bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small‐ and intermediate‐angle neutron scattering from amorphous and semicrystalline polyethylene terephthalate
Authors: McAlea K. P. , Schultz J. M. , Gardner K. H. , Wignall G. D. 
Published: April 2003

AbstractSmall‐ and intermediate‐angle (0.006 < Q < 0.25 Å) neutron scattering experiments have been performed on polyethylene terephthalate (PET). Amorphous and semicrystalline samples with deuterated PET molecular weights of 24,200 and 40,500 were prepared. The average value of R/M determined in the small‐angle region for the amorphous samples is 0.406, in close agreement with the experimental θ‐solvent (0.398–0.420) and theoretical (0.394) values for unperturbed dimensions. The intermediate‐angle results for the amorphous sample are consistent with the random coil prediction to Q = 0.08 Å, but beyond this Q value there is some deviation from Gaussian behavior. The semicrystalline samples show a decrease in the radius of gyration as measured in the small‐angle region and an increase in intensity (when compared to the amorphous data) in the intermediate‐angle region, especially for the low‐molecular‐weight material. These results suggest that crystallization in PET is accompanied by greater molecular reorganization than has previously been observed in most bulk polymers.
Determination of the thermodynamic polymer‐polymer interaction parameter of miscible blends prepared from two crystalline polymers
Authors: Zhang Huanzhi , Prud'Homme Robert E. 
Published: April 2003

AbstractThe melting points of miscible blends prepared from two crystalline polymers, poly(caprolactone) (PCL), and Saran a random copolymer of vinylidene chloride with vinyl chloride [P(VCl2‐VC)], vinyl acetate [P(VCl2‐VA)], or acrylonitrile [P(VCl2‐AN)], have been measured by differential scanning calorimetry as a function of the crystallization temperature. The equilibrium melting points of these blends have been determined by Hoffman‐Weeks plots. From two series of data, one of which was obtained by measuring the melting points of PCL crystals and the other by measuring the melting points of Saran crystals, the thermodynamic polymer‐polymer interaction parameters of PCL/Saran blends have been calculated over the full range of composition. The two series of data merge into a smooth curve, which is composition dependent, despite the fact that the melting points of PCL and P(VCl2‐VC) or P(VCl2‐VA) are very different at 58.1, 183.5, and 184.2°C, respectively. Calculations using the “equation of state” Prigogine‐Flory thermodynamic theory indicate that the temperature dependence of the thermodynamic interaction parameter in typical polymer blends is small, which agrees with the experimental results.
Characterization of linear low‐density polyethylene: Cross‐fractionation according to copolymer composition and molecular weight
Authors: Mirabella Francis M. , Ford Emory A. 
Published: April 2003

AbstractThe structure of ethylene copolymers modified by α‐olefins has become an area of intense investigation since the successful commercialization of so‐called linear low‐density polyethylene (LLDPE) resins. The molecular structure of a series of typical commercial LLDPE copolymers was investigated and compared to LDPE and HDPE. The commercial LLDPE resins studied contained about 7% by weight of butene‐1. The resins were fractionated according to short‐chain branching content by a technique called temperature rising elution fractionation. Size exclusion chromatography, x‐ray diffraction, 13C nuclear magnetic resonance, intrinsic viscosity, and differential scanning calorimetry were used to fully characterize the whole polymers as well as fractions of a selected LLDPE resin. A broad set of data was assembled in this work to investigate the short‐chain branching, long‐chain branching, and the molecular‐weight distribution of these commercial resins. The melting behavior of the LLDPE resins was found to be strikingly different from that of LDPE and HDPE. The broad and multimodal melting envelope of the LLDPE resins was found to be due to a broad and multimodal short‐chain branching distribution. No significant long‐chain branching was found in the LLDPE resins. The short‐chain branching was found to decrease with the increase of molecular weight in a typical commercial LLDPE resin. The unique physical properties of these resins are certainly strongly controlled by the expression of the distinctive heterogeneous comonomer incorporation in the solid‐state morphological structure. The physical and mechanical properties of these materials should be ultimately understandable on the basis of the unique morphology which results from the extremely heterogeneous incorporation of modifying α‐olefin in these commercial LLDPE resins.
Polymer blend complexes based on coordination chemistry
Authors: Agarwal P. K. , Duvdevani I. , Peiffer D. G. , Lundberg R. D. 
Published: April 2003

AbstractThe preparation, rheology, and mechanical properties of a family of blends composed of transition‐metal neutralized sulfonated ethylene‐propylene‐diene elastomers (S‐EPDM) and styrene‐4 vinylpyridine copolymers (SVP) are described. These polymeric materials contain relatively low levels of interacting groups (≤ 10 mol%), which are, however, sufficient for forming an intermolecular complex. A distinguishing characteristic of these blends is that the rheology and mechanical properties are strongly influenced by a coordination‐type bonding between the transition metal and the basic nitrogen unit. As a result, markedly improved and enhanced physical properties are observed, especially when the stoichometric ratio of the interacting moieties are approached (SO/N = 1/1). This enhancement in properties is clearly exhibited in melt viscosity data, dynamic mechanical data, and thermal data. The blend morphology is also altered by complex formation, as is observed in scanning electron microscopy of the blends from which one of the ingredients was selectively extracted. At the stoichometric ratio, the blend of the olefinic elastomeric ionomer and the styrenic thermoplastic copolymer approaches a single‐phase system. Such blends are otherwise completely immiscible when the coordination‐type interacting groups are absent from either of the individual components. Accordingly, it was observed that nontransition‐type (Na, Mg) counterions have only a marginal effect on the compatibility of these blends, as is the case in the completely unfunctionized blend components.
Static fatigue fracture of polyethylene: A morphological analysis
Authors: Barry D. , Delatycki O. 
Published: April 2003

AbstractThe fracture properties of a number of high‐density polyethylenes were evaluated and related to their morphology. The resistance to initiation of fracture is related to the resistance to voiding of the materials and the rate of coalescence of voids. The propensity of the materials to void has been shown to be related to the size of the amorphous region. The resistance to propagation of the fracture is also related to the above factors as well as the ease of stretching and rupture of fibrils. The ease of fibril formation has been shown to be related to the degree of perfection of the crystallites.
Effect of antiplasticization on gas sorption and transport. I. Polysulfone
Authors: Maeda Y. , Paul D. R. 
Published: April 2003

AbstractThe addition of tricresyl phosphate, N‐phenyl‐2‐naphthylamine, and 4,4′‐dichlorodiphenyl sulfone to polysulfone causes changes in thermal and mechanical properties of the glassy mixtures associated with antiplasticization, i.e., reduction in glass transition temperature and increase in stiffness. These changes are also found to be accompanied by reductions in sorption of carbon dioxide and the permeability coefficients for helium, carbon dioxide, and methane at low diluent concentrations with reversal of these trends at higher levels as also occurs for the mechanical properties. Detailed analyses of data for carbon dioxide are given in terms of the dual sorption and mobility models often used for glassy polymers. The mobility for gas transport was found to decrease with diluent addition. The major cause for the decreased sorption is the reduction in glass transition temperature accompanying addition of the diluents. The changes in transport behavior approximately parallel the changes in mechanical behavior. These trends are not even qualitatively correlated with estimates of the excess volume changes associated with addition of the diluents to polysulfone.
Chromism of soluble polythienylenes
Authors: Rughooputh S. D. D. V. , Hotta S. , Heeger A. J. , Wudl F. 
Published: April 2003

AbstractThermochromism and solvatochromism of solutions of poly(3‐alkylthienylenes) are reported. The experimental results indicate the presence of two coexisting phases: polymer in solution and polymer in microcrystalline aggregates. From the concentration independence of the thermochromism, it is concluded that the transition is fundamentally driven by a single chain mechanism, and that the aggregation (microcrystallization) of the poly(3‐alkylthienylene) macromolecules can occur only after the single chain conformational change has occurred.
X‐ray studies on the deformation of an aromatic polyimide
Authors: Russell T. P. , Brown H. R. , Grubb D. T. 
Published: April 2003

AbstractThe deformation of the aromatic polyimide poly{N,N′‐bis(phenoxyphenyl)‐pyromellitimide} (PMDA‐ODA) has been investigated by x‐ray scattering. PMDA‐ODA, which exhibits a smecticlike ordering in the bulk can be elongated up to 70% at room temperature without a distinct yield point. Under strain, the diffraction pattern of the intramolecular spacing occurring at a Bragg spacing of 15.4 Å is elliptical. The ellipticity shows that the molecule changes its repeat distance along the chain axis. This may result from bond angle and bond length distortions. Consistent with this is a rapid recovery well below the glass transition temperature where all but 20% strain is recovered. This localized extension, however, cannot account fully for the macroscopic deformation applied, and, as such, a global orientation of the chains occurs, as evidenced by the arcing of the diffraction profiles. The retention of the intrachain reflection indicates that bundles of chain segments ordered in a smectic fashion orient as a unit maintaining a lateral chain‐segment alignment. Finally, the scattering vector at which a small‐angle scattering reflection occurs was found to be correlated to the coherence length determined by a Scherrer analysis of the ca. 15.4 Å intramolecular reflection. As the strain increased, the intensity and spacing of the small‐angle scattering reflection increased parallel to the stretching direction and decreased perpendicular to this. This suggests that the origin of the small‐angle scattering reflection arises from electron density fluctuations along the chain axis, as is typically seen in semicrystalline polymers.
Time‐temperature superposition and dynamic mechanical behavior of atactic polystyrene
Authors: Cavaille J. Y. , Jourdan Corinne , Perez J. , Monnerie L. , Johari G. P. 
Published: April 2003

AbstractThe dynamic mechanical behavior of monodisperse atactic polystyrene (mol. wt. 98,000) has been measured in the frequency range, 10−5 to 10 Hz and temperature range 359–374K. The time‐temperature superposition of the entire data in the frequency range of overlap seems less satisfactory in both the real and imaginary components of the complex shear modulus, G′ and G″, respectively. The lack of adequate superposition becomes pronounced in the tan ϕ (G″/G′) plots. The tan ϕ plots provide a more discerning criteria for the superposition than the G′ or G″ spectra.An analysis based on an earlier model for anelastic deformation shows that of the several changes that may occur in the dynamic mechanical behavior on heating of polystyrene, the predominant ones are both an increase in the size of the microshear domains and the correlations of movement of segments near entanglements. These decrease the contribution to the modulus on heating near Tg so that the time‐temperature superposition is vitiated.
Mobility of anionic spin probes in water‐containing nylon 6 film
Authors: Hamada Kunihiro , Iijima Toshiro , McGregor Ralph 
Published: April 2003

AbstractThe rotational mobility of anionic spin probes in water‐containing nylon 6 film was investigated by means of electron spin resonance (ESR) measurements for comparison with the results for nonionic spin probes reported previously. The extrema separation of the ESR spectra, 2Az′ increased with time owing to the evaporation of water. In the higher temperature region, 2Az′ increased steeply with time at first, and then more slowly, whereas for the nonionic spin probes, 2Az′ increased gradually and monotonically with time. This fact suggests that the anionic probe molecules are more strongly affected by water than the nonionic ones, i.e., the former probes are located in hydrophilic regions and the latter in hydrophobic regions. T50G, which can be empirically correlated with the glass transition temperature of the polymer Tg decreased with increasing water content. The decreasing tendency for the anionic spin probes was stronger than that for the nonionic ones. This fact also indicates that the local environment around the probe molecules varies from probe to probe. The rotational correlation time τR decreased markedly with an increase in water content. The Arrhenius plots of τR showed two crossover points. The crossover points in the higher temperature region Tn decreased greatly with increasing water content. The difference in Tn between dried and water‐containing films was larger than that for T50G. The activation energy for rotation, E, also decreased with increasing water content. It is suggested that water concentrates around the anionic spin probes and makes their rotation much easier.
Chord intercepts in the two‐dimensional cell model
Authors: Schulze G. E. W. , Willers R. 
Published: April 2003

AbstractThe two‐dimensional cell model is defined by the following conditions of its formation: athermal nuclei may be randomly (Poisson) distributed in a thin amorphous film. From these nuclei spherulites may start to grow instantaneously, circularly, and at the same rate. Where two spherulites touch growth stops, and all points of contact form a straight intersection between neighboring spherulites. Finally, if the film contains spherulites only, each spherulite (cell) is completely limited by straight intersections, forming an irregular polygon. All irregular polygons of the film together form a planar irregular net of straight intersections. In quantitative microscopy this net is characterized by a “lineal analysis.” A straight line (Rosiwal's line) is arbitrarily put into the plane of the net. The net divides Rosiwal's line into chord intercepts of different lengths. The distribution of these lengths is analytically derived in the present paper by use of the theory of probability.
Ionic species produced by mechanical fracture of solid polymer. III. Anions from polytetrafluoroethylene
Authors: Sakaguchi M. , Kinpara H. , Hori Y. , Shimada S. , Kashiwabara H. 
Published: April 2003

AbstractThe tetracyanoethylene anion radical (\documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document}) was detected by ESR spectroscopy in polytetrafluoroethylene (PTFE), which had been mechanically fractured in vacuo with tetracyanoethylene (TCNE) at 77 K. The assignment of \documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document} was carried out by ESR spectral simulation on the basis of an anisotropic effective hyperfine tensor that included a forbidden transition term. The \documentclass{article}\pagestyle{empty}\begin{document}${\rm TCNE}^{ \cdot ^ - } $\end{document} is formed by abstraction of an electron by TCNE from the anion that is produced by heterogeneous scission of the carbon‐carbon bond in the main chain of PTFE. At least 16% of the scission of the main chains of PTFE occurs by a heterogeneous process to produce the anions. Approximately 50% of the anions decay during annealing for 30 min at 220 K in the dark, and all anions decay within 15 min at 325 K.
Polymer–cosolvent systems. XI. Polystyrene dissolved in mixtures of diethyl ether and nitromethane
Authors: Cowie John M. G. , McEwen Iain J. 
Published: April 2003

AbstractThe ternary system nitromethane (1) +diethyl ether (2) +polystyrene (3) has been examined by determining the demixing behavior of the polymer in the temperature–solvent composition plane. Enhanced solvation of the polymer is evidenced by the ability of the mixture to dissolve very high molecular weight (107g/mol) polystyrene at intermediate solvent compositions compared with the behavior in the two solvents separately. The cosolvent action of the mixture is analyzed in terms of modern theories of polymer solution free volume.
Theoretical analysis of conformational energies, unperturbed dimensions, and dipole moments of poly(dichlorophosphazene)
Authors: Saiz Enrique 
Published: April 2003

AbstractA theoretical analysis of the conformational energies of poly(dichlorophosphazene) (PDCP) is presented. The results indicate that the bond pair PNP possesses a considerable conformational freedom, whereas the bond pair NPN is relatively rigid. This difference explains the low glass transition temperatures Tg and large end‐to‐end distances measured for polyphosphazenes. A statistical model containing four rotational isomers (ie., trans, gauche, cis, and negative gauche) is developed and used to calculate unperturbed dimensions and dipole moments of PDCP. The results, obtained at 25°C with n = 400 skeletal bonds (200 repeating units), were Cn = 〈r2〉0/nl2 = 13.5; CT = 103d(ln〈r2〉0)/dT = −3.0 K−1; Dn = 〈μ2〉/nμ = 0.35; DT = 103d(ln〈μ2〉)/dT = −3.4 K−1. All the calculated magnitudes are extremely sensitive to the energy Eσ that controls the statistical weights of the conformations tg, tc, tg−, gt, ct, and g−t relative to tt for the bond pair PNP. A qualitative explanation for this sensitivity is discussed.
Double‐modulation and conventional ESR spectra of spin‐labeled crosslinked polystyrene
Authors: Andreis M. , Rakvin B. , Veksli Z. 
Published: April 2003

AbstractThe recently introduced method of detecting homogeneous linewidths from inhomogeneously broadened ESR spectra using the double‐modulation technique has been applied in parallel with the conventional method to study molecular motion in crosslinked polystyrene. The rotational correlation time in the slow‐motion region determined from the homogeneously broadened line varied from 1.68 × 10−5 to 8.0 × 10−6 s between 150 and 340 K. Double‐modulation spectra appear to be very sensitive to local motion at low solvent concentration. The influence of crosslink density and solvent concentration on both local and overall motion is analyzed.
Crystallization studies of poly(ε‐caprolactone).I. Morphology and kinetics
Authors: Phillips Paul J. , Rensch Gregory J. , Taylor Kevin D. 
Published: April 2003

AbstractThe crystallization behavior of three molecular weight samples of poly(ε‐caprolactone) has been studied as a function of temperature. Crystallization begins in the form of axialities and changes to spherulite growth as time progresses, presumably owing to the molecular weight distribution. Determinations of equilibrium melting point and analyses of growth kinetics are complicated by a major lamellar thickening process occurring at the crystallization temperature. Secondary nucleation analyses of spherulitic growth rates, carried out assuming a similar growth face to that of polyethylene, result in values of σσe. Use of the Thomas–Stavely relation to calculate a value of σ results in values of fold‐surface free energy, σe, similar to that of polyethylene.
Dynamic mechanical behavior of poly(vinyl‐methyl ether)‐poly(styrene) blends
Authors: Cavaille J. Y. , Perez J. , Jourdan C. , Johari G. P. 
Published: April 2003

AbstractThe dynamic mechanical behavior of 10 and 20% poly(vinyl methyl ether)‐polystyrene blends has been studied in the frequency range 10−5 Hz to 5 Hz and temperature range 100–450 K. Isochronal plots of modulus G′ and loss factor, tan ϕ, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process at intermediate temperatures but below Tg may be inferred from the breadth of the G″ frequency curves in the transition zone of both blends. This process, at 280 < T < 300 K, is independent of PVME concentration and seems to be associated with the local modes of motions of PS chains. The rheological behavior of the blends shows them to be compatible up to 20% PVME. Their G′ and G″ data cannot be shifted along a frequency axis to produce a satisfactory master curve. The departure from thermorheological simplicity is much more clearly observed in the tan ϕ than in the modulus‐frequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near Tg. A molecular model of the growth of microshear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior.
Dielectric relaxation and aging effect in interpenetrating network polymers of poly(urethane)‐poly(methyl methacrylate)
Authors: Mai C. , Johari G. P. 
Published: April 2003

AbstractThe permittivity and loss of poly(methyl methacrylate) (PMMA) network crosslinked with trimethylol‐1,1,1 propane and its interpenetrating network polymers with 10, 34, and 50% (by weight) poly(urethane) have been measured from 100 to 400 K over a frequency range of 12 to 1 × 105 Hz. Two relaxation processes, γ and β, are observed in the PMMA network, and a third process, αpu, in the 10% poly(urethane) IPN. At higher concentrations of poly(urethane), the γ process is removed from the temperature‐frequency range of our study. Crosslinking in pure PMMA slows the segmental motions involved in the β process and raises its activation energy. Physical aging of the 10 wt% poly(urethane)‐PMMA causes its γ process to become indiscernible and the αpu process to become better resolved. A discussion of these results in terms of local regions of segmental motion is provided.
Submillimeter infrared absorption and chain conformations of poly(vinylidene fluoride) and copolymers. I. Crystalline and amorphous contributions
Authors: Latour M. , Moreira R. L. 
Published: April 2003

AbstractFar infrared spectra of poly(vinylidene fluoride) and several copolymers (with hexafluoropropylene, chlorotrifluoroethylene, and tetrafluoroethylene) have been obtained between 15 and 55 cm−1. After correction of the interference phenomenon affecting the measurements, the absorption coefficient and the imaginary part of the dielectric constant have been calculated. We show how these parameters are affected by the chain conformation and copolymer composition. The behavior of the crystalline and amorphous phases have been studied. The effects of mechanical and electrical stresses are considered.