bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic melt rheology of poly(styrene‐co‐vinylpyridine) and their methyl iodide salts
Authors: Bazuin C. G. , Eisenberg A.
Published: April 2003

The dynamic melt rheology of random copolymers of polystyrene with 2–9 mol% 4‐vinylpyridine was examined in their quaternized and nonquaternized forms. Time–temperature reducibility applies in all cases. Relative to the glass transition, the master curves of the nonquaternized materials are identical. Melt flow in the quaternized materials is mildly retarded, the extent increasing with ion content. At the highest ion contents, the relaxation processes appear to be of Arrhenius type. As in the glass transition region, the ionic interactions in the plateau and terminal zones are thermally labile.
Dynamic mechanical properties of plasticized polystyrene‐based ionomers. I. Glassy to rubbery zones
Authors: Bazuin C. G. , Eisenberg A.
Published: April 2003

The plasticizing effect of a nonpolar and a polar diluent in ionomers was studied by dynamic mechanical methods in the glassy to rubbery regions. Specifically, a carboxylate and a sulfonate polystyrene‐based ionomer were investigated with variation of diethylbenzene content and of glycerol content. It was found that the nonpolar diluent plasticizes the transition by formation of ionic aggregates as well as lowering the glass transition temperature. However, the ionic regions of the carboxylate ionomer are plasticized more than those of the sulfonate ionomer. This corroborates the results of other studies which had found that the sulfonate groups in ionomers interact more strongly than the carboxylate groups. The polar diluent causes the ionic transition to disappear; this is probably due to solvation of the ions by the diluent.
Nucleation‐controlled growth. Observations on (110) twinned polyethylene crystals
Authors: Colet M.‐Ch. , Point J. J. , Dosiere M.
Published: April 2003

The growth of (110) twinned crystals of a sharp fraction of linear polyethylene (Mw/Mn = 1.10) of moderate molecular weight (Mw = 17,000) is followed during crystallization by the isochronous decoration method. New morphological features are observed. The fast‐growing tip of our laths presents, in addition to the two (100) facets usually observed, a possibly stable small reentrant (110) corner. This is a situation intermediate between the facies described by Dawson and Keller. Moreover, the slow tip of our laths presents various degrees of asymmetry with respect to the junction plane. A new characteristic length Ln = j/i is introduced to explain our morphological observations on (110) twinned crystals: j is the nucleation rate at a reentrant corner and i the nucleation rate on a smooth facet. Three linear growth rates Ghkl are calculated as a function of the length L of the face (hkl): Ghkl and Gĥkl or G′hkl are respectively the growth rates of a face bordered by two salient corners and by a reentrant corner. A distinction between Gĥkl and G′hkl is introduced to take into account the relative sizes of the two faces of the reentrant dihedral angle. The major points of the discussion concern (i) the stability of the (110) reentrant corner of the fast tip of the lath, (ii) the nearly constant shape of the twinned crystals, (iii) the effects of dislocations incorporated in the fast edge of the laths, and (iv) the various asymmetries observed in the slow tip of our laths. Theories of surface nucleation‐controlled growth explain our various morphological observations on (110) twinned PE crystals, and growth usually proceeds in regime II.
Characterization of PDMS model junctions and networks by solution and solid‐state silicon‐29 NMR spectroscopy
Authors: Beshah Kebede , Mark James E. , Ackerman Jerome L. , Himstedt Alan
Published: April 2003

The application of 29Si solution and solid‐state cross‐polarization/magic‐angle spinning (CP/MAS) nuclear magnetic resonance (NMR) techniques to the study of structural features in polydimethylsiloxane (PDMS) model endlinked elastomeric networks is explored. The relationship between the topological (network) functionality of a structural moiety, which determines network mechanical properties, and its chemical (spectral) functionality, which is reported by the NMR, is discussed. The second‐order spectral shifts corresponding to topographical functionality variation within a chemical functionality class are usually sufficiently well resolved in these networks to allow positive identification of a variety of structural features. The basic PDMS repeat unit, OSi(CH3)2, is found to possess an axially symmetric chemical shift tensor with σ∥ = −56.8 ppm downfield from TMS, and σ⊥ = −4.4 ppm. This axial symmetry does not result from rapid reorientation about the chain axis. The NMR spectrum reveals defects in model endlinked networks. In the case of vinyl‐endlinked systems, the defects are ascribed to the formation of elastically ineffective loops. Hydroxyl‐endlinked systems contain either loops or else trifunctional junctions (hydrolyzed before chain coupling could take place) and dangling chain ends. The CP/MAS technique provides an order‐of‐magnitude reduction over standard solution techniques in the time to acquire a spectrum from a network not containing paramagnetic doping. 13C spectra of PDMS systems are not as informative as 29Si spectra.
Structural changes induced in tussah silk (Antheraea pernyi) fibroin films by immersion in methanol
Authors: Tsukada Masuhiro
Published: April 2003

The crystalline transition induced by immersion in a methanol/water mixture of tussah silk fibroin (from Antheraea pernyi) film obtained by casting from a 1% solution was studied by x‐ray diffraction, differential scanning calorimetry, and infrared spectroscopy. The molecular conformation of the fibroin, consisting mostly of the α‐helix and random‐coil forms, was transformed into a random‐coil and β‐rich conformation containing only a small amount of α‐helix after immersion for no more than 5 min. The intersheet packing of the β‐crystal of the original tussah silk fibroin film was imperfect in the early stage of immersion. However, crystallization proceeded further when the immersion time exceeded 10 min. As a result the sheets in the β‐form crystal became closely packed because of the decrease in the content of the random‐coil form. The exothermic peak, which appeared at 226°C in the original fibroin and was attributed to the random‐coil → β‐structure transition, disappeared completely after immersion for 5 min.
Positronium annihilation in amine‐cured epoxy polymers
Authors: Jean Y. C. , Sandreczki T. C. , Ames D. P.
Published: April 2003

Positronium annihilation spectroscopy (PAS) has been used to study the microstructural properties of amine‐cured epoxy polymers. We have determined the free‐volume “hole” sizes in these polymers by comparing the observed ortho‐positronium lifetimes with the known lifetime–free volume correlation for low‐molecular‐weight systems. The free volumes for four epoxies with different crosslink densities are found to vary significantly over the temperature range between −78° and 250°C. The free‐volume holes for these polymers are found to range from 0.025 to 0.220 nm3. Two important transition temperatures were found: one corresponds to the glass transition temperature Tg determined by differential scanning calorimetry (DSC), and the other occurs about 80–130°C below Tg. The sub‐Tg transition temperature is interpreted tentatively as being where hole size reaches dimensions adequate for positronium trapping or else the onset temperature for local mode or side‐chain motions. These two transition temperatures plus two additional onset temperatures are found to be correlated with crosslink densities calculated from stoichiometry.
Dielectric relaxation studies of dipolar aromatics in polyethylene I. Spherulitic low‐density polyethylene
Authors: Jang Y. T. , Phillips P. J.
Published: April 2003

Dielectric relaxation studies have been used as a means of investigating the behavior of aromatic molecules dissolved in a semicrystalline polymer. All molecules show a relaxation in the vicinity of the γ loss peak of polyethylene, while several show an additional peak at lower temperatures. The latter is interpreted as an indicator of molecular motions below the glass transition and the former is to be associated with the onset of molecular motions on a local scale as the glass transition is approached. The α loss process of polyethylene is seemingly unaffected by the presence of the molecules. Integration of loss curves shows that, at most, 50% of the molecules are able to relax but that the fraction relaxing increases with increasing temperature, suggesting the presence of a wide distribution of sites within the polymer.
Relaxation mechanism of epoxide resin cured with acid anhydrides. III. Effect of alkyl side chains on mechanical and dielectric β relaxations
Authors: Ochi Mitsukazu , Iesako Hiroshi , Shimbo Masaki
Published: April 2003

Mechanical and dielectric β relaxations were investigated for bisphenol‐A‐type epoxide resin cured with succinic anhydrides with and without substituent linear or branched alkyl side chains. The dielectric β relaxation is due solely to the motion of the diester segment which is formed in the network from the reaction with the acid anhydride. The mechanical β relaxation is attributed to the motion of both the diester segment and another nonpolar segment, i.e., the linear alkyl side chain. Thus it is concluded that the long alkyl side chain in the diester segment not only restricts the motion of that segment, but also introduces additional motion of the side chain itself.
A quantitative electron microscopic study of the crystalline structure of ethylene copolymers
Authors: Voigt‐Martin I. G. , Alamo R. , Mandelkern L.
Published: April 2003

Quantitative thin‐section electron microscope studies were made on compositional fractions of ethylene copolymers crystallized under several extreme conditions. The co‐units chosen were such that the chains contained either ethyl, hexyl, or acetate side groups. Certain general features are independent of the chemical nature of the co‐unit. It was found that up to about 2 mol % co‐unit content lamellae are observed in all copolymers which were slowly cooled from the melt. The lateral dimensions of lamellae are not as large as in corresponding homopolymers and the lamellae are segmented. As the branch content increases the lamellae become shorter and eventually degrade into small crystallites. Within this broad outline of behavior, differences between the copolymer types are discerned and discussed. By comparison with the Raman LAM it is shown that quantitative values for the crystallite size distribution are obtained by the electron microscopy method used. Furthermore, when the specimen consisted of well‐ordered lamellar stacks the degree of crystallinity obtained from the electron micrographs was in quantitative agreement with the enthalpy of fusion.
Solvent‐induced crystallization. I. Crystallization kinetics
Authors: Durning C. J. , Rebenfeld L. , Russel W. B. , Weigmann H. D.
Published: April 2003

The kinetics of crystallization of quenched poly(ethylene terephthalate) (PET) films during the imbibition of methylene chloride (MeCl2) vapor is studied by density measurements. The effects of film thickness (0.0025–0.086 cm) and temperature (0–38°C) were examined. The data suggest that MeCl2 transport controls the crystallization in thick films and at elevated temperatures, but that spherulite growth controls in thin films and at reduced temperatures. The application of a mathematical model developed previously supports this mechanistic interpretation of the data.
Effect of flow on solutions of rodlike molecules
Authors: Bahar Ivet , Erman Burak
Published: April 2003

A flow field imposed on a solution of rodlike particles tends to align the rods owing to friction between the fluid and the rods. The potential energy of rods in a steady‐state, homogeneous, and irrotational flow is superposed on the equilibrium Gibbs free energy of the quiescent solution to obtain the total free energy. The exact lattice treatment of Flory and Ronca is used in formulating the problem. Effects of flow on the orientational distribution function of rods and phase separation are analyzed with particular reference to elongational and pure shear flows. Calculations carried out for various compositions and flow characteristics reveal the presence of a region where the order parameter is sensitive to changes in prevailing flow conditions. Experimental determination of orientation by measuring flow birefringence is discussed.
Longitudinal acoustic mode in polymers. VIII. Nature of mass perturbations in terminally brominated paraffins
Authors: Chang Chih , Krimm S.
Published: April 2003

Raman spectra have been obtained of the longitudinal acoustic mode (LAM) in α‐BrC20H41 and α, ω‐BrC20H40Br, and compared with such spectra for n‐C20H42. Normal coordinate analyses of these three molecules clearly account for (i) the frequency decreases on Br substitution; (ii) the presence of doublet LAM modes in both brominated molecules; and (iii) the decrease in the total intensity of the LAM mode resulting from the added masses, as distinct from the increase predicted by the elastic rod model. These results thus provide experimental support for predictions made from normal coordinate and intensity analyses regarding the influence on LAM bands of mass perturbations at the ends of paraffinic chains.
Vibrational spectroscopic studies of conformation of poly(oxyethylene). II. Conformation–spectrum correlations
Authors: Matsuura Hiroatsu , Fukuhara Koichi
Published: April 2003

Detailed normal‐coordinate analysis has been carried out on a large number of conformers of model molecules of poly(oxyethylene); the model molecules treated are CH3(OCH2CH2)nOCH3 with n = 2,3, and 6. The systematic treatment provides well‐defined correlations between conformation and vibrational spectra of poly(oxyethylene). The vibrations in the region 1050–800 cm−1, which are associated with the CO and CC stretching and CH2 rocking modes, are highly dependent on the conformation of the polymer chain. On the basis of these correlations, the infrared and Raman spectra of the molten state and of the aqueous solution are interpreted in terms of the conformational states. The analysis indicates that the following conformational fragments are present in these phases: GT‐TG (T: trans; G: gauche), TT‐TG, GT‐GG, TT‐TT, and TT‐GG for the CH2CH2OCH2CH2 group, and TGT and TGG for the OCH2CH2O group. Conformational fragments GT‐TG′ and GT‐G′G′ are also possible in the analogy to GT‐TG and GT‐GG.
Molecular aggregation of solid aromatic polymers. III. Small‐angle X‐ray scattering from aromatic polyamideimide film
Authors: Kochi Masakatsu , Isoda Satoru , Yokota Rikio , Kambe Hirotaro
Published: April 2003

Molecular aggregation in polytrimellitamideimide (PAI) was investigated by small‐angle x‐ray scattering (SAXS). PAI films annealed above the glass transition temperature show a scattering peak characteristic of two‐phase structure. A one‐dimensional model was used to analyze these SAXS curves. The more ordered phases are produced at higher annealing temperature. The average thickness of the ordered lamellae is comparable with the repeating length of the main chain. The relative difference of electron density between two phases is only a few percent, which shows that the two‐phase structure of PAI, like that of aromatic polyimide, differs essentially from that of ordinary crystalline polymers.
Solution properties of semirigid polyquinolines. I. Size‐exclusion chromatography with light‐scattering detection of poly[2,2′‐(P,P′‐oxydi‐P‐phenylene) 6,6′‐oxybis(4‐phenylquinoline)]
Authors: Cotts P. Metzger
Published: April 2003

An aromatic semirigid polyquinoline, poly[2,2′‐(p,p′‐oxydi‐p‐phenylene) 6,6′‐oxybis(4‐phenylquinoline)], has been studied in dilute solution using viscometry, light scattering, and size‐exclusion chromatography coupled with low‐angle light‐scattering detection (SEC/LALS). The SEC/LALS technique permits determination of the intrinsic viscosity and absolute molecular weight for a series of narrow fractions without preparative fractionation. Aggregation that was observed in dilute chloroform solutions was found to be related to protonation of the polyquinoline by HCI present in chloroform. Unperturbed dimensions calculated from the SEC/LALS results show the chain to have nearly freely rotating dimensions, as expected for a chain composed of long (12‐Å) rigid segments connected by ether linkages.
Structural relationships in blends of isotactic polypropylene and polymers with aliphatic sequences
Authors: Lotz B. , Wittmann J. C.
Published: April 2003

Blends of isotactic polypropylene and polyethylene or polyamides often display highly unusual crystalline morphologies in which the chain axes of the helical and linear polymers are at large angles to each other. These crystalline morphologies are explained on the basis of a specific epitaxial relationship that rests on the existence, in the (010) plane of iPP, of rows of methyl groups nearly 5‐Å apart. The structural basis of all the observed morphologies is the parallel alignment of the aliphatic segments of the PE or polyamides and of the iPP methyl rows (or vice versa) and matching of the near 5‐Å distances between PE or PA chains and iPP methyl rows. The implications of this unusual epitaxial relationship with respect to the apparent “universality” of polymer nucleating agents are examined.
Blends of a chlorinated poly(vinyl chloride) with a polyurethane
Authors: Garcia Dana
Published: April 2003

Blends of a 67% chlorinated poly(vinyl chloride) with a low‐molecular‐weight polyurethane are partially miscible over the 0–80% urethane compositional range. A single, composition‐dependent glass transition temperature is observed from both DSC and dynamic mechanical measurements. The blends exhibit a cocontinuous morphology with domain sizes varying from 0.15 to 1.5 μm. These results point out that the relation between miscibility characteristics and domain size is a complex one, not only dependent upon the degree of miscibility, but also on the nature of the blend components and the test method used. Thus the domain size for a certain degree of miscibility is not a universal constant as was previously believed. The melt rheology of the blends as a function of composition is strongly “positive deviating” from the log additivity rule and fits a simplified version of the McAllister model. The strongly “positive deviating” rheological behavior of the blends is most likely a result of the cocontinuous morphology which makes the system behave as a highly entangled network.
A dielectric study of secondary relaxations and the “memory effect” in two compatible polystyrene blends
Authors: Pathmanathan K. , Johari G. P. , Faivre J. P. , Monnerie L.
Published: April 2003

Dielectric permittivities and loss tangents of 10 and 30% poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO)–polystyrene (PS) blends and 10 and 25% poly(vinyl methyl ether) (PVME)–polystyrene blends have been measured from 80 to 360 K at 1 and 10 kHz. The PPO‐PS blends have two secondary relaxations below Tg and the PVME‐PS blends have three regions. All blends have a β process which appears near 290 K, is independent of PPO or PVME concentration, and is associated with the local modes of motions of PS chains. It is suggested that the β process of PS allows a dipolar reorientation of the PPO or PS chain segments by creating more favorable surroundings for the motions of the latter. The effect of physical aging in the PPO‐PS blend is substantial but the “memory effect” is significantly less. This is due to the lower contribution to tanδ from the β process of the blend.
Hydrogen bonding in polymer mixtures
Authors: Kwei T. K. , Pearce Eli M. , Ren Fan , Chen J. P.
Published: April 2003

The enthalpy–infrared frequency shift correlation for simple acids and bases is extended to study hydrogen bonding in polymer systems. The acidity of a polymer is calibrated by comparing the shifts in hydroxyl absorption frequency of the acidic polymer when mixed with a series of bases with the corresponding spectral shifts of known acids with the same bases. The basicity of a polymer is calibrated by measuring the hydroxyl frequency shifts of known acids when mixed with the basic polymer. For polymers containing carbonyl groups, the shift in carbonyl absorption is also a measure of basicity. The acidity and basicity constants obtained for polymers are in good agreement with the values for small‐molecule analogs. The enthalpies of hydrogen bond formation in polymer mixtures are calculated from the acidity or basicity constants.
Chain retraction, length fluctuations, and small‐angle neutron scattering in strained polymer melts
Authors: Viovy Jean Louis
Published: April 2003

We propose a possible explanation for an apparent contradiction between the Doi–Edwards (DE) theory and time‐resolved small‐angle neutron scattering experiments. The original DE theory predicts that a chain in a melt subjected to a step‐elongation undergoes a reduction of its dimensions in both the parallel and perpendicular directions to the strain axis, before returning to an isotropic conformation by reptation. In the present paper, we propose a crude model to compare the relative effect of retraction and of the chain length fluctuations, introduced later by Doi to explain the M power law of viscosity of polymer melts. We show that length fluctuations are able to screen retraction in most experimental situations available to small‐angle neutron scattering, whereas that is not the case for viscoelasticity. Quantitative predictions are consistent with the experimental data presently available.
Infrared spectroscopy of ethylene–vinyl chloride copolymers
Authors: Bowmer T. N. , Tonelli A. E.
Published: April 2003

This paper continues an investigation into the ethylene–vinyl chloride copolymers prepared by partial reduction of poly(vinyl chloride). The infrared spectra of the copolymers have been obtained and the individual resonances assigned. Each infrared band has been quantitatively analyzed in terms of peak position (cm−1) and intensity, and correlations with the sequence microstructure (dyad, triads, etc.) have been determined. The infrared resonances have been found to be sensitive to long sequences; i.e., (V)x or (E)x where x ≥ 10. Sequences of up to 10–15 monomer units were seen to affect the position (cm−1) and intensity of CH stretching and bending frequencies. Methylene rocking bands between 850 and 700 cm−1 were observed to be sequence dependent with V(E)xV resonanting at 860, 750, or 730 cm−1 for x = 0, 1 and 2, or ≥3, respectively. The CCl stretching resonances, which are well known for their conformational complexity in pure PVC, were found to be dominated by sequence length effects reducing to two bands at 665 and 610 cm−1 characteristic of and isolated CHCl unit in a long methylene chain.
Energy transfer in polymers and nitroxide decay during photolysis
Authors: Bauer D. R. , Briggs L. M. , Gerlock J. L.
Published: April 2003

When polymeric materials doped with nitroxides of the 2,2,6,6‐tetramethylpiperidine type are exposed to light, the nitroxide concentration decreases. The two mechanisms for the decrease of the nitroxide are the reaction of nitroxide with free radicals produced during photolysis of the polymer to form amino ethers and the abstraction of hydrogen atoms by excited‐state nitroxides to form hydroxyl amines. Excited‐state nitroxides can be formed in two ways: by direct absorption and by energy transfer. In this paper, the effect of energy transfer on the rate of decay of the nitroxide signal is studied, and measurements of nitroxide decay are used to probe energy transfer in crosslinked polymeric coatings. A simple kinetic scheme is used to interpret nitroxide decay during photolysis of both solutions and polymers containing benzophenone. These results are used to show that the slope of the line relating nitroxide decay rate to nitroxide concentration is essentially determined by energy transfer from a coating‐based chromophore to nitroxide. The nitroxide decay assay is also used to study the effectiveness of a benzotriazole ultraviolet light absorber as a quencher.
Interpretation of differences in temperature and pressure dependences of density and concentration fluctuations in amorphous poly(phenylmethyl siloxane)
Authors: Ngai K. L. , Fytas G.
Published: April 2003

Differences in the temperature and pressure dependences of the relaxation times of a slow diffusional process and the α structural relaxation pose an interesting problem. This feature, observed by dynamic light scattering in amorphous poly(phenylmethyl siloxane), is related to another basic feature of lack of thermorheological simplicity discovered by Plazek in polystyrene, poly(vinyl acetate), and amorphous polypropylene. A quantitative explanation based on the predictions of a general coupling theory of relaxations has been found. The coupling theory also predicts the Kohlrausch fractional exponential time correlation function exp[−(tτ*)1−n] at long times, as observed by photon correlation spectroscopy, and crossover to an exponential time dependence exp–(t/τ0) at short times, as frequently assumed in Brillouin scattering. An additional relation between τ* and τ0 predicted by the theory is confirmed also by the experimental data.
Thermoreversible gelation of cellulose acetate solutions studied by differential scanning calorimetry
Authors: Altena F. W. , Schroder J. S. , Van De Huls R. , Smolders C. A.
Published: April 2003

Thermoreversible gels of cellulose acetate can be obtained by cooling concentrated cellulose acetate solutions in solvent‐nonsolvent mixtures of dioxane and water. Upon heating the gels, endothermic effects were observed with differential scanning calorimetry. The heat effects are ascribed to the melting of a crystalline phase consisting of cellulose triacetate units. The endothermic peaks appear only after long aging periods of up to several days. Melting points generally decrease and heats of melting increase with increasing polymer concentration and with increasing nonsolvent content. The maximum degree of crystallinity is estimated as 8%. The kinetic effects of varying the water content in the solvent mixture are discussed.
An improved method of correcting diffusion coefficients from gravimetric data for edge effects
Authors: Grayson Michael A.
Published: April 2003

A method of correcting gravimetric data for diffusion through the sample edges to obtain true diffusion coefficients is presented. This method is compared with existing methods to show that it has the best accuracy for thick slab or cubic sample geometries.
Heat capacities and entropies of liquid, high‐melting‐point polymers containing phenylene groups (PEEK, PC, and PET)
Authors: Cheng Stephen Z. D. , Wunderlich Bernhard
Published: April 2003

The heat capacity at constant pressure of liquid PEEK, poly(oxy‐1,4‐phenylene‐oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene), has been measured by scanning calorimetry from 420 to 680 K, and that of PC, poly(4,4′‐isopropylidenediphenylene carbonate), from 325 to 610 K. These new data were combined with data‐bank data for PC and PET, poly(ethylene terephthalate), over wide temperature ranges. An addition scheme for liquid heat capacities of similar macromolecules has been obtained. In addition, values of absolute entropy, residual entropy for the glassy state, enthalpy, and Gibbs function are estimated for these three polymers. Both melting and glass transition temperatures have been confirmed. The heat capacity increases at the glass transition temperature have been determined by making use of previously calculated solid‐state heat capacities.
Interpretation of small‐angle x‐ray and neutron scattering data for perfluorosulfonated ionomer membranes
Authors: Kumar Satish , Pineri Michel
Published: April 2003

In small‐angle x‐ray and neutron scattering studies of ion‐containing polymers, it is observed that there is a maximum in the intensity and also an increase in the intensity at very low Q. Several ion clustering models have been proposed in the literature to explain the peak and the intensity increase. The SAXS data of Gierke et al. and the SANS data of Roche et al. are considered in this paper in order to elucidate the possible cluster morphology in perfluorosulfonated ionomer membranes. For these samples the occurrence of the SAXS peak is accounted for quantitatively; it is shown to arise from the interference between ionic aggregates (clusters), assuming them to be noninteracting hard spheres. In these calculations the volume fraction of the clusters (the cluster is assumed to be constituted of SO3−, a cation, and a swelling agent, which is water in the present case) is determined from water absorption values, equivalent weight, and from the density of the dry polymer. The size of the ionic clusters is chosen to match the calculated and observed peak positions. In these calculations it is assumed that all the ions are in clusters. The calculated peak value of the relative intensity invariant is found to be within ±15% of the experimentally observed intensity invariant for samples of different equivalent weight, and in different cationic form, soaked or boiled in water. Samples equilibrated at lower levels of humidity showed greater deviations. The deviations become smaller if either or both of two assumptions are made; that with a decrease in humidity (i) the percentage of clustering ions decreases, (ii) a fraction of the polymer chains is present in the clusters. This work gives credence to the thought that the small‐angle scattering peak in ion‐containing polymers is not a Bragg peak. This invalidates the conventional method of comparing the macroscopic and microscopic degrees of swelling. Previous SAXS work on dense groups of particles has neglected a term which is shown to be important at low angles. We found that this term is capable of qualitatively explaining the observed increase in intensity at low angles in perfluorosulfonated ionomers. The possibility of the presence of an intercluster potential, which can also contribute to the increase in intensity at these angles, is also discussed.
CO2 sorption in uniaxially drawn atactic polystyrene
Authors: Carfagna C. , Nicodemo L. , Nicolais L. , Campanile G.
Published: April 2003

The CO2 solubility in oriented and unoriented atactic polystyrene films has been investigated. Orientation does not change the nature of the sorption process; however, it decreases the level of solubility. Both the Langumir sorption term and the Henry's‐law contribution are affected by orientation. The decrease of solubility is correlated with an increase of density due to orientation. A simple experiment has been described to evaluate the depression of the glass transition temperature of polystyrene containing dissolved carbon dioxide.
Structure of the polyion complex between poly(sodium P‐styrene sulfonate) and poly(diallyl dimethyl ammonium chloride)
Authors: Oyama Hideko Tamaru , Frank Curtis W.
Published: April 2003

Stoichiometric and nonstoichiometric polyion complex films were prepared from poly(sodium p‐styrene sulfonate) and poly(diallyl dimethyl ammonium chloride). X‐ray photoelectron spectroscopy revealed that the ionic groups in the complex are more ionized than in each component polymer. Fluorescence measurements showed that the complex had a main emission peak around 300 nm, whereas the peak for its original polyanion occurred at 324 nm. With the monomer and excimer peaks of the phenyl rings taken to be at 294 and 324 nm, respectively, the ratio of excimer to monomer emission intensities increased in proportion to the mole fraction of polyanion in the observed range 0.44–0.59. There was no discontinuity at the stoichiometric composition. Furthermore, the change in peak position shows that the local aggregation of phenyl groups in the polyanion was destroyed by complexation with the polycation through Coulombic forces. These results, together with the visual observation of the transparency of the films, mean that the mixing between polyanion and polycation chains in the polyion complex is on the molecular level and that this polymer alloy is miscible.
Thermodynamics of linear reversible deformation
Authors: Göuritz D.
Published: April 2003

The change in internal energy of a body on stretching can be determined by means of deformation calorimetry. Theoretically the changes in thermodynamic properties on stretching can be deduced from Hooke's law and the Thomson expression dQ = β0TL df, which gives the amount of heat dQ absorbed when the force is changed from f to f+df; β0 is the linear expansion coefficient of the isotropic specimen, T the absolute temperature, and L the length of the deformed specimen. This has been demonstrated here for the deformation of a metal, and of isotropic and oriented polyethylene.
Effects of tertiary amine accelerators on curing of epoxide resins
Authors: Shimbo Masaki , Nakaya Takashi , Takahama Takashi
Published: April 2003

The effects of seven tertiary amine accelerators on curing of bisphenol‐type epoxide resins using azelaic acid as a curing agent have been investigated. The structure of the cured resins is characterized and reaction and structure schemes are proposed. The reaction mechanism and the resulting structure of the resin depend on the basicity of the accelerator. With increasing accelerator basicity crosslinking in the cured resin increases. Characterization results indicate that the network structure consists of ether bonds or a mixture of ether and ester bonds; the linear structure consists of only ester bonds. The structure and, therefore, the properties of the cured epoxide resin may thus be regulated by selection of the amine basicity.
The dielectric β‐relaxation of poly(bis‐benzimidazobenzisoquinolinones)
Authors: Śamigasiewicz Stefan , Kowalski Bogdan
Published: April 2003

The dielectric relaxation of poly(bis‐benzimidazobenzisoquinolinones) has been studied in the frequency range from 101 to 105 Hz and at temperatures from −150 to +80°C. The data show that the relaxation is due mainly to diffusion of water in the polymer with simultaneous reorientation of water dipoles.
Tensile flow and stress–strain behavior over a wide temperature range for poly(butyl methacrylate) with a broad molecular weight distribution
Authors: Vinogradov G. V. , Dreval V. E. , Borisenkova E. K. , Kurbanaliev M. K. , Zabugina M. P.
Published: April 2003

The poly(butyl methacrylate) studied is a polymer with a normal molecular weight distribution and a relatively low molecular weight close to Mc, the critical molecular weight from the viscosity–molecular weight relation. The polymer was subjected to uniaxial extension and shear over a temperature range which included Tg. It was found that in the region of Tg an increase in applied stress is accompanied by a decrease both in the temperature shift factor aT and in the activation energy for relaxation and rupture of polymer melts. Close attention is given to the long‐term durability of the polymer. As is expected in the temperature range below Tg, its dependence on the stress is exponential, whereas at temperatures above Tg a power law fits the data. In the latter case a log‐log plot of the long‐term durability versus stress can be represented by two intersecting straight lines which can be replotted as a generalized straight line if the long‐term durability values are normalized by the viscosity.
Chain entanglement and viscoelastic properties of molten polymers
Authors: Ajji A. , Carreau P. J. , Schreiber H. P. , Rudin A.
Published: April 2003

Linear low‐density polyethylenes (LLDPES) and polypropylene (PP) have been recovered from solutions of varying initial polymer concentration. Melts of these polymers show significant reductions in viscosity and elasticity, and the effects are attributed to changes in the entanglement density of the polymer. Measurements of entanglement densities have been attempted from experimental values of the apparent zero‐shear melt viscosity. These indicate that solution treatments in trichlorobenzene at 135°C reduce the entanglement density more effectively in PP than in LLDPE. In all cases the observed effects are reversible by annealing at elevated temperatures. Analytic data point to entanglement changes as the true origin of changes in viscoelastic properties, since solution treatments produce no changes in molecular weights and weight distributions, and the samples tested are free of solvent residues.
Morphology of a phase‐separated and a molecular composite PBT/ABPBI polymer blend
Authors: Krause Stephen J. , Haddock Tim , Price Gary E. , Galen Lenhert P. , O'brien Joseph F. , Helminiak Thaddeus E. , Adams W. Wade
Published: April 2003

The structure and morphology of homopolymers and blends of rigid‐rod poly(p‐phenylene benzobisthiazole) (PBT) and semiflexible coil poly[2,5(6)benzimidazole] (ABPBI) were examined by wide‐angle x‐ray diffraction and scanning and transmission electron microscopy. When samples were processed from a solution where the total polymer concentration of 30% PBT/70% ABPBI blend was greater than a critical concentration, large‐scale phase separation occurred and 0.1–4 μm ellipsoidal particles were present in a ductile matrix. The ellipsoids were chiefly composed of aggregates of well‐oriented 10‐nm PBT crystallites, while the matrix material was chiefly ABPBI. When the concentration was less than a critical concentration, the solution was optically homogeneous. In processing of fiber and film samples from the homogeneous solution, large‐scale phase separation was inhibited by rapid coagulation in a water bath. After heat treatment, these samples were found to contain crystallites of both PBT and ABPBI with lateral dimensions of ordered regions no larger than 3 nm. The PBT homopolymer was dispersed in the matrix at the molecular level in ordered regions at a scale no larger than 3 nm, resulting in a rigid‐rod molecular composite. In the rigid‐rod molecular composite fiber both the molecular‐level dispersion and high orientation contributed to higher values of strength and modulus compared to the properties of a phase‐separated fiber. The strength and modulus of highly oriented fiber were only 25% higher than those of planar isotropically oriented film, suggesting that the level of dispersion of rod molecules is more important than orientation of the reinforcing phase in rigid‐rod molecular composites.
Ferroelectric order and phase transition in polytrifluoroethylene
Authors: Oka Yoshio , Koizumi Naokazu , Murata Yukinobu
Published: April 2003

Polarization‐reversal currents and x‐ray profiles under a high dc field were measured on polytrifluoroethylene (PTrFE) samples prepared by melt crystallization at different cooling rates. The results for PTrFE were found to be analogous to those for copolymers of vinylidene fluoride and trifluoroethylene [P(VDF/TrFE)] with low VDF content. Slow‐cooled and quenched samples showed different x‐ray profiles but the same IR spectra. For the slow‐cooled samples, a polarization reversal was clearly observed as a peak in polarization current, offering evidence for ferroelectric order in PTrFE. The ferroelectric behavior was found to be unlike that of typical ferroelectric polymers. There are two processes in a polarization reversal, i.e., partial depolarization reversal, accompanied by crystalline phase transitions. It is noted that no ferroelectric order was observed for the quenched sample which, however, becomes pyroelectric by poling as revealed by our previous studies. We speculate on possible crystal structures of PTrFE based on the published structure models and the present results. The relation between the ferroelectricity and the previously reported pyroelectricity is also discussed.
Theory of relaxational interaction in linear polymers
Authors: Volkov V. S. , Vinogradov G. V.
Published: April 2003

The theory of nonlinear viscoelasticity of linear polymers is considered in the single‐molecule approximation. The dynamics of a macromolecule among similar molecules is studied with the use of the bead‐spring model. It is assumed that the surroundings of the molecule are equivalent to the simplest viscoelastic fluid with a single relaxation time. The viscoelastic drag force is determined by means of the relaxation equation. It is demonstrated that the viscoelasticity of the macromolecule's environment together with frame invariance leads to anisotropy of the mobility of the molecule. This proves to be of paramount importance in the description of nonlinear viscoelasticity of entangled polymers.
Dilation of polyethylene by sorption of carbon dioxide
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori
Published: April 2003

The dilation of low‐density polyethylene accompanied by the sorption of CO2 was measured by microscopy under pressures up to 50 atm at temperatures from 25 to 55°C. The dilatometry measurement, which is also applied to the determination of the thermal expansion coefficient, is directly performed by a cathetometer. The dilation of LDPE by sorbed CO2 is linear with concentration. The buoyancy correction is described for the CO2 sorption isotherms in LDPE. The partial molar volume of CO2 in LDPE, calculated from the dilation and the sorption isotherms, is almost independent of temperature.
Topotactic transitions of the tetramer of P‐acetoxybenzoic acid
Authors: Volksen W. , Geiss R. , Economy J.
Published: April 2003

Thermal and electron diffraction studies of single crystals derived from the tetramer of p‐acetoxybenzoic acid have revealed the presence of two consecutive crystallographic transformations, i.e., topotactic transitions. Thus, differential scanning calorimetry of the oligomer indicated two irreversible phase transitions, an endotherm followed by an exotherm, between 150 and 180°C, in addition to the crystal‐to‐nematic transition at 260°C. Electron diffraction analysis further elucidated the transformation occurring during thermal treatment of the original oligomer. Hence it could be shown that the solution‐crystallized material (α form) underwent a solid–solid phase transition to the β modification at a temperature corresponding to the observed endotherm. This β form then converted to a more stable modification (β′ form) which represented a superlattice structure derived from the β modification.
Crystallizing crazes: The probable source of solvent stress cracking resistance in a polyester/polycarbonate blend
Authors: Kambour R. P. , Chu C. , Avakian R. W.
Published: April 2003

The addition of a miscible phthalate polyester to BPA polycarbonate results in a remarkable improvement in stress cracking resistance in strong swelling agents. Comparative measurements of solvent craze initiation resistance, craze strengths, degrees of swelling, and crystallization behavior have been made. The results indicate that the improvement in cracking resistance probably results from stabilization of the craze fibrils by crystallization of the polyester before and/or during fibril formation.
Poly(m‐phenylene disulfide): Antimony pentafluoride doping and infrared spectroscopy
Authors: Bertinelli F. , Bizzarri P. Costa , Casa C. Della , Saltini S.
Published: April 2003

Poly(m‐phenylene disulfide) treated with SbF5 gives an unstable blue‐black material. Heating of doped samples at 155°C leads to some stabilization to ambient conditions; doped and heated pellets exhibit a conductivity of 10−9 and 10−5 S/cm for vapor and liquid doping, respectively. To investigate backbone modifications, polymer powders have been treated with large amounts of liquid SbF5 and an analysis of the IR spectra of the extracted samples has been tried in comparison with that of pristine polymer. Evidence for SbF ion has been found in the IR spectra of the complexes.
Use of blocked electrodes in thermally stimulated depolarization current measurements
Authors: Topića M.
Published: April 2003

The use of blocked electrodes in thermally stimulated depolarization current (TSDC) measurements has been studied on phenol–formaldehyde novolac resin blocked by one or two Teflon foils. The measurements were performed after polarization at different temperatures Tp separately for the Teflon and the resin. Blocking decreases the effectiveness of a nominal polarizing field and suppresses the background current. It is explained here for the first time that the charge released from the charged Teflon interferes with the conductivity relaxation peak of the resin. The influence of the blocking is very dependent upon Tp, and this dependence is specific in regard to the type of current peak. The application of blocking at different Tp is recommended for the determination of the origin of peaks in TSDC measurements.
Theoretical study of sequence distributions in polydienes. I. Statistical treatment
Authors: Wang Zhiyu , Yan Deyue
Published: April 2003

In this paper, the sequence distribution of polydienes is studied systematically by means of statistics. The discriminants for Bernoullian and various Markovian processes are obtained. In addition, the condition of statistical stationarity and a series of relationships among frequencies of occurrence of sequences with different lengths are given. When the polydiene consisting of only two structural units is taken into account, the statistical treatment of this paper degenerates into that for vinyl polymers.
Theoretical study of sequence distributions in polydienes. II. Non‐steady‐state analysis of a bernoullian process
Authors: Yan Deyue , Wang Zhiyu
Published: April 2003

With the aid of the non‐steady‐state kinetic method, the sequence distribution of polydienes conforming to a Bernoullian process is treated theoretically. The expressions for sequence length distribution, the probability functions, and other structural parameters are derived in closed form. The results obtained show that at the beginning of polymerization all the parameters mentioned vary with reaction time, monomer conversion, and the ratio of initial concentrations of monomer to initiator, but monotropically approach their respective limits which are identical with those derived from statistics.
Infrared absorption study of organic polyiodide chain complexes
Authors: Oza A. T.
Published: April 2003

Study of infrared absorption spectra of α‐cyclodextrin and its KI‐I2 and HI‐I2 complexes and those of Coumarin and its KI‐I2 complex reveals changes in the spectra of α‐cyclodextrin and Coumarin in the range 400–1800 cm−1. New bands in the COC stretching range are caused by charge transfer interactions of iodine with oxygen atoms in α‐cyclodextrin and Coumarin. Other changes in the spectra are ascribed to hydrogen bonding between water molecules and cyclodextrin molecules, water of crystallization, and structural effects.