminate. © 1994 John Wiley & Sons, Inc.
23Na NMR in urethane cross‐linked polyether solid polymer electrolytes
Authors: Forsyth M. , Smith M. E. , Meakin P. , MacFarlane D. R. 
Published: April 2003

AbstractSodium triflate/polyether urethane polymer electrolytes ranging in concentration from 0.05 molal to 1.75 molal have been investigated via 23Na static solid‐state NMR. Room temperature spectra and spin lattice relaxation times were consistent with a single narrow resonance indicating the presence of only mobile ionic species. The concentration and temperature dependence of relaxation times, chemical shifts, and linewidth have been investigated. The results suggest either a single species or rapid exchange between a number of species (even at temperatures below the glass transition temperature, Tg). The linewidth decreases with increasing concentration of ions and remains temperature independent below Tg. Below Tg a maximum quadrupolar interaction constant of 2 MHz is calculated. The addition of plasticizer to the polymer electrolyte causes significant chemical shift changes that depend on the solvent donicity of the plasticizer. The linewidth and T1 relaxation times also depend on the Tg of the plasticized systems. Previous 23Na NMR literature results are reviewed and qualitative models developed to account for the variation in results. © 1994 John Wiley & Sons, Inc.
Analysis of the cure‐dependent dielectric relaxation behavior of an epoxy resin
Authors: Deng Yong , Martin George C. 
Published: April 2003

AbstractThe dielectric relaxation behavior of an epoxy‐amine resin was investigated using the Williams‐Watts relaxation function. Phenomenologically, the dielectric features of the resin during cure are similar to those of stable materials. The distribution parameter of the dipole relaxation decreases from the onset of cure to a conversion near the gel point and then maintains a constant value. Based on the experimental observations and theoretical considerations, a single‐frequency approach has been proposed for extracting the relaxation time of maximum loss. The relaxation data so obtained are independent of the measurement frequency and are in agreement with those acquired directly from the dipole loss peaks. © 1994 John Wiley & Sons, Inc.
Ostwald ripening in an immiscible hydrogenated polybutadiene and high‐density polyethylene blend
Authors: Mirabella, Jr. Francis M. , Barley Jeffrey S. 
Published: April 2003

AbstractThe long‐time regime coarsening in a phase‐segregated blend of hydrogenated polybutadiene (HPB) with high‐density polyethylene (HDPE) was studied. The blend consisted of 10 wt% of HPB in a HDPE matrix. The morphology of the system was studied by etching the HPB particles from the HDPE matrix and observing the etched specimens in a scanning electron microscope. The average volume of the HPB particles was found to increase with storage time in the melt, and to follow a temporal exponent of 1 in agreement with the predictions of the Ostwald ripening theory. This indicated that the particles coarsen by the evaporation‐condensation mechanism on which the Ostwald ripening theory is based. The rate constant from the Ostwald ripening theory was calculated and compared to the rate constant determined from the experimental data. The theoretical rate constant, K, calculated from Ostwald ripening theory, was 3.6 × 10−18 cm3/s compared to an experimentally determined rate constant of 4.8 × 10−18 cm3/s. The agreement between the theoretical and experimental rate constants was quite good. The significance attached to the good agreement between the theoretical and experimental rate constants might be mollified to some extent by the uncertainty involved in the parameters used to calculate the theoretical rate constant; viz. the interfacial tension, mutual‐diffusion coefficient, and equilibrium concentration of the HPB in the matrix phase that are not known to high accuracy. In reality, because other theories were used to determine the interfacial tension, mutual‐diffusion coefficient, and equilibrium phase compositions, this study was a test of several theories simultaneously. However, the agreement of the experimental temporal exponent and rate constant with the predictions of Ostwald ripening theory strongly indicates that the HPB/HDPE system coarsens by the evaporation‐condensation mechanism upon which the Ostwald ripening theory is based. © 1994 John Wiley & Sons, Inc.
The influence of short branches on the α, β and γ‐relaxation processes of ultra‐high strength polyethylene fibers
Authors: Ohta Yasuo , Yasuda Hiroshi 
Published: April 2003

AbstractDynamic mechanical measurements were conducted for several kinds of ultra–high‐strength polyethylene fibers with different methyl branch contents. As is the case with conventional polyethylene materials, UHSPE fibers also exhibit α, β, and γ‐relaxation dispersions. Each relaxation process is the function of both the tensile moduli and the branch contents of UHSPE fibers. It was also found that the γ‐process of UHSPE fibers is dominated mainly by the localized molecular motion in the crystalline part, such as a dislocation mode of crystallite defects, which is very sensitive to the branching content. From the time and temperature superposition of the frequency dispersion experiments, it was found that activation energies for both the α2‐process and α3‐process increase proportionally to the methyl branch content, while the α1‐process is not so affected by the branch content. This result shows that the incorporated branch sites in the crystalline part effectively hinder the chain‐to‐chain slippage; meanwhile, they have not hindered the slippage at the grain boundary so far, which also enables us to explain the creep improvement of UHSPE fibers through branch incorporation with the same mechanism. © 1994 John Wiley & Sons, Inc.
Investigation of the microstructure of poly(diallyldimethyl‐ammonium chloride) by nitrogen‐14(15) NMR spectroscopy
Authors: Masterman T. Craig , Dando Neal R. , Weaver Douglas G. , Seyferth Dietmar 
Published: April 2003

AbstractCPMAS 13C and 15N solid‐state NMR spectroscopy, as well as solution state 14N NMR spectroscopy, was used to investigate the microstructure of poly (diallyldimethylammonium chloride). The results of these studies, supported by 14N NMR studies of model compounds, were in agreement with the earlier conclusion of other workers (via solution state 13C NMR spectroscopy) that the polymer consists of a chain of five‐membered pyrrolidinium rings, A. magnified image © 1994 John Wiley & Sons, Inc.
Polymer‐solvent demixing under tension. Isotope and pressure effects on liquid‐liquid transitions, VII. Propionitrile–polystyrene solutions at negative pressure
Authors: Imre Attila , Van Hook W. Alexander 
Published: April 2003

AbstractLiquid‐liquid demixing in propionitrile‐polystyrene solutions has been observed (−2 < P/MPa < 4) using a Berthelot tube technique. The experimental isopleths join smoothly to ones gathered at positive pressure by another technique. The equation of state used to describe the transitions thus appears to be valid across the entire liquid range. © 1994 John Wiley & Sons, Inc.
The effect of water on the transport of oxygen through nylon‐6 films
Authors: Gavara Rafael , Hernandez Ruben J. 
Published: April 2003

AbstractThe effect of presence of water on the transport of oxygen through films of Nylon‐6 was evaluated at 5, 23, and 40°C by permeation experiments. Through the oxygen permeability experiments it was found that the diffusion of oxygen through Nylon‐6 is not a simple Fickian process and the total diffusion process can be expressed by a bimodal diffusion mechanism. Permeability, solubility, and diffusion coefficients were determined as a function of water activity for both mechanisms. The effect of sorbed water on the oxygen diffusion and solubility in the polymer is presented as a function of the state of water in the polymer and as a result of the molecular competition between water and oxygen. © 1994 John Wiley & Sons, Inc.
Analytic model for surface‐induced molecular weight segregation in thermoplastic composites
Authors: Pangelinan Adriano B. , McCullough R. L. , Kelley Michael J. 
Published: April 2003

AbstractAn analytic model based on a random‐walk formulation for absorbing barriers is presented. The range of applicability of the model is established from results derived from Monte Carlo simulations. The model takes into account the influences of neutral, repulsive, and attractive polymer‐surface interactions on the spatial variation of species concentrations in the vicinity of a surface. The model predicts that the lower molecular weight species of a polydisperse mixture will accumulate in the vicinity of a surface to create an interphase region. The extent of this surface‐perturbed interphase region is on the order of three times the radius of gyration of the longest species of the mixture. The degree of molecular weight segregation is dependent upon the breadth of the molecular weight distribution. © 1994 John Wiley & Sons. Inc.
Luminescent polymers with discrete emitter units
Authors: Musfeldt J. L. , Reynolds John R. , Tanner D. B. , Ruiz Jose P. , Wang Jiping , Pomerantz Martin 
Published: April 2003

AbstractOptical absorption and photo‐luminescence measurements were performed on a series of semiconducting polymers, based upon phenylene linkages, that have discrete emitter units. In these polymers, broken conjugation has been achieved in two ways: by introducing metalinkages between various numbers of para‐connected aromatic groups or by severe steric distortion of a fully conjugated main chain. In either case, electronic states are localized on relatively small units, resulting in a large (π, π*) band gap. The band gap decreases with increasing emitter unit conjugation, as expected. Blue light emission was observed from these materials, with the peak emission wavelength red shifted (by greater than 1 eV on average) from the peak absorption. © 1994 John Wiley & Sons, Inc.
Curie transition, ferroelectric crystal structure, and ferroelectricity of a VDF/TrFE(75/25) copolymer 1. The effect of the consecutive annealing in the ferroelectric state on curie transition and ferroelectric crystal structure
Authors: Kim Kap Jin , Kim Gwan Bum , Vanlencia Catherine L. , Rabolt John F. 
Published: April 2003

AbstractWe have completely deconvoluted multiple ferroelectric‐to‐paraelectric phase transitions of a VDF/TrFE copolymer often observed on DSC by consecutive annealing below the Curie transition temperature and obtained three clear endothermic peaks resolved well from each other. We could also increase the Curie transition temperature by using the consecutive annealing performed in the ferroelectric state. Annealing time, as well as annealing temperature, was found to affect the Curie transition behavior significantly. Each ferroelectric crystalline phase was characterized by IR, Raman scattering, x‐ray diffraction, and DSC measurements. The ferroelectric phase, having higher Curie transition temperature, has been found to have more trans sequences and less gauche defects and to require larger thermal energy for the Curie transition. © 1994 John Wiley & Sons, Inc.
Density profile of spin cast polymethylmethacrylate thin films
Authors: Wu Wen‐li , Orts William J. , Van Zanten John H. , Fanconi Bruno M. 
Published: April 2003

AbstractThe density profiles of polymethylmethacrylate (PMMA) thin films on silicon (111) single crystal wafers were investigated via neutron reflectivity measurements. Films were prepared by spin casting PMMA onto silicon wafers from o‐xylene solution followed by annealing under vacuum at 90°C for 5 h. A ∼45 Å thick layer at the free polymer surface was observed in the as‐prepared samples that has a density about half the value of bulk PMMA. After heating above 110°C, this diffuse layer disappeared and the thin film density profile was transformed to one with a sharp free polymer surface. This transition was found to be irreversible. © 1994 John Wiley & Sons, Inc.
An experimental study on saturation swelling of styrene–acryronitrile copolymer particles with styrene and acrylonitrile monomers
Authors: Nomura Mamoru , Liu Xiang , Ishitani Kouichi , Fujita Kazumi 
Published: April 2003

AbstractThe saturation swelling behavior of styrene and acrylonitrile (SAN) copolymer particles with a styrene (St) and acrylonitrile (AN) comonomer mixture was investigated experimentally. The effects of the copolymer composition and the compositional inhomogeneity in SAN Copolymer particles on their swelling behavior were examined. The experimental results show that both the copolymer composition and the compositional inhomogeneity in SAN copolymer particles have little or no influence on the swellability of SAN copolymer particles with a St and AN comonomer mixture, as long as the weight fraction of AN monomer units in SAN copolymer particles is less than a certain value between 0.6 and 0.8. With increasing AN content in the copolymer particles beyond this value, however, the swellability of SAN copolymer particles gradually decreases. Semiempirical equations are proposed, which correlate the saturation concentration of each monomer in SAN copolymer particles as a function of the comonomer composition in the monomer droplets and the overall copolymer composition in SAN copolymer particles. © 1994 John Wiley & Sons, Inc.
Morphology of melt‐pressed latex films examined by scanning and freeze‐fracture electron microscopy
Authors: Sosnowski Stanislaw , Li Lin , Winnik Mitchell A. , Clubb Brian , Shivers Richard 
Published: April 2003

AbstractWe report freeze‐fracture transmission electron microscopy (FFTEM) and scanning electron microscopy (SEM) studies of films prepared by melt‐pressing micrometer‐size polystyrene (PS) and poly(methyl methacrylate) (PMMA) latex samples prepared by surfactant‐free emulsion polymerization. Film samples were prepared in two ways intended to influence the nature of packing in the solid: slow evaporation of water at 40°C and 1 atm, or freezedrying. These powder samples were then gently pressed into transparent films using a Carver press. Samples prepared from freeze‐dried latex are much less ordered then those from slowly dried dispersions. Two kinds of close packing, face‐centered cubic (fcc) and body‐centered cubic (bcc), may exist in different parts of an individual sample. An excellent example of bcc ordering was observed in a sample prepared by slowly drying a PMMA latex dispersion. Under very similar conditions, small regions of both fcc and bcc ordering were observed in PS samples. However, distortion of ideal bcc or fcc packing produces the same pattern of fracture. © 1994 John Wiley & Sons, Inc.
Synthesis and mesophase characterization of liquid crystalline polyesters with bulky, rigid, lateral substituents
Authors: Khan N. , Price D. M. , Bashir Z. 
Published: April 2003

AbstractThe synthesis and characterization of aromatic polyesters containing various symmetrically di‐substituted hydroquinone monomers is described. The homopolyesters made from these monomers and terephthalic acid (TA) did not melt. Copolyesters of TA with mono‐ and di‐substituted hydroquinone formed liquid crystalline melts. Optical microscopy showed schlieren, marbled, and droplet textures characteristic of the nematic phase. DSC experiments were also in accord with mesophase formation as multiple transitions characteristic of first‐order phase changes were found. In general, the crystal‐nematic transition was about 300°C, whereas the nematic‐isotropic change was over 400°C. All the polyesters were prone to decomposition near or above the isotropization temperature. © 1994 John Wiley & Sons, Inc.