bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐pressure phases in polymers. III. The nature of the high‐pressure phase in cis‐polyisoprene
Authors: Phillips P. J. , Edwards B. C.
Published: April 2003

The morphology and growth of the disordered hexagonal phase which crystallizes in films of cis‐polyisoprene at pressures in excess of 3 kbar is discussed. A two‐stage growth process is proposed consisting of nucleation and crystallization followed by a pressure‐enhanced thickening process. The phase is metastable and is replaced by normal spherulitic growth at long times. It transforms into lamellar sheafs with higher than usual lamellar thicknesses when pressure is lowered at constant temperature.
Crystal structure of poly(m‐phenylene isophthalamide)
Authors: Kakida Hideto , Chatani Yozo , Tadokoro Hiroyuki
Published: April 2003

The crystal structure of poly(m‐phenyulene isophthalamide) was determined by x‐ray analysis. The triclinic cell, with a = 5.27 Å, b = 5.25 Å, c (fiber axis) = 11.3 Å, α = 111.5°, β = 111.4° and γ = 88.0° and space group P1, contains one monomeric unit. The crystal density is 1.47 g/cc. The molecules in the crystal are contracted by 1 Å per monomeric unit from the fully extended conformation, and the planes of the benzene rings and adjacent amide groups make angles of about 30°. The crystal is composed of molecular chains connected by NH···O hydrogen bonds along the a and b axes forming a “jungle gym” network structure. The low tensile modulus of this polymer as compared with that of poly(p‐phenylene terephthalamide) is attributed to the contracted molecular conformation.
Ion recombination luminescence in polymer glasses induced by electron irradiation. I. High‐vinyl polybutadiene
Authors: Böhm Georg G. A.
Published: April 2003

The luminescence of 1,2‐polybutadiene was measured during and following irradiation with 1.4‐MeV electrons at 90 °K. Measured under isothermal conditions, the light intensity at first increases sharply on start‐up of irradiation, and then reaches a plateau after several seconds. The equilibrium value was found to be linearly dependent on the dose rate employed. The postirradiation luminescence decay measured at 90°K follows second‐order kinetics.

The light emitted by the irradiated sample during warm‐up to room temperature is characterized by the appearance of four intensity maxima at 118, 168, 223, and 261 °K. The first three peaks are attributable to the onset of local motion, whereas the peak at 223 °K is caused by the long‐range motion occurring at the glass‐to‐rubber transition. A preirradiation of the polymer in vacuo causes an increase in these four peaks as well as the formation of a new maximum at 143 °K.

Intermittent exposure of the irradiated sample to light of wavelengths λ > 450 nm causes the isothermal luminescence decay to be interrupted by a burst of light emitted by the sample during and shortly following the light exposure. This treatment also results in considerably reduced intensity maxima during warm‐up to room temperature. An interpretation of the findings reported is given on the basis of reactions involving primary and secondary transient species produced during irradiation and on the molecular parameters of the polybutadiene.
Thermal–mechanical studies on a heterocyclic polymer (BBB). I. Tensile creep and recovery
Authors: Berry G. C.
Published: April 2003

Creep and recovery measurements have been used to study the thermal–mechanical properties of polybisbenzimidazobenzophenanthroline‐dione (BBB) over the temperature interval 30–500°C (in vacuo). The creep measurements were augmented by x‐ray diffraction, isothermal contraction, and solubility measurements. It is found that extensive intermolecular association giving a supramolecular structure with (nearly) planar polymeric repeat units stacked in a “graphite‐like” array dominates the properties of BBB, and that this structure is maintained at temperatures as high as 500°C. The principal mode of creep gives rise to fully recoverable Andrade creep for which the strain depends on the cube‐root of time.
A dielectric study of the amorphous fraction in oriented nylon 610
Authors: Yemni Tarik , Boyd Richard H.
Published: April 2003

Since some dielectric loss peaks can be assigned to amorphous phase motions, it would appear that dielectric measurements should be a good probe to study the effects of macroscopic plastic deformation on the structure of the amorphous phase. We report here results of measurements of dielectric constant and loss in nylon 610 measured both parallel (∥) to and perpendicular (⊥) to the extrusion direction in specimens prepared by extrusion through a die at 160°. It is found that the intensity of the (∥) loss was nearly zero and the (⊥) loss intensity was greatly reduced compared to unoriented material. The other relaxation parameters (loss width and location) were largely unaffected. Since the amide dipole is nearly perpendicular to the chain axis and alternates in direction in the extended conformation, a considerable degree of chain alignment parallel to the draw direction is indicated. These results therefore show considerable permanent amorphous phase orientation even though the deformation was carried out 100° above its glass temperature.
A Raman study of the phase transition in crystalline trans‐1,4‐polybutadiene
Authors: Hsu S. L. , Krimm S.
Published: April 2003

Raman spectroscopy has been used to analyze the characteristics of the crystal–crystal phase transition of trans‐1,4‐polybutadiene. The low‐ and high‐temperature structures were found to coexist at the transition. The Raman spectra obtained at high temperature can be understood on the basis of the change in chain conformation associated with the phase transition.
Carbon dioxide sorption and transport in polycarbonate
Authors: Koros W. J. , Paul D. R. , Rocha A. A.
Published: April 2003

The solubility, permeability, and diffusion time lag for carbon dioxide in polycarbonate are reported at 35°C for pressures ranging from 1 atm to 23 atm. The solubility data are very well described by the dual sorption mechanism model, Henry's law plus Langmuir adsorption, proposed for glassy polymers. Both the permeability and time lag decrease with increased CO2 pressure. These observations are not consistent with the proposal that CO2 sorbed by the Langmuir contribution is totally immobilized; however, all of the results are entirely consistent with an extension of this proposal which considers partial immobilization. The data have been quantitatively analyzed in terms of this partial immobilization model, and the results suggest for polycarbonate at 35°C that the CC2 sorbed by the Langmuir portion of the isotherm behaves as if it has only about 10% of the mobility of the gas sorbed by the Henry's law part of the isotherm. The results have also been interpreted in terms of a concentration‐dependent diffusion coefficient which is shown to be mathematically equivalent to the partial immobilization model. The latter model was also formulated in thermodynamic terms, whereby fugacity was used rather than pressure, and diffusion coefficients were defined in terms of chemical potential gradients rather than concentration, but the consequences of these changes proved to be minor and no better. The significance of these observations and their interpretation is discussed.
The effect of strain rate on craze yielding, shear yielding, and brittle fracture of polymers at 77°K
Authors: Imai Yasufumi , Brown Norman
Published: April 2003

The tensile strength of poly(methyl methacrylate) (PMMA), polycarbonate (PC), polychlorotrifluoroethylene, and polysulfone was measured in liquid nitrogen over the strain rate range of 2 × 10−4 to 660 min−1. These polymers deformed by crazing which was induced by the liquid nitrogen. The stress versus log strain rate curve was sigmoidal in that its slope increased and then decreased with strain rate. Above a critical strain rate of about 200 min−1, which varied somewhat with the polymer, crazing was not observed with the optical microscope; the behavior became brittle, and the tensile strength became constant. The nonlinear behavior of stress versus log strain rate at low strain rates was associated with a decrease in activation volume with increasing strain rate whereas the nonlinear behavior at high strain rates was associated with an increase in density and decrease in length of the crazes with strain rate. The strain rate effect was the basis for calculating the diffusion coefficient of nitrogen into the polymers at 77°K.

The shear deformation mode of PC was measured under compression and under tension. The compressive strength versus log strain rate was linear throughout the entire range giving a compression shear activation volume of 360 Å3. The shear tensile strength of PC varied only slightly with strain rate when compared to the compressive strength. The brittle fracture stress of PMMA, in the absence of crazing, in compression and in tension, did not vary with strain rate.
Conformational and packing stability of crystalline polymers. VI. Stable chain packing of polyethylene
Authors: Tai Kazuo , Kobayashi Masamichi , Tadokoro Hiroyuki
Published: April 2003

The stable packings of polyethylene chains were investigated by intermolecular potential energy calculations based on various chain‐assembly models. The structures of the two crystal modifications of polyethylene (i.e., orthorhombic and the monoclinic), together with their cell constants and the setting angles, were well reproduced. The packing modes of polymethylene chains found in various alkane derivatives were also explained by the energy minima of the chain‐assembly models. In these calculations, several sets of potential functions were tried and three sets of functions were found to reproduce conformations of single polymer chains, the cell constants of polyethylene at low temperature, and those at room temperature.
Temperature‐induced reversible changes in long spacing in oriented polyethylene
Authors: Pope D. P. , Keller A.
Published: April 2003

The possible explanations for the temperature‐induced reversible changes in long spacing in polymers are reviewed. The observation of particularly large changes in certain irradiated samples of oriented low‐density polyethylene is reported. By combining these results with those obtained by DSC and other means it is concluded that the spacing changes are caused by partial melting of small lamellae within the lamellar stacks which alters the mean periodicity. The requirement of an irregular lattice explains why the effect is observed primarily in bulk samples and especially in materials which contain intrinsic irregularities.
Optical and swelling properties of macroscopic “single crystals” of an S–B–S copolymer. I. Samples possessing a lamellar morphology
Authors: Folkes M. J. , Keller A.
Published: April 2003

Samples of an S–B–S three block copolymer exhibiting a lamellar morphology have been prepared, in which the macrolattice formed from the segregated amorphous is uniformly oriented throughout the sample volume. The associated optical anisotropy has been studied in the unswollen state and in the presence of preferential solvents for the polybutadiene phase. The results obtained are consistent with form birefringence being the dominant contribution to the observed birefringence. There is a small contribution from a slight molecular orientation, corresponding to polystyrene chains perpendicular to the lamellar surfaces. The form birefringence is appropriately modified when the sample is in the swollen state by molecular orientation produced in the polybutadiene, due to the anisotropic dimensional changes in the sample. The implication of the results as regards the nature of the polybutadiene phase is also discussed.
Optical and swelling properties of macroscopic “single crystals” of an S–B–S copolymer. II. Samples possessing a cylindrical morphology
Authors: Folkes M. J. , Keller A. , Odell J. A.
Published: April 2003

A study is reported of the anisotropic swelling behavior of “single crystal” samples of an S–B–S two‐phase copolymer, Kraton K102, on imbibing a selective swelling agent. This material consists of a hexagonal array of polystyrene cylinders in a matrix of polybutadiene. Initially the material expands reversibly, perpendicular to the cylinders. Low‐angle x‐ray studies show that this corresponds to expansion of the hexagonal lattice and indicates lateral expansion of the matrix material. Birefringence changes can be broadly ascribed to the changes in form birefringence.

Subsequently, irreversible expansion occurs along the rod direction. x‐ray diffraction studies combined with electron microscopy indicate a transformation of the cylindrical microstructure into a more complex arrangement. This often appears to be an arrangement of spheres, packed on a hexagonal or square lattice, but this cannot completely account for the x‐ray results. Some micrographs suggest the existence of a more complex network of the polystyrene microphase units.
Electron donor–acceptor properties of thin polymer films on silicon. II. Tetrafluoroethylene polymerized by RF glow discharge techniques
Authors: Anderson H. R. , Fowkes F. M. , Hielscher F. H.
Published: April 2003

Metal–insulator–semiconductor (MIS) techniques were used to show that 86–210 nm thick plasma‐polymerized tetrafluoroethylene films on silicon stored only negative charge (electron acceptors). This property persisted at a reduced level when a 7 nm thick inner layer of hydrolyzed γ‐aminopropyltriethoxysilane was combined with an outer layer of plasma‐polymerized tetrafluoroethylene. The dispersion force contribution to the surface energy, γds, for the fluorocarbon films was found to be 6 mJ/m2(erg/cm2) which is comparable with the lowest values found in the literature. X‐ray photoelectron spectroscopy (XPS) revealed a substantial content of CF3groups in the fluorocarbon films. This finding coupled with the reported effects of noncrystallinity, crosslinking, and branching on the surface energies of fluorocarbon systems were used to explain the low surface energy and electrophilicity of the plasma‐deposited poly(tetrafluoroethylene)s.
Fracture toughness predictions in polycarbonate
Authors: Gerberich W. W. , Martin G. C.
Published: April 2003

The concepts of fracture mechanics have been used to analyze the fracture toughness of polycarbonate in terms of the polymer relaxation properties. By considering the temperature rise at the tip of a growing crack; a model is proposed which describes the viscoelastic energy loss in the fracture process. The model was used to predict the fracture toughness of polycarbonate as a function of test temperature.
A raman spectroscopic determination of the interlamellar forces in crystalline n‐alkanes and of the limiting elastic modulus Ec of polyethylene
Authors: Strobl G. R. , Eckel R.
Published: April 2003

A simple treatment based on continuum mechanics shows that weak interlamellar forces in crystalline n‐alkanes should result in a characteristic upward shift of the frequencies of the longitudinal acoustical (LA) modes, which is independent of the chain length and decreases inversely with the mode order. A raman spectroscopic determination of the LA mode frequencies of a series of different n‐alkanes confirms the theoretical conclusion and permits a derivation of a force constant characteristic of the interlamellar forces. The discussion results in a new formula valid for the LA mode frequencies of the orthorhombic n‐alkanes in the acoustical limit and yields a new determination of the limiting elastic modulus Ec of crystalline polyethylene. The value obtained, Ec = 2.9 × 1012 dyne/cm2, is markedly smaller than the value derived by Schaufele and Shimanouchi neglecting the influence of the interlamellar forces on the LA mode frequencies.
Osmotic coefficient of a polyelectrolyte solution with a mixture of monovalent counterions
Authors: Dolar D. , Škerjanc J.
Published: April 2003

An analytical solution of the Poisson‐Boltzmann equation is presented for the cell model of a polyelectrolyte solution with two species of monovalent counterions of different size. On this basis the osmotic coefficient is calculated as a function of the mole fraction of counterions and their radii. It is shown that the degree of binding of the smaller ion species increases as its mole fraction decreases.
The relationship between the physical structure and the mechanical properties of polycarbonate
Authors: Morgan Roger J. , O'Neal James E.
Published: April 2003

The room‐temperature tensile mechanical properties and fracture topographies of polycarbonate are reported as a function of strain rate, sample preparation, and thermal history above and below Tg. The bulk physical structural changes produced by various thermal treatments were monitored by density, yield stress, and differential scanning calorimetry observations. Ordered regions do not form in bulk polycarbonate at or below 145°C. The changes produced in the mechanical properties of polycarbonate on annealing below Tg, relative to a quenched or 145°C equilibrium‐state glass, are caused by liquidlike packing changes in free volume. In room‐temperature tensile a 125°C–6 day annealed glass exhibits transitional behavior from shear free volume, such as quenched and 145°C equilibrium‐state glasses, this transition occurs at higher strain rates. Polycarbonate embrittles as a result of the cessation of shear yielding and reversion to a crazing failure mode with a corresponding decrease in molecular flow and energy to failure.

Density measurements indicate that ordered regions do start to grow immediately above 145°C in bulk polycarbonate. This phenomenon allows precrystalline and/or crystalline entities to grow below the bulk Tg in thin films and on the free surfaces of thick films where mobility restrictions are less severe than in the bulk. From bright‐field transmission electron micrographs of thin films and carbon–platinum surface replicas of etched thick films it is suggested that the observed spherical precrystalline structures are aggregates of 50–60 Å ordered molecular do mains.
Enthalpy relaxation of rigid poly(vinyl chloride)
Authors: Straff R. , Uhlmann D. R.
Published: April 2003

The changes which take place on annealing rigid PVC in the vicinity of the glass transition have been followed by differential scanning calorimetry. The changes appear as an increase in the glass‐transition temperature and a decrease in the enthalpy with time of annealing. For annealing at 75°C, the enthalpy after 50–100 hr approaches the value characteristic of the equilibrium liquid state. The results obtained for annealing at 65°C and 75°C are in accord with those expected for the relaxation of an amorphous material, and are at variance with those expected on the basis of crystallization taking place on annealing. The enthalpy relaxation process is characterized by a distribution of activation energies centered about 18.8 kcal mole−1, and seems to reflect a multiplicity of molecular processes.
Spectrum of light scattered from viscoelastic gels
Authors: Munch J. P. , Candau S. , Duplessix R. , Picot C. , Herz J. , Benoit H.
Published: April 2003

Spectra of polarized light scattered from model networks of polystyrene swollen by benzene have been measured by optical mixing spectroscopy. Various series of networks of different functionalities and different lengths of the elastic chain elements have been investigated. A theoretical expression for the characteristic time constant of fluctuations has been derived from rubber elasticity theory. An analysis of the experimental results within the framework of this theory allows determination of the frictional constants of the gels.
Phase equilibrium and glass‐transition temperatures in plasticized amorphous bisphenol‐A polycarbonate
Authors: Onu A. , Legras R. , Mercier J. P.
Published: April 2003

Glass‐transition temperatures and phase separation have been studied in amorphous bisphenol‐A polycarbonate plasticized with pentaerythritol tetranonanoate (PETN), trimellitic acid, tridecyloctyl ester (TMDO), and tritolyl phosphate. (TTP). Phase separations occur with partially compatible plasticizers like PETN or TMDO. With PETN, for compositions situated in the miscibility gap, the system is composed of a pure plasticizer phase and of a plasticized polymeric phase characterized by a transition temperature of 110°C. In the case of TMDO and additional phase separation occurs below 55°C and two plasticized polycarbonate phases are observed. In compositions falling in the region where the could point curve crosses the glass‐transition diagram the phase separation may be delayed by quick cooling. TTP is completely compatible with polycarbonate and the variation of the glass‐transition temperature follows a Gordon and Taylor equation.
Glass transitions of ethyl acrylate‐based ionomers
Authors: Matsuura H. , Eisenberg A.
Published: April 2003

The glass‐transition temperatures of a series of copolymers of ethyl acrylate and acrylic acid neutralized with various cations were investigated. It was found that a plot of Tg as a function of ion content, for every type of ion investigated here, gives an unusual sigmoidal curve, which can be correlated with the onset of the failure of time–temperature superposition in viscoelastic studies, as will be shown in a future publication. Also, all of the Tg versus concentration curves for the various counterions can be superposed if the plots are made against cq/a, where c is the metal acrylate content, q the cation charge, and a the distance between centers of charge. Furthermore, in one region of water content, a linear relation is obtained between the glass transition and the water content (in weight‐%) independent of the ion concentration over wide ranges of ion content. Finally, above an ion concentration of 12 mole‐%, the rate of change in Tg per water molecule per ion pair at constant ion content, (∂Tg/∂n)c is linear but with different slopes above and below two water molecules per ion pair.
A crystallographic study of polymers exhibiting side‐chain crystallization
Authors: Hsieh H. W. S. , Post B. , Morawetz H.
Published: April 2003

Fibers were drawn from polymers of octadecyl acrylate, octadecyl methacrylate, N‐octadecylacrylamide, and a series of N‐substituted acrylamides with a second amide group in the side chain as well as from copolymers of octadecyl and methyl esters of acrylic and methacrylic acid. Wide‐angle and small‐angle x‐ray diffraction patterns were recorded for these materials. The interpretation of the characteristic difference between the behavior of the polycrylates and polymethacrylates, as proposed by Platé and his collaborators, is found to be inconsistent with a number of features of the experimental evidence. In the case of poly(octadecyl methacrylate) the data allow the estimation of two parameters of the electron density distribution in the side‐chain crystallites. With polyacrylamide derivatives, a second amide group in the side chain is found to destabilize the side chain crystallites. The bahavior of the copolymers is very complex and exhibits, in one case, evidence for a long periodicity parallel to the fiber axis.
Nuclear magnetic relaxation and molecular motion in poly(vinylidine fluoride)
Authors: McBrierty V. J. , Douglass D. C. , Weber T. A.
Published: April 2003

Pulsed NMR T1, T2, and T1ρ measurements are reported for poly(vinylidine fluoride) (PVF2). The results demonstrate clearly the presence of four relaxation processes, three amorphous and one crystalline. The α relaxation is undoubtedly a crystalline one, while β and γ are both amorphous, in agreement with earlier conclusions from dielectric and dynamic mechanical measurements. The fourth relaxation (β′) observed initially in the mechanical measurements of Kakutani, but undetected in dielectric experiments, has been confirmed in our results and the process is described by an activation energy of 15.1 kcl/mole. Motion of folds on the surface of crystal lamellae is deemed to be the responsible mechanism for the β′ relaxation. Two models have been considered in the interpretation of the α process; rotation of crystalline chains in the vicinity of defects and rotational oscillation of restricted amplitude of all crystalline chains about the main chain axes. Rotation of amorphous chains is a possible mechanism for the γ process while motions of a general nature are responsible for the β relaxation. Our experimental results again indicate that spin diffusion plays an important role in the overall NMR response of the polymer.
Surface properties of styrene–ethylene oxide block copolymers
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami
Published: April 2003

Hydrophobic–hydrophilic block copolymers were prepared by “living” anionic polymerization. They consist of polystyrene and poly(ethylene oxide) blocks, and are soluble in water. Their interfacial properties were investigated, employing aqueous solutions. The block copolymers lowered the surface tension of water in analogy with the low molecular weight surfactants such as sodium lauryl sulfate and heptaethylene oxide n‐dodecyl ether. Their aqueous solutions exhibited solubilization properties differing from those of polyethylene glycol. Therefore, it is thought that the polystyrene blocks produce solubilization phenomena. In samples of the same styrene content, the precipitation temperature of a high molecular weight copolymer in water was lower than that of a low molecular weight copolymer at the same concentration in the same solvent. The surface tension and precipitation temperature of aqueous solutions seem to be influenced by molecular weight and composition.
Strains induced upon drying thin films solvent‐cast on flexible substrates
Authors: Chow T. S. , Liu C. A. , Penwell R. C.
Published: April 2003

Solvent coating is an important commercial technique utilized in fabricating thin films. In certain cases, undesirable strains may be built into the composite as the solvent is removed. The stress field in a two‐layer sample and its distribution along the interface have been analyzed. By considering the shrinkage of the solvent cast film equivalent to applying an axial compressive load, interfacial expressions were derived which are valid for solvent drying of solution cast films. Experimental procedures and measurements are presented for the solvent casting of thin brittle films onto flexible polymeric substrates. Interfacial strains are determined and their dependence on accurate material property measurements is evaluated. The relation between the bulk and interfacial strain is illustrated.
Crystallization of bisphenol‐A polycarbonate. I. Influence of trimellitic acid tridecyloctyl ester on the kinetics of crystallization
Authors: Gallez F. , Legras R. , Mercier J. P.
Published: April 2003

The crystallization of bisphenol‐A polycarbonate plasticized by trimellitic acid tridecyloctyl ester (Morflex 525) has been studied. A half‐crystallization time of 100 min is observed at 170°C with 10% of plasticizer compared with a figure of 18,000 min for the unplasticized material. The kinetic study is limited to the primary crystallization process which can be described by an Avrami equation; however, the Avrami coefficients are much higher than usual. Studies on the effect of the preparation procedure of the samples and of premelting indicate that nucleation is at least partially heterogeneous.
The morphology of polyethylene prepared by γ‐ray‐induced polymerization in various solvents
Authors: Arai Hidehiko , Wada Takeshi , Kuriyama Isamu
Published: April 2003

Polyethylenes were prepared by γ‐ray‐induced polymerization in ethyl and n‐butyl alcohols, tert‐butyl alcohol containing 5 vol‐% of water, 2,2,5‐trimethylhexane, 2,2,4‐trimethylpentane, and cyclohexane in the temperature range 25–90°C. The morphology of the polymers as‐polymerized and studied by electron microscopy depends on three factors through the degree of undercooling: the affinity of the solvent, polymerization temperature, and the polymer molecular weight. Large lamellar crystals are formed even in the alcohols when at least two of them are chosen properly.
Small‐angle x‐ray and light scattering studies of the morphology of blends of poly(ϵ‐caprolactone) with poly(vinyl chloride)
Authors: Khambatta F. B. , Warner F. , Russell T. , Stein R. S.
Published: April 2003

Solvent‐cast films of blends of poly(ϵ‐caprolactone) (PCL) with poly(vinyl chloride) (PVC) were examined by low‐angle x‐ray scattering and by small‐angle light scattering. X‐ray scattering from crystalline compositions were analyzed using the Tsvankin–Buchanan technique and led to values of the repeat period of the lamellar structure and the thickness of the crystalline and amorphous layers. With increasing content of PVC, the amorphous layer thickness increased sufficiently to accommodate the PVC, leading to values of the linear crystallinity consistent with macroscopic measurements by density and DSC techniques up to about 50% PVC by weight. Above this concentration, the lamellar structure no longer appeared to be volume filling. At high concentration of PCL, the polymer consisted of volume‐filling spherulites containing the lamellar substructure. Spherulite sizes were measured by light scattering and absolute light scattering intensities were consistent with calculations based upon the degree of crystallinity and anisotropy of the spherulites. Compositions containing more than 60% PVC were amorphous. Low‐angle x‐ray scattering was interpreted in terms of the Debye–Bueche theory which leads to values for a correlation distance lc and the mean‐square electron density fluctuation 〈η2〉 (which was also obtained from the invariant). By the method of Porod, the correlation distances were resolved into persistence lengths within the two phases, which were determined as a function of composition. The fluctuation 〈η2〉 was analyzed in terms of a two‐phase model to show that its value was somewhat larger than would be obtained if the phases were composed of the pure components. It was not possible to uniquely determine their compositions. The data were consistent with the existence of a transition zone of the order of 30 Å thick between phases.
Persistence vectors for polypropylene, polystyrene, and poly(methyl methacrylate) chains
Authors: Yoon D. Y. , Flory P. J.
Published: April 2003

Persistence vectors a ≡ 〈r〉 are calculated for polypropylene, polystyrene, and poly(methyl methacrylate) chains as functions of chain length and stereochemical constitution. Differences between the progressions of a with chain length for these vinyl polymers are related to their conformational characteristics. The preferences of the syndiotactic chains for the tt dyad conformation are manifested most strikingly in the behavior of this vector.
Molecular orientation in poly(ethylene terephthalate) by means of laser–raman spectroscopy
Authors: Purvis J. , Bower D. I.
Published: April 2003

The intensity of the Raman scattering from uniaxially oriented amorphous poly(ethylene terephthalate) tapes at wave number shifts of 1732, 1616, 1286, 857, and 632 cm−1 has been observed for various combinations of incident and scattered light polarization vectors with respect to the draw direction. An attempt has been made to analyze the data to provide values of 〈P2(ζ)〉 and 〈P4(ζ)〉, where Pn(ζ) is the nth order Legendre polynomial in ζ,ζ is the cosine of the angle between the draw direction and a typtical chain axis in the polymer, and the angle brackets denote the average value over all repeat units. This attempt was successful for the 1616 and 632 cm−1 lines but less successful for the other three, although the data for the 1732 and 1286 cm−1 lines could be analyzed to provide quantities proportional, but not equal, to 〈P2(ζ)〉. In the analysis and discussion two possible models were considered for the conformation of the terephthaloyl residues in the amorphous polymer but it was not possible to reject either model conclusively. The results suggest, in agreement with previous studies by other methods, that the drawing of PET at 80°C takes place essentially as the extension of a rubberlike network which is frozen on subsequent cooling to room temperature.
Changes in light scattering from poly(ethylene terephthalate) and nylon 6 films upon stretching in relation to the deformation mechanism
Authors: Konda Atsuo , Nose Kenkichi , Ishikawa Hiroshi
Published: April 2003

Unoriented T‐die flat films of nylon 6 and PET films annealed at 90°C were stretched in water at 80°C. Amorphous PET films were stretched in water at 65–75°C. Changes in the light scattering patterns from these samples upon stretching were investigated. One of the observed LS patterns from the stretched samples is the Hv eight‐leaf pattern consisting of four lobes and streaks. In the nylon 6 and heat‐treated PET showing this pattern, spherulitic patterns can be seen in polarization microscopy. The microscopic spherulitic superstructure may possibly be the factor responsible for producing the lobe‐and‐streak pattern. On the other hand, many microscopic eight‐leaf patterns can be observed in amorphous unannealed PET showing the lobe‐and‐streak pattern. These microscopic patterns are due to retardation at stress concentrations around impurities and nuclei. The superstructure giving these microscopic patterns must be the origin of the lobe‐and‐streak pattern from unannealed PET. Another scattering pattern, the Vv cruciform pattern, was observed in both stretched nylon 6 and unannealed PET. This pattern is due to an orientation change across the slip lines observed under a polarizing microscope. It is noted (1) that the appearance of the slip lines in PET coincides with the occurrence of oriented crystallization on stretching, (2) that the lobe‐and‐streak pattern from PET in which orientation crystallization has taken place is fairly stable to heat treatment and does not disappear until just before melting, and (3) that the superstructures produced at low stretching seem to be deformed on further stretching, in accordance with affine deformation theory.
Thickening of crystals during rapid heating. II. Crosslinked polyethylene and methoxymethylated nylon 6
Authors: Sakurai Kensuke , Oota Teruhisa , Miyasaka Keizo , Ishikawa Kinzo
Published: April 2003

The effect of modification of polymer chains on crystal thickening during heating was investigated with an apparatus devised for rapid measurement of small‐angle x‐ray diffraction. Thickening of crystals still occurred even at a heating rate of 18°C/min in polyethylene irradiated with gamma ray doses of 30–300 Mrad, and the melting point was depressed. These results showed that the melting point depression due to irradiation is not due to a restriction on crystal thickening but rather to crystal lattice distortion. On the other hand, although methoxymethylation of nylon 6 completely inhibits crystal thickening, the melting point increases or decreases depending on the temperature of annealing preceding methoxymethylation. From these results we are led to conclude that irradiation and methoxymethylation are not effective means of obtaining the relation between melting point and crystal thickness.
The scattering of light from thin polymer films: Multiple scattering. II. Effect of depolarization
Authors: Natarajan Raj T. , Prud'Homme Robert E. , Bourland L. , Stein Richard S.
Published: April 2003

A procedure is described to include the effect of depolarization of the originally plane‐polarized incident light beam as it passes through a thin polymer sample on the intensity of multiple light scattering. The multiple scattering gives rise to “polarization scrambling” in which, for example, Hv scattering measurements involve multiple scattered rays which may have undergone some Vv scattering. These phenomena reduce the angular dependence of scattering since large intensities originally occurring at small values of θ are rescattered so as to enhance intensities at other angles. Correction factors for both Hv and Vv scattering are presented.
A kinetic effect in the environmental stress cracking of polyethylene due to liquid viscosity
Authors: Shanahan M. E. R. , Schultz J.
Published: April 2003

An Interesting kinetic effect in the environmental stress cracking (E.S.C.) of polyethylene has been observed, in which the liquid viscosity plays an important role. E.S.C. of a low density, high melt index polyethylene due to silicone oils has been studied using constant load creep experiments. For relatively low stresses, it has been found that the time to fracture is independent of the viscosity of the silicone oil, all other factors being approximately equal. However, at high stresses, the time to fracture increases with increasing viscosity for a given stress. This effect has been shown to be due to the relative ease with which the liquid penetrates a growing crack and thus always be at the crack front. Times to fracture for viscous liquids at high stresses are longer since crack propagation continues partially with and partially without liquid contact, fracture rate being much slower when not in the presence of the liquid.
Directional anisotropy of dielectric β‐relaxation in oriented poly(ethylene terephthalate)
Authors: Hsu Bay‐Sung , Kwan Sik‐Hung
Published: April 2003

The dielectric β‐relaxation in oriented poly(ethylene terephthalate) was investigated over wide ranges of frequency and temperature, with the electric field applied at inclinations of 0°, 45°, and 90° to the draw direction. Pronounced directional anisotropy is observed over the entire range of temperature and frequency. With the external field parallel to the draw direction the dielectric loss is considerably smaller than the value obtained with the field normal to the draw direction. The value obtained with the electric field at 45° to the draw direction is intermediate between the other two. On the other hand, the activation energy is largest for 0° inclination and smallest for 90° inclination. It is suggested that motions of the dipoles involve localized rocking of the molecular chain backbone, particularly when the external electric field is parallel to the chain direction.
Mechanical relaxations in γ‐ray‐polymerized polyethylene
Authors: Arai Hidehiko , Kuriyama Isamu
Published: April 2003

Dynamic mechanical properties of cold‐compacted films of polyethylene prepared by γ‐ray‐induced polymerization in bulk at 30°C are discussed in connection with the fine structure. The cold‐compacted films show a broad α‐relaxation at a lower temperature than do single‐crystal mats or melt‐crystallized polymer. From the effects of annealing and swelling by carbon tetrachloride on the relaxation, it is concluded that the α‐relaxation, like the α‐relaxation in the single‐crystal mats, originates from molecular motions within lamellar crystals. This is consistent with the finding that these films are composed of stacked small irregular lamellar crystals. The γ‐relaxation is also similar to that in crystal mats.
Light scattering from spherulitic materials
Authors: Blum L. , Frisch H. L.
Published: April 2003

The azimuthal angular dependence of the depolarized component of the light scattered from spherulitic materials is derived by an algebraic method that avoids the difficult angular integrations of the usual approach. The result appears as a sum of products of two factors, a molecular factor, that depends only on the structure and the scattering angle θ, and a geometrical factor that depends only on the azimuthal angle ϕ and the scattering angle θ. The molecular factors are evaluated for models of spherulitic structure that assume a constant tilt of the optical polarizability tensor. The radial distribution, in principle, is arbitrary, and an evaluation for the layered spherulite is made. If the tilt angle is ω when the azimuthal patterns depend only on a linear combination of P2(cos ω) and P4(cos ω), where Pn(x) is the Legendre polynomial of order n. In our theory the VH scattering pattern is a four‐leaf clover whose axes are restricted by the theory to be at either 0 or 45° to the polarization directions.
Poly(styrene sulfonic acid)–poly(vinylidene fluoride) interpolymer ion‐exchange membranes. II. Ultrafiltration properties
Authors: Gryte Carl C. , Gregor Harry P.
Published: April 2003

Highly porous interpolymer ion‐exchange membranes of poly(styrene sulfonic acid) and poly(vinylidene fluoride) have been investigated under pressure filtration with KCI, Na2SO4, erythrosin, and bovine serum albumin as solutes in the feed solution. The rejection of the ionic solutes is governed by a Donnan exclusion of electrolyte from the membrane phase. A model for the transport behavior is proposed that includes both diffusive and convective salt transport. The calculated rejections agree adequately with the observed data.
The effect of sorbed oxygen on the γ and δ dielectric relaxations in polystyrene
Authors: Pochan J. M. , Hinman D. F.
Published: April 2003

The γ and δ relaxations of polystyrene (PS) are rendered more active dielectrically by sorbed oxygen. This effect, coupled with comparative work on molecularly similar systems has led to the assignment of the γ relaxation to a rotational libration of the phenyl ring in PS. Specific interactions of the pendant phenyl ring with molecular oxygen to induce off‐axis dipole moments in the phenyl moiety is proposed. It is concluded that this interaction is strong enough to influence the dielectric relaxation strength of other relaxations in PS. It is further concluded that because of the interactions occuring in aromatic polymers containing sorbed oxygen, care must be taken to exclude oxygen or to vary its content, in order that intrinsic motions in the polymer system can be studied.
Studies of molecular relaxation of poly(propylene oxide) solutions by dielectric relaxation and brillouin scattering
Authors: Yano S. , Rahalkar R. R. , Hunter S. P. , Wang C. H. , Boyd R. H.
Published: April 2003

Dielectric relaxation and Brillouin scattering are jointly used in studying molecular relaxation in poly(propylene oxide) (PPO) and its solutions in methylcyclohexane. The dielectric method was applied to the more concentrated (100%, 80%, 60%, by volume) solutions over a wide temperature and frequency range (30 Hz to 8 GHz) in order that the variation in activation energy characteristic of a glass‐forming substance could be delineated. The present work extends previous work on the undiluted polymer to higher frequencies so that range of 12 decades in the dielectric loss maximum fmax as a function of temperature is now available. The “Antoine” equation is found to represent the behavior of log fmax, of the bulk concentrated solutions very well. The more dilute (40%, 20%) solutions were studied only in the high‐frequency (GHz) region since phase separation occurred at low temperatures. Both the temperature and dilution effects were interpreted in terms of free‐volume theory. Brillouin scattering spectra were obtained at several scattering angles and a wide range of temperatures. A maximum in the curve of hypersonic attenuation versus temperature was observed in each polymer solution. The attenuation maximum shifts toward lower temperature upon dilution, in agreement with the dielectric relaxation result. The Brillouin scattering follows different activation parameters and evidences a more rapid process than does the dielectric relaxation. It is speculated that it monitors a secondary or subglass relaxation, due perhaps, to damped torsional oscillations.
Isothermal and nonisothermal creep of lightly crosslinked cis‐1,4 polybutadiene
Authors: Caruthers J. M. , Cohen R. E.
Published: April 2003

A nonisothermal creep experiment has been analyzed to ascertain its suitability for determining the temperature dependence of low activation energy viscoelastic processes in elastomers far above Tg. The nonisothermal method was employed to determine the activation energy for creep near 35°C in a lightly crosslinked cis‐1,4 polybutadiene elastomer at small strains within the linear viscoelastic region, and at various large deformations up to rupture. The observed activation energy was essentially independent of the level of strain, and the value of ΔHa (∼11 kcal/mole) determined via the nonisothermal creep method was in good agreement with the result (∼12 kcal/mole) obtained via time‐temperature superposition of isothermal linear viscoelastic creep data. The nonisothermal data allowed for an estimate of the volume of the “flow unit” associated with the controlling viscoelastic creep mechanism, attributed here to slippage of entanglements within the lightly crosslinked network.
Extensional infrared orientation
Authors: Wool Richard P.
Published: April 2003

In evaluating molecular orientation by dynamic infrared techniques, it is shown, subject to certain restrictions, that an extensional mechanism plays an important role in the measured orientation. Dichroic measurements can indicate a change in segmental orientation without any change occurring in the chain axis orientation. Extensional orientation was evaluated for a general helical molecule in terms of singular and coupled vibrational modes. Significant orientation changes can occur by the extensional mechanism, the sign and magnitude of which depend on the components of the transition moment vector.
Incompatibility of polymer solutions. I. Binodals and spinodals in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Vrij A.
Published: April 2003

The incompatibility of polystyrene (PS) and polyisobutylene (PIB) in toluene is characterized by binodals obtained from phase separation and spinodals obtained from light scattering at zero scattering angle. From these the interaction parameter χ23, between unlike polymer segments was calculated. It appears to be dependent on molecular weight and composition. The nature of χ23, especially its low value, is discussed.
Incompatibility of polymer solutions. II. Concentration and angle dependence of the light scattering in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Laven J. , Broeckman A. , Vrij A.
Published: April 2003

Light scattering experiments are described on the system polystyrene (PS) + polyisobutylene (PIB) + toluene at constant temperature. At a fixed concentration of the nearly “invisible” PIB the light scattering at various angles was measured as a function of varying PS concentration up to the region of incompatibility. For interpretation of the results use is made of an extension of the classical fluctuation theory for multicomponent systems to finite scattering angles. The experimental data can be described qualitatively with this theory. Addition of a second polymer has little influence on the size of the other polymer. The variation of the light scattering with the wavelength can be explained in terms of the (negative) adsorption of one polymer by the other.
Incompatibility of polymer solutions. III. Critical opalescence in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Vrij A.
Published: April 2003

The angular dependence of light scattering from the homogeneous ternary system polystyrene + polyisobutylene + toluene was measured at a fixed (critical) concentration as a function of temperature. On approaching the critical temperature the scattering becomes very large and strongly angle‐dependent. The experiments show that the interaction range rG is of the same order of magnitude as the molecular radius of gyration of the polymer, but cannot be set equal to it as in the case of a binary system of one polymer in a single solvent. The temperature dependence of the various interaction parameters does not depend on the molecular weights of the polymers.