bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrically conductive elastomeric TCNQ complexes
Authors: Ikeno S. , Yokoyama M. , Mikawa H. 
Published: April 2003

AbstractNew elastomeric ionene polymers containing poly(tetramethylene oxide) chain units were synthesized. The electrical conductivities of the salts of these polymers with (the anion radical of tetracyanoquinodimethane) (simple salt) and with neutral TCNQ added (doped salt) were investigated. Each cationic site in the polycationic polymer chain is separated by a long elastic chain unit, and consequently, moieties in the simple salt are expected to be well separated. Unexpectedly, doping with neutral TCNQ caused a marked decrease in the specific resistivity and the activation energy. Although the simple salt is elastic, doping with neutral TCNQ increased the stiffness of the material. The room‐temperature specific resistivity of the doped salts was in the range of 103 to 104 Ω cm. The marked change of electrical and mechanical properties brought about by doping with neutral TCNQ is discussed in terms of a structural model in which phase separation of the ionic part from the nonionic elastic units has been assumed.
Four‐center‐type photopolymerization in the crystalline state. XI. Crystal structure of p‐phenylenediacrylic acid diethyl ester above the crystal transition point
Authors: Nakanishi Hachiro , Ueno Katsuhiko , Sasada Yoshio 
Published: April 2003

AbstractThe crystal structure of p‐phenylenediacrylic acid diethyl ester above the transition point was determined at 70°C by x‐ray diffraction. No significant differences in molecular arrangement are found between the structures of the α2 form (above the transition point) and the α1 form (at room temperature). Since the α1 form is photopolymerized, it is concluded that selective dimerization in the α2 form results not form the crystal structure of the monomer, but from the deterioration of molecular arrangement by the formation of dimer.
Melting and crystallization of poly(vinylidene fluride) under high pressure
Authors: Matsushige Kazumi , Takemura Tetuo 
Published: April 2003

AbstractPrecise melting and crystallization temperatures of extended‐chain and folded‐chain crystals of form I and folded‐chain crystals of form II poly(vinylidene fluoride) under high pressure have been obtained by microdifferential thermal analysis (DTA). Upon heating at pressures above 4000 kg/cm2, the micro‐DTA thermogram of form II crystallized from the melt at atmospheric pressure shows melting of the form II structure and the melting of the folded‐chain and extended‐chain crystals of form I, formed through recrystallization processes. These features were clarified by supplemental methods. The bandwidth seen in electron micrographs of the extended‐chain crystal of form I obtained by crystallization under high pressure was in the range of 1500 to 2000 Å. At atmospheric pressure, the extended‐chain crystal of form I melted at 207°C, approximately 17°C higher than the folded‐chain crystal of form I and 31°C higher than the folded‐chain crystal of form II.
Effect of particle shape at finite concentration on the elastic moduli of filled polymers
Authors: Chow T. S. 
Published: April 2003

AbstractThe elegant approach of Eshelby, developed for dilute dispersions, is generalized to include the interaction of filler with filler. It is then utilized to determine the five elastic moduli of filled polymer containing aligned ellipsoidal particles at finite concentrations φ. The anisotropic particle shape is characterized by an aspect ratio ρ of an ellipsoid. The present theory compares well with available experiments in the literature. The experimentally verified Kerner equation for spherical particles and rule of mixtures for the longitudinal Young's modulus at ρ → ∞ are special cases of our new results.
Effect of particle shape at finite concentration on thermal expansion of filled polymers
Authors: Chow T. S. 
Published: April 2003

AbstractRelations are derived for the linear and volumetric thermal expansion coefficients of a filled polymer containing aligned ellipsoidal inclusions at finite concentrations. The analysis follows a procedure recently developed for elastic moduli by application of a generalized approach of Eshelby. The well‐known Kerner equation is shown to be a limiting case of the present finding. From data on glass in epoxy resin, we conclude that the volumetric expansion varies only slightly with the aspect ratio of an ellipsoid; however, the longitudinal and transverse, linear, expansions show a strong dependence on the particle shape.
Isotactic poly(pentene‐1): Polymorphism of form I
Authors: Moser M. , Boudeulle M. 
Published: April 2003

AbstractThe polymorphism of isotactic poly(pentene‐1) form I was studied by x‐ray diffraction. Upon quenching from the melt at a temperature below 25°C, the films crystallized in a stable monoclinic form, which we have designated as form I (a = 22.4 ± 0.2 Å, b = 6.49 ± 0.05 Å, c = 21.2 ± 0.2 Å, β = 91 ± 1°). For higher quenching temperatures, a metastable form, form I′, appeared, which transforms to the normal modification upon aging (monoclinic, with: a = 24.3 ± 0.2 Å, b = 6.50 ± 0.05 Å, c = 19.3 ± 0.2 Å, β = 96 ± 2°). Both modifications have a 31 helical conformation. Limited changes in the packing mode could explain this polymorphism.
Structural relationships in the solid‐state synthesis of poly(bis‐phenyl glutarate diacetylene)
Authors: Day David , Lando Jerome B. 
Published: April 2003

AbstractThis study was undertaken to determine the crystal structure of poly(bis‐phenyl glutarate diacetylene) (poly(BPG)). It was found that this material crystallizes in a C2/c (centrosymmetric) space group. The x‐ray refinement revealed a solid solution of the monomer and polymer. It was determined that the only movement that occurs during polymerization is in the diacetylene rod (a rotation of 33°) and in adjacent phenyl groups (a rotation of 19° and a swing of 6°), while all other atomic positions in the side group remain essentially the same. An infrared investigation and the final refined atomic coordinates with their standard deviations indicates that the BPG crystal was polymerized to an extent of 35%.
Exploratory analysis of the influence of substitutional impurities on the electronic properties of poly(sulfur nitride)
Authors: Parry David E. , Thomas John M. 
Published: April 2003

AbstractThe results of extended Huckel calculations are reported for an isolated (SN)x chain in which some of the S2N2 units of the extended one‐dimensional chain are replaced by (SCH2)2 units. It is found that, inter alia, the metallic behavior of the unsubstituted parent is retained but that the conductivity is lowered to an extent governed by the nature and degree of substitution.
Crystallization of poly(tetramethyl‐p‐silphenylene–dimethylsiloxane) (TMPS–DMS) block copolymers: Morphology and kinetics
Authors: Li H. M. , Magill J. H. 
Published: April 2003

AbstractThe crystallization behavior of random block copolymers of (tetramethyl‐p‐silphenylenesiloxane) and dimethylsiloxane has been studied over a wide range of temperature and composition. The copolymer melting temperature, glass transition temperature, rate of crystallization, crystallinity, and density decrease in magnitude as the dimethylsiloxane block content are raised in this two‐component system. The crystal end‐surface (interfacial) energy increases as the dimethylsiloxane mole fraction decreases in accord with other morphological observations. The morphological changes observed in these copolymers are consistent with the conclusions deduced from the crystallization kinetics. Negatively, birefringent spherulites are observed over the entire crystallization range investigated.
Cooperative model for the mechanical deformation of polymers
Authors: Joseph S. H. 
Published: April 2003

AbstractA model for the mechanical behavior of solid polymers is proposed in the form of a linear elastic network with transitions. A simplified version of the model involving a single column of two‐site activated processes is found to be a mean‐field system. The failings of this system as a description of yield and glass transition relaxation behavior lead to two extensions to the system: that of many available sites in each activated process, and that of a finite number of such processes in the whole system. These extensions reduce the properties of the system to those of a single activated flow process with a temperature‐dependent activation energy. Agreement is found between this result and time‐temperature shift measurements in the α transition region of several polymers, together with an explanation of the dependence of yield stress on temperature for one of these polymers that is physically more reasonable than the usual constant activation energy proposal.
Calorimetric studies of poly(ethylene terephthalate) stretching over a wide temperature range
Authors: Andrianova G. P. , Arutyunov B. A. , Popov Yu. V. 
Published: April 2003

AbstractHeat effects and structural transformations in amorphous crystallizable poly(ethylene terephthalate) (PET) during uniaxial stretching accompanied by neck formation, have been investigated by calorimetric and x‐ray methods over a wide range of temperatures and deformation rates. At small deformation (not exceeding 1–2%) and at temperatures below the glass transition temperature of the polymer, PET behaves as an elastic body. Upon stretching at a constant rate, constant heat power is absorbed, heat effects during loading and unloading coincide completely, and no hysteresis is observed. At large deformations (of the order of 50%), cold drawing develops in this temperature range. The internal energy change in cold drawing is zero within experimental error. A periodic heat release during the self‐oscillation regime of drawing PET corresponds to periodic changes in stress, in the rate of the neck formation, and in the appearance of the sample. The temperature limits of the region where crystallization resulting from an uniaxial drawing of the polymer is possible, have been determined, and the heat effect of this phase transition has been measured. Orientation crystallization develops only from 70 to 94°C. These limits are insensitive to changes in deformation rate within one decimal order. The structure of PET in this temperature range has been investigated. The heat of phase transition of orientation crystallization of PET has been determined from the relationship between the measured values of the internal energy change during this process and the limiting degree of crystallinity for the stretched samples. This heat proves to be 5.5 ± 0.1 cal/g.
Induced crystallization of poly(ethylene terephthalate) on small metallic nucleating particles
Authors: Gutzow I. , Dochev V. , Pancheva E. , Dimov K. 
Published: April 2003

AbstractThe induction period for the onset of crystallization was determined in poly(ethylene terephthalate) in the presence and absence of small metallic particles. Two kinds of substrates were used: single microcrystals “transplanted” from the water‐soluble inorganic polymer (NaPO3)x and powders of the same metals (Au, Pt, and Ir). The nucleating activity ϕ of the substrates was determined on the basis of classical nucleation theory. Values of ϕ obtained for PET are compared with the corresponding values in the (NaPO3)x melt and with theoretical concepts.
Molecular conformation and craze fracture
Authors: Haward R. N. , Daniels H. E. , Treloar L. R. G. 
Published: April 2003

AbstractA craze may fracture either by the breaking of covalent bonds or by a process of “viscous rupture” involving the movement of bulk material in the craze. In the latter case it is necessary that the majority of the chain ends of the polymer molecules passing through the craze‐matrix interface terminate within the craze. We have therefore calculated the probability of a polystrene macromolecule spanning a thin craze and shown that for viscous rupture a craze in a normal commercial polystyrene must be something more than 40 nm thick. As the measured craze thicknesses have generally exceeded 100 nm, a viscous fracture process is clearly possible, though, of course, chain rupture is not excluded by the argument. More difficulties arise when fracture occurs within a specified region of the craze and the possibility of a bond fracture under these circumstances is briefly discussed.
Electron density calculation for polyoxymethylene in cylindrical coordinates by a new fourier method
Authors: Takahashi Yasuhiro , Tadokoro Hiroyuki 
Published: April 2003

AbstractThe electron density of the polyoxymethylene molecule was calculated in cylindrical coordinates by a newly derived Fourier method. The density due to hydrogen could be obtained in addition to that from carbon and oxygen. This method is generally applicable to a helical polymer whose unit cell contains only one molecule composed of a number of chemical repeat units in the fiber identity period.
Effect of polymorphism on the CH stretching region of the infrared spectrum of polyethylene
Authors: Painter P. C. , Runt J. , Coleman M. M. , Harrison I. R. 
Published: April 2003

AbstractA complex fine structure in the CH stretching region of the infrared spectrum of deformed polyethylene single crystals is reported. The deformed crystals are shown to be transformed from the orthorhombic crystal form to a monoclinic structure. The previously deduced C2/m monoclinic structure does not account for the appearance of the new bands. An alternative but similar monoclinic structure is proposed. The symmetry of this structure is consistent with the Fermi resonance interactions required for the observation of these bands.
A theory for the drawing of oriented crystalline polymers
Authors: Arridge R. G. C. , Barham P. J. 
Published: April 2003

AbstractThe load‐elongation behavior during the postneck drawing stage in the deformation of crystalline polymers is shown to be modeled quantitatively by an aligned short‐fiber composite in which crystalline fibrils form the reinforcing phase in a matrix of less well‐ordered material. Three modes of deformation are distinguished in the model and are shown to correspond to the observed loadelongation relations in polyethylene and polypropylene. The regions are (I) elastic–plastic crystals in an elastic matrix, (II) elastic–plastic crystals in an elastic–plastic matrix, (III) elastic crystals in an elastic–plastic matrix. A requirement of the theory is that the flow stress in the crystals is little affected by temperature whereas that in the matrix falls as the temperature rises. Expressions are given for stress in terms of the applied strain and the relevant parameters of the system: concentration of fibrils, length and diameter of fibrils, and elastic and yield properties of fibrils and matrix.
Thermal properties of some hydrogenated poly(α‐methyl styrenes)
Authors: Gipstein Edward , Barrall E. M. , Yoon Do Y. , Lyerla James 
Published: April 2003

AbstractThe Synthesis of poly(isopropenyl cyclohexane) via the hydrogenation of poly(α‐methyl styrene) is described. Depending on the reaction time and catalyst system a homopolymer or a copolymer is obtained. Under the conditions of synthesis both materials are highly syndiotactic. For the pure hydrogenated homopolymer (>99.9%) the glass transition temperature was found to be 185.4°C, about 20°C above Tg of poly(α‐ethyl styrene). Contrary to expectations, the glass transitions of the 92/8, 33/67 poly(isopropenyl cyclohexane‐co‐methyl styrene) and poly(α‐methyl styrene) are almost identical, as are the decomposition temperature ranges. Thermal data indicate that the decomposition mechanism of the copolymers and hydrogenated homopolymer is random scission. The thermogravimetric curves also indicate that the copolymers are random. Thus, chain stiffness appears not to increase rapidly with hydrogenation of this highly syndiotactic polymer.
NMR study of diffusion of butane in linear polyethylene
Authors: Zupančič I. , Lahajnar G. , Blinc R. , Reneker D. H. , Peterlin A. 
Published: April 2003

AbstractThe diffusion coefficient of butane in linear polyethylene at room temperature as a function of the vapor pressure of butane was measured by the spin‐echo method with a pulsed magnetic field gradient. For the Special morphology of randomly oriented stacks of parallel lamellas the detour factor is 1/3. As long as the blocking factor and migration through the lamellas can be neglected, the local diffusion coefficient Da of the small molecules through the amorphous layers in the direction parallel to the lamellas is three times the apparent diffusion coefficient D derived from the decay of the amplitude of the spin echo under the assumption of an infinitely extended homogeneous medium. The diffusion coefficient and the spin–spin relaxation time both increase exponentially with increasing pressure, i.e., butane concentration in the polymer, while the spin‐lattice relaxation time is pressure independent and seems to be determined by interaction with the amorphous polyethylene matrix.
Delayed yielding of polycarbonate under constant load
Authors: Narisawa Ikuo , Ishikawa Masaru , Ogawa Hiroyuki 
Published: April 2003

AbstractThe time‐dependent yielding of glassy polycarbonate subjected to constant tensile loads has been studied. Application of a constant stress of a magnitude between the yield stress and the stress required for propagation of a neck in constant strain tests results in inhomogeneous yielding after a well‐defined time lag. This delay time increases with decreasing stress and temperature. The critical stress for slowly cooled material is greater than that for quenched material in which the delay time is divided in two regions. The delay time is regarded as the time required for the initiation of inhomogeneous yielding at either edge of the specimen and growth over a certain distance across the specimen. Geometrical observations revealed that the inhomogeneous yielding is shear yielding which is initiated due to stress inhomogeneities caused by mechanical imperfections at the edge of the specimen. The Eyring treatment of delayed yielding can describe fairly well the stress and temperature dependence of the delay time.
Analysis of the equations of state of polyolefin melts in terms of the simha‐somcynsky hole theory
Authors: Zoller Paul 
Published: April 2003

AbstractPressure–volume–temperature data on melts of low‐density polyethylene, polypropylene (PP), poly(butene‐1) (PBT), and poly(4‐methylpentene‐1) (PMP) previously reported by us have been evaluated in terms of the Simha–Somcynsky hole theory of polymeric liquids by a determination of the reducing parameters P*, V*, and T* for each system. Literature data on the reducing parameters of linear polyethylene and of a branched polyethylene of intermediate density are also considered. Agreement with theory is best for the polyethylenes and deteriorates markedly in the series PBT:PP:PMP. These higher polyolefins have very low values of P*, thus suggesting a deficiency of the Simha–Somcynsky theory at high reduced pressures P̃ = P/P*. In these polyolefins, systematic variations of the reducing parameters (and molecular parameters derived therefrom) are noted and discussed. Correlations found previously between T* and the moleculer weight M0 of the effective segment of the theory or its hard‐core volume M0V* are obeyed by the polyethylenes only. The higher polyolefins show serious deviations from these correlations.
Diffusion studies of poly(ethylene terephthalate) crystallized by nonreactive liquids and vapors
Authors: Makarewicz P. J. , Wilkes G. L. 
Published: April 2003

AbstractThe diffusion of vapors and liquids which induce crystallization in initially amorphous, unoriented poly(ethylene terephthalate) (PET) films was studied. It was determined that these vapors and liquids penetrate the polymer as distinct fronts, and the kinetics of this penetration and the weight uptake kinetics both follow apparent Fickian behavior. Distinct cavitation advanced into the polymer at the penetrant front–dry polymer interface in certain PET–liquid systems, and phenomenological explanations of its existence and of the general diffusion process observed are offered. Finally, the diffusion of the highly interactive liquids dioxane and methylene chloride into cold‐drawn PET was studied and shown to occur considerably more slowly than does the diffusion of these liquids into unoriented films.
Mechanical property studies of poly(ethylene terephthalate) crystallized by nonreactive liquids
Authors: Makarewicz P. J. , Wilkes G. L. , Budnitsky Y. 
Published: April 2003

AbstractThe mechanical properties of initially amorphous, unoriented poly(ethylene terephthalate) (PET) films crystallized in acetone and dioxane at room temperature were studied under tensile testing conditions. It was found that the nature of the liquid, the morphology it induced, and its significant residual level trapped within the PET following this type of crystallization all influenced the observed mechanical behavior. Further, thermally treating PET at 70, 90, and 174°C prior to the liquid treatments appeared to inhibit the effects of the liquids on the resultant mechanical behavior. Finally, because these liquids penetrated the polymer as distinct fronts, laminate‐type structures were generated in the films. It then was shown that an ideal parallel element laminate could adequately model the mechanical behavior of the films.
Gelation and precipitation of copolymers from solution
Authors: Benson R. , Maxfield J. , Axelson D. E. , Mandelkern L. 
Published: April 2003

AbstractThere are several reports in the literature to the effect that when isotactic polystyrene crystallizes from moderately dilute solution, lamellas (precipitate) form at high crystallization temperatures and gels at low temperatures. We report here the occurrence of a very similar phenomenon during the crystallization of ethylene‐butene‐1 copolymers. The observations for the latter system can be given a straightforward explanation based on the demonstrated compositional fractionation that occurs on crystallization. Low co‐unit content copolymers are associated with lamellas. Gels invariably contain much higher co‐unit content. A generalization of these findings is invoked to explain the previous polystyrene results. A new resonance detected by 13C NMR experiments in this polymer can be ascribed to head–head sequences.
Determination of the distribution of straight‐chain segment lengths in crystalline polyethylene from the Raman LAM‐1 band
Authors: Snyder Robert G. , Krause Steve J. , Scherer James R. 
Published: April 2003

AbstractIt is shown how the shape of the longitudinal acoustic vibration observed in the low‐frequency region of the Raman spectra of crystalline polymers can be used to obtain a quantitative distribution of lengths of straight‐chain segments associated with polymer lamellas. The procedure is demonstrated for a “solid‐state” extrudate of polyethylene and for a bulk‐crystallized specimen of the same polymer. Equations relating the shape of the LAM‐1 band to the shape of the distribution curve are given. The low intensity observed for the LAM‐3 mode relative to LAM‐1 is explained quantitatively without recourse to end effects. LAM‐5 has been observed for bulk‐crystallized polyethylene. For the extrudate we find the distribution of lengths of straight‐chain segments to have a tail on the long‐length side which is not present for the bulk‐crystallized sample. The Raman technique is shown to provide new morphological data unattainable at present by other methods.