bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of molecular weight on the refractive index increments of polystyrene, poly(ethylene glycol), poly(propylene glycol), and poly(dichlorophenylene oxide) in solution
Authors: Binboga Nevin , Kisakürek Duygu , Baysal Bahattin M. 
Published: April 2003

AbstractThe variation of refractive index increments with molecular weight has been studied using solutions of polystyrene (2.2 × 103 < Mw < 1.8 × 106), poly(ethylene glycol) (1.0 × 103 < Mw < 2.0 × 104), and poly(dichlorophenylene oxide) (3.3 × 103 < Mw < 4.8 × 105) in toluene and poly(propylene glycol) (1.2 × 103 < Mw < 4.0 × 103) in benzene. The refractive index increments of polyglycols containing aliphatic ether moieties are negative in these solvents. However, poly(dichlorophenylene oxide) polymers, which contain aromatic ether moieties, give positive values. Linear and branched halogenated poly(phenylene oxide)s show an asymptotic approach of the refractive index increment to the same limiting value, but the approach is more rapid for the branched polymer.
Lattice imaging of radiation‐sensitive polymer crystals
Authors: Tsuji Masaki , Roy Saroj K. , St. John Manley R. 
Published: April 2003

AbstractThe total end‐point dose (i.e., the electron irradiation dose necessary for complete destruction of the crystal lattice) was measured at 120 kV and room temperature for poly(ethylene oxide), polyethylene, isotactic polystyrene (i‐PS), poly(p‐xylylene), ramie and bacterial cellulose, and lobster chitin. On the basis of the results obtained, the possibility of lattice imaging of polymer crystals is discussed. As reported in an earlier preliminary paper, 1.1‐ and 0.55‐nm lattice fringes were resolved in i‐PS single crystals by using a conventional transmission electron microscope equipped with a device for low‐dose imaging. In this paper, the detailed procedure for lattice imaging of i‐PS crystals is described and various features of the lattice images are discussed.
The bulk viscoelastic properties of poly(styrene‐co‐sodium styrene‐p‐carboxylate)
Authors: Brockman N. L. , Eisenberg A. 
Published: April 2003

AbstractThe effect of up to 7.82 mol % ionic groups on the stress relaxation and dynamic mechanical (torsion pendulum) properties of poly(styrene‐co‐sodium styrene‐p‐carboxylate) was studied. The results obtained were compared with those reported elsewhere for polymers containing the same ionic groups at a different position on the polystyrene backbone (styrene‐sodium methacrylate copolymers) and with polymers containing different ionic groups at the same position (styrene‐sodium styrene‐p‐sulfonate copolymers). The results of these comparisons showed that positioning of ionic groups affects the size of ionic aggregates formed, while their type dictates the strength of the forces within the aggegrates.
Predicting glass transition temperatures of linear polymers, random copolymers, and cured reactive oligomers from chemical structure
Authors: Wiff D. R. , Altieri M. S. , Goldfarb I. J. 
Published: April 2003

AbstractA reliable semiempirical method for predicting glass transition tempertures of linear polymers, random copolymers, and selected crosslinked networks from knowledge of only their chemical structure is presented. For cases in which new moieties not in the database are encountered, a scaling technique of similar moiety contributions has proven successful. The basic database was composed of 178 linear homopolymers ranging from aliphatic to aromatic heterocyclic polymers and 12 random copolymers. The crosslinked networks investigated in this study involved only diacetylene end‐group reactions.
Orientation behavior of high‐modulus polyoxymethylene produced by microwave heating drawing
Authors: Takeuchi Y. , Yamamoto F. , Nakagawa K. , Yamakawa S. 
Published: April 2003

AbstractThe orientation behavior of high‐modulus polyoxymethylene tapes produced by tensile drawing with microwave heating has been investigated over the draw ratio range 10–29. Young's modulus E increases monotonically with draw ratio λ and reaches 55 GPa. The volume fraction of taut tie molecules (TTMs) in the amorphous phase has been estimated by using a Takayanagi model for oriented tapes. The increase in E at draw ratios of less than 10 is mainly due to the increase in crystalline orientation (crystalline orientation function, 0.00 → 0.99). The increase in E at draw ratios of more than 10 is due to the increase both in crystallinity (volume‐fraction crystallinity, 0.84 → 0.95) and in TTM (TTM fraction, 0.14 → 0.40). The maximum Young's modulus obtainable by this method of drawing is estimated to be ca. 72 GPa from the relation between 1/E and 1/λ2.
Picosecond relaxations in hydrated polyamide‐6 observed by millimeter‐wave spectroscopy
Authors: Nie C. S. , Kremer F. , Poglitsch A. , Bechtold G. , Genzel L. 
Published: April 2003

AbstractAbsorption measurements at millimeter‐wave frequencies (50–151 GHz) are reported for dried and hydrated polyamide‐6. The measurements were extended over the temperature range from liquid helium to room temperature using the oversized‐cavity technique. For dried polyamide‐6 (water content ≤ 0.5% w/w), a nearly linear increase with frequency and an exponential increase with temperature of the absorption coefficient is found between 50 and 300 K. This frequency and temperature dependence is described by relaxation processes in asymmetric double‐well potentials. The observed relaxation times are on a picosecond time scale, thus suggesting an assignment to the NH…OC hydrogen bonds and the adjacent peptide unit (OCNH). Hydration results in an increase of the absorption over the whole temperature and frequency range. This is attributed to the fact that the water of hydration is adsorbed in the neighborhood of the hydrogen bonds and changes their dynamical properties. This interpretation is supported by IR‐spectroscopic measurements of the shift of amide I and amide II after hydration.
Rheological properties of rodlike polymers in solution. 2. Linear and nonlinear transient behavior
Authors: Venkatraman S. , Berry G. C. , Einaga Y. 
Published: April 2003

AbstractRheological and rheo‐optical studies are reported for isotropic solutions of the mesogenic rodlike polymer poly(1,4‐phenylene‐2,6‐benzobisthiazole) (PBT). Several PBT samples were used with average contour lengths from 95 to 135 nm. Concentrations were varied over a range just below the concentration Cc for the formation of an ordered (nematic) state. The predictions of a single‐integral constitutive equation of the BKZ type utilizing experimental estimates of the distribution of discrete relaxation times is compared with experimental data on the steady‐state viscosity ηκ, the recoverable compliance function Rκ, and the steady‐state flow birefringence as functions of the shear rate κ, with satisfactory results. The relaxation of the shear stress and the flow birefringence on cessation of steady‐state flow at shear rate κ are also compared with the single‐integral constitutive equation, and it is found that in the nonlinear response range the data can be superposed over a wide range in κ. The overall behavior is qualitatively similar to that for flexible chains, which can also be fitted by the single‐integral constitutive equations over similar ranges of η0R0κ, with η0 and R0 the limiting values of ηk and Rκ for small κ. Of course, the dependence of η0 and R0 on concentration and molecular weight differs markedly for rodlike and flexible‐chain polymers.
Crystallographic changes in cryogenically pulverized polymers
Authors: Lovinger Andrew J. , Belfiore Laurence A. , Bowmer Trevor N. 
Published: April 2003

AbstractCryogenic pulverization of polymers in liquid nitrogen results in a variety of physical and chemical changes, of which crystallographic transformations are among the earliest. These have been investigated in detail for isotactic polystyrene using x‐ray and calorimetric techniques. Amorphization was found to occur rapidly, but with concomitant decreases in crystallite sizes of only a limited extent. These changes can to a large degree be reversed upon annealing at high temperature. Similar behavior is seen also in other polymers possessing stronger intermolecular cohesion, such as polyesters and polyamides. In polymers susceptible to mechanically induced phase transformations, cryogenic pulverization causes polymorphic changes en route to amorphization: these include formation of the monoclinic phase in polyethylene and of the β phase in poly(vinylidene fluoride). Based on these results, a model is proposed for the mechanism of pulverization that incorporates both thermal and mechanical effects; this model suggests a two‐phase structure of the pulverized, particles, consisting of an amorphous skin that surrounds a damaged crystalline core.
Small‐angle polarized light scattering by spherulites
Authors: Champion J. V. , Killey A. , Meeten G. H. 
Published: April 2003

AbstractThe light‐scattering matrix for a three‐dimensional spherulite is derived within the Ray‐leigh‐Gans‐Debye light‐scattering approximation. New expressions for the polarized, small‐angle light‐scattering intensities IVV and IVH are derived from the scattering matrix. These expressions are compared with the IVV and IVH expressions derived for a spherulite by Stein and Rhodes. For the case of a weakly anisotropic spherulite having an average refractive index mismatch with its surroundings, the two sets of expressions predict different IVV and IVH intensities. In particular, our expressions show that the IVVand IVH patterns usually attributed to the spherulitic anisotropy and crystallinity are also predicted for an isotropic sphere. This is in accord with recent experiments.
Study of poly[bis(p‐toluene sulfonate) diacetylene] films prepared by a modification of the Langmuir–Blodgett technique
Authors: McCaffrey Robert R. , Prasad Paras N. , Fornalik Mark , Baier Robert 
Published: April 2003

AbstractCoherent this films of poly[bis(p‐toluene sulfonate) diacetylene] were successfully formed by modified Langmuir–Blodgett techniques using two methods: (i) Photopolymerization of the monomer film at the gas/liquid interface and then transfer to a solid substrate, and (ii) transfer of the monomer film to the solid substrate and subsequent photopolymerization on the substrate itself. The films thus obtained were characterized by traditional force–area isotherms while on pure water subphases. Segments were transferred at either 1 or 10 dyn/cm surface pressure, in different stages of photopolymerization, to glass or germanium substrates. The films on the substrate were characterized by the methods of multiple attenuated‐internal‐reflection infrared spectroscopy, ellipsometry, contact‐potential measurement, and laser Raman spectroscopy. Our results show that the films are multimolecular and about 100 Å thick. Of special interest were the observation of significant anisotropy of oriented dipoles and the ability to obtain excellent spectral data for these very thin oriented films. Raman spectroscopic features are similar to those observed for the bulk polymer, even in the low‐frequency region. Polarized Raman spectroscopy confirmed the presence of local anisotropy in these films.
Unit‐cell dilation in model ethylene copolymers
Authors: Marks B. S. , Carr S. H. 
Published: April 2003

AbstractSingle crystals of model ethylene copolymers have been grown in dilute solution. The effects of narrow molecular weith distribution (MWD) and a perfectly random distribution of ethyl branches (ca. 17 per 1000 main‐chain carbon atoms) on the unit cell of this ethylene copolymer analog were examined. X‐ray diffraction on dried powder samples revealed expansions of up to 1.5% in a and 0.5% in b. a increased as a mild function of molecular weight; the dependence of b on MW was not as clearly defined. Electron diffraction studies on isolated suspensiongrown single crystals yielded lattice parameters much more strongly expanded. The large expansion in the basal plane of the unit cell is hypothesized to be accompanied by a fore‐shortening of the projected c‐axis distance. This is accomplished by and orthorhombic‐to‐hexagonal polymorphic transformation in which the chains are hypothesized to adopt a disordered helical conformation. The driving force for this transformation is electron irradiation damage of the single‐crystal specimens. The rapidity of the transformation is believed to be due to the model polyethylene crystals being in a higher‐energy, defect‐containing condition prior to irradiation.
Relationship between the functional group concentrations and the infrared reflection–absorbance of polyacrylonitrile films
Authors: Sergides C. A. , Chughtai A. R. , Smith D. M. , Schissel P. 
Published: April 2003

AbstractThe optical constants n and k of polyacrylonitrile (PAN) were determined in the infrared region 3100–700 cm−1 by using theoretical calculations and experimental reflectance spectra. Tests of the validity of the results obtained showed excellent agreement between the measured and the predicted k values. One k value was determined experimentally (k = 0.6155 at V = 2285 cm−1) and showed excellent agreement with that calculated theoretically (k = 0.6153). The p‐polarized light was found to be more sensitive than the s‐polarized light to the absorbance of PAN films at 77° incidence angle. This sensitivity increased rapidly with p‐polarized light for film less than 0.5 μm thick. From the optical constants obtained for p‐polarized light at 77° angle of incidence, the sensitivity of the infrared reflection‐absorbance (IR‐RA) measurements to changes in the functional group concentrations in PAN films was determined for film thicknesses in the region 0.01‐10.0 μm. The IR‐RA measurements of the CN group and the skeletal mode were for a PAN film thickness of about 0.1 μm.
Simplified analysis of gas/polymer selective solubility behavior
Authors: Koros William J. 
Published: April 2003

AbstractInteractions of penetrants with gas separation membrane materials can have both desirable and undesirable consequences. Improved permselectivity resulting from specific polymer/penetrant interactions must be balanced against potentially undesirable plasticization effects resulting from such interactions. Consideration is given to the utility of gas solubility measurements in low‐molecular‐weight solvents as an aid to understanding solubility data for polymer/gas systems. The solubility coefficients of gases in low‐molecular‐weight liquids and in polymeric media of similar chemical structure tend to be quite different in magnitude. “Equation‐of‐state” and combinatorial entropy differences for the free energy of mixing of gases with low‐molecular‐weight solvents and high‐molecular‐weight polymers presumably cause this discrepancy. The above complications are minimized and useful trends identified by considering the so‐called solubility selectivity comprised of ratios of absolute gas solubilities in both low‐and high‐molecular‐weight media of similar chemical natures. For example, both acetone and methyl acetate are highly sorptive of CO2 and display a high degree of solubility selectivity for CO2 relative to CH4. These two solvents have mass densities of carbonyl groups that are similar to that in cellulose acetate and poly(methyl methacrylate). Both of these polymers are also highly sorptive of CO2 and have solubility selectivities for CO2 relative to CH4 that are similar to that of acetone and methyl acetate. Anomalous behavior is encountered in the case of Kapton poly(ether diimide), which contains a high density of carbonyl groups (four per repeat unit). On the basis of the behavior of the other carbonyl‐rich polymers, it was expected that Kapton would show high solubility selectivity for CO2 relative to CH4, but this was not observed. A hypothetical explanation for the Kapton behavior is presented. In addition, possible advantages of the Kapton‐type behavior are discussed in the context of the reported good plasticization resistance of polyimides.
A new model for the molecular conformation in polyoxymethylene crystals
Authors: Saruyama Y. , Miyaji H. 
Published: April 2003

AbstractNonintegral indices are found for the extra meridional reflections in the x‐ray diffraction of drawn polyoxymethylene. The index of one of the extra reflections is estimated at 00l: l = 2.830 ± 0.003. A new model for the molecular conformation which accounts for the nonintegral indices is proposed. The new model is a helix with defects at constant intervals along the helix axis. The defect is an unwinding of the helix by 20° around the helix axis. This defect is believed to be characteristic of crystals of helical polymers. The interval between the defects is estimated as 18 monomers. The crystal structure with these defects is consistent with precise measurements of the layer line positions.
Configurational studies on amylose. II. Moments and distribution functions
Authors: Yamaguchi Saburo , Hayashi Hisao , Hamada Fumiyuki , Nakajima Akio 
Published: April 2003

AbstractStatistical mechanical averages of vectors and tensors characterizing the configuration of amylose chains have been calculated. These quantities are expressed in the reference frame affixed to the first glucose unit, the x axis being situated along the O(4)—O(1) virtual bond vector, and the Y axis in the plane of the virtual bond and the O(4)—C(4) bond. The persistence vector a as defined by the average of the end‐to‐end vector r converges slowly to the limiting persistence vector a∞ with increasing chain length. Configurational averages of the Cartesian tensors formed from the displacement vector ρ = r − a have been computed up to seventh rank according to the generator matrix method. The density distribution functions Wα (ρ) evaluated for xu = 40 by using the three‐dimensional Hermite polynomial expansion truncated at the term involving the tensor of seventh rank are approximately cylindrically symmetric about one of the principal axes of the second‐moment tensor <ρ×2. The density distribution function Wα(ρ) is slightly asymmetric even for xu = 80.
Statistical description of spherulite patterns
Authors: Piórkowska E. , Gałeski A. 
Published: April 2003

AbstractA statistical description of spherulitic morphology and its formation resulting from primary nucleation and radial propagation is presented. Two‐ and three‐dimensional cases are considered. The general formulas are valid for any time‐dependent mode of primary nucleation and can be modified for a time‐dependent propagation rate. Various distance distributions of boundaries and inner points of the final pattern and at intermediate stages of its formation as well as the degree of conversion and the distance correlation of primary nuclei are derived. Detailed derivations are carried out for three model modes of primary nucleation, athermal, thermal, and mixed. It is also shown that the degree of conversion from mixed‐mode nucleation does not follow the Avrami plot. The total surface of boundaries in bulk, total length of boundaries on a plane, and numbers of multiple boundary points are also calculated for all modes of primary nucleation. The relations are confirmed by computer simulation of primary nucleation and radial propagation of spherulites on a plane and in bulk.
Depolarization field effect on the ferroelectric behavior of polymers
Authors: Ikeda Susumu , Jimbo Masashi , Kobayashi Shin'Ichi , Wada Yasaku 
Published: April 2003

AbstractThe effect of the depolarization field in crystallites on the ferroelectric behavior of polymers is discussed on the assumption that the crystallite is a prolate ellipsoid with its major axis directed along the electric field. The theory relates the polarization P and the electric field E in the crystallite to the overall values P and E for the polymer. The determination of the P‐E hysteresis of a crystallite from the P‐E hysteresis is given with examples for poly(vinylidene fluoride) (PVDF) and vinylidene fluoride (VDF)–trifluoroethylene (TrFE) copolymer. The ratio R = J/(Ps − P), with J the switching current density and Ps the saturation polarization of polymer, is proved to be free from the depolarization field effect and the plot of logR against logarithmic time is shown to have merit for characterization of switching behavior. Examples of the curves are given for PVDF and VDF‐TrFE copolymers. The temporal change of local electric field in the unreversed domains in the crystallite in the course of polarization reversal is predicted by the theory and this change is proved to be a significant mechanism of switching acceleration.
Sorption and diffusion of a tribasic acid dye in nylon 6 membrane in the presence of NaCl
Authors: Kawana Y. , Komiyama J. , Petropoulos J. H. , Iijima T. 
Published: April 2003

AbstractMeasurements of sorption and diffusion of a tribasic acid dye in nylon 6 membranes in the presence of NaCl are reported and critically analyzed by the dual‐mode sorption and diffusion models consisting of either simple partition plus ion exchange, or simple partition plus “Langmuir” modes. It is shown that the former treatment, which is the physically more realistic one, also provides a generally better fit to the data.
Far‐infrared studies of microphase separation in sulfonated ionomers
Authors: Peiffer D. G. , Hager B. L. , Weiss R. A. , Agarwal P. K. , Lundberg R. D. 
Published: April 2003

AbstractFar‐infrared spectra of a series of un‐neutralized and neutralized lightly sulfonated polystyrenes with varying sulfonation levels have been investigated to seek spectroscopic evidence for microphase separation known to control the physical properties of these polymers. Broad, strong absorbance bands, not found in the spectrum of unmodified polystyrene, are observed in the spectra of the sulfonated analogs. The effects on the far‐infrared spectra both of sulfonation level and of the mass and charge of the neutralizing cation are discussed in terms of cation motion and the formation of ion‐rich domains.
Small‐angle scattering analysis of hard‐microdomain structure and microphase mixing in polyurethane elastomers
Authors: Leung Louis M. , Koberstein Jeffrey T. 
Published: April 2003

AbstractThe microdomain structure of a series of segmented polyurethane block copolymers is characterized by small‐angle x‐ray and neutron scattering analyses. The materials contain hard segments formed from 4,4′‐ diphenylmethane diisocyanate (MDI) and butanediol (BD), and range in hard‐segment content from 20 to 80% by weight. The results provide evidence for a transition from discrete to continuous hard‐microdomain morphology as the hard‐segment content is increased above ca. 50%. The measured concentration dependences of the interdomain spacing, specific interfacial area, diffuse microphase boundary thickness, and scattering invariants are used to examine the validity of present models for hard‐microdomain structure. The observed behavior corresponds well with the general predictions of a lamellar model wherein partially coiled hard‐segment sequence configurations are allowed. The thickness of the hard microdomains extracted from the model corresponds to approximately four hard‐segment repeat units. Scattering invariant calculations are used together with determinations of the soft‐microphase glass transition temperatures to examine possible models for microdomain mixing. These calculations suggest that both the hard and soft microphases are phase mixed.