bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of low molar mass diluents on the microstructure of ionomers
Authors: Fitzgerald J. J. , Weiss R. A. 
Published: April 2003

AbstractThe effect of polar and nonpolar low molar mass diluents on the microstructure of lightly sulfonated polystyrene (SPS) ionomers was studied using electron spin resonance spectroscopy, small‐angle x‐ray scattering, and dynamic mechanical analysis. Nonpolar diluents primarily affected the hydrocarbon ‐ rich phase, while polar diluents partitioned into the ion‐rich regions and disrupted the supramolecular structure. The ionic clusters remained intact, even at elevated temperatures, upon the addition of nonpolar solvents such as dodecane and dioctylphthalate. More polar solvents such as methanol and glycerol swelled the ionic domains and promoted increased mixing of the two phases.
A dielectric relaxation study of plasticization of poly(ethyl methacrylate) by carbon dioxide
Authors: Kamiya Yoshinori , Mizoguchi Keishin , Naito Yasutoshi 
Published: April 2003

AbstractPlasticization of poly(ethyl methacrylate) (PEMA) by CO2 is investigated by dielectric relaxation spectroscopy. The dissipation factor of a dielectric cell containing the film and air gaps is measured as a function of frequency (1–10,000 kHz) and CO2 pressure (0–60 atm) over the temperature range 35–115°C. A maximum in the frequency dependence of the dissipation factor, which is attributed to the α relaxation of PEMA, shifts to higher frequency with increasing temperature, pressure, or concentration. The apparent activation energy of the isosteric relaxation decreases from 28 to 23 kcal/mol as the concentration is increased from 0 to 90 cm3 (STP)/cm3 (polym). The relaxation peak temperature at fixed frequency decreases with increasing concentration. The effect of hydrostatic pressure on the dielectric relaxation is estimated and compared with values for the PEMA‐He and PEMA‐Ar systems. The plasticizing effect of sorbed CO2 is discussed on the basis of the relaxation data.
Static and dynamic light scattering of poly‐(α‐methyl styrene) in toluene in the dilute region
Authors: Kim S. H. , Ramsay D. J. , Patterson G. D. , Selser J. C. 
Published: April 2003

AbstractThe scattered intensity function S(q, c) and the intermediate scattering function S(q, c, τ) of poly‐(α‐methyl styrene) (Mω = 5.71 × 105, 1.17 × 106, and 2.96 × 106) in toluene in the dilute concentration region were measured as functions of concentration and scattering vector q. In infinitely dilute solution, the intensity function S(q, 0) agrees well with the Debye function for u < 7, where u is (qRg)2. At finite concentration S(q, c) varies from its thermodynamic value at low u to the single chain value at high u. Theoretical calculations of S(q, c) are in quantitative agreement with the observed scattering function in very dilute solutions. The intermediate scattering function S(q, c, τ) is a single exponential decay with decay rate Dmq2 for u ≪ 1. For u > 1, S(q, c, τ) is nonexponential, and when analyzed with a discrete inversion method, yields a bimodal distribution of decay rates. Both components are well represented as single exponential decays. D0 can be obtained from the slower component. The decay rate of the faster component is a continuous function of u and approaches q2 dependence at high u.
Sorption and dilation properties of poly(p‐phenylene sulfide) under high‐pressure carbon dioxide
Authors: Bourbon Dominique , Kamiya Yoshinori , Mizoguchi Keishin 
Published: April 2003

AbstractSorption and dilation properties of the system poly(p‐phenylene sulfide) (PPS) and carbon dioxide have been investigated at pressures up to 50 atm over the temperature range 25–85°C. The shapes of the sorption isotherms are in agreement with those predicted by the dual‐mode theory. Analysis of the sorption and dilation isotherms confirms the occurrence of an isothermal glass transition. This occurrence and its corresponding disappearance in the range investigated is discussed. Values of the partial molar volume of CO2 sorbed in PPS are calculated below and above the isothermal transition. Compared with sorption by other polymers, these values were about the same in the glassy state, but were smaller in the rubbery state. Under 50 atm CO2 at 85°C crystallization of amorphous PPS was observed. The crystallinity estimated from the solubility before and after crystallization is about 20%.
Thermal cycling of glasses. III. Upper peaks
Authors: Hutchinson J. M. , Ruddy M. 
Published: April 2003

AbstractThe response of glasses to three‐step thermal cycles in which the glass is poorly stabilized prior to reheating has been examined both theoretically and experimentally. Theory predicts that, during the heating stage of these cycles, a type of peak (called an upper peak) occurs which is quite different from the type of peak (called a main peak) observed for well‐stabilized glasses. The dependence of the upper peak temperature and height on the experimental variables defining the thermal cycles have been derived theoretically, and have been compared with experimental data for polystyrene. All of the features predicted theoretically have been verified experimentally. In particular, the variation of the upper peak temperature is insensitive to the structure (or nonlinearity) parameter x, and cannot therefore lead to its evaluation. On the other hand, it is shown that, given the value of x obtained, for example, by the peak‐shift method, then an analysis of the upper peak height can yield information about the width of the distribution of retardation times.
Miscibility and isomorphic cocrystallization in blends of ferroelectric copolymers of vinylidene fluoride and trifluoroethylene
Authors: Tanaka Hajime , Lovinger Andrew J. , Davis Don D. 
Published: April 2003

AbstractThe miscibility in binary blends of ferroelectric copolymers of vinylidene fluoride (VF2) and trifluoroethylene ( F3E) has been investigated over the full range of blend compositions for three different random copolymers containing 52, 65, or 73 mol % VF2. We found these copolymers miscible in the melt with each other but not with the parent homopolymer, PVF2. In thin solid films we demonstrated, for all blend compositions, the very rare phenomenon of isomorphic cocrystallization in both the ferroelectric and paraelectric phases of the 52 + 65 and the 65 + 73 mol % VF2 copolymers. However, the blend having the largest compositional difference (52 + 73 mol % VF2) was found to consist of two separate ferroelectric and paraelectric phases. These results demonstrate the very close chemical and structural similarities required for coexistence of two different macromolecules within a single crystalline lattice. Moreover, they allow us to probe the compositional limits for such similarity in both the ferroelectric and the paraelectric lattices. Phase diagrams of these blends have been constructed and are discussed. The Curie transition is shown to be an exceptionally sensitive probe of compatibility in the ferroelectric phase.
Phase size/composition dependence in immiscible blends: Experimental and theoretical considerations
Authors: Favis B. D. , Willis J. M. 
Published: April 2003

AbstractThe influence of composition on phase size in immiscible polymer blends is examined both experimentally and theoretically. It was found for eight noncompatibilized blends, of widely varying particle size morphology, that a master curve of phase size versus log‐relative composition could be obtained by shifting the data along the volume fraction axis. The magnitude of the shift factors (aϕ) correlates with the interfacial tension and viscosity ratio of the systems. The theoretical dependence of the master curve is proportional to ϕ + ϕ2 dependence as in Tokita's theory, but estimation of the coefficients to the ϕ and ϕ2 terms indicates that the influence of power and shear stress on breakdown of the dispersed phase is significantly overestimated by the theory. A master curve is also generated for four compatibilized blends and the dispersed phase sizes are significantly less dependent on composition.
Crystallization kinetics and melting of caprolactone random copolymers
Authors: Goulet Louise , Prud'homme Robert E. 
Published: April 2003

AbstractSpherulitic growth rates and overall rates of crystallization of poly(ε‐caprolactone‐co‐ε‐methyl‐ε‐caprolactone), poly(CL‐co‐MCL), were analyzed over a composition range from pure poly (ε‐caprolactone) (PCL) to a copolymer containing 40% MCL with an equation which contains the classical nucleation and transport terms, but adds an entropic factor to the nucleation term. Using this new equation, linear plots were obtained with slopes corresponding to the value of the nucleation parameter (KG2) The experimental KG2 value, (9.6 ± 0.5) × 104 K2, is independent of the comonomer content; also, the same KG2 value is obtained from measurements of the overall rate of crystallization and from growth rate analysis. The interfacial free energy (σe) is 112 ± 5 erg/cm2. The melting behavior of PCL and poly(CL‐co‐MCL) is also reported. Equilibrium melting temperatures were determined by the Hoffman‐Weeks extrapolation method. It was found, using the melting point depression method, that 71% of the MCL units are incorporated into the PCL crystals at equilibrium. According to the Z criterion proposed by Lauritzen, Regime II applies to the crystallization kinetics of all polymers investigated. Finally, the value of the Avrami parameter n is reported.
Isothermal refolding in crystals of long alkanes in solution. I. Effect of surface ‘self‐poisoning’
Authors: Ungar Goran , Organ Sally J. 
Published: April 2003

AbstractLamellar thickening in folded‐chain crystals of the n‐alkane C198H398 in solution has been shown to occur at the crystallization temperature. The transformation is from crystals with their chains folded in half to extended‐chain crystals, with no observable intermediate forms. This conforms with the extensive existing evidence that integer‐folded forms are thermodynamically preferable. Measurements of the kinetics of lamellar thickening have revealed an unexpected maximum in the thickening rate as a function of temperature: above 75°C, thickening slows down with increasing temperature. This unprecedented result is an indirect consequence of another, equally puzzling, anomaly: the rate of extended‐chain nucleation at the side faces of folded‐chain crystals decreases with increasing solution concentration. This unique observation is attributed to “self‐poisoning” of the lateral surface of the growing nucleus by frequent folded‐chain depositions which inhibit the process of molecular extension. The same effect has been invoked previously to explain the anomalous crystallization rate minima in long alkanes and its present manifestation under different circumstances is regarded as an important independent validation of the concept of “self‐poisoning.”
Transfer‐matrix theory of the crystal–columnar transition in polymeric liquid crystals
Authors: Xu Bing‐Chang , Taylor Philip L. 
Published: April 2003

AbstractThe statistical–mechanical problem of the transition between crystalline and columnar phases in a main‐chain liquid–crystalline polymer is treated in a simple model in which only longitudinal motions of the polymer chains are permitted. A mean‐field approximation for the interchain potential is used to obtain a self‐consistent equation for the crystalcolumnar transition temperature. When applied to typical homopolymers this theory correctly predicts transition temperatures above the degradation temperature; when applied to a crude model of a random copolymer a temperature in the observed range is predicted.
Relaxations in thermosets. XVIII. Ultrasonic studies of curing kinetics of ethylene‐diamine‐cured epoxide
Authors: Alig I. , Lellinger D. , Johari G. P. 
Published: April 2003

AbstractVelocity and attenuation of longitudinal acoustic waves in a frequency range of 5–16 MHz have been measured during the curing of diglycidyl ether of bisphenol‐A with ethylene diamine. The velocity monotonically increases and reaches a limiting value and the attenuation reaches a maximum and thereafter decreases as curing proceeds. Both kinds of data have been transformed into a complex‐longitudinal‐modulus formalism. The complex‐plane plots of the longitudinal modulus show an arc‐skewed shape at the long (curing) time end. It is fitted, for the initial phase of curing, to a stretched exponential decay function with an exponent γ = 0.22 to 0.28. These results then are considered in terms of a process with a negative feedback between molecular diffusion and chemical reactions to obtain the increase in the relaxation time with the curing time. This increase is sigmoidal. Calculations of the complex longitudinal modulus show the consistency of our formalism.
Gel processing of electrically conductive blends of poly(3‐octylthiophene) and ultrahigh molecular weight polyethylene
Authors: Moulton Jeff , Smith Paul 
Published: April 2003

AbstractThe mechanical and electrical properties of solution‐processed [or gel‐spun] blends of poly(3‐octylthiophene) and ultrahigh molecular weight polyethylene are discussed. Tensile drawing at elevated temperatures of the phase‐separated blends resulted in significant improvements of the mechanical properties, in comparison with those of the neat conducting polymer, with values of the Young's modulus reaching > 40 GPa and tensile strengths in excess of 2 GPa. Doping of the undrawn polyblend fibers with iodine vapor or FeCl3 resulted in materials of useful levels of electrical conductivity covering the full range of 10−15 to 10 S/cm. A distinct percolation threshold for electrical conductivity was not observed, even at poly(3‐octylthiophene) concentrations as low as 0.5 w/w %; the electrical conductivity of the latter blend, after doping with iodine vapor, was 8 × 10−8 S/cm.
Influence of uniaxial draw on near‐surface structure in poly(ethyleneterephthalate)
Authors: Walls Dennis J. , Coburn John C. 
Published: April 2003

AbstractRelative amounts of surface crystallinity and amorphous structure and their respective surface orientations were examined as a function of depth from the surface for a series of uniaxially drawn poly(ethyleneterephthalate) (PET) films using polarized attenuated total‐reflectance infrared spectroscopy (ATR‐IR). Qualitative depth resolution on a scale from ca. 0.5 to 5 μm is obtained. The results indicate a higher degree of extended trans segments and a higher degree of extended trans orientation near the surface in the machine direction, relative to the bulk film. These quantities also increase with increasing uniaxial draw ratio. No evidence for orientation of the gauche conformer at the surface as a function of uniaxial draw ratio is observed. All conclusions are consistent with the presence of increased crystallinity at the surface of the films. Increases in trans structure and orientation measured by ATR‐IR measurements are consistent with bulk crystallinity measurements from density and x‐ray scattering measurements.
The effect of annealing on slow crack growth in an ethylene‐hexene copolymer
Authors: Lu X. , Qian R. , McGhie A. R. , Brown N. 
Published: April 2003

AbstractA quenched ethylene‐hexene copolymer was annealed in the temperature range of 86 to 127°C. The morphological changes were monitored by differential scanning calorimetry (DSC) and density. The slow crack growth resistance tested at 80°C was a maximum at an annealing temperature of 113°C and a minimum of 123°C. The lifetimes can be varied by more than a factor of 20 depending on the thermal treatment. The increase in slow crack growth resistance between 86 and 113°C is attributed to an increase in the strength of the crystals by becoming more perfect and to the conversion of loose tie molecules into taut tie molecules. The decrease in strength between 113 and 123°C is attributed to the decrease in tie molecules when a large fraction of the as‐quenched crystals begin to melt.
Influence of polymer structure inhomogeneity on oxygen quenching of phenanthrene phosphorescence in poly(methyl methacrylate)
Authors: Bagryansky V. A. , Korolev V. V. , Tolkatchev V. A. , Bazhin N. M. 
Published: April 2003

AbstractDecay kinetics of phenanthrene phosphorescence in atactic poly(methyl methacrylate) have been studied at 130–170 K in the presence of dissolved oxygen. The kinetics show anomalous behavior and cannot be described in terms of homogeneous diffusion of oxygen. Analysis of the dependence of the kinetics on oxygen concentration shows that such behavior is well accounted for by a polychromatic model assuming a dispersion of diffusion coefficients due to the inhomogeneity of the polymer structure. Possible errors in determining the diffusion coefficient from the phosphorescence quantum yield on the assumption of homogeneous diffusion are discussed. © 1992 John Wiley & Sons, Inc.
Phenomenology and mechanisms of unidimensional stress‐dependent micromolecular transport in a stiff‐chain polymer. I. Unoriented cellulose acetate
Authors: Sanopoulou M. , Petropoulos J. H. 
Published: April 2003

AbstractThe longitudinal penetration of micromolecular liquid solvents (acetone, dioxane) or swelling agents (methylene chloride, methanol) into unoriented (unstretched) cellulose acetate film has been studied in detail by a variety of techniques, including observation of visible penetrant fronts, birefringence profiles, colored tracer microdensitometry, and microinterferometry. The results, in conjunction with those of Part II, provide a fuller picture of the relevant phenomenology than was previously available, leading to further insight into the mechanism of micromolecular transport in stiff‐chain polymers and its dependence on the nature of the penetrant and the structural changes of the swelling polymer. © 1992 John Wiley & Sons, Inc.
Phenomenology and mechanisms of unidimensional stress‐dependent micromolecular transport in a stiff‐chain polymer. II. Uniaxially oriented cellulose acetate
Authors: Sanopoulou M. , Petropoulos J. H. 
Published: April 2003

AbstractThe study of micromolecular transport in cellulose acetate film reported previously is here extended by investigation of the effect of different degrees of semipermanent uniaxial macromolecular orientation, produced by prestretching the film under suitable conditions. The changes noted in penetration rate and kinetics and in birefringence, tracer microdensitometry, and microinterferometry profiles for penetration along and across the axis of preferred orientation, are reported in detail and their implications in terms of the transport mechanism are discussed. © 1992 John Wiley & Sons, Inc.
The in situ reactive compatibilization of nylon‐6/polystyrene blends using anhydride functionalized polystyrenes
Authors: Park Inha , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractNylon‐6/polystyrene (PS) blends were reactively compatibilized by addition of various anhydride functionalized polystyrenes. The morphology of the blends was examined using a scanning electron microscopy (SEM) technique. The particle size of the dispersed styrenic phase was about 3.2 μm for the uncompatibilized 8/2 Nylon‐6/PS blend while those of the compatibilized blends were decreased by as much as two orders of magnitude depending on the amount and type of the functionalized polystyrene (FPS) added. Several low‐molecular weight polystyrenes with terminal anhydride groups, prepared by two different functionalization methods, were examined. The effect of molecular weight on particle size reduction depended on the basis of comparison, mass of additive, or moles of anhydride units. A high‐molecular weight random copolymer of styrene and maleic anhydride was most effective when compared on a mass basis. The increase in adhesion between the Nylon‐6 and the styrenic phases caused by the in situ reaction was evaluated by a lap shear technique. The free polystyrene, Nylon‐6, and Nylon‐FPS copolymer formed were separated by solvent extraction technique using formic acid and toluene. The extent of coupling reaction between the functionalized polystyrenes and Nylon‐6 ranged from 25 to 43%. © 1992 John Wiley & Sons, Inc.
Photoelasticity of textured heterogeneous polymer materials
Authors: Patlazhan S. A. 
Published: April 2003

AbstractThe photoelastic properties of textured polymer composites are considered for the high deformation limit. Photoelasticity equations for incompressible polymers are derived in the correlation function theory approximation. It is shown that the birefringence may be zero for critical stretching across the texture axis. This effect can be used to measure the dispersion of shear moduli of polymer composites. © 1993 John Wiley & Sons, Inc.
Microphase separation of block copolymer solutions in a flow field
Authors: Albalak Ramon J. , Thomas Edwin L. 
Published: April 2003

AbstractFilms of polystyrene–polybutadiene–polystyrene (PS/PB/PS) triblock copolymer and polystyrene‐poly(ethylene/propylene) (PS/PEP) diblock copolymer were cast from toluene solutions subjected to hydrodynamic flow at room temperature using a device based on a novel casting method we term ‘roll‐casting.’ Polymer solutions were rolled between two corotating eccentric cylinders while at the same time the solvent was removed at a controlled rate. As the solvent evaporated, the block copolymers microphase separated into globally oriented structures. A discussion of the flow field that develops during roll‐casting is presented and specific attention is given to the importance of the shear and elongation rates present. For the triblock and diblock, respectively, the processed structures consisted of polystyrene cylinders assembled on a hexagonal lattice in a polybutadiene matrix, and unidirectional lamellae of alternating polystyrene and polyethylene/propylene. Small‐angle x‐ray scattering (SAXS) and transmission electron microscopy (TEM) indicated the near single‐crystal structure both types of films. SAXS also showed the styrene cylinders and the alternating lamellae to be packed closer together in roll‐cast films than in simple quiescently cast films. A molecular orientation mechanism is proposed to describe both these results as well as the changes in packing and in macroscopic sample dimensions measured after complete solvent evaporation and after sample annealing. © 1993 John Wiley & Sons, Inc.
Poly(ethylene oxide) electrolytes containing mixed salts
Authors: Yang H. , Farrington G. C. 
Published: April 2003

AbstractAn unusual conductivity enhancement occurs in PEO‐based ZnBr2/LiBr electrolytes of composition, [xZnBr2 + (1 − x)LiBr](PEO)16 with x = 0.00, 0.05, 0.50, 0.75, 1.00. The conductivity of the mixed‐salt electrolytes is higher than that of either pure salt electrolyte. The highest conductivity, observed for x = 0.5, is two orders of magnitude higher than that of pure LiBr(PEO)16 and one order higher than ZnBr2(PEO)16. In contrast, the conductivity of mixed Mg (CIO4)2/LiCIO4 electrolytes, [xMg(CIO4)2 + (1 − x) LiCIO4](PEO)16 where x = 0.00, 0.20, 0.50, 0.80, 1.00, increases monotonically with the mole fraction of the higher conductivity component, LiCIO4(PEO)16. The conductivity and differential scanning calorimetry (DSC) results suggest that the conductivity enhancement in the ZnBr2/LiBr electrolytes results from a change in charge carrier type and concentration, whereas the conductivity change in the Mg(CIO4)2/LiCIO4 electrolytes arises from a change in the microscopic viscosity of the electrolytes. © 1993 John Wiley & Sons, Inc.