bluuebunny/crossref_metadata_2025 huggingface dataset:
Melting and internal motion in highly alternating copolymers of ethylene and carbon monoxide
Authors: Starkweather Howard W.
Published: April 2003

The melting point of the 1:1 copolymer of ethylene and CO is 244°C. It falls rapidly as the percent CO is reduced indicating that the heat and entropy of fusion are 0.60 kcal and 1.15 e.u./mol of chain atoms, respectively. These are lower than the values for polyethylene. Dynamic mechanical measurements showed loss peaks at −100° and 25°C. The low temperature γ‐relaxation which is also seen in dielectric data appears to be a local mode relaxation with an activation energy of about 12 kcal/mol. The room temperature relaxation is associated with a large decrease in the modulus and a large increase in the dielectric constant. It is probable that the low entropy of fusion is due in part to extensive motion in the crystal.
Kinetics and mechanism of the quaternization of poly(4‐vinyl pyridine) with 1‐bromopropane
Authors: Boucher E. A. , Mollett C. C.
Published: April 2003

The kinetics of the quaternization of poly(4‐vinyl pyridine) with 1‐bromopropane in sulfolane has been studied in the temperature range 308–348°K with data points covering the whole conversion range. The results have been analyzed according to the neighbouring‐group model with rate constants k0, k1, and k2 for reaction of pyridyl groups with zero, one, and two already reacted neighbors. Allowing for limiting reaction at about 95%, the experimental results substantiate the model with K = k1/k0 = 0.80 ± 0.03, and L = k2/k0 = 0.37 ± 0.03, which are independent of temperature. The temperature dependence of k0 values gives an activation energy of 66.22 ± 4.20 kJ mol−1. It is still not possible to decide whether steric or electrostatic factors are responsible for K and L values less than unity. Other systems are mentioned where side reactions occur.
Thermodynamic fluctuations and light scattering from monodisperse polymer solutions
Authors: Cohen Claude
Published: April 2003

An expression for the free energy of a monodisperse polymer solution which incorporates volume changes upon mixing is obtained from a two‐component van der Waals model. When contributions to the thermodynamic quantities from the hard‐core interactions are neglected, expressions similar to those of Flory–Huggins–Debye for the spinodal and critical conditions are obtained. Partial molecular volumes instead of the pure molecular volumes appear in these expressions. The thermodynamic fluctuations of the system, which cause the Rayleigh and Brillouin light scatering, are also expressed in terms of the parameters of the polymer solution in a simple fashion. A limitation to the standard Debye procedure of associating the excess scattering to the solute concentration fluctuations is pointed out.
Deformation band studies of oriented polyethylene and polyethylene terephthalate
Authors: Duckett R. A. , Goswami B. C. , Ward I. M. , Zihlif A. M.
Published: April 2003

Deformation bands formed at the yield point in tensile tests on oriented high‐density polyethylene have been studied by optical microscopy and wide‐angle x‐ray (WAXS) diffraction. The observations of the rotation of the optical extinction direction are shown to obey a simple scheme proposed previously by us: the principal directions of the refractive index ellipsoid within the deformation bands are everywhere parallel to the principal axes of the plastic strain ellipsoid, zero strain referring to the isotropic state. This result is similar to that obtained previously for polyethylene terephthalate (PET) and polypropylene despite the much higher crystallinity obtained with polyethylene. Independent measurements of the molecular reorientation in the deformation bands made using wide‐angle x‐ray scattering broadly confirm the optical measurements. The results taken together suggest that the material within the band, whether crystalline or not, becomes realigned about the new direction of maximum elongation as if controlled by the deformation of an effective molecular network.
Some elastic and thermoelastic properties of two organophosphazene polymers
Authors: Mark J. E. , Yu C. U.
Published: April 2003

Samples of the alkoxyphosphazene polymer [P(OCH3)2N]x and the aryloxyphosphazene polymer [P(OC6H5)(O‐p‐C6H4C2H5)N]x were crosslinked using γ‐radiation. The resulting elastomeric networks were characterized, in elongation, with regard to both their stress‐strain relationships and their stress‐temperature (“thermoelastic”) properties. Values of the ratio 2C2/2C1 of Mooney–Rivlin constants used to characterize the stress‐strain isotherms were found to be similar to those of other elastomeric networks of comparable degree of crosslinking. The thermoelastic data show the energetic component of the retractive force to be positive for the alkoxy polymer, but negative for the aryloxy polymer. Although it is not difficult to suggest a possible molecular explanation for some of these thermoelastic results, a definitive interpretation would require reliable information on the conformational characteristics of the skeletal bonds in the polyphosphazene chain.
Diffusion in polymer—solvent systems. I. Reexamination of the free‐volume theory
Authors: Vrentas J. S. , Duda J. L.
Published: April 2003

The free‐volume theory describing diffusion in polymer–solvent systems is reexamined. Calculation of the specific free volume for such systems is discussed, and equations are presented for the determination of the self‐diffusion coefficients of the polymer and the solvent. Conditions under which the mutual diffusion coefficient can be deduced solely from free‐volume considerations are clarified, and a more general version of the free‐volume diffusion theory proposed by Fujita is presented. The further restrictions needed for the theory of Fujita are discussed, and it is concluded that these additional restrictions are responsible for failures of the Fujita theory.
Internal viscosity in the dynamics of polymer molecules
Authors: Macinnes D. A.
Published: April 2003

We consider the internal viscosity (IV) of polymer molecules in solution, and investigate how the IV might depend on solvent viscosity η0. From the Kirkwood model of a polymer, we derive in a nonrigorous manner two equations containing an IV, one equation valid for low η0 and the other for high η0, and we show that in these respective cases the coefficient of the IV is independent of η0 and linearly dependent on η0.
Light scattering from crystalline superstructure in tubular‐extruded polybutene‐1 films
Authors: Hashimoto Takeji , Todo Akira , Murakami Yukinobu , Kawai Hiromichi
Published: April 2003

Light scattering from polybutene‐1 films prepared by tubular extrusion was studied in order to investigate its crystalline superstructure and the deformation mechanism. Analysis of the light‐scattering patterns together with electron micrographs, indicate the existence of sheaflike crystalline superstructures. The sheaves are aligned nearly side by side with their axes preferentially oriented perpendicular to the machine direction. The Hv scattering patterns exhibit a “butterfly” appearance. Analysis of the patterns in terms of scattering and azimuthal angles at which the scattering intensity is a maximum yields information on the size and shape of the sheaflike texture. The information should be of importance in studies of anisotropic crystal growth caused by molecular orientation in the melt and of the deformation mechanism of the texture. The deformation behavior should be representative of that of different parts of spherulites, at least qualitatively; the deformation of the texture along the machine and transverse directions corresponds to deformation of equatorial and meridional regions of a spherulite, respectively.
TSC and dielectric study of multiple relaxations in poly‐L‐proline
Authors: Guillet Jacques , Seytre Gérard , Chatain Daniel , Lacabanne Colette , Monpagens Jean Claude
Published: April 2003

The thermally stimulated current (TSC) technique has been used to perform a detailed study of the complex relaxation modes observed in poly‐L‐proline II. Each mechanism has been resolved into elementary processes, each well described by using the assumption of a single relaxation time following an Arrhenius equation. This resolution allows us to predict the complex dielectric constant for temperatures between 77 and 400°K and frequencies between 10−6 and 104 Hz. In the range where experimental results are available, the predicted energy losses are in very good agreement with those measured by DC transient experiments, the pendulum technique without contacting electrodes, and the AC bridge. We discuss the probable origin of the various relaxation modes. The relaxation observed at the highest temperature may be attributed to electrons trapped at the boundaries between paracrystalline and crystalline regions. From the changes in the relaxations caused by bound water, we conclude that there are two types of water interacting with the macromolecular substrate. With increasing water content, the relaxation modes observed may first be due to water tightly bound between two carbonyl groups of adjacent chains and second, to increased stiffness of the poly‐L‐proline chain from more mobile water.
Solubility of ethylene in liquid, low‐density polyethylene to 69 atmospheres
Authors: Cheng Y. L. , Bonner D. C.
Published: April 2003

Ethylene solubility in low‐density polyethylene has been measured using the piezoelectric sorption method from 0 to 69 atm at 126, 140, and 155°C. The measured solubility data indicate lower ethylene solubility in polyethylene at a given temperature and pressure than a previously published extrapolation of infinite‐dilution results. The data are interpreted using the Flory–Huggins solution theory.
Studies on the α and β forms of isotactic polypropylene by crystallization in a temperature gradient
Authors: Lovinger Andrew J. , Chua Jaime O. , Gryte Carl C.
Published: April 2003

Samples of isotactic polypropylene (PP) were zone‐solidified in temperature gradients up to 300°C/cm at growth rates down to 3 μm/min. Oriented α‐type spherulites were obtained only by nucleation. While β nucleation is extremely rare, the β phase is easily initiated by growth transformations along the oriented α front. Since the β phase was found to grow considerably faster than the α phase, the α‐to‐β transformation points diverge across the sample, interrupting growth of the oriented α fibrils. This causes subsequent nucleation to yield teardrop‐shaped α spherulites.

Differential scanning calorimetry (DSC) studies of zone‐solidified PP show the β‐phase to be favored by slow growth rates, high temperature gradients, and large degrees of superheat in the melt—all of which tend to suppress nucleation. Differential thermograms of largely β‐PP obtained at a heating rate of 1°C/min show the actual melting and recrystallization of the β spherulites into the α form.
On the connectivity of modified glass networks
Authors: Holliday L.
Published: April 2003

The concept of network connectivity is applied to inorganic oxide glasses of hybrid structure. In order to describe these materials which are ripe for investigation, a new terminology is put forward. By using this terminology, some new lines of research can be readily identified. The way in which the physical properties of these novel materials will change with structure is discussed in broad terms, with particular reference to the glass transition temperature.
Temperature dependence of the dynamic mechanical properties of filled polymers
Authors: Lee Biing‐Lin , Nielsen Lawrence E.
Published: April 2003

A theory has been developed to explain the jump in the relative modulus of filled polymers near the glass transition temperature Tg and the subsequent decrease in relative modulus at temperatures above the glass transition temperature. The theory is based upon the concept that there are some particle–particle contacts in doublets and in agglomerates containing a larger number of particles. Below Tg motion of particles at the contact points is possible because of the high modulus of the polymer. At Tg particle–particle motion mostly ceases because of the low modulus of the polymer. At higher temperatures, the mismatch in the coefficients of expansion allows some motion to occur at points of contact and slippage may occur at the polymer–particle interfaces, so the modulus decreases. It is shown theoretically and experimentally that both the elastic modulus and the mechanical damping depend upon the nature of the surface of the particles.
Solid‐state thermal polymerization of 2,4‐hexadiyne‐1,6‐diol
Authors: Bloor D. , Stevens G. C.
Published: April 2003

The solid‐state thermal polymerization of 2,4‐hexadiyne‐1, 6‐diol has been studied by a variety of methods. Pure monomer heated under vacuum or in an inert gas atmosphere is found to polymerize readily, unlike material heated in air. X‐ray diffraction reveals that samples anneal during polymerization. Initially, a long chain polymer is formed, but above 20% conversion a less perfect product is obtained. Measurements suggest a complex molecular rearrangement during the nonideal phase of polymerization. Possible models for this process are discussed.
On the electrical polarization of polymer single crystals in suspension
Authors: Leute U.
Published: April 2003

A model is proposed for the electrical polarization that causes the orientation and, hence, the electric birefringence of a suspension containing single crystals of a poly(ethylene oxide)–polystyrene diblock copolymer or a poly(ethylene oxide) homopolymer. It serves to describe how an electric dipole moment lying in the plane of the single crystal can be induced by protons migrating in poly‐(ethylene oxide). The resulting Kerr effect is calculated up to saturating fields, and the observed dispersion of the polarization in high frequency fields is explained as a space charge relaxation phenomenon. The estimated relaxation time agrees satisfactorily with published experimental data.
X‐ray structure determination of isotactic poly(2‐vinylpyridine)
Authors: Puterman M. , Kolpak F. J. , Blackwell J. , Lando J. B.
Published: April 2003

The structure of isotactic poly(2‐vinylpyridine) has been determined from x‐ray fiber data utilizing rigid‐body least‐squares refinement techniques. The polymer exists as a threefold helix with three chains passing through a hexagonal unit cell having the dimensions a = b = 15.49 Å and c = 6.56 Å (fiber axis) and space group P31 or P32. The asymmetric unit consists of three monomeric units (one in each chain), resulting in three crystallographically independent chains in the unit cell. The results show that two of the chains are interlocked through pyridine ring interactions whereas the third chain is less restricted. A statistical structure is proposed in which any two chains in the unit cell can be interlocked, provided they have the same sense. Such a situation permits a completely statistical structure in which half the chains in any crystallite are oriented upward and the other half downward.
Proton magnetic resonance studies of the phase structure of bulk‐crystallized linear polyethylene
Authors: Kitamaru R. , Horii F. , Hyon S.‐H.
Published: April 2003

The broad‐line proton NMR spectra of melt‐crystallized samples of polyethylene covering a very wide range in molecular weight have been analyzed in terms of contributions from three components: (1) a crystalline region with crystals of orthorhombic form; (2) a noncrystalline region with liquid‐like character which produces a Lorentzian contribution to the spectrum; and (3) an intermediate region in which the rotation of methylene groups about C—C bonds is partly hindered. The relative mass fractions as well as the character of these components depend greatly on the molecular weight. Samples of low molecular weight (e.g., ⩽30,000) are predominantly composed of lamellar crystalline regions with a minor amount of interfacial regions and no liquid‐like interzonal regions. As the molecular weight increases beyond 45,000, an interzonal region with a liquid‐like character associated with a higher molecular mobility is produced. Above a molecular weight of 100,000, this liquid‐like character becomes pronounced with an increase in molecular mobility in the interfacial region.
Models for spin relaxation in dilute solutions of randomly coiled polymers
Authors: Jones Alan Anthony , Stockmayer Walter H.
Published: April 2003

Models for the interpretation of magnetic relaxation in a randomly coiled macromolecule in dilute solution are considered. Expressions are given for the spin‐lattice relaxation time and the nuclear Overhauser enhancement resulting from modulation of the dipole–dipole interaction by three specific independent and mutually competitive types of macromolecular motion. Overall molecular rotation is characterized by a single exponential correlation time and internal anisotropic rotation by the well‐known Woessner theory. A simple description of backbone motion is presented based upon a three‐bond crankshaft motion and the concept of limited coupling among backbone bonds. The resulting correlation function is numerically similar to that recently proposed by Valeur, Jarry, Gény, and Monnerie from a somewhat different standpoint. Representative calculations for appropriate ranges of the model parameters are made for a 13C nucleus relaxing by heteronuclear dipole–dipole interaction with a single 1H nucleus.
Phenyl group rotation in polystyrene and the nature of twofold anisotropic internal rotation
Authors: Jones Alan Anthony
Published: April 2003

A review of the experimental evidence for phenyl group rotation in various polystyrenes and improvements in the interpretation of spin relaxation data for dilute solutions of randomly coiled polymers led to a new calculation of the correlation time for phenyl group rotation from nuclear magnetic resonance (NMR) data. Both 13C and 19F NMR data were reconsidered by using a model which includes motional modulation of the dipole–dipole interaction by overall rotatory diffusion, backbone rearrangements, and internal anisotropic rotation. The choice of a twofold potential to characterize local resistance to internal phenyl group rotation strongly influences the estimate of the rate of phenyl group rotation. The magnetic resonance data are found to be consistent with a correlation time for phenyl group rotation which is one to six times longer than the average correlation time for backbone rearrangement.
Measurement of pole figures and orientation functions for Valonia cellulose
Authors: Tanaka Fumio , Okamura Keizo
Published: April 2003

The x‐ray pole‐figure technique has been applied to the study of orientation in Valonia cellulose. It is found that the maximum of the orientation distribution of the (220) poles of crystallites in Valonia cell walls is precisely normal to the cell wall surface, and the pole population is denser in the longitudinal direction than in the transverse direction. The orientation is interpreted as a typical uniplanar‐axial orientation after Heffelfinger and Burton's classification: a uniplanar orientation in (220), and two types of uniaxial orientation in the (220) and (400) planes based on the unit cell parameters for Valonia cellulose. The degree of biaxial orientation of the (220), (220), and (400) plane normals as well as three principal crystallographic axes are shown by Desper's equilateral triangle plots.
Thermostimulated depolarization currents in thermorheologically simple materials
Authors: Solunov Ch. A. , Ponevsky Ch. S.
Published: April 2003

A theory is presented which makes possible the calculation of the dielectric parameters for a distributed dipole relaxation from thermostimulated depolarization current (TDC) data. The theory is applicable to dielectrics which obey the time–temperature superposition principle, i.e., for thermorheologically simple materials. The shift factor, the activation energy, the dielectric relaxation strength, the density of the isothermal displacement current, and the distribution function of relaxation times of the β relaxation in poly(methyl methacrylate) are calculated. The TDC investigations were carried out over the temperature range of −136 to 90°C. The values for the activation energy U = 26.4 kcal/mole and the dielectric relaxation strength Δϵβ = 2 are in good agreement with values obtained from dynamic measurements. A criterion for checking the validity of the time–temperature superposition principle by TDC is suggested.
In vacuo photocurrent measurements of plasma polymerized styrene films
Authors: Morita S. , Shen M. , Ieda M.
Published: April 2003

Photoconductivity measurements were carried out on plasma polymerized styrene (PPS) in vacuo, in air, and in subsequently re‐evacuated conditions. Samples with two gold electrodes (Au‐PPS‐Au) and gold‐aluminum electrodes (Au‐PPS‐Al) were used. Positive short circuit photocurrents in the direction of illumination were observed in both types of specimens. In the case of Au‐PPS‐Au, photocurrent threshold was about 1.6 eV in vacuo for the virgin film, which is attributed to the energy of hole generation in bulk. Residual free radicals were assumed to be the acceptors in this mechanism. In the case of Au‐PPS‐Al, electron injection from aluminum was thought to be a more likely mechanism, with an estimated barrier height of approximately 2.6 eV.
Molecular conformations in polyethylene after recrystallization or annealing at high pressures
Authors: Olley R. H. , Bassett D. C.
Published: April 2003

Information on molecular conformations inside polyethylene lamellas following high pressure treatments is obtained by comparing observed and predicted length distributions of nitrated samples. Three types of conformation are inferred. The commonest is that molecules are folded with chain ends included in lamellas, except that ends are not turned in by less than ∼600 Å from a surface. This situation accounts in detail for the previously observed agreement between the number fracture‐surface distribution of crystal thicknesses and the gel permeation chromatography (GPC) weight distribution following nitration. The second conformation, found especially for samples of low polydispersity, is also of folded molecules but with chain ends excluded from lamellas. This particular case justifies rigorously the initial assumption of folding. Finally there are examples where the molecular length distribution is substantially lower than the crystal thickness distribution, implying that molecular length is not the upper limit of crystal thickness and that molecules can be fully extended inside lamellas.
The fatigue process in highly oriented nylon 6 fibers
Authors: Narisawa Ikuo , Ishikawa Masaru , Ogawa Hiroyuki
Published: April 2003

The micromechanism of the fatigue process in highly oriented nylon 6 fibers is discussed on the basis of changes in mechanical and structural properties during fatiguing. Experimental results show that the fatigue process can be divided into two stages. The characteristic features in the initial period are increases in breaking strength, long period, and molecular orientation, and a reduction in dye penetration. In the second period, after about 500 cycles, breaking strength and orientation decrease slightly, and the long period, permanent strain, and dye penetration increase with duration of fatiguing. It is demonstrated that the structural changes mainly occur in the amorphous regions of the fiber structure. The structural and mechanical changes in the initial period lead to the conclusion that the initial cyclic strain causes strain hardening caused by extended tie chains which do not rupture. A combination of load bearing by tie chains and sliding motion of the fibrillar elements can explain the progressive degradation of the fiber during the second stage of fatiguing.
Segmental orientation in blends of poly(ϵ‐caprolactone) with poly(vinyl chloride) and nitrocellulose
Authors: Hubbell Douglas S. , Cooper Stuart L.
Published: April 2003

Binary blends of polycaprolactone (PCL) with poly(vinyl chloride) (PVC) and nitrocellulose (NC) have been shown to be compatible over a wide range of composition. In this study, segmental orientation was determined by dynamic, differential infrared dichroism for each component in the PVC and NC blends with PCL. In compatible amorphous blends, PCL orientation behavior was essentially the same as for the orientation of NC or the isotactic segments of PVC. Syndiotactic PVC segments showed higher orientations, reflecting the greater intrachain stiffness of the microcrystalline PVC phase. PCL segments in the blends where the PCL component was semicrystalline were found to exhibit orientation characteristics which were quite different from the orientation of the nitrocellulose and PVC components of the blends. By assuming that the NC orientation represented the response of the amorphous PCL, the orientation of the crystalline PCL was determined for a NC blend using a simple model of additive dichroism response. In PVC blends, a similar analysis using the amorphous‐component response of PVC was made. In both cases the results from the dichroism model showed fair agreement with the PCL unit cell C‐axis orientation from independent dichroism calculations.
A fiber composite model of highly oriented polyethylene
Authors: Barham P. J. , Arridge R. G. C.
Published: April 2003

A fiber composite model of highly drawn polyethylene is presented. Quantitative predictions and calculations are made using shear‐lag theory. The drawing process is shown to occur in two stages, a neck and a postneck taper. It is shown that there is an empirical linear relationship, with a high correlation, between the parameter x in shear‐lag theory (which involves the aspect ratio of the reinforcing elements and the square root of the ratio of matrix shear modulus to the Young's modulus of the reinforcing elements) and the 3/2 power of the taper draw ratio. It is concluded that crystalline fibrils (the reinforcing elements) deform homogeneously during the secondary, taper drawing process. The increase in aspect ratio resulting from this homogeneous deformation is held to be responsible for the increase in tensile modulus owing to the increased efficiency of the fibrils as reinforcing elements. The model is also used to explain the self‐hardening process exhibited by these fibers and, using measurements of density of hardened fibers, to predict that immediately after the neck the aspect (length to diameter) ratio of the crystalline reinforcing elements is ca. 2 and that the shear modulus of the matrix material in as‐drawn fibers is ∼103N/m2 and does not change significantly during the taper‐drawing process.
Light scattering studies of mixtures and fractions of linear polyethylene
Authors: Mandelkern L. , Go S. , Peiffer D. , Stein R. S.
Published: April 2003

Previous work on the small‐angle light scattering of polyethylene films, to determine the supermolecular structure, has been continued. One of the main efforts has been the study of a binary mixture whose low molecular weight component forms well defined spherulites and whose high molecular weight component yields a poorly defined rod‐like morphology. The addition of the high molecular weight fraction causes a progressive deterioration of the initial spherulitic morphology; a relatively small amount of the high molecular weight species causes a major decrease in the spherulitic size. However, there are no indications of any spherulitic structures when the weight fraction of the high molecular weight species is 0.5 or greater. The isothermal crystallization of a fraction M = 6.6 × 105 was also studied. Spherulites were formed at low crystallization temperatures while at the higher crystallization temperatures the morphology became nondistinct. Preliminary studies with solvents indicate that high molecular fractions, which do not form spherulites when crystallized in the pure state, do so when crystallized from highly swollen solutions.
Light scattering from epoxy‐elastomer resins: A study of statistical methods in heterogeneity analysis
Authors: Boisserie C. , Marchessault R. H.
Published: April 2003

The solid‐state light scattering from ABE (acrylonitrile butadiene epoxy) copolymers was studied as a function of rubber content by measuring the intensity distribution of scattered light under Vv polarization conditions. The range of heterogeneity has been quantified by the Debye–Bueche statistical treatment and by comparison with simulated scattering envelopes. The data indicate that below a critical rubber concentration of 20% the rubbery phase precipitates as spherical domains of nearly constant size. Phase inversion occurs at a rubber concentration of 20% and is accompanied by a maximum in polydispersity of the dispersed phase. Beyond this concentration, epoxidic domains are imbedded in a rubber and epoxy matrix. As a result of comparison of Debye–Bueche parameters with simulated values of these, it is concluded that the correlation distance is very sensitive to the presence of a small number of large particles.
A fourier transform infrared spectroscopic investigation of polyethylene single crystals. I. Methylene wagging mode
Authors: Painter P. C. , Havens J. , Hart W. W. , Koenig J. L.
Published: April 2003

The application of the spectral subtraction routine to the determination of the morphology of polyethylene single crystals is discussed in detail. An analysis of the CH2 methylene wagging mode is presented. A band at 1346 cm−1 is observed to be unique to polyethylene single crystals. The assignment of this band to a regular, tight fold structure is discussed.
Conformational study of isotactic poly[(S)‐5‐methyl‐1‐heptene] and poly[(S)‐2‐methylbutyl vinyl ether] by IR spectroscopy
Authors: Benedetti Enzo , Chiellini Emo
Published: April 2003

Infrared (IR) investigation of structurally analogous optically active polymers such as poly[(S)‐5‐methyl‐1‐heptene (1)] and poly[(S)‐2‐methylbutyl vinyl ether (2)] was carried out in the solid state, in the molten state, and in solution. Vibrational data are in accordance with the existence of helical conformations in solution and in the molten state for both polymers, confirming the previous suggestions based on optical rotation measurements. In particular, an accurate examination of the spectral region between 850 and 700 cm−1, where characteristic absorptions of the sec‐butyl group occur, enables us to assign the medium intensity band at 827 cm−1 (present in both polymers in the solid state) to the GTTG−T conformation of the side chains.
Effect of molecular orientation on the swelling of nylon 6
Authors: Inoue K. , Hoshino S.
Published: April 2003

The effect of molecular orientation on the linear swelling of nylon 6 caused by absorption of water was studied using two kinds of oriented films, melt drawn and cold drawn. The molecular orientation causes anisotropy in swelling at all humidities such that the swelling is larger in the orientation direction than in the directions perpendicular to it. The large contribution of crystalline orientation to this phenomenon was expected for the melt drawn film which has practically no amorphous orientation. An analysis with a two‐phase morphological model reveals that the distance between the crystallites is a prominent factor controlling the degree of linear swelling, and that the anisotropy of swelling arises from the change in the distribution of crystallites due to orientation. By comparing the result for the melt drawn film with that for the cold drawn film, which has considerable amorphous orientation, it was proven that molecular orientation in the amorphous phase where swelling actually occurs does not depend so much on the degree of swelling as on the distribution of crystallites.
Configurational properties of aromatic polyesters: Dipole moments of poly(diethylene terephthalate) chains
Authors: Riande E.
Published: April 2003

Dielectric constants have been determined for a fraction of poly(diethylene terephthalate) in benzene at several temperatures. The data indicate that the dipole moment ratio 〈μ2〉/Nm2 is somewhat higher than that of poly(ethylene oxide), and its temperature coefficient is in the vicinity of zero. Both the dipole ratio and its temperature coefficient are in very good agreement with those predicted by the rotational isomeric state theory. Using this theory, the unperturbed dimensions of poly(diethylene terephthalate) were calculated and it was found that (〈r2〉/M)∞ = 0.80 Å2 (g mol wt)−1, a value intermediate between those of poly(ethylene oxide) (0.57) and poly(ethylene terephthalate) (1.05).
Dimensional changes in ultradrawn polyethylene
Authors: Capiati Numa J. , Porter Roger S.
Published: April 2003

Samples of ultradrawn high density polyethylene were studied by thermomechanical analysis. The purpose was to study the dimensional changes in polyethylene morphologies of extreme orientation. Dimensional changes were measured from −140 to +70°C with a precision of better than 1%. A negative thermal expansion coefficient was observed along the length (c axis) of the fibers containing the polyethylene morphologies of extreme orientation. A change in negative coefficient is observed between −35 and −45°C. The sign and magnitude of the expansion coefficient confirm, along with other evidence, the existence of extended chain structures in these morphologies. A series‐parallel model has been developed for the ultradrawn polyethylenes to describe the dimensional changes with temperature.
Unperturbed dimensions of random and alternating styrene/n‐alkyl methacrylate copolymers
Authors: Podešva J. , Bohdanecký M. , Kratochvíl P. , Samay G.
Published: April 2003

The steric factors σ of homopolymers of ethyl, n‐butyl, and n‐octyl methacrylate, of equimolar random and alternating copolymers of these monomers with styrene, and of polystyrene, were determined by measuring intrinsic viscosities in a good solvent (butanone, 25°C) and extrapolating the data thus obtained to zero molecular weight of the polymer. For all comonomeric pairs under investigation, the σ2 of an equimolar random copolymer and, particularly, of an alternating copolymer, is higher than the arithmetic mean (σ + σ)/2 of the σ2 values of the parent homopolymers. The positive deviation from the linear dependence of σ2 on the copolymer composition, expressed as an increment of σ2, is proportional to the mole fraction of alternating dyads in the copolymer chain with in the limits of experimental error. The effect of copolymer microstructure on the unperturbed dimensions of the chains has been compared for equimolar copolymers of styrene with methyl, ethyl, n‐butyl, and n‐octyl methacrylate by using a relative increment ξ defined as the ratio of σ2 of the alternating copolymer to (σ + σ)/2. The dependence of ξ on the number of carbon atoms in the alcohol substituent of the methacrylate component of the copolymer seems to exhibit a maximum for ethyl methacrylate.
Stress‐induced diffusion of macromolecules
Authors: Tirrell Matthew , Malone Michael F.
Published: April 2003

A framework for analysis of stress‐induced diffusion is presented. Diffusion of macromolecules is considered to be driven by gradients of entropic potential arising from distortion of the molecular conformation by deformation, as well as by gradients of concentration of individual molecular weight species. Resulting concentration profiles in circular capillary flow have been calculated for a system containing a single macromolecular species. Significant variations in concentration with capillary radius are predicted at full development. Estimates of the dynamics of development of these profiles indicate that the length to diameter ratios needed to see a measurable effect are proportional to the Peclet number, which may be quite large for macromolecular fluids depending on the geometry and flow velocity of the system. This effect may have implications in the rheology, chromatography, and technological uses of macromolecular fluids.
Power law relationship between yield stress and shear modulus for glassy polymers
Authors: Kitagawa M.
Published: April 2003

The published data on the yielding of glassy polymers under a variety of testing conditions reveal that the yield stress increases with the elastic modulus. However, fundamental understanding of the interrelation has not yet been established. In this paper, a power law relation between the shear yield stress τy and the shear modulus G is presented: T0τy/Tτy0 = (T0G/TG0)n, where T is the absolute temperature, T0. is reference temperature, and τy0 and G0 are, respectively, the shear yield stress and the shear modules at T0. The exponent n takes a value 1.63 for amorphous polymers without exception, whereas it is about 0.8–0.9 for crystalline polymers. The exponent 1.63 for amorphous polymers is in good agreement with the value derived from the approximation of the Bowden–Raha dislocation analog. This law may enable us to investigate a model for the yielding of glassy polymers.
Investigation of heterogeneities in solid polyethylene by small angle neutron scattering
Authors: Ullman Robert , Summerfield George C. , King John S.
Published: April 2003

Small angle neutron scattering was applied to the investigation of heterogeneities in solid poly‐ethylene. The heterogeneities arise from the contrast between amorphous and crystalline regions and also from the presence of a small fraction of voids. The method is easily put on an absolute basis by calibration with an incoherent scatterer, in this case, cyclohexane.
Texture and molecular chain mobility in cold‐deformed linear polyethylene
Authors: Arai Hidehiko , Hayakawa Naohiro , Tamura Naoyuki , Kuriyama Isamu
Published: April 2003

The fine texture and molecular motion in rolled (draw ratios λ = 2, λ = 5), cold‐drawn (λ = 6), and hot‐drawn (λ = 6), linear polyethylene (Sholex 6050) films were studied by small‐angle x‐ray scattering, wide‐line nuclear magnetic resonance (NMR), and dynamic viscoelastic measurements. NMR spectra of the rolled (λ = 5) and cold‐drawn samples show a small narrow component at room temperature. For these cold‐deformed samples, a gradual decrease in the second moment is observed well below the α relaxation temperature and a new relaxation appears in the same temperature region in the logarithmic decrement versus temperature. This relaxation is absent in the original and hot‐drawn samples. It is concluded that the new relaxation arises from molecular motion in intermediate regions where molecular chains are less mobile than in the amorphous state.
Étude par rayons X de copolymères téléchéliques butadiène acide méthacrylique
Authors: Moudden A. , Levelut A. M. , Pineri M.
Published: April 2003

The telechelic polybutadiene–methacrylic acid copolymer (Hycar CTB) containing 2 mole percent acid and neutralized (5–100%) by alkali ions, Na+, K+, and Cs+, has been studied by small‐angle x‐ray scattering. Salt groups form clusters, and the average value of the radii of gyration is approximately 8 Å; this value seems to be independent of the nature of the cation and the degree of neutralization. The existence of a low‐angle maximum in the scattering intensity gives evidence of a mean distance of 80 Å between clusters in the fully neutralized sample. This distance increases slightly with a decreasing degree of neutralization. A more precise analysis of the small‐angle scattering curve gives further information on the cluster structure: the ionic groups may form small bilayer disks while the polymer chains maintain a regular distance of 80 Å between the disks.
Green's function analysis of the vibrational spectra of polymer chains. I. Several approaches to the problem
Authors: Kozyrenko V. N. , Kumpanenko I. V. , Mikhailov I. D.
Published: April 2003

Various methods of solving the dynamical equation for defect polymers are discussed. It is shown that the Green's function (GF) can be conveniently used to reduce the order of the characteristic equation to the number of the degrees of freedom of a repeat unit in the case when the perturbation caused by each of the defects is localized within it. In the general case, the order of the reduced determinant depends on the range of the interaction forces between the defect unit and the regular chain.

For a polymer chain containing one or two defect units, the Green's function method allows us to obtain the exact solution of the dynamical equation, while for a high concentration of randomly distributed defect units various approximation methods can be used. As a possible approach to the solution of the latter problem we suggest using either one of the versions of the perturbation theory (the dilute limit, the coherent potential approximation) or the cluster approximation.
Quasielastic scattering of neutrons from freely jointed polymer chains in dilute solutions
Authors: Akcasu A. Ziya , Higgins Julia S.
Published: April 2003

Starting with Kirkwood's Fokker–Planck equation for the polymer configuration‐space distribution function and using the Zwanzig–Mori projection operator technique we have calculated the scattering law S(q,w) for a freely jointed model polymer chain in a dilute solution. When memory effects are neglected, the theory predicts a Lorentzian for S(q,w) with a halfwidth Ω(q), which we have determined as a function of the momentum transfer q for all values of q. The results are compared with recent neutron scattering experiments on deuterated polytetrahydrofuran and polystyrene in dilute solution in CS2. It is found that the observed q dependence of Ω(q) is represented satisfactorily by the present theory with a bond length b of about 6.3 Å for polystyrene and 3.8 Å for polytetrahydrofuran, and a friction coefficient ζ = 4πη0b where η0 is the viscosity of the solvent.
Deformation mechanisms of constrained polymer chains. II. Deformation energetics of tie molecules
Authors: McCullough R. L. , Eisenstein A. J. , Weikart D. F.
Published: April 2003

Energy‐deformation characteristics for the primary T, S, and U conformational units of tie molecules were obtained from the analysis of data generated from a constrained minimization algorithm. Energy‐deformation profiles (covering the range from compact equilibrium defect structures to the fully extended chain) are reported for the S0 and S1 members of the Sλ family and for the U00 member of the Umn family. Estimates of the energy content V0 and the elastic modulus E were obtained from the computed energy‐deformation data in the vicinity of the equilibrium Structure—S0 → {60°, 180°, −60°}, V = 1.7 kcal/mole, E = 60 kcal/cm3 [250 × 1010 dyn/cm2];S1 → {60°, 180°, 180°, 180°, −60°}: V = 1.7 kcal/mole, E = 25 kcal/cm3 [100 × 1010 dyn/cm2]; and U00 → {60°, 180°, 60°, 180°, 60°}: V = 2.7 kcal/mole, E = 80 kcal/cm3 [340 × 1010 dyn/cm2]. Although the elastic modulus of the U00 unit is comparable to the elastic modulus of the fully extended chain, the highenergy content of this unit (V0 = 2.7 Kcal/mole) prohibits a significant population and thereby mitigates an appreciable reinforcing effect from this rigid unit. A model for a surrogate force constant is introduced to generalize the results from this study to any member of the Sλ or Umn family as well as any combination of Sλ and Umn units. This generalization provides a basis for estimating the deformation characteristics of tie molecules comprised of various populations of these primary conformational building blocks.
Low‐temperature relaxations in styrene‐crosslinked polyester networks. III. Influence of water concentration and chemical structure on the γ relaxation
Authors: Cook Wayne D. , Delatycki O.
Published: April 2003

The intensity of the water‐induced γ relaxation (see ref. 1) in crosslinked polyester networks in creases rapidly at low water concentrations (0 to 0.5% by weight). At higher water concentrations (0.5 to 3.0%) the intensity of the γ relaxation approaches a constant value. The shift of the relaxation peak to lower temperatures shows a similar pattern of behavior. These results have been related to the fraction of water involved in the relaxation and the changing nature of the relaxation sites with the increase in water concentration. The important role that fumarate units play in the γ relaxation has also been confirmed; however, the chemical nature of the relaxing unit appears to be more complex than was originally considered. Two models are proposed for this behavior.
ESR study of pressure and temperature dependence of free‐radical decay in poly(vinyl chloride)
Authors: Szöcs F. , Klimová M.
Published: April 2003

Gamma‐irradiated poly(vinyl chloride) was annealed at various temperatures (80 to 140°C) and pressures (0.1 to 800 MN m−2). Rate constants and activation volumes of free‐radical decay were determined from the changes of the electron spin resonance (ESR) spectra before and after annealing. The pressure and temperature dependence of the rate constant is compared with the pressure and temperature dependence of the mechanical relaxation parameters. The correlation between the kinetics of radical reactions and the kinetics of the molecular motions in the α‐relaxation region is discussed.
Electron microscopic study of dendritic growths on the anode during prebreakdown conditions in an organic residual gas
Authors: Moretti Paul , Mesnard Guy
Published: April 2003

Anodic growths on tungsten electrodes as a result of an applied electrostatic field with an atmosphere of benzonitrile (from about 5 × 10−4 to 10−5 torr) are studied as a function of many parameters. In order to observe the growth phenomena at high resolution in situ, the experiments were performed in an electron microscope. The growth rate of the dendrites is found to be irregular; an expression for dependence on the electric field is proposed to explain the evolution of needle length versus time t:

The mechanism of branching is also discussed.
Conformational behavior of styrene–p‐chlorostyrene triblock copolymers in dilute solutions. I. Composition dependence of conformational behavior
Authors: Shima Mikiko , Ogawa Etsuyo , Ban Seiko , Sato Mari
Published: April 2003

Dilute solution properties of (styrene‐p‐chlorostyrene) triblock copolymers in various solvents were studied over a wide range of molecular weight and composition. Viscosity and osmotic pressure results indicate that the conformational behavior of the BmAnBm and AmBnAm copolymers (A = styrene; B = p‐chlorostyrene; m and n denote the number of units) are similar in nonselective solvents such as toluene and 2‐butanone, but different in selective solvents such as carbon tetrachloride and cumene. Short‐range and long‐range interaction parameters of the block copolymers were determined by applying the Stockmayer–Fixman method to viscosity data and also by application of the equation relating the osmotic virial coefficient and the excluded volume. The results show that the unperturbed dimensions of the block copolymers vary linearly with composition, and long‐range interaction parameters in nonselective solvents can be expressed by those of the parent homopolymers, the chemical composition, and values of the interaction parameter βAB between styrene and p‐chlorostyrene monomeric units.
Interaction between styrene–ethylene oxide block copolymers and sodium lauryl sulfate in aqueous solution
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami
Published: April 2003

Interactions of water‐soluble AB block copolymers of polystyrene and poly(ethylene oxide) with sodium lauryl sulfate (SLS) in aqueous solution were investigated by high‐resolution proton magnetic resonance (NMR). The viscosity in aqueous SLS solution was also measured. From the NMR results in D2O, it appears that molecular motions of the polystyrene blocks of the copolymer in aqueous solution are activated by interaction between the polystyrene blocks and the added SLS. From solution viscosity, on the other hand, it is apparent that a complex is formed between the copolymer and SLS and that it exhibits typical polyelectrolyte properties. The polyelectrolyte character is attributable largely to intrachain repulsions between like charges of the SLS anions adsorbed on the poly(ethylene oxide) blocks of the copolymers since the polystyrene blocks are insoluble in water and the styrene content is less than 10%.