bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation on the chain‐folding structure of an ethylene–propylene copolymer by selective degradation
Authors: Patel G. N. , Keller A. , Martuscelli E. 
Published: April 2003

AbstractA renewed explanatory study is reported on the fold structure and branch location in single crystals of an ethylene–propylene copolymer by means of the ozone degradation method. By analogy with concurrent studies on linear polyethylenes a distribution of fold lengths is inferred, this distribution being broader, more uniform, and spreading deeper into the crystal interior in the case of the copolymer than for the linear polyethylene. Perhaps the most salient points of the work is that in contrast to nitric acid the oxidation by ozone does not obscure then characteristic CH3 infrared absorption band enabling the branch content to be followed during degradation. The single exploratory experiment of the present work reveals that while there is a certain amount of preference for the branches to accumulate near the fold surface, a substantial portion of them can still be located in the crystal interior. The potential of the present method for a more systematic study is indicated.
Current reversal in the thermally stimulated current spectra of polyethylene
Authors: Hashimoto Toshimasa , Shiraki Masao , Sakai Tetsuya 
Published: April 2003

AbstractPolyethylene thermoelectrets were prepared under static electric fields ranging from 70 to 750 kV/cm at various polarization temperatures. Thermally stimulated current (TSC) spectra were observed for those samples in the high‐temperature region above room temperature. The TSC spectra of polyethylene were complex and were composed of two current peaks, of opposite polarity and dependent on the applied voltage and temperature. This result suggests that there are two trapping mechanisms which result in different charge injection modes. In addition, TSC spectra were obtained on polyethylenes of various morphologies to examine the relationship between the mechanical relaxations and the trapping mechanisms.
The solid‐state thermal polymerization of bis(p‐toluene sulphonate) of 2,4‐hexadiyne‐1,6‐diol. III. An ESR study
Authors: Stevens G. C. , Bloor D. 
Published: April 2003

AbstractElectron spin resonance (ESR) observations of the solid‐state thermal polymerization of bis(p‐toluene sulphonate) of 2,4‐hexadiyne‐1, 6‐diol at 60°C, 70°C, and 80°C are reported. The weak paramagnetism observed in polycrystalline samples is interpreted in terms of departures of the polymer chain from an equilibrium conformation. Decomposition occurs at 70°C and 80°C during the final phase of polymerization producing additional paramagnetic centers. Lineshape parameters measured during polymerization show changes which we attribute to changes in the delocalization and mobility of the paramagnetic center. We conclude that the nature of paramagnetism in crystalline conjugated diacetylene polymers is a chain defect property characteristic of interband electronic states close to the valence band.
Piezoelectric properties of oriented deoxyribonucleate films
Authors: Ando Yutaka , Fukada Eiichi 
Published: April 2003

AbstractThe piezoelectric effect due to shear in oriented films of DNA is strongly dependent on the relative humidity at which the films are equilibrated. Below about 60% relative humidity, the sign of the piezoelectric modulus is negative and its magnitude passes through a maximum with increasing temperature. This type of polarization appears to be due to the stress‐induced orientation of dipoles in sugar‐phosphate main chain. Above 75% relative humidity, water molecules are adsorbed by the bases and stabilize the ordered structure of double strand helices. In this crystalline state, the sign of the piezoelectric modulus is positive and its magnitude decreases markedly at about−75°C. This type of polarization appears to be due to the stress‐induced orientation of dipoles in bases attached to the main chain. From comparisons between piezoelectric, elastic, and dielectric measurements, it is concluded that the piezoelectric relaxation observed at−75°C and 75% relative humidity is mainly due to the dielectric relaxation of the bases in the double helix.
Low‐frequency dielectric behavior of hydrated poly(L‐proline)II
Authors: Guillet J. , Seytre G. , May J. F. , Chatain D. , Lacabanne C. 
Published: April 2003

AbstractThe dielectric behavior of poly(L‐proline) II has been studied by the dc transient method and a contactless pendulum technique. The comparison of measurements performed with and without contacting electrodes shows that the static and low‐frequency dielectric behavior are due to bulk phenomena. Both mechanisms are strongly dependent upon the water content of the sample. At low hydration, the static conduction may be attributed to an electronic process. The observed low‐frequency relaxation can be characterized by a relaxation time which increases with the water content. This behavior can be explained by an increase in stiffness of the poly(L‐proline) chain: two adjacent carbonyl groups of the chain may be hydrogen bonded by two water molecules.
Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. IV. Crystal orientation mechanism of nylon‐6 under uniaxial stretching
Authors: Matsuo Masaru , Hattori Hiroshi , Nomura Shunji , Kawai Hiromichi 
Published: April 2003

AbstractA model relating crystal orientation to the deformation of nylon‐6 spherulites under uniaxial stretching is discussed in terms of the orientation distribution functions of reciprocal lattice vectors of crystal planes, such as the (002) and (200) planes. The distribution functions calculated from the model are compared with those obtained from x‐ray diffraction experiments. It is found that the crystalaaxis and, consequently, the direction of hydrogen bonds within the crystal (α modification) orient parallel to the lamellar axis in the undeformed state, and that the crystal orientation behavior of nylon‐6 is much different from that of low‐density polyethylene, being characterized by much smaller values of the reorientation parameters of crystallites within orienting lamellae.Moreover, small‐angle light scattering forHvandVvpolarization is also calculated on the basis of the spherulite deformation model by taking the nylon‐6 crystal as having orthogonal–biaxial symmetry in optical anisotropy. It is concluded that theHvscattering can be realized in terms of the proposed model for spherulite deformation by taking into account a considerable contribution of hydrogen bonds to the molecular polarizability, so as to make the polarizability along the crystalaaxis larger than that along thebaxis. In other words, this conclusion suggests positively birefringent spherulites in the nylon‐6 samples studied.
Piezoelectric properties of oriented films of poly(γ‐methyl D‐glutamate)
Authors: Koga Kazunori , Kajiyama Tisato , Takayanagi Motowo 
Published: April 2003

AbstractThe dynamic piezoelectric stress constant e*25 of drawn films of poly(γ‐methyl D‐glutamate) (PMDG) cast from solutions in α‐helix‐promoting solvents 1,2‐dichloroethane (DCE) and chloroform and from the nonhelicogenic solvent dichloroacetic acid (DCA) was measured from −180°C to 200°C at 110 Hz. The drawn and annealed films cast from chloroform show a small peak for the real part of piezoelectric stress constant −e′25 in the temperature range of the mechanical α2‐crystalline relaxation, which is caused by the distortion motion of the backbone chain of the α‐helix. On the other hand, drawn films cast from DCE show the peak of the real part of the piezoelectric stress constant, whose magnitude decreases in the range of the mechanical α1‐crystalline relaxation or the β‐relaxation processes, which were previously ascribed, respectively, to mutual slipping of α‐helices and to the micro‐Brownian motion of disordered regions. Also, −e′25 becomes virtually zero near 180°C where the α2‐relaxation is located. These results suggest that the polarization change induced by applied strain is caused by distortion of the backbone chains in the α‐helix. Near 0°C, the temperature range of the side‐chain mechanical relaxation, −e′25 exhibits a marked peak both for films cast from chloroform and from DCE. The maximum value of −e′25 and the orientation function of the α‐helix axis are linearly related and extrapolation of −e′25,max to unit orientation function gives 1.3 × 104 cgs esu which corresponds to 2.4 Debye per residue. This value corresponds reasonably to the value of 3.71 Debye for the permanent dipole moment of NHCO bond if the correction for crystallinity is made. This result also indicates the piezoelectric properties of PMDG arise from distortion of the backbone chain of the α‐helix induced by applied strain.
Domain structure of nylon 6 fibers
Authors: Reimschuessel A. C. , Prevorsek D. C. 
Published: April 2003

AbstractStained and unstained sections of nylon 6 fibers are examined by means of transmission electron microscopy. Data are presented regarding dimensions and shape of macrofibrils, microfibrils, amorphous, and crystalline domains of the microfibril and the spacing between the microfibrils. The new results support the conclusions of a previous SAXS and diffusion study carried out with the same fibers.
Nonlinear relaxation of stress and birefringence in simple extension of 1,2‐polybutadiene
Authors: Noordermeer Jacobus W. M. , Ferry John D. 
Published: April 2003

AbstractRelaxation of stress and birefringence in simple extension has been studied for two samples of 1,2‐polybutadiene with 95% and 88% vinyl content and weight‐average molecular weight 1.9 and 2.9 × 105, respectively. The extension ratio, λ, ranged from 1.14 to 2.08, temperatures from 0 to 15°C, and times, reduced to 0°C, up to 3 × 105 sec. The stress‐optical coefficient C was negative and positive, respectively, for the two samples, the difference being attributable to opposite signs and very different magnitudes of the contributions of the 1,2 and 1,4 moieties to the birefringence. For each polymer, C was independent of time but increased (algebraically) with temperature. For one polymer a very minor dependence of C on λ was observed. At any instant of time, the dependence of both stress and birefringence on λ could be described by equations of the Mooney–Rivlin form with coefficients C1,C2 and B1,B2, respectively. At short times the contributions of the C1 and C2 terms to the stress and of the B1 and B2 terms to the birefringence are roughly equal. With increasing time, C1 and B1 decrease gradually while C2 and B2 remain constant over several decades in time. Finally, C2 and B2 decrease rather rapidly. A tentative interpretation of these phenomena in terms of motions of entanglements is given.
Thermally stimulated and isothermal depolarization currents in low‐density polyethylene
Authors: Fischer P. , Röhl P. 
Published: April 2003

AbstractThermally stimulated and isothermal depolarization currents of three low‐density polyethylenes are investigated in the temperature range 80–320°K. The thermally stimulated current spectra can be analyzed in terms of a continuous relaxation time spectrum. This spectrum can be resolved into three Gaussian distributions of activation energies centered near 140°K (γ‐relaxation), 205°K, and 245°K (β‐relaxation) in agreement with electrical and mechanical loss factor measurements. The experimental observation are explained in terms of reorienting dipoles, coupling the molecular motion to the electrical field.
Relaxation time spectrum of dipolar reorientation in low‐density polyethylene
Authors: Fischer P. , Röhl P. 
Published: April 2003

AbstractThe Fröhlich model of discrete reorienting dipoles has been extended to include a continuous spectrum of relaxation times and applied to the measurement of thermally stimulated and isothermal depolarization currents of low‐density polyethylenes. The experiments can only be interpreted if the detailed history of polarization and depolarization prior to the actual current measurements are taken into consideration. With certain simplification the spectrum of activation energies can be directly derived from the complete thermally stimulated current profile.
Dynamic mechanical properties of poly‐α‐olefins containing ring structures in side chains
Authors: Seefried C. G. , Koleske J. V. 
Published: April 2003

AbstractDynamic loss modulus curves have been determined over a temperature range beginning at liquid nitrogen temperature for poly‐α‐olefin polymers containing various ring structures, i.e., phenyl, cyclohexyl, cyclopentyl, and naphthyl, in the side chain. Glass transition and appropriate secondary relaxation temperatures were observed for each polymer. Separation of each pendant ring structure from the main backbone chain by successive additions of methylene units results in lower glass‐transition temperatures. Comparison of polymers with similar side chains and different ring structures shows that the respective glass‐transition temperatures decrease in the order naphthyl > cyclohexyl > phenyl > cyclopentyl. Secondary relaxation peaks were obtained at about −150°C for polymers containing the cyclohexyl and cyclopentyl rings. A similar peak was observed for the polymer possessing a phenyl ring separated from the main chain backbone by two methylene units. The comparable polymer containing the naphthyl ring structure exhibited a broad secondary relaxation peak centered at −20°C. The polymers possessing cyclohexyl rings separated from the main chain backbone by one or two methylene units had an additional low temperature peak at −80°C. The molecular mechanism associated with this relaxation may be related to intramolecular transformations of the cyclohexyl ring between its “chair–chair” conformations.
Ultrathin sectioning of rubbery block copolymers: Thickness test and observations of separate microphase units
Authors: Odell J. A. , Dlugosz J. , Keller A. 
Published: April 2003

AbstractA technique is described which enabled exceptionally thin sections of rubbery material to be cut for electron microscopy, and applied to samples of polystyrene‐polybutadiene‐polystyrene (SBS) copolymers which contain the segregated S phase in the form of cylinders arranged in a regular hexagonal macrolattice throughout the macroscopic specimen, with center to center distance of 300 Å. The technique consisted of sectioning the material hardened by a combination of osmic acid treatment and cooling with liquid air. By this method longitudinal sections containing single layer S rods could be obtained as verified by appropriate tilting tests. Such sections enabled the viewing of single cylinders without overlap which in turn enables the study of the structure of individual cylinders and the effect of various treatments on this structure. Examples quoted include the yielding or breaking of individual cylinders on longitudinal deformation of the macroscopic sample relating to our mechanical studies to be reported elsewhere. The technique also enabled sectioning in the swollen state of samples which are not sectionable other wise and this leads to the recognition of new structures and results in an overall improvement of image quality even when the thinness itself is not the prime requirement.
Quantitative information from x‐ray diffraction of nylon‐6 yarns. II. Physical aspects of some quantitative parameters
Authors: Huisman R. , Heuvel H. M. 
Published: April 2003

AbstractA mathematical model developed in an earlier paper describes the experimental x‐ray profiles of equatorial nylon‐6 reflections in terms of Pearson VII functions. The present paper deals with the physical aspects and interpretations of the interrelations of the parameters obtained and the relation between these parameters and the results of other types of measurements. It was found that the growth of the crystallites perpendicular to the chain axis is not isotropic, the strongest growth being in the direction of the hydrogen bonds. Growth and perfection of the crystallites are found to be highly correlated. Large crystals are related to short distances between the planes containing the hydrogen bonds and so to densely packed, i.e., perfect unit cells. This correlation forms the basis for the observed similarity between our quantification technique and the method of the crystal perfection index introduced by Statton. Curve resolution, however, makes the method better applicable for poorly crystallized samples. Comparison of the results with those of small‐angle x‐ray scattering gave a high degree of consistency with respect to the determined crystal size. In the literature mention is made of a relation between the dimensions and the melting point of the crystals; this relation is confirmed by comparing the appropriate x‐ray parameters with DTA results of methoxymethylated nylon 6‐yarns.Information about the γ‐phase can be obtained from equatorial and meridional reflections. The expected relationship between the relevant peak areas was established. This reported evidence shows the physical validity of the parameters obtained using the Pearson VII model for the analytical description of x‐ray reflections of nylon‐6 yarns.
The effect of casting solvent on the material properties of poly(γ‐methyl‐D‐glutamate)
Authors: Mohadger Youseph , Wilkes Garth L. 
Published: April 2003

AbstractThe effect of casting solvent on the material properties of poly(γ‐methyl‐D‐glutamate), PMDG, was investigated. The specific solvents used were chloroform, trifluoroacetic acid, dichloroacetic acid, methylene chloride, hexafluoroisopropanol, and tetrachloroethane. The different nature of these solvents controlled the degree of α, β, or random coil contents of the final film. The effect of the morphology on material properties induced by the respective solvents was investigated by dynamic mechanical measurements of the dry films, stress strain behavior of both wet and dry films as well as by wide‐angle x‐ray diffraction, small‐angle light scattering, and optical microscopy. Infrared spectroscopy was used to help determine α or β content. It was found that the casting solvent has considerable influence on material behavior and morphology. These differences are reflected in both the dynamical mechanical (small strain) and stress–strain (large strain) measurements as well as the x‐ray scattering and optical microscopy. It was noted by light scattering that all films gave rise to anisotropic rod scattering with the exception of the β film cast from trifluoroacetic acid. This latter film appeared to be optically isotropic.
Molecular transitions in an alternating copolymer of ethylene and chlorotrifluoroethylene
Authors: Sibilia John P. , Schaffhauser Robert J. , Roldan Luis G. 
Published: April 2003

AbstractThree transitions have been found with peaks at 130°C (α), 88°C (β), and −65°C (γ), by mechanical relaxation techniques for a quick‐quenched sample of an alternating copolymer of ethylene and chlorotrifluoroethylene. The intensity of the α transition was found to increase with an increase in crystalline content. It was observed at 150°C by infrared and x‐ray diffraction techniques and by mechanical relaxation spectra on an annealed sample. X‐ray diffraction and dichroic infrared measurements were conducted on oriented specimens as a function of temperature. These data showed that the β transition was accompanied by a change in lateral bonding distances in the crystalline phase and a conformational change attributed to an “unkinking” of the molecular chain. The β transition was found to be related to the amorphous phase and the onset of the β peak corresponded to the transition at 35°C found by infrared techniques and previously by a torsional modulus method. It was tentatively assigned to the glass transition. A more definitive assignment of the β transition would depend on a detailed structural analysis of the γ transition. The γ peak was not studied in detail in the present work.
Vibrational analysis of polyethylene terephthalate and its deuterated derivatives
Authors: Boerio F. J. , Bahl S. K. , McGraw G. E. 
Published: April 2003

AbstractThe Vibrational analysis of polyethylene terephthalate, polyethylene‐d4 terephthalate, and polyethylene terephthalate‐d4 has been carried out using a valence force field calculated from the infrared and Raman spectra of a series of low molecular weight aromatic esters. The Raman spectra for polyethylene‐d4 terephthalate and polyethylene terephthalate‐d4 are presented and band assignments for these compounds and polyethylene terephthalate are discussed.
Methyl rotation in polydimethylsiloxane studied by neutron transmission
Authors: Amaral L. Q. , Vinhas L. A. , Herdade S. B. 
Published: April 2003

AbstractNeutron transmission of polydimethylsiloxane has been measured as a function of neutron wavelength in the range 4–10 Å, at room temperature. Scattering cross sections per hydrogen atom have been obtained and the slope (12.2 ± 0.2) barns/Å has been derived. Comparison with calibration curves relating the slope to the barrier hindering internal rotation as well as comparison with calculated neutron cross sections using the Krieger–Nelkin formalism for different dynamical situations indicates practically free rotation of CH3 groups about their C3 symmetry axes.
Localized flow birefringence of polyethylene oxide solutions in a four roll mill
Authors: Crowley D. G. , Frank F. C. , Mackley M. R. , Stephenson R. G. 
Published: April 2003

AbstractWe report flow birefringence observations of polyethylene oxide solutions in a four roll mill where the flow field in the central region of the mill approximates well to that of pure shearing flow. When flow birefringence is observed it is seen to be highly localized within a region close to the “outgoing” asymptotic plane of flow. The phenomenon can be explained in terms of the flow birefringence corresponding to high extension of some polymer chains where the localization is caused by the chains requiring sufficient time in the flow field to become extended. This explanation has important consequences in all “persistently extensional flows” and can explain the origin of previously published results of localized flow birefringence observed for polyethylene solutions in axial compression and axial extensional flows.
Dynamic viscoelastic behavior of ABA block polymers and the nature of the domain boundary
Authors: Kraus Gerard , Rollmann K. W. 
Published: April 2003

AbstractDynamic viscoelastic properties of block copolymers of styrene with butadiene or isoprene are consistent with the growth of a diffuse interphase or interlayer as block lengths decrease. Under the conditions of the present study the interlayer does not lead to a secondary loss maximum between the two domain glass transitions. The pattern of shifts of the loss maxima characteristic of the domain Tg's suggests strongly that the interlayer composition profile must be asymmetric with an average volume composition rich in styrene. Typical block polymer viscoelastic behavior is observed even beyond the point at which the interlayer attains 100% of the polymer volume. Such block polymers no longer contain compositionally pure phases, but are visualized as retaining a residual domain structure in which composition fluctuates between ever narrowing limits as blocks become shorter, approaching homogeneity and the mechanical behavior of random copolymers.