bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of high speed electrons on the structure of polyethylene terephthalate
Authors: Slovokhotova N. A. , Sadovskaya G. K. , Kargin V. A.
Published: April 2003

Polyethylene terephthalate (PET) films were irradiated with high speed electrons in vacuo. Their infrared spectra, solubility, and degree of swelling in o‐chlorophenol were measured as a function of the irradiation dose. The investigation has shown that irradiation causes both crosslinking and degradation. In the absence of air, crosslinking predominates over chain scission. The irradiation dose required for crosslinking of PET by far exceeds that required for crosslinking of polystyrene. Irradiation of PET is accompanied by the formation of polyphenyl systems. The initial partly crystalline PET becomes completely amorphous on irradiation. Irradiation causes isomerization of O(CH2)2O groups in the polymer chain from the trans to the gauche form. Isomerization of O(CH2)2O groups under irradiation may be interpreted as indicating that a part of the ionizing radiation energy is dissipated and transformed into thermal energy.
Infrared dichroism and molecular conformation of α‐form poly‐γ‐benzyl‐L‐glutamate
Authors: Tsubio Masamichi
Published: April 2003

Precise measurements were made of the dichroic ratios of several absorption bands of α‐form poly‐γ‐benzyl‐L‐glutamate. From the results obtained, directions were determined for the transition moments of these bands, and possible orientations are given for the peptide, ester, and phenyl groups in the polymer with respect to its fiber axis. On the basis of these orientations a model is proposed for the molecular conformation of this polypeptide.
Equation of state for monolayers of chain molecules
Authors: Llopis J. , Subirana J. A.
Published: April 2003

An equation of state for high linear polymer monolayers is discussed. It is shown that different theoretical approaches should be considered according to the range of surface concentration of the monolayer. For high dilution the theory here proposed is similar to that used in bulk solutions of polymers. An ideal temperature T = θ for which the second virial coefficient vanishes is defined. The behavior of these monolayers for higher concentrations can be explained by considering energetic interactions. In these conditions the chain configuration entropy becomes negligible. The difficulties involved in developing a theory for temperatures lower than θ have also been considered.
Tacticity as a problem in copolymerization: Influence of neighboring units on reactivity of growing chains
Authors: Ham George E.
Published: April 2003

Most copolymerizations and stereoregular homopolymerizations have been interpreted in the past solely in terms of the contributions of the terminal units in growing chains to reactivity with adding monomers. Equations are presented which offer the opportunity of weighing the specific contributions of all significant terminal sequences of several units on monomer reactivity. Rigorous proof of the validity of the “penultimate” equation is offered for the first time.
Block copolymers of α‐olefins prepared from macromolecules with long chain lifetimes
Authors: Kontos E. G. , Easterbrook E. K. , Gilbert R. D.
Published: April 2003

It has been shown that certain Ziegler‐type catalysts, i.e., mixtures of TiCl4 with lithiumaluminium alkyls or VOCl3 with aluminum chloroalkyls, produce “living” macromolecules having lifetimes of the order of several days or more in the homo‐ and copolymerization of α‐olefins. The long‐lived macromolecules made it possible to prepare stereoblock copolymers of α‐olefins consisting of blocks of random copolymers alternating with blocks of homopolymers with a certain steric isometry and with a wide range of physical properties. Some of the relationships existing between the molecular structure and the physical properties of these model block copolymers have been studied and compared with random copolymers and homopolymers of α‐olefins. Crystallizable elastomers composed of amorphous random copolymer blocks of ethylene and propylene or ethylene and butene‐1, alternating with homopolymer blocks of ethylene, propylene, or butene‐1 are discussed. In particular, the homogeneity of the products, the stress–elongation behavior, the x‐ray diffraction patterns in the unstretched and stretched states, and the physical properties of the reinforced and vulcanized products of the crystallizable stereoblock rubbery copolymers are presented.
Interaction of carboxyl‐containing butadiene–styrene rubbers with polyamides and ε‐caprolactam
Authors: Tutorskiǐ; I. A. , Smelyǐ; Z. I. , Bystrov V. M.
Published: April 2003

Mixtures of carboxylated butadiene–styrene rubbers containing 30% styrene, and 1, 3, 4, 5, 10, and 15% methacrylic acid (MAC) were investigated with ε‐caprolactam in a melt or in masticated mixtures for 10 hr. at 220°C. The lactam was found to add to the rubber both in the presence and in the absence of water, as was shown by extraction of the resultant specimens with acetone, followed by formic acid and determination of nitrogen in the extracts. The compression heating of carboxylated butadiene–styrene rubber containing 30% styrene and 1% methacrylic acid with ε‐caprolactam at 200–220°C. leads to addition of the lactam to the rubber. BF3 served as reaction catalyst. Methods have been developed for the synthesis of graft and modified carboxylated butadiene–styrene rubbers and polyamides through the stage of rubber acid chlorides and sodium (potassium) derivatives of the polyamides. The rubber acid chlorides are obtained according to the reaction:
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The polyamides derivatives, according to the reaction:
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and
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Modification of the carboxylated butadiene–styrene rubber with ε‐caprolactam was carried out according to the reaction:
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or
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Rubbers with a MAC content of 0.3% to 10% were employed. The modified rubbers possess greater strength characteristics than the original carboxylated polymers. They are less soluble in pure benzene and soluble in benzene–ethyl acetate mixtures. Insoluble, crosslinked polymers are obtained on reaction of the rubber acid chlorides with sodium substituted polyamides. Under particular conditions soluble products are formed. The products possess enhanced adhesion to polyamide films and ensure a strong bonding between rubber and fabric in rubber textile goods.
Polyethers. XIII. The effects of catalyst concentration and oxygen on the polymerization of 4‐halo‐2,6‐dimethylphenol
Authors: Price Charles C. , Chu Nan Shieh
Published: April 2003

The oxidative polymerization of haloxylenol has been found to be markedly faster than earlier reports. With 10 mole‐% of ferricyanide initiator it was complete in less than 1 min. at 5°C. Oxygen can act as initiator but also results in a decreased molecular weight. Increase in ferricyanide initiator concentration from 1 to 10 mole‐% resulted in a remarkable increase in conversion and a small increase in molecular weight. Polymer prepared with ferricyanide initiator under nitrogen had a large excess of halogen over phenolic endgroups, rather than the one‐to‐one ratio, found earlier for polymer prepared under air.
Evaluation of the molecular weight distribution and crosslink density of the sol and gel components by intrinsic viscosity measurements
Authors: Kotliar A. M.
Published: April 2003

A theory is developed utilizing the partitioning of a partially crosslinked polymer into sol and gel fractions when the initial molecular weight may be expressed as a Schulz‐Zimm or sum of Schulz‐Zimm distributions. The results show that the initial molecular weight distribution may determined from the ratio of the initial and sol fraction intrinsic viscosities. The treatment is also extended to the case where chain degradation accompanies the cure. The theory also permits the evaluation of the gel, sol, and overall crosslink index and coefficient of each component distribution of the polymer as a function of the weight soluble fraction. The components may be the same kind or different kinds of polymers or copolymers. The computed results for a two‐component system clearly show how the differences between the molecular weights or the distributions of the two components influence the difference between the crosslink indices of the two components in the vulcanized gel.
Electron microscope studies on polyethylene and polypropylene
Authors: Bailey G. W.
Published: April 2003

Replication techniques for electron microscopy have been used to relate the microstructural characteristics and physical properties of polyethylene and polypropylene. This study included polymer particles and molded pads. The low penetrating power and damage from heating prevents the direct examination of polymer particles in the microscope. Replication, however, has given details of the surface structure of these particles. The spherulitie structure of these polymers in molded form has been determined by replicating etched surfaces. Marked differences in the spherulitic structure of polyethylene and polypropylene have been observed The effect of molecular weight on spherulitic structure of both polymers has also been established.
Network polymers. II. Experimental study of swelling
Authors: Lloyd W. G. , Alfrey T.
Published: April 2003

The swelling behavior of vinyl‐divinyl network polymers has been studied. Various monovinyl monomers (styrene, vinyltoluene, p‐tert‐butylstyrene, a series of n‐alkyl methacrylates), divinyl monomers (divinylbenzene, ethylene dimethacrylate), and contacting solvents (ranging from n‐alkanes to water) have been used. Attention is directed to the effects of introducing an initial good‐solvent diluent at the time of polymerization. Results are interpreted in terms of changes of the free energies of solvent‐Polymer mixing and network deformation. The relaxed volume of the network is shown to be closely related to the volume at which it is formed. The network modulus increases with increasing divinyl content and decreases sharply with increasing initial dilution. With high crosslinking and moderate initial dilution, an interesting special case arises: the volume of formation of the network, its relaxed volume, and its equilibrium swollen volume are all almost identical, and the swollen volume is essentially independent of polymer–solvent interaction. Networks prepared from monomers with large pendant groups exhibit a built‐in dilution effect.
Polythiosemicarbazides. I. Preparation and properties of the polymers and some simple metallic chelates
Authors: Campbell Tod W. , Tomic Ernst A.
Published: April 2003

The condensation of N,N′‐diaminopiperazine with methylenebis(4‐phenyl isothiocyanate) proceeded easily in dimethyl sulfoxide solution to give a high molecular weight, soluble, polythiosemicarbazide (I).
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In agreement with the known behavior of monomeric thiosemicarbazides, the polymer reacted readily with various metal ions to give metallic chelates. These chelates did not have the expected thermal stability, however.
“Directional” membrane permeability in polymer–vapor systems
Authors: Petropoulos J. H.
Published: April 2003

A theoretical study is presented of the dependence of the vapor permeability of suitable nonhomogeneous polymer membranes on the sense of flow This is based on a simple model of a binary membrane in which the component phases A, B are either intimately mixed, with the composition of the mixture varying continuously across the membrane, or formed into a laminate AB. The influence of various parameters (which represent either properties of the component phases or the experimental conditions) on the magnitude of these flow reversal effects has been investigated. The results have proved useful as an indication of the capability of such membrane valves and of the conditions for optimum performance, as well as for the understanding of the behavior of experimental systems.
Sliding in polytetrafluoroethylene crystals
Authors: Flack H. D.
Published: April 2003

Stress–strain relationships are calculated for three models of the deformation of monocrystalline polytetrafluoroethylene, \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm CF}_{\rm 2} \rlap{--} )_n $\end{document}. The physical models comprise either sliding one molecule or one plane of molecules parallel to the molecular chain axis past its stationary neighbors. The potential energy is calculated for each stage of deformation by semiempirical methods by use of 6‐exp and dipole–dipole interactions. Application of Eyring's activated complex theory leads to stress–strain relationships. These are compared with results of friction measurements on PTFE.
Evidence for ionic clusters in butadiene–methacrylic acid copolymers neutralized with various salts
Authors: Pineri M. , Meyer C. , Levelut A. M. , Lambert M.
Published: April 2003

Effects of neutralization on butadiene–methacrylic acid copolymers have been studied. In Hycar CTB with 2% acid groups, small‐angle x‐ray scattering gives evidence of some cation clustering and leads to a value of the mean radius of 5.6 Å for the clusters and a value of the distance between them of 70 Å. When the concentration of salt is increased there is no appreciable change in the distance between clusters or in their size, but their number increases. The structure of clusters has been studied by electron paramagnetic resonance in copolymers neutralized with copper salts. The appearance of a line as in the monohydrated acetate salt permits one to define the structure of clusters consisting of two Cu2+ and four RCOO− ions with two H2O or RCOOH molecules. When the temperature is increased, the signal corresponding to Cu2+–Cu2+ pairs disappears. In high molecular weight butadiene methacrylic acid copolymers with 9% acid groups, we have found the ion pair clusters gathered into larger clusters. In dynamic mechanical properties, a relaxation peak appears at 340°K. We interpret this as due to breaking and possible re‐forming of dipolar associations.
Assessment of nonrandom crosslinking in polymer networks by small‐angle light scattering
Authors: Wun K. L. , Prins W.
Published: April 2003

The angle‐dependent, isotropic light scattering exhibited by a diluent‐swollen, ideal network is theoretically derived and compared with the light scattering exhibited experimentally by swollen real networks. In good diluents the difference is a measure of the spatial nonrandomness of the degree of crosslinking. A nonrandomness index (NRI) is introduced in terms of the Rayleigh ratios at zero scattering angle. A procedure is given for reliably obtaining the zero‐angle Rayleigh ratio from experimental data at finite angles (2–30°). Measurements are reported for a series of poly(2‐hydroxyethyl methacrylate) (PHEMA) networks, prepared at varying stages of dilution (in ethylene glycol, EG) and varying amounts of crosslinker (ethylene glycol dimethyacrylate, EGDMA). The theoretical Rayleigh ratios are calculated by employing the equilibrium degrees of swelling, refractive indices, and Young's moduli of the gels, measured in EG. The NRI is found to decrease upon decreasing the dilution during network formation and upon increasing the average crosslinking density. The NRI provides a probe of the network structure on a (sub)microscopic level. It is suggested that the NRI is closely correlated with the performance of elastomers under mechanical loading conditions.
Crystalline texture of injection‐molded nylon 6
Authors: Mencik Zdenek , Chompff Alfred J.
Published: April 2003

Injection‐molded specimens of nylon 6 were examined by x‐ray diffraction as a function of depth in three characteristic directions. A skin and a core were always found to be present which differed in the degree of crystalline perfection and crystal modification. While the core of pure nylon 6 was found to be not oriented, the core of specimens containing nucleating agents was found to contain a typical texture of the monoclinic modification of nylon 6 in which the distribution probability of the a* and c* axes resembles ellipsoids with three unequal axes. A model explaining this texture as due to degenerated (deformed) spherulites is proposed. With a transcrystalline nylon 6 specimen the direction of the fastest growth in the unit cell (which forms the radius of spherulites) is found to be close to the a axis.
Relation of elastic modulus to crosslink and entanglement concentrations in rubber networks
Authors: Langley Neal R. , Polmanteer Keith E.
Published: April 2003

The theory of rubber elasticity relates the elastic modulus of unfilled amorphous rubber to the concentration of elastically effective strands. A theoretical relation between this concentration and the concentrations of potential entanglements, random tetrafunctional crosslinks, and chain ends was proposed recently. In the present work, the new relation was combined with the theory of rubber elasticity and verified experimentally. Polydimethylsiloxane samples were cured by 60Co irradiation and were extensively extracted to determine gel fraction, which was used to calculate concentrations of crosslinking and scission due to irradiation. Equilibrium modulus values determined from creep tests were in excellent agreement with those calculated using the new relation if the average spacing between potential entanglements is 116 (CH3)2SiO units. Thus, in typical commercial silicone rubbers, the contribution to the modulus from trapped entanglements is greater than the direct contribution from crosslinks. The new relation allows the calculation of crosslink concentrations from modulus measurements on other unfilled rubbers once the potential entanglement spacing of the polymer is determined.
Cellulose triacetate single crystals grown from solution at high temperature without inclusion of solvent
Authors: Chanzy H. D. , Roche E. J.
Published: April 2003

Single crystals of cellulose triacetate II (CTA II) free of crystallization solvent can be grown from dilute solution in mixtures of dibenzyl ether and n‐tetradecane. Good results are obtained by using a polymer fraction with a degree of polymerization of 60 and a mixture of 70% n‐tetradecane and 30% dibenzyl ether at 245°C. The lamellar crystals produced are lozenge‐shaped with the longer diagonal parallel to the a axis of the lattice and with {110} as the growth faces. Twin growth occurs frequently with {110} as a twinning plane and less frequently with {210}.
Isotope effect in gas transport. II. Effect of the glass transition on the size of the free volume element
Authors: Ziegel K. D. , Eirich F. R.
Published: April 2003

A diffusive gas‐transport isotope effect is used to estimate the size of the free volume element above and below the glass transition for poly(ethyl methacrylate) and poly(vinyl fluoride). The cavity size, as measured by the hydrogen probe molecule, is apparently larger in the glassy region for both polymers than it is above Tg. It is postulated that the number of free volume elements essentially decreases below Tg, so that the total free volume, which is the sum of all such elements, is smaller below the glass transition, in accord with density measurements on bulk polymers.
Gel‐permeation chromatographic studies of cellulose degradation. III. Methanolysis of cellulose
Authors: Manley R. St. John
Published: April 2003

The molecular weight distribution in various celluloses degraded by methanolysis has been studied by gel‐permeation chromatography. It is shown that the accessible portion of the sample apparently degrades preferentially into molecular fragments with a size distribution centered on species with a degree of approximately 8. This result is interpreted as indicating the presence of weak links in the cellulose chains.
Unperturbed dimensions of isotactic poly(tert‐butylethylene oxide)
Authors: Doddi Namassivaya , Forsman W. C. , Price C. C.
Published: April 2003

The root‐mean‐square end‐to‐end distances of isotactic poly(tert‐butylethylene oxide) fractions were determined in xylene at 80°C from intrinsic viscosity measurements and in o‐dichlorobenzene at 80 and 100°C by light scattering. The characteristic dimension (〈L2〉0/M)1/2 was 1.04 × 10−8 cm in xylene and 0.9 and 0.7 × 10−8 cm in o‐dichlorobenzene at 80 and 100°C, respectively. The value in xylene corresponds to a C∞ of 15.9. This observation and the large negative temperature coefficient of (〈L2〉0/M)1/2 suggest that poly(tert‐butylethylene oxide) exists in a helical block conformation under these experimental conditions. This conclusion is in agreement with earlier reported NMR measurements.
Polymer characterization by refractometry
Authors: Beevers R. B.
Published: April 2003

In the use of refractometry for polymer characterization, it is shown that interpretation of data through use of a molar refractivity as defined by the Lorenz‐Lorentz equation is more accurate than by use of the parachor. The disagreement between experimental and calculated values of the unit molar refractivity may be attributed to the arbitrary definition of the residue unit and the method of summation of group refractivities. In general, refractive index should depend on molecular weight and the conditions of polymerization, but this may depend on the dielectric properties and volume fraction of the domains comprising chain ends, initiator fragments, and free volume. The effect of polymer conformation on the molar refractivity of polyisoprene is found to be slight. For copolymer systems, there is a linear dependence of refractive index on weight fractional composition only where there is little order. The refractive index of a copolymer is not independent of the nature of the distribution of the residues along the chain.
Elastic modulus of poly(isobutylene oxide) crystals parallel to the chain axis
Authors: Kaji Keisuke , Shintaku Tadashi , Nakamae Katsuhiko , Sakurada Ichiro
Published: April 2003

The elastic tensile modulus of the crystalline regions parallel to the chain axis E1 for poly(isobutylene oxide) (PIBO) was determined by an x‐ray diffraction method. The stress‐strain (σ—ε) curve calculated from the meridional reflection of (002) shows an inflection point at about 75 MN/m2 or an extension of 0.25%. The observed moduli below and above this point are 29 and 47 GN/m2, respectively, at room temperature. The initial lower modulus agrees well with the value, 29.7 GN/m2, calculated on the basis of the double zigzag structure of PIBO chain determined by Kaji and Sakurada. The higher modulus may be due to an intrachain steric hindrance between the hydrogen atoms of the methylenic group in the main chain and those of the two side methyl groups.
Thickening of crystals during rapid heating. I. Linear polyethylene and nylon‐6
Authors: Sakurai Kensuke , Miyasaka Keizo , Ishikawa Kinzo
Published: April 2003

The change of long spacing in polyethylene and nylon‐6 during heating at 18°C/min. was measured with an apparatus devised for rapid measurement of the small‐angle x‐ray diffraction. The apparatus made it possible to obtain a diffraction profile in 1.8 sec. Long spacings increased notably at high temperatures near the melting point, as has been observed during low‐rate heating. However, the increase in long spacing during heating was very small in a methoxymethylated nylon‐6 sample. This suggests that the increase in the long spacing at high temperature is due to the thickening of crystals. The long spacing in polyethylene samples in the vicinity of the melting point is apparently independent of thermal history.
The viscoelasticity of polymer solutions: Comparison of theory and experiment
Authors: Wang Francis W. , Zimm Bruno H.
Published: April 2003

The theory of the preceding paper is compared with previously unpublished experimental results on the viscoelastic properties of two polystyrene fractions of molecular weight 1.9 × 106 and 1.2 × 106 in nitropropane, which is very nearly a theta solvent, and in toluene, a good solvent. At the concentrations used, around 1%, the theory predicts extensive departures from non‐draining toward free‐draining behavior; these effects are observed. The theory similarly fits experimental data of Johnson on a sample of polystyrene of molecular weight 860,000 in decalin and dioctyl phthalate in the same concentration range.
The effect of inertia on the intrinsic viscosity of polymers
Authors: Szu Shousun C. , Hermans J. J.
Published: April 2003

For the model of an elastic dumbbell, i.e., two beads connected by a Hookean spring, the Langevin equations for the beads are formulated. It is taken into account that the friction force contains terms resulting from the inertia of the liquid. The contribution of the dumbbell to the viscosity is calculated from the rate of energy dissipation. When the inertia of the liquid is neglected, the viscosity contribution reduces to Kramers' result and is independent of the mass of the beads. When the inertia terms are added, the result is nearly independent of this mass, but shows a dependence on the density of the liquid. In liquids of low viscosity, the extra term resulting from the inertia may be as large as 25% of the total viscosity contribution.
Random chain scission of polystyrene in electron irradiated solution
Authors: Herrick Carlyle S.
Published: April 2003

Main‐chain scission was the predominant effect when dilute solutions of three linear polystyrenes in 1‐methylnaphthalene and polybenzyl oligomer received up to 2000 megaroentgen of 1.5‐MeV electrons. Values of energy per scission were independent of dose and of the same magnitude as literature values in dioxane and benzene solutions when compared at the same dose rate. In all cases as irradiation progressed, Mw/Mn approached a value of 2 and Mz/Mw approached a value of 1.5 characteristic of a random distribution. Starting from one initial distribution, random numbers were used to simulate random chain scission. A 500 MR (megaroentgen) distribution calculated in this manner matched the experimental distribution after a 500 MR irradiation.
Gel permeation chromatography: Examination of column efficiency
Authors: Cooper Anthony R.
Published: April 2003

Gel permeation chromatographic (GPC) separations have been performed with several commercially available column packing materials. The results have been analyzed in the conventional manner to obtain the ratio of weight average to number‐average molecular weight, Mw/Mn, for solutes with narrow molecular weight distribution. Various other parameters proposed to measure the efficiency of GPC columns have been evaluated and compared. It is proposed that the experimentally determined value of Mw/Mn for a series of different molecular weight samples with similar, narrow distribution for a given set of columns is a convenient parameter for comparing column efficiency in GPC. This parameter may be calculated from a single chromatogram unlike resolution, R, resolution index, RI, or specific resolution, RS, which require a pair of chromatograms. Results from the Mw/Mn method are usually in agreement with those from the R, RI, and RS calculations but one exception has been found. The number of theoretical plates calculated from the elution of a small molecule or from the polymer peak bears little relation to efficiencies predicted from the proposed Mw/Mn method or from R, RI, or RS.
Electron delocalization contribution to single crystal thermal expansion of a polydiacetylene
Authors: Baughman R. H. , Exarhos G. J. , Risen W. M.
Published: April 2003

The thermal expansion contribution due to temperature‐dependent π‐electron delocalization is evaluated from spectral measurements on a single crystal polydiacetylene (poly‐2,4‐hexadiyne‐1,6‐diol bisphenylurethane). The observed temperature independence of backbone associated vibrations (less than ±1 cm−1 change in νCC and νCC between 25 and 90°C) implies that thermal conformational fluctuations and equilibrium defect formation (which produce a negative thermal expansion coefficient) do not measurably affect π‐electron delocalization. The separation of equilibrium defects is either much longer than that of nonequilibrium defects or much longer than required to appreciably limit π‐electron delocalization in an effectively defect‐free polymer. Arguments presented indicate that, in the experimental temperature interval, the observed thermal expansion coefficient in the chain direction is over an order of magnitude larger than the delocalization‐associated contribution.
Asymptotic relations between shear stresses and normal stresses in general incompressible fluids
Authors: Coleman Bernard D. , Markovitz Hershel
Published: April 2003

It is shown that in the general theory of incompressible simple fluids with fading memory there are, for several types of nonsteady shearing motions, simple universal asymptotic relations between the shear stress S12 and the first normal stress difference N1 = S22 – S11. The kinematical situations considered include initiation of steady shearing, rest after steady shearing, and sinusoidal oscillation. In, for example, relaxation following cessation of a steady shearing flow with rate of shear κ, there holds, to within an error O(κ4):

This and the other derived universal relations between N1 and S12 are either consequences of, or are closely related to a general asymptotic formula [B. D. Coleman and W. Noll, Revs. Mod. Phys., 33, 239 (1961), eq. (6.15)] expressing N1 as an integral of the product of the shear relaxation modulus and the square of the history of the relative shear strain.
Effects of swelling and annealing on the viscoelastic behavior of the melt‐crystallized and solution‐crystallized polypropylene
Authors: Inamura Isamu , Ochiai Hiroshi , Yamamura Hitoshi
Published: April 2003

The effects of swelling and annealing treatments on viscoelastic behavior were studied in melt‐crystallized and solution‐crystallized samples of isotactic polypropylene (iso‐PP) over the temperature range −150 to 150°C. The log E″ versus T curves exhibited α, β, and γ peaks in order of decreasing temperature. The β peak of the melt‐crystallized sample shifted to higher temperatures after annealing, but was not affected by swelling. The α peak of melt‐crystallized polymer was affected by swelling treatments. It increased in height and shifted to lower temperatures almost linearly with the volume fraction of absorbed solvent. The magnitude of the shift was independent of the solvent species—toluene, p‐xylene, tetralin, carbon tetrachloride—however, it depended significantly on the temperature at which the sample had been heat treated. For solution‐crystallized polymer, no peaks in log E″ were observed in the temperature range of the β peak of melt‐crystallized material, but the α peak appeared larger and broader, and at higher temperature than the corresponding peak in the melt‐crystallized polymer. After swelling or annealing, the low‐temperature component of the α peak of the solution‐crystallized sample decreased in height and at the same time a new loss peak appeared at −55 and 0°C, respectively, is swollen and annealed samples. In particular, in the case of annealing treatments, the high‐temperature component of the α peak shifted to still higher temperatures. From these results on the solution‐crystallized sample it can be deduced that the segmental motions in the amorphous phase are very strongly constrained by surrounding crystalline phases as compared with those in the amorphous phase of the melt‐crystallized sample, and the constraints imposed on the segmental motions are released to a great extent by both treatments. Finally, swelling effects on the γ peak were examined. The γ peak of the melt‐crystallized sample decreased in height after swelling. On the other hand, the γ peak of the solution‐crystallized sample separated into two peaks, which might be attributed to the mechanical relaxations in the crystalline and amorphous phases.
Flow properties of poly(methyl methacrylate) solutions
Authors: Graessley William W. , Pennline Henry W.
Published: April 2003

Viscosity and normal stress behavior were measured for poly(methyl methacrylate) samples of various average molecular weights in diethyl phthalate solution at 30 and 60°C. All samples conformed approximately to the most probable distriution (M̄w/M̄n = 2). Concentrations ranged from 0.113 to 0.38 g/ml, and M̄w from 53,800 to 1,620,000. Despite considerable evidence in the literature of unusual linear viscoelastic behavior for this polymer, its nonlinear properties appear to be rather conventional. The viscosity–shear rate master curve was similar to that found earlier for concentrated solutions of polystyrene and poly(vinyl acetate) of comparable molecular‐weight distribution. The viscosity time constant τo parallels τR, the characteristic time of the Rouse model, although the residual dependence of τo/τR on concentration and molecular weight appears to be slightly different from that for polystyrene and poly(vinyl acetate). Similar conclusions apply to the recoverable compliance Je,o estimated from the normal stress behavior of each solution, and its relationship to the Rouse model compliance JR.
Effect of polymerization temperature on the original morphology of polyethylene prepared by γ‐ray‐induced polymerization
Authors: Arai Hidehiko , Wada Takeshi , Kuriyama Isamu
Published: April 2003

Polyethylene was prepared by γ‐ray‐induced polymerization in the temperature range 0–180°C. The morphology and the physical properties of the polymer as polymerized were studied by electron microscopy, differential scanning calorimetry, and gel permeation chromatography. Aggregates of small lamellar crystals with irregularly growing faces were produced below 55°C. Aggregates of large spherical particles were formed above 60°C together with hemispherical particles which adhered to the substrate. A few lamellar crystals of triangular or amoeba‐like shapes were also found above 55°C. The polymers formed below 55°C showed a sharp single endothermic DSC peak and a bimodal molecular‐weight distribution, while the sample above 60°C had a double endotherm and a unimodal molecular‐weight distribution. These facts suggest that the mechanism of crystallization during polymerization below 55°C is different from that above 60°C. The melting point, however, decreased continuously with increasing polymerization temperature and was much lower than that of extended‐chain crystals. The results show that the polyethylene, as polymerized, is composed of folded‐chain crystals irrespective of the reaction temperature.
Rheological effects of structure formation in polymer melts
Authors: Andrianova G. P.
Published: April 2003

The viscosity of a number of molten polystyrenes and polypropylenes obtained in various ways from solutions is found to be very strongly dependent on the history of dissolution of the polymer (the concentration of the solution and the “goodness” of the solvent), and on the presence of certain organic oligomeric compounds in very small amounts. The viscosity of the melt may be orders of magnitude less than that of the original samples. The present discussion of these effects is based on the concept of structure formation in amorphous polymers. The structure formed on the solution appears to be very stable with respect to heating and prolonged standing at elevated temperature, although it (and hence the viscosity) strongly depends on the initial concentration of the solution and the nature of the solvent. The role played by additives, present in amounts of small fractions of a percent, is accounted for by the fact that the melt retains the microheterogeneity of the medium. The material moves without its micromosaic structure being disturbed, and the role of the additives is reduced to surface (with respect to structural elements) phenomena.
Study of the low‐frequency motions in poly(ethylene terephthalate) (PET) by neutron inelastic scattering
Authors: Berghmans H. , Groeninckx G. , Hautecler S.
Published: April 2003

By neutron inelastic scattering, a complex low‐frequency spectrum is obtained for PET. This is attributed to the complicated structure of the monomer unit, a large number of intramolecular modes being possible. Most of them were identified using infrared and Raman data. Some indication of the presence of intermolecular modes below 200 cm−1 was found in the dependence of resolution and intensity on temperature in this frequency domain. The existence of these intermolecular modes was further supported by the spectra obtained from oriented or annealed crystalline samples.
Molecular weight distribution and mechanical behavior of PBI fibers
Authors: Wiff D. R. , Gehatia Matatiahu , Wereta Anthony
Published: April 2003

Two different polybenzimidazole (PBI) samples have been investigated in order to correlate the differences in molecular weight distribution (MWD) with changes in the elastic modulus and strength of undrawn and drawn fibers. It has been found that within the weight‐average molecular weight range (7,000 ≤Mw≤ 13,000) there was no obvious correlation withMwandMn. However, one sample had a narrow unimodal molecular weight distribution and the other a wide bimodal molecular weight distribution. The small percentage of high molecular weight present in the latter sample gave its fibers better mechanical properties. X‐ray diffraction studies showed that the orientation in both drawn fiber samples was equal. This isolated the effects of the molecular weight distribution on mechanical properties.
Crystallization during polymerization of diazomethane. II. Studies of model compounds and chain extension of etched polyethylene single crystals by chemical reaction
Authors: Lee Chung Jen , Wunderlich Bernhard
Published: April 2003

In order to study the mechanism of crystallization during polymerization, a method to produce living oligomer crystal nuclei was developed. The living oligomers are diazoketones prepared from their carboxylic acids or acid chlorides. These diazoketones were proved to be reactive toward boron trifluoride etherate. The complex could be further chain‐extended through a living polymerization mechanism with diazomethane. The optimal conditions for the reactions were worked out using model compounds. These reactions were then applied to chain extension of etched polyethylene single crystals. The reactions were confirmed by a combination of time‐dependent differential thermal analysis, molecular weight determination, nuclear magnetic resonance and infrared analysis. The importance and potential application of such reactions for the study of nucleation and crystallization, and final properties of the resulting polymers are discussed.
Incompatibility in polymer solutions: Light scattering of two polymers in a single solvent
Authors: Vrij A. , Van Den Esker M. W. J.
Published: April 2003

The fluctuation theory of light scattering for moderately concentrated polymer solutions is extended in a phenomenological fashion to include angle‐dependent terms up to sin2 (θ/2). The treatment is based on an uncoupling of the center of mass and segment contributions to the free enthalpy. In particular, equations are derived for three‐component mixtures containing two polymer and one solvent component. These are applied near the region of incompatibility. The results are compared with Debye's theory of critical opalescence. It is found that the Debye l parameter should be of the order of magnitude of the radii of gyration of the polymer molecules. This is confirmed by some experiments.
Dielectric relaxation in concentrated solutions of poly(γ‐benzyl‐L‐glutamate)
Authors: Adachi Keiichiro , Hirose Yumiko , Ishida Yoichi
Published: April 2003

Measurements of dielectric constant and loss, broad‐line nuclear magnetic resonance, and differential thermal analysis of concentrated solutions of poly(γ‐benzyl‐L‐glutamate) (PBLG) were carried out to determine the effects of intermolecular interactions on the mobility of the side group and the solvent (dichloromethane or dioxane). Only one dielectric loss peak due to the cooperative motion of the side group and the solvent was found. The activation energy of this relaxation process varied from 3 to 47 kcal/mole with increasing concentration of PBLG from 20 to 100% by weight accompanied with steep increases at about 40 and 80%. This result is explained as due to entanglement of neighboring side groups. In NMR, narrowing of the line was observed near the temperature where the dielectric loss was observed. The glass transition was also observed by differential thermal analysis. From these results it was concluded that the relaxation observed in PBLG solution and in pure PBLG have the nature of primary or α relaxations.
Conformation of poly(dimethyl siloxane) and polystyrene in solution measured by polarized Raman scattering
Authors: Speak R. , Shepherd I. W.
Published: April 2003

Depolarization ratios ρ have been measured over ranges of temperature T and molecular weight M for polystyrene (PS) dissolved in cyclohexane (1002 cm−1 Raman band) and for poly(dimethyl siloxane) (PDMS) dissolved in benzene (2907 cm−1 Raman band). The ranges in the case of PS are 15 < T < 65°C and 2 × 103 < M < 4 × 105 and in the case of PDMS are −3 < T < 60°C and M = 104. Measurements were also made of PDMS radii of gyration using conventional light scattering. The results are interpreted in terms of a theory connecting rotational isomeric populations with polymer extension. In the case of PDMS, an experimental value of the proportionality constant for trans isomers (D2 = −3.9 ± 0.9) is deduced. This is closer to the theoretical value than previous estimates but there is still some discrepancy. In the case of PS the isomeric changes resulting from extension are independent of M for M > 104. Deviations are observed for lower M.
Viscoelasticity of dilute chain‐molecule solutions: Evaluation of hydrodynamic interaction
Authors: Wang Francis W.
Published: April 2003

The viscoelastic properties of chain molecules varying in flexibility and length have been calculated by use of the bead‐spring model theory of Zimm. In the evaluation of the hydrodynamic interaction parameter, the number of springs in the bead‐spring model, N, has been selected from the range in which the properties predicted by the theory are insensitive to the value of N. The results for limiting viscosity number agree with those predicted by the Yamakawa–Fujii theory of the limiting viscosity number of wormlike chains. The theory also fits the experimental data of Johnson on a sample of polystyrene of molecular weight 860,000 in theta solvents at infinite dilution. The viscoelastic properties of some moderate molecular weight deoxyribonucleic acid solutions are predicted to deviate from the non‐free‐draining behavior toward the free‐draining behavior.
Nuclear spin relaxation in poly(diethylsiloxane)
Authors: Froix M. F. , Beatty C. L. , Pochan J. M. , Hinman D. D.
Published: April 2003

Earlier work showed that heating causes poly(diethylsiloxane) to undergo a first‐order transition from a semicrystalline solid to a more mobile viscous—crystalline material. The latter is composed of two phases and analogies between polymer and liquid crystal morphology and behavior have been made. The viscous—crystalline phase in PDES appears to be unique since the literature is devoid of other documented examples. In this study, spin—lattice and spin—spin relaxation times were measured over a wide temperature range. They show a glass transition at 138°K, a crystal—crystal transition at 206°K, and a transition around 250°K which results from translational motion of the polymer chains with respect to each other. This motion is observed in the amorphous phase at a lower temperature than in the crystalline phase. Translational motion in the crystalline phase is observed on melting of the crystallites. The spin—spin data permitted monitoring of the molecular motions in each phase and the data suggest that these phases exert some influence on the molecular motions of each other. The viscous—crystalline phase in PDES may represent a unique model for studying and understanding “precrystalline” behavior and structure in amorphous solids.
Dielectric relaxation studies in poly(hexamethylenesebacate) (HMS), poly(2‐methyl‐2‐ethyl propylenesebacate) (MEPS), poly(2,5‐dimethylbutylene sebacate) (DBS), and block copolymers of HMS and MEPS
Authors: Pochan John M. , Hinman Darlyn F.
Published: April 2003

The α and β dielectric relaxations of poly(hexamethylenesebacate) (HMS), poly(2‐methyl‐2‐ethyl propylenesebacate) (MEPS), poly(1,4‐ dimethylbutylene sebacate) (DBS) and block copolymers of HMS and MEPS have been studied. The α relaxation is amenable to a W.L.F. analysis and is associated with the glass transition of the polymers. This relaxation moves to higher temperatures with increasing HMS content in HMS/MEPS block copolymers. All the polymers studied exhibit psuedo‐activation energies of ∼32 kcal/mole at the glass transition. It is concluded that because the superposition principle is operative in the block copolymers, the glass transition must be very similar in both polymers and morphology and degree of crystallinity do not greatly affect this transition. The β relaxation which has been associated with segmental relaxation of polymethylene segments in polymers is also shown to be a function of HMS/MEPS block copolymer composition and chemical structure. This relaxation takes place at lower temperatures with increased HMS content in the blocks and also shifts to lower temperatures with side chain substitution adjacent to the carbonyl group in the polymer. It is concluded that the β relaxation takes place in the amorphous and crystalline regions of the polymer.
Electro‐osmosis of water through a cellulose acetate membrane
Authors: Srivastava R. C. , Jain Abhay K.
Published: April 2003

Experiments on electro‐osmosis of water through a cellulose acetate membrane have been reported and the data analyzed in the light of nonequilibrium thermodynamics. The linear phenomenological equations have been found to be valid. Study of the directional dependence of phenomenological coefficients has revealed the anisotropic character of the membrane. Efficiency of energy conversion for both electro‐osmosis and streaming potential has been calculated and the results have been analyzed in the light of thermodynamic theories.
The elongation and time dependence of the crystallinity of low‐density polyethylene
Authors: Peiffer D. , Hong S. D. , Stein R. S.
Published: April 2003

It has been presumed in studies of the orientation of low‐density polyethylene and its time dependence that the degree of crystallinity remained constant with elongation and did not vary with time following elongation. This paper represents a test of this hypothesis by several methods. The change in crystallinity accompanying stretching has been followed by a modification of an x‐ray method for uniaxial orientation proposed by Ruland in which diffraction peaks are resolved into crystalline and amorphous components and their respective areas are determined by two‐dimensional integration over both the Bragg angle and the azimuthal angle of diffraction. The weight‐fraction crystallinity is then determined from the ratio of the weighted crystalline area to the total area. There appears to be no significant variation in crystallinity up to 50% sample elongation for both slowly and rapidly stretched samples at room temperature. The dynamic crystallinity change accompanying small amplitude vibration has also been determined by the dynamic x‐ray diffraction technique and found to be negligible over a wide range of frequency. The degree of crystallinity has also been evaluated from the absolute infrared absorbance of crystallinity‐sensitive bands and has also been found to be independent of elongation at room temperature up to 80% elongation. Changes have also been observed by this method during relaxation at constant length following rapid extension and have also been found to be negligible. These results also indicate negligible changes in rotational isomer population. Consequently, we conclude that changes observed during relaxation and vibration arise from orientational changes rather than changes in the degree of crystallinity.