bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluorescence depolarization in polymers: The microviscosity of bulk polybutadiene and of solutions in cyclohexane
Authors: Barkowski D. , Mersch W. , Dorfmüller Th. 
Published: April 2003

AbstractThe reorientational relaxation of 9‐cyananthracene fluorescent label molecules has been measured in bulk polybutadiene and solutions with cyclohexane by a fluorescent depolarization technique. The procedure adopted consists in the incorporation of an Arrhenius temperature dependence of the orientational relaxation time in the Perrin equation, thus obviating the necessity of an independent determination of the intrinsic polarization ratio P0 and enabling one to obtain the preexponential factors and the activation energies of the reorientational relaxation times. The most noteworthy result in our view is the validity of the Arrhenius equation for the effective microviscosity as opposed to the validity of the Fulcher–Vogel–Tamann equation with a glass point of T0 = 136 K for the shear viscosity of a polymer solution (90%).
A study of the PE–PTFE system. II. ESCA measurements
Authors: Nagarajan S. , Stachurski Z. H. , Hughes M. E. , Larkins F. P. 
Published: April 2003

AbstractSamples of polyethylene and polytetrafluorethylene were sintered at 200°C. The samples were cleaved and cut, and the two types of surfaces were studied by ESCA. The possibility of chemical interaction between the two polymers and the formation of a transitional layer is postulated on the basis of the results. A morphological model of the structure of these samples is given.
Single crystals of cellulose IVII: Influence of the cellulose molecular weight
Authors: Buleon A. , Chanzy H. , Froment P. 
Published: April 2003

AbstractThe influence of the degree of polymerization (DP) of cellulose was evaluated in the preparation of micron‐sized cellulose IVII lamellar crystals in order to ascertain whether a regular chain‐folded morphology could develop during their growth. For this purpose, sharp fractions of cellulose acetate were collected by preparative gel permeation chromatography. Aliquots of these fractions were deacetylated and crystallized in dilute solutions containing water, methylamine, and DMSO, and held at 150°C under pressure. Well‐developed cellulose IVII lamellar crystals were obtained with fractions of DP 22–24 whereas higher‐DP material gave polycrystalline aggregates. This behavior indicates that large lamellar crystals of cellulose IVII can be obtained only with unfolded short cellulose chains. The occurrence of chain‐folded crystals with high–DP cellulose samples cannot be demonstrated.
Structural studies of ultrahigh‐modulus polyethylene using nitric acid etching and gel permeation chromatography. II. Influence of polymer molecular weight, draw temperature, and annealing
Authors: Capaccio G. , Ward I. M. 
Published: April 2003

AbstractThe technique of nitric acid etching followed by gel permeation chromatography has been used to determine the crystal length distribution in ultrahigh‐modulus polyethylenes. The crystal length distribution has been studied as a function of draw ratio, polymer molecular weight, processing conditions, and annealing. The results confirm that although there is a considerable broadening of the crystal length distribution on drawing, the majority of crystals have lengths less that 500 Å. There are detailed changes in the length distribution due to changes in draw temperature, molecular weight, and annealing which are not always reflected in corresponding changes in the long period determined from small‐angle x‐ray scattering. Possible reasons for these discrepancies are discussed.
Solution behavior of metal sulfonate ionomers. II. Effects of solvents
Authors: Lundberg R. D. , Phillips R. R. 
Published: April 2003

AbstractPrevious studies on the dilute‐solution behavior of sulfonated ionomers have shown these polymers to exhibit unusual viscosity behavior in mixed solvents of low polarity. These results have been interpreted as arising from specific solvation effects by the solvents with the metal sulfonate groups which persist as ion pairs. The consequences of ion pair interactions and their solvation are exceptional thickening behavior at low polymer levels as compared to unfunctionalized polymers, and anomolous solution viscosities with varying temperature. These studies have now been extended to single‐component solvents which traverse a range of polarities. Using the sodium salt of lightly sulfonated polystyrene (S‐PS) as a model system, the authors found the solution behavior in low‐polarity solvents (tetrahydrofuran) to be consistent with that observed previously for mixed solvents; ion pair interactions predominated. However, in polar solvents such as dimethyl sulfoxide or dimethyl formamide, these polymers behave as classic polyelectrolytes even at sulfonate levels below 2 mol %. The behavior of the S‐PS acids is similar to that observed for the metal salts. To a first approximation these two behaviors, ion pair association and polyelectrolyte behavior, are dependent on solvent polarity. In some cases it is possible to induce polyelectrolyte behavior in a S‐PS/solvent combination exhibiting ion pair interactions by the addition of very low levels of a polar cosolvent, such as water. These results again demonstrate the selectivity of the solvent‐sulfonate interactions.
Effect of substituents in the styrene ring on the dynamic mechanical relaxations of a styrene‐crosslinked unsaturated polyester resin
Authors: Douglas William , Pritchard Geoffrey 
Published: April 2003

AbstractThe dynamic mechanical properties of a series of polyester resins made from a maleic/phthalic anhydride‐based unsaturated polyester crosslinked with each of styrene, 4‐methyl styrene, 4‐ethyl styrene, 4‐n‐butyl styrene, 4‐isopropyl styrene, tertiary butyl styrene, 4‐chlorostyrene, and 3,4‐dichlorostyrene were studied. The order of the α transition temperatures was as expected from that for the homopolymers, except in the case of the chlorostyrenes, for which dipolar interactions with the polyester chain may be important. The styrene bridges appeared to be involved in a steric interaction (and in the case of the chlorostyrenes, a dipolar interaction) with the β relaxing ester species. It is suggested that both the γ and γ′ relaxations involve similar interactions between the matrix and the relaxing moieties. For the 4‐n‐butyl styrene resin, an additional relaxation below −170°C was observed, and is ascribed to relaxation of the n‐butyl group.
Calculation of the nonlinear stress of polymers in oscillatory shear fields
Authors: Helfand Eugene , Pearson Dale S. 
Published: April 2003

AbstractComplex moduli are calculated for the lowest‐order deviations from linearity of the stress in an oscillatory shear field. The calculations involve solution of an equation, recently proposed by Doi, which goes beyond the “independent alignment approximation” of the Doi‐Edwards theory of polymer dynamics. The new equation incorporates various reptative motions of a polymer in the effective constraining tube induced by entanglements, viz. Brownian motion along the tube and the systematic motion in response to changes in the length of the tube accompanying affine deformation.
Additive moduli for crosslinked epoxies
Authors: Hartmann Bruce , Lee Gilbert 
Published: April 2003

AbstractUltrasonic measurements were made on a series of eight crosslinked polyepoxides over the temperature range from 0 to 60°C at a frequency of 2 MHz. From these measurements the bulk (K) and shear (G) moduli were calculated. These data were then analyzed in terms of molecular component properties. Proceeding by analogy with Rao's rule for liquids, the authors found that K is not an additive property but the function U = V(K/ρ)1/2γ is an additive property. Here V is molar volume, ρ is the density, and γ is the Gruneisen parameter (for interchain vibrations). A similar relation was found to hold for shear modulus. In particular, G is not an additive property but W = V(G/ρ)1/2g is an additive property, where g = (1/2α) (∂ InG/∂T)p – 1/2 is the shear analog of the Gruneisen parameter. Using U and W, calculations were made of K and G as functions of temperature for the eight epoxies. These results agree with the measured values within the experimental uncertainty of the measurements.
Distribution spatiale des dommages produits par les ions Kr (1 MeV/amu) et Cl (1 MeV/amu) dans le triacétate de cellulose
Authors: Moliton J. P. , Boutinaud C. , Decossas J. L. , Vareille J. C. , Teyssier J. L. , Delaunay B. 
Published: April 2003

AbstractOur earlier results on ασ and heavy‐ion‐radiation damage in cellulose triacetate (CTA) are compared with those of previous authors on UV‐and γ‐radiation damage in the same material. Thus the common effects of these different methods of irradiation can be distinguished from those characteristic of the radiation employed. With heavy‐ion radiation the production of stable radicals is accompanied by C—O cleavage. In the case of Kr (1 MeV/amu) ions, the number of free radicals produced is investigated, without distinguishing the species, by using the scavenger technique in the solid phase, combined with UV spectroscopy. On the other hand, C—O cleavage is observed by IR spectroscopy, with its inherent selectivity. A statistical study shows that the experimental curves representative of the evolution of the optical transmittance ratio before and after irradiation L(N) versus the ion fluence N are of exponential type:

where β is a parameter related to the volume damaged by a single ion and, therefore, to the latent track size. The latter is approximated by a cylinder whose height is equal to the range of the ion. For Kr8+ (1.1 MeV/amu) the track length is 21 μ. For each type, damages are localized within a radius of 250 Å for free‐radical yields, 148 Å for cellulosic chain cleavages, 108 Å for deacetylation, and 100 Å for opening of pyrannosic rings. The track length is 14 μ for Cl6+ (1 MeV/amu), while the radius of the cylinder in which free radicals are produced is only 80 Å.
Observations par microscopie électronique de traces d'ions lourds dans le triacétate de cellulose
Authors: Vareille J. C. , Decossas J. L. , Moliton J. P. , Teyssier J. L. , Delaunay B. 
Published: April 2003

AbstractTracks of heavy charged particles have been observed in cellulose acetate by conventional electron microscopy (100 kV) and by high voltage microscopy (1, 2 MV). The tracks are formed of successive islets following each other at distances of 70‐150 Å. With the evolution of the diameter of these zones is shown the existence of a highly perturbed cylindrical volume (diameter 400 Å for the case of krypton) corresponding to regions in which free radicals have been created. The different techniques used do not allow observation of the latent track because of the complications of energetic phenomena: the electron beam current density being limited, the contrast is small and hence the resolution is restricted.
Pressure‐volume‐temperature properties of blends of poly(2,6‐dimethyl‐1,4‐phenylene ether) with polystyrene
Authors: Zoller P. , Hoehn H. H. 
Published: April 2003

AbstractThe pressure‐volume‐temperature (PVT) properties of blends of poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPO) with polystyrene (PS) have been studied experimentally in both the glassy and melt states at 0, 20, 40, 50, 60, 80, and 100% PPO content. In all compositions a strong glass transition was observed varying linearly with composition. For all but the 40% PPO composition this was the only transition, indicating molecular compatibility of the components in these blends. The 40% PPO composition showed a very weak second transition near the glass transition of pure PS. A small amount of phase separation may have occurred in this blend. The data for the glassy and melt states were fitted to an empirical equation of state based on the Tait equation. The volume of the melts at constant pressure and temperature showed a virtually linear dependence on composition. Any negative excess volume of mixing compatible with the data would have to be very small, smaller than expected from previous measurements in the glassy state. Various properties relating to the glassy and melt states and to the glass transition were evaluated and are discussed as a function of composition. It was found that most properties of the glasses could not be modeled by simple functions of composition.
Theoretical equation of state of polymer blends: The poly(2,6‐dimethyl‐1,4‐phenylene ether)–polystyrene pair
Authors: Jain R. K. , Simha R. , Zoller Paul 
Published: April 2003

AbstractA recent theory of multicomponent fluids is applied for the first time to a compatible binary polymer blend. Good accord between the experimental pressure‐volume‐temperature measurements over the whole range of compositions by Zoller and theoretical predictions obtains. In particular, satisfactory predictions of high pressure from low‐pressure information result. From the interplay between experiment and theory, the scaling quantities and thus the characteristic self‐ and cross interaction parameters are derived. The excess volumes are discussed and estimates of excess enthalpies presented. The theory predicts the actual enthalpy of the components or mixtures once the scaling parameters have been determined by means of volume‐temperature data at atmospheric pressure. Enthalpy measurements to test these predictions are highly desirable.
Crystalline order in polyethylene: A 13C NMR CP/MAS solid‐state T1 study
Authors: Axelson D. E. 
Published: April 2003

AbstractThe carbon‐13 spin‐lattice relaxation times T1 of the crystalline components of four solid ethylene‐octene copolymers have been studied as a function of thermal history, branching number, and branching distribution. Slowly cooled samples (1 deg/min from melt to room temperature) exhibited similar or longer T1s with respect to the same sample quench cooled (from the melt into 20°C water). The greater the degree of branching and the more homogeneous the branching distribution, the shorter were the observed crystal lattice T1s. Differences of up to a factor of 3 in T1 were observed for the same sample undergoing the two thermal treatments. Different degrees of branching homogeneity (for the same total number of branches) resulted in differences approaching a factor of 7 for samples with the same thermal history. These variations were attributed to the differing effects of side‐chain disruption of the crystal lattice.
Stress response and energy dissipation in a linear viscoelastic material under periodic triangular strain loading
Authors: Yang Ting Qing , Chen Yu 
Published: April 2003

AbstractA general equation is derived for the stress response of a linear viscoelastic material to periodic strain excitation at constant strain rates. The energy dissipated in any cycle, especially in a steady‐state loop, is discussed. The results can be used to analyze test results in determining mechanical properties of polymers. A simple Maxwell model and a three‐parameter Maxwell model are used to illustrate the calculation of stress response and energy dissipation under constant‐strain‐rate loading.
Small‐angle x‐ray and neutron scattering studies of amorphous polymer blends
Authors: Russell T. P. , Stein R. S. 
Published: April 2003

AbstractDilute mixtures of poly(ε‐caprolactone) (PCL) in poly(vinyl chloride) (PVC), poly(p‐iodostyrene) (PpIS) in polystyrene, and deuterated polystyrene (d‐PS) in protonated poly(o‐chlorostyrene) (PoCIS) were investigated by means of small‐angle x‐ray scattering and small‐angle neutron scattering. The radii of gyration of PCL in PVC and of d‐PS in PoCIS were found to be expanded over the θ values by 50 and 30%, respectively. Values of the second virial coefficient were positive although errors prevented definitive evaluation of the interaction parameter. PpIS was found to aggregate, with both the radius of gyration and molecular weight increasing with concentration. Concentrated mixtures of PCL and PVC were also investigated by using the Debye–Bueche correlation function analysis. Correlation distances indicated good mixing throughout the entire composition range.
Affinity of a hindered phenol antioxidant for reagents in hydrocarbon media: A low‐temperature dielectric relaxation study
Authors: Gilchrist John Le G. 
Published: April 2003

AbstractLow‐temperature dielectric loss measurements reveal a tendency of 4‐methyl‐2, 6‐di‐tert‐butyl phenol (the antioxidant BHT) to associate with various reagents in hydrocarbon media. The affinity with carbonyl groups appears to be particularly appreciable. It is suggested that this may have a bearing on the antioxidant activity of this type of compound.
NMR spectroscopic, osmometric, and viscometric study of association of syndiotactic poly(methyl methacrylate) in dilute solutions
Authors: Spěváček J. , Schneider B. , Bohdanecký M. , Sikora A. 
Published: April 2003

AbstractAssociation of syndiotactic (s) poly(methyl methacrylates) (PMMAs) in toluene, benzene, and acetonitrile has been studied by NMR spectroscopy, osmometry, and viscometry. It was found that in solutions of highly syndiotactic PMMA in toluene, most of the polymer exists in the associated state. Association takes place by means of stereospecific intermolecular and intramolecular interactions of long parallel syndiotactic sequences. The minimum length of syndiotactic sequences necessary for association of s‐PMMA in toluene is 7–8 monomer units. Viscosity data indicate that in dilute solutions the associated structures appear as large formations which do not have the character of compact particles. The formation of the aggregates of PMMA is a relatively slow process. A model of the structure of the aggregates of s‐PMMA in toluene is proposed. As compared with that in toluene, the tendency to aggregation in benzene and acetonitrile is negligible. Integral parameters currently used for the characterization of polymer‐solvent interaction, like “good” or θ solvent, are not suitable for predicting the tendency of s‐PMMA to aggregation. The formation of aggregates evidently has some connection with the effect of the solvent upon the conformational structure of syndiotactic sequences.
Diffusion‐controlled growth of lamellar crystals in an isotactic polystyrene–polyphenylene oxide blend
Authors: Hachmann U. , Petermann J. 
Published: April 2003

AbstractThe growth rates of lamellar crystals grown onto preseeded fibrillar crystals (“shishes”) in isotactic polystyrene and blends of isotactic polystyrene (iPS) with polyphenylene oxide are followed by using transmission electron microscopy. The preseeded fibrillar crystals avoid the problem of timedependent primary nucleation. The time dependence of lamellar growth is investigated. At a concentration of 50% PPO in iPS, the lateral lamellar growth rate of the precipitating isotactic polystyrene crystals conforms to a time law characteristic of diffusion‐controlled growth (R ∝ t1/2). Diffusion coefficients are estimated from the growth kinetics. The method could prove a simple means of measuring diffusion coefficients in polymer blends in which one component is crystallizable.
The effect of interlamellar forces on the longitudinal acoustic mode of polyethylene crystals
Authors: Runt J. , Hanrahan B. D. , Harrison I. R. 
Published: April 2003

AbstractThe fold periods and longitudinal acoustic modes [LAMs] for isothermally crystallized polyethylene (PE) single crystals were determined in the dried state and in the presence of decalin and silicone oil. Upon swelling with decalin, the fold period increased by 7% while the LAM peak frequency decreased by approximately 1 cm−1. Several possible explanations for the change in LAM frequency are discussed but the exact interpretation is open to question. No change in fold period was observed upon soaking a dried crystal mat in silicone oil. This fold period invariance along with the fact that silicone oil has no effect on the melting point of PE crystals indicates that there is no significant interaction between the oil and the methylene groups on the crystal surface. The effect of suspending crystals (which have never been dried down) in silicone oil should only be to increase the average interlamellar distance and, therefore, to reduce any interlamellar forces. It is shown that the LAM peak frequency for crystals suspended in silicone oil is the same as that for the dried crystals, indicating that interlamellar forces do not exert a significant perturbing influence on the LAM of polyethylene crystals.
A new look at the crystallization of polyethylene. II. Crystallization from the melt at low supercoolings
Authors: Chivers R. A. , Barham P. J. , Martinez‐Salazar J. , Keller A. 
Published: April 2003

AbstractThis article is part of the general project laid out in Part I (ref. 9) and is concerned with obtaining information on primary (unthickened) crystals of polyethylene formed at low supercoolings. For this, a technique had to be devised by which crystallization could be speeded up so as to eliminate or at least reduce lamellar thickening. Indeed we were able to increase the rate of crystallization by an order of magnitude using a technique which we have called enhanced self‐nucleation. Using this technique we find that when viewed under an optical microscope, spherulites crystallize uniformly over the field of view, and not, as is usual, by a radial growth process. Isothermal crystallization in bulk linear polyethylene has been studied by means of the enhanced self‐nucleation technique as a function of crystallization time by using Raman LAM and melting points to assess variations of fold length Data have been obtained at very much shorter times than before. At short times, we find a constant fold length; at longer times the crystals thicken linearly with the logarithm of time. Values of the initial fold length for crystallization temperatures between 118 and 130°C are presented. Associated with the thickening at short times we find an induction time which increases with temperature.
Highly conductive meta derivatives of poly(phenylene sulfide)
Authors: Elsenbaumer R. L. , Shacklette L. W. 
Published: April 2003

AbstractChanges in the backbone structure of several meta derivatives of polyphenylene sulfide upon doping with AsF5 have been investigated by IR spectroscopy. Poly(m‐phenylene sulfide) does not form a conducting complex with AsF5 unless reacted under conditions where carbon‐carbon bonds form intramolecularly between phenyl rings. This assertion has been verified by comparison of the IR spectra of poly(m‐phenylene sulfide) and a newly synthesized derivative, poly(thio‐3,7‐dibenzothiophendiyl), after doping with AsF5. This new derivative forms a complex with AsF5 which exhibits a conductivity of 18.5 S/cm. A sulfone‐containing derivative has also been synthesized, poly[thio‐3,7‐(dibenzothiophene‐5,5‐dioxide)‐diyl]. With this polymer, a much lower conductivity, 10−3 S/cm, was obtained after exposure to AsF5.
Bisphenol‐A polycarbonate–poly(butylene terephthalate) transesterification. I. Theoretical study of the structure and of the degree of randomness in four‐component copolycondensates
Authors: Devaux J. , Godard P. , Mercier J. P. 
Published: April 2003

AbstractThis article is the first of a series devoted to various aspects of exchange reactions in molten bisphenol‐A polycarbonate–poly(butylene terephthalate) mixtures. The statistical aspects of exchange reactions between two polycondensates of different chemical structure are considered. This theoretical approach enables us to calculate the mean lengths of the various sequences as well as several expressions for the degree of randomness in four‐component copolycondensates from triad or dyad concentrations as determined by NMR spectroscopy.