bluuebunny/crossref_metadata_2025_split huggingface dataset:
Entanglement between dissimilar chains in compatible polymer blends: poly(methyl methacrylate) and poly(vinylidene fluoride)
Authors: Wu Souheng 
Published: April 2003

AbstractThe plateau modulus and zero‐shear melt viscosity of binary compatible blends of poly(methyl methacrylate) and poly(vinylidene fluoride) were measured by dynamic oscillation and shear creep, and used to analyze the entanglement between dissimilar chains and its effect on melt viscosity. It is found that dissimilar chains are less likely to entangle with each other than similar chains, resulting in a large reduction of zero‐shear melt viscosity in this system.
Determination of the crystalline and noncrystalline molecular orientation in oriented polypropylene by infrared spectroscopy
Authors: Mirabella Francis M. 
Published: April 2003

AbstractThe application of orientation to enhance the properties of a wide range of macromolecular materials has stimulated an interest in the characterization of the effects of such orientation processes. In semicrystalline polymers, this requires the characterization of the orientation in both the crystalline and noncrystalline phases. An infrared dichroism method was developed to simultaneously measure the orientation in the crystalline and noncrystalline phases of polypropylene. The method was applied to a series of melt‐crystallized and gel‐crystallized polypropylene specimens drawn up to a maximum of about 50 ×. The Hermans orientation functions of each phase were determined. The crystalline orientation was found to increase rapidly and approach perfect orientation at relatively low draw ratio (i.e., > 10 × ). However, the noncrystalline orientation was found to increase much more slowly up to about 50 × draw ratio. The Youngs modulus was found to increase nearly linearly up to about 50 × and to correlate with the increase in the noncrystalline‐orientation function and not with the crystalline‐orientation function.
A visualization study of polyethylene terephthalate flow using a pseudohyperbolic die geometry
Authors: Ihm Dae Woo , Cuculo John. A. 
Published: April 2003

AbstractFlow visualization studies were made during extrusion by using a hyperbolic die, streak photography, and flow birefringence techniques. Velocity was found to be a linear function of position along the die axis. This is equivalent to a constant elongational strain rate. Considering that the hyperbolic die maintains the stretching rate achieved in the upstream over an extended time period, this profile seems to be the optimum die design for maximum chain‐ordering potential. A unique analysis of the birefringence and velocity distribution data allowed determination of characteristic relaxation time for the PET melt of 5.5 × 10−3 at 285°C.
Ionomeric blends. V. FTIR studies of ionic interactions in polyurethane‐styrene blends
Authors: Tannenbaum Rina , Rutkowska Maria , Eisenberg Adi 
Published: April 2003

AbstractFTIR spectra of blends of lightly sulfonated polystyrene (PS‐SSA) with polyurethanes (PU) containing a tertiary nitrogen in the chain extender were recorded. These blends exhibit a two‐phase behavior, but the individual components are not phase separated. Earlier dynamic mechanical studies suggested the occurrence of proton transfer from the sulfonic acid to the tertiary nitrogen, which enhanced the miscibility via ionic interactions and resulted in the formation of a miscible blend between the PS‐SSA and the hard segment of the PU, the soft segment being excluded. FTIR studies of these blends now confirm the proton transfer mechanism. A new absorption band at 3428 cm−1 corresponds to a stretching vibration of an N+−H bond. The 1012 cm−1 band of the SO3H group, which strongly depends on the degree of protonation, shifts to lower frequency. The symmetric stretching vibration of the SO group, which occurred at 1043 cm−1, shifts to lower frequency as well, suggesting a lower polarization of the SO dipole due to the removal of H+.
Polystyrene in cyclopentane: Dilute solution properties from the upper critical to the lower critical solution temperature
Authors: Berry Guy C. , Casassa Edward F. , Liu Pi‐Yao 
Published: April 2003

AbstractDilute solutions of polystyrene in cyclopentane are studied with four narrow‐distribution polymer fractions ranging in molecular weight from 1.6 × 105 to 1.8 × 106. Light scattering (total intensity) and viscosity measurements cover a temperature range spanning both “theta” temperatures: the limiting upper critical solution temperature (19.6°C) and the limiting lower critical temperature (154.5°C). Within experimental uncertainty, chain dimensions are the same at the two theta temperatures. Correlations among second virial coefficients, mean‐square molecular radii of gyration, and intrinsic viscosities, are analyzed. Temperature and molecular‐weight dependences are correlated satisfactorily in terms of the excluded‐volume parameter z that is central to the “two‐parameter” theories of dilute solution behavior. The data can also be correlated in the framework of the newer renormalization theories.
Laser light scattering study of polyacrylamide gels
Authors: Sellen D. B. 
Published: April 2003

AbstractLaser light scattering experiments with polyacrylamide gels containing diffusing bovine plasma albumin are described. Complete heterodyne beating has not been assumed, and an account is given of a novel method for finding the degree of spectral broadening by scanning angles of scatter while measuring the temporal autocorrelation function. Results obtained by this method for polyacrylamide gels and un‐cross‐linked solutions in the absence of diffusing protein, are compared with those of other authors. In the presence of the protein there is a complex interaction between the diffusion coefficient of the protein and the coefficient associated with the diffusing fluctuations in segment density of polyacrylamide. The diffusing protein dominates at low gel concentrations, and the gel density fluctuations dominates at high gel concentrations. It is proposed that the protein preferentially occupies the less dense regions of the gel, so that at low gel concentrations, where it diffuses faster than the gel fluctuations, it tends to cancel them out, whereas at high gel concentrations where the protein is highly impeded by the gel structure, it tends to be carried along by the gel density fluctuations.
Increase in crystallinity in poly(vinylidene fluoride) by electron beam radiation
Authors: Pae K. D. , Bhateja S. K. , Gilbert J. R. 
Published: April 2003

AbstractWe examine the influence of high‐energy radiation and subsequent aging and orientation on the degree of crystallinity of poly(vinylidene fluoride) (PVDF) films. In particular, PVDF films were exposed to electron beam radiation (doses up to 50 Mrad) and aged at room temperature for varying lengths of time followed by uniaxial orientation. The degree of crystallinity of these films was found to increase significantly with increasing radiation dose. In addition, a further substantial increase in the degree of crystallinity was observed upon subsequent aging of irradiated films at room temperature. Upon orientation, in addition to a further rise in the degree of crystallinity, the crystallites were observed to undergo the α form → β form transformation, the latter phase being the polar phase effective for piezo‐electric/pyroelectric activity.
Configurational effects on polystyrene rejection from microporous membranes
Authors: Adamski Robert P. , Anderson John L. 
Published: April 2003

AbstractDilute solutions of polystyrene in chloroform were filtered through track‐etched mica membranes. The pores of each membrane were smaller than the mean unperturbed dimension of the polymer molecules. Three configurations of polystyrene were used: linear, comb‐branched, and star‐branched. The data for the linear polystyrenes show that the reflection coefficient σ decreases with solvent flow rate per pore q in a manner independent of molecular weight. At low flow rates the rejection is quantitatively described by 1 − σ ∼ q1.69. Comparisons among the three configurations show that as the extent of branching increases, σ increases at given solvent flow rate. It is concluded that filtration studies with well‐defined porous membranes can provide a relative measure of deformability among various configurations of polymeric species.
High‐energy ion implantation of polymers: Poly(ethylene terephthalate)
Authors: Balik C. M. , Said M. A. , Carlson J. D. 
Published: April 2003

AbstractThe effect of high‐energy ion implantation of oxygen into a thin film of poly(ethylene terephthalate) (PET) was studied by Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC). Mylar samples 13 μm thick were implanted with 6‐MeV oxygen ions at fluences ranging from 5 × 1012 to 2 × 1014 ions/cm2. The DSC data showed a substantial loss of crystallinity, even at the lowest fluence, which extended deeper into the polymer film than the predicted range for oxygen deceleration in PET. Solubility measurements indicated the presence of cross‐linking, especially at the highest fluence, but bands due to cross‐linking could not be detected in the infrared. The trans/gauche ratio for the glycol group conformation was measured by a pair of conformationally sensitive infrared bands. Surprisingly, the conformation of the glycol segments did not change appreciably with increasing fluence, although crystallinity decreased and degree of cross‐linking increased. The implications these results have on possible mechanisms of chemical and physical alterations of the polymer structure by ion implantation are discussed.
Solution properties of ultrahigh molecular weight polymers. VII. Conformational characteristics of poly(butyl methacrylate)
Authors: Simionescu Bogdan C. , Ioan Silvia , Simionescu Cristofor I. 
Published: April 2003

AbstractThe paper is concerned with light scattering studies on solutions of ultrahigh molecular weight poly(butyl methacrylate). The dependence of the radius of gyration and of the second virial coefficient on the weight‐average molecular weight of the polymers was established in methyl ethyl ketone, dimethylformamide, and CCl4. Short‐range and long‐range interactions were discussed in terms of the steric factor σ, of the interaction parameter B, and of the interpenetration function ψ(z).
Dynamic mechanical properties of homogeneous copolymers of ethylene and 1‐alkenes
Authors: Clas S.‐D. , McFaddin D. C. , Russell K. E. 
Published: April 2003

AbstractThe dynamic mechanical properties of homogeneous copolymers of ethylene with 1‐butene, 1‐octene, and 1‐octadecene prepared by means of a vanadium‐based catalyst system have been determined. The 1‐butene copolymers show α′ and α transitions in the 20–60°C temperature range, whereas the 1‐octene and 1‐octadecene copolymers show single α transitions. The intensity of the β transition increases with comonomer content in 1‐butene and 1‐octene copolymers and also with the amount of interfacial material present. In ethylene‐1‐octadecene copolymers, this intensity is comparatively low, even though there is about 20% interfacial material present. The implications of these results with regard to the nature of interfacial material are discussed.
Polymerization beyond the gel point. I. The molecular weight of sol as a function of the extent of reaction
Authors: Argyropoulos Dimitris S. , Berry Richard M. , Bolker Henry I. 
Published: April 2003

AbstractTheoretical expressions for describing the weight‐average molecular weights of the soluble fractions from polymerizations obtained beyond the gel point were tested experimentally. The theory of branching processes and a recursive approach essentially based on the method of Macosko and Miller were found to be virtually equivalent. The soluble fractions produced from the stoichiometric polymerization of 1,3,5‐benzenetriacetic acid (BTA) with decamethylene glycol (DMG) gave molecular weights and distributions in excellent qualitative agreement with the theory. The results are interpreted in terms of intramolecular cyclization, diffusion, and the presence of microgel particles.
Effect of molecular weight distribution and structure of LDPE on its deformation behavior in a high‐temperature region
Authors: Enikolopian N. S. , Akopian E. L. , Styrikovitch N. M. , Ketchekian A. S. , Nikolskii V. C. 
Published: April 2003

AbstractThe effect of molecular weight distribution (MWD) (the low‐molecular weight “tail” in particular) on the deformation behavior of low‐density polyethylene (LDPE) during uniaxial stretching was studied over the temperature range from 293 K to the melting point. Four types of film samples were used: untreated polyethylene (PE), the same PE subjected either to solvent extraction or to thermal degradation, and PE with extracted fractions replaced by a low‐molecular weight paraffin analog. Graphs of elongation at break εb versus temperature always exhibited a minimum that occurred in the neighborhood of 370 K. The shape of the curve, the amount that εb decreases with increasing temperature, as well as the absolute values of εb strongly depend on the type of sample. The εb for a degraded PE is markedly lower than that for an untreated one. On the other hand, the extraction of low‐molecular weight fractions leads to a higher εb, especially in the premelting region. The low‐molecular weight “tail” has a different effect from that of added paraffin. This appears to be due to the plasticizing effect of the latter. The effect of temperature is much more pronounced on the work of deformation (Ad) than on εb. The results obtained were interpreted on the assumption that structural (phase) inhomogeneity of LDPE is the key factor determining the deformation behavior of polymer over the studied temperature range.
Structure‐permeability relationships in silicone polymers
Authors: Stern S. A. , Shah V. M. , Hardy B. J. 
Published: April 2003

AbstractPermeability coefficients P for He, O2, N2, CO2 CH4, C2H4, C2H6, and C3H8 in 12 different silicone polymer membranes were determined at 35.0°C and pressures up to 9 atm. Values of P for CO2, CH4, and C3H8 were also determined at 10.0 and 55.0°C. In addition, mean diffusion coefficients D and solubility coefficients S were obtained for CO2, CH4, and C3H8 in 6 silicone polymers at 10.0, 35.0, and 55.0°C. Substitution of increasingly bulkier functional groups in the side and backbone chains of silicone polymers results in a significant decrease in P for a given penetrant gas. This is due mainly to a decrease in D, whereas S decreases to a much lesser extent. Backbone substitutions appear to have a somewhat lesser effect in depressing P than equivalent side‐chain substitutions. The selectivity of a silicone membrane for a gas A relative to a gas B, i.e., the permeability ratio P(A)/P(B), may increase or decrease as a result of such substitutions, but only if the substituted groups are sufficiently bulky. The selectivity of the more highly permeable silicone membranes is controlled by the ratio S(A)/S(B), whereas the selectivity of the less permeable membranes depends on both the ratios D(A)/D(B) and S(A)/S(B). The permeability as well as the selectivity of one silicone membrane toward CO2 were significantly enhanced by the substitution of a fluorine‐containing side group that increased the solubility of CO2 in that polymer.
Structural changes in poly(L‐alanine) induced by heat treatment
Authors: Tsukada Masuhiro , Nagura Masanobu , Ishikawa Hiroshi 
Published: April 2003

AbstractStructural changes in poly(L‐alanine)(PLA), a model compound related to tussah silk fibroin, induced by heat treatment have been studied by differential thermal analysis, x‐ray diffraction, and infrared spectroscopy. PLA heated below 300°C shows x‐ray patterns very similar to those of the α‐helix crystalline phase, in addition to the diffraction patterns due to the β structure. Samples heated at 368°C exhibit predominantly the diffraction patterns due to the β crystalline phase. From infrared spectra, PLA samples heated below 280°C are found to be composed of all three molecular conformations: β sheet, random coil, and α helix. The intensity of the infrared absorption at 650 cm−1 (amide V) assigned to the random coil conformation is decreased by heat treatment above 325°C. The content of the β‐sheet structure remains almost constant when the specimen is heated below 325°C, and increases abruptly on heating to around 335°C, while the random coil content is decreased abruptly by heat treatment above 335°C. The α‐helix content does not change, regardless of heat treatment. It is suggested therefore that the random coil conformation of PLA transforms directly into the β sheet on heat treatment above 335°C.
The effect of electron irradiation on the structure and mechanical properties of highly drawn polyethylene fibers
Authors: Klein P. G. , Woods D. W. , Ward I. M. 
Published: April 2003

AbstractTwo very different high‐modulus polyethylene fiber samples, a low molecular weight melt‐spun and drawn fiber, and a high molecular weight gel‐spun and drawn fiber, have been subjected to electron beam irradiation to various doses in vacuum and in the presence of acetylene. The gel content after irradiation in acetylene was found to be much greater than for an equivalent dose in vacuum. The gel content–dose relationship could not be described by either Charlesby–Pinner analysis or the Inokuti equation. This is attributed to the polydispersity and the complications introduced by the unique morphologies of highly drawn fibers. Following previous studies, the tensile creep behavior was interpreted in terms of a model comprising two thermally activated processes in parallel, a low stress process relating to the amorphous network, and a high stress process relating to the continuous crystal fraction. Analysis of the creep behavior of the melt‐spun, low molecular weight fiber irradiated in vacuum revealed crosslinking in the amorphous regions and chain scission in the crystal. Chain scission was found to be much reduced when irradiating in acetylene, for which a mechanism has been proposed. The creep rates and activation volumes of the high molecular weight, gel‐spun fiber were found to be significantly lower, probably due to the unique morphology. In this case the dominant effect of irradiation on the mechanical properties can be attributed to chain scission rather than crosslinking.
Heat capacity measurements in carboxylic polyelectrolyte solutions
Authors: Yamashita F. , Kwak Jan C. T. 
Published: April 2003

AbstractApparent molal heat capacities as a function of the degree of neutralization have been determined for dilute aqueous solutions of poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), copoly(maleic acid‐ethylene) (MAEt), and copoly(maleic acid‐styrene) (MASt) using direct flow microcalorimetry. Apparent molal volumes were measured as well. Both molal heat capacity and molal volume decrease with increasing ionization of the polymer. The effect of the hydrophobic interactions of the methyl group or phenyl group was obtained from the difference in the molal quantities of PMA and PAA, or MASt and MAEt. No evidence of hydrophobic effects, as determined from the heat capacity, was found for the conformational transition of PMA, but the hydration of the phenyl groups in MASt was found to be changed significantly at a degree of neutralization of 0.4.
A comparison of spin relaxation and local motion between symmetrically and asymmetrically ring‐substituted bisphenol units in dissolved polycarbonates
Authors: Ratto J. A. , Inglefield Paul T. , Rutowski R. A. , Li K.‐L. , Jones Alan Anthony , Roy Ajoy K. 
Published: April 2003

AbstractCarbon‐13 and proton spin‐lattice relaxation times were measured at two field strengths on solutions 10% by weight of two polycarbonates in C2D2Cl4 from −20 to +120°C. The first polycarbonate is an asymmetrically substituted form with one chlorine on one of the two phenylene aromatic rings of the bisphenol unit, whereas the second polycarbonate is symmetrically substituted with two chlorines on each of the two rings. The nuclear spin relaxation data are interpreted in terms of several local motions likely in these polymers. Segmental motion was described by the Hall–Helfand correlation function. Segmental motion in the monosubstituted polycarbonate is somewhat slower than in unsubstituted polycarbonate, whereas segmental motion in the tetrasubstituted polycarbonate is considerably slower. Phenylene ring rotation is observed in unsubstituted polycarbonate and in the monosubstituted polycarbonate above 40°C. Below 40°C in the monosubstituted species, and at all temperatures in the tetrasubstituted species, ring rotation is replaced by ring libration as the predominant motion contributing to spin lattice relaxation. In addition, the rotational motion of the two types of rings in the asymmetric monosubstituted form are very similar although not identical. The substituted ring is slightly less mobile than the rings of unsubstituted polycarbonate. This indicates a strong coupling of ring motion, although the coupling leads to less than synchronous motion. Methyl group rotation is present in both polymers and is little affected by the various structural modifications.
Solute–solvent interactions of oligo(m‐benzamide)s in N,N‐dimethylacetamide
Authors: Kojima Takakazu , Hamada Masahiko , Miyahara Masa‐Aki , Hosaka Yoshinobu 
Published: April 2003

AbstractStudies on solute–solvent interactions of oligo(m‐benzamide)s in N,N‐dimethylacetamide (DMA) have been carried out. The enthalpies of solution have been measured for oligo(m‐benzamide)s and oligo(m‐phenylene)s in DMA and benzene. Contributions of enthalpies of cavitation and dispersion interaction to the enthalpy of transfer from benzene to DMA, ΔHtr (Ben → DMA), have been examined for oligo(m‐phenylene)s. A considerable contribution of excess enthalpy, ΔHE (Ben → DMA), to ΔHtr (Ben → DMA) has been found, which increases with the number of benzene rings of the solute. By assuming that ΔHE (Ben → DMA) of diphenyl (DP) is equal to that of benzanilide (BA) in DMA, the amide hydrogen bond enthalpy of BA in DMA, ΔH estimated by “the pure base method” corrected for the enthalpies of cavitation and dispersion interaction. The ΔH value has been given by the following expression including the unknown solubility parameter of BA, δBA:

The evaluation of δBA has resulted in the conclusion that −ΔH is smaller than 10.9 kJ mol−1. Moreover, ΔHtr (TMU → DMA) for oligo(m‐benzamide)s has been examined. It has been shown that the amide hydrogen bonding ability of DMA is lower than that of TMU. The linearity of the plot of ΔHtr (TMU → DMA) against the number of amide bonds in the molecule has been explained by the increase in hydrogen bond enthalpies with the number of amide bonds in the molecule.
Crystallization of bisphenol a polycarbonate induced by supercritical carbon dioxide
Authors: Beckman Eric , Porter Roger S. 
Published: April 2003

AbstractSupercritical carbon dioxide readily induces crystallization in bisphenol A polycarbonate. Crystallization begins within one h of exposure to the CO2 at temperatures and pressures as low as 75°C and 100 atm. The degree of crystallinity increases sharply as the CO2 pressure is raised from 100 to 300 atm but levels off thereafter. This behavior is likely due to a minimum in the Tg of the polycarbonate/CO2 mixture owing to the opposite effects of the pressure on the Tg of the polymer and on the equilibrium weight fraction of CO2 absorbed. Percent crystallinities of over 20%, comparable to that achieved using acetone or other organic liquids, have been obtained after 2 h exposure to supercritical CO2. Since polycarbonate degasses quickly and quantitatively at ambient temperature and pressure, the high Tg of bisphenol A polycarbonate can be regained in the crystallized material without further vacuum treatment.