bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer fractionation. II. The analytical problem
Authors: Koningsveld R. , Staverman A. J. 
Published: April 2003

AbstractComplete fractionations into 5, 10, and 20 fractions were calculated by a numerical method based on the Flory‐Huggins theory in order to evaluate various procedures for determining the molecular weight distribution from fractionation data. If the initial distributions are wide, the differential distribution cannot be accurately reconstructed, not even if each fraction is characterized by two average molecular weights (instead of one, as is customary). In addition to this inadequacy in the evaluation procedure there are the experimental errors which further detract from the accuracy of the result. The integral distribution can, in some cases, be approximated fairly well by means of the Schulz method, provided that the polymer is separated into many fractions with narrow distributions. However, the integral distribution thus obtained does not reflect details in the differential distribution. Polymer fractionation does not appear to be a suitable procedure for accurate determination of the differential distribution. From the assembled material, a thermodynamic method has been derived which seems to hold out better prospects. It should enable the differential distribution to be directly determined from a detailed analysis of the liquid–liquid phase relationships, provided the free energy of mixing function of the system is known.
Low‐temperature dispersion related to methylene units of a polymer main chain
Authors: Dammont F. R. , Kwei T. K. 
Published: April 2003

AbstractPolymers containing dynamically isolated polymethylene segments of various lengths were obtained from the reaction of bisphenol‐A‐diglycidyl ether with α,ω‐diamines. On the basis of the mechanical damping data of these polymers, it was established that the shortest polymethylene segment to show the −125°C. γ dispersion, characteristic of polyethylene, must consist of at least five carbon atoms.
Viscoelastic properties of polybutadienes—linear and lightly crosslinked near the gel point
Authors: Valentine Robert H. , Ferry John D. , Homma Terutake , Ninomiya Kazuhiko 
Published: April 2003

AbstractViscoelastic properties of four linear and three very lightly crosslinked polybutadienes (microstructure about 50% trans) were studied. Of the latter, two had not reached the gel point, and their molecular weight distributions were determined by sedimentation velocity analysis; the third was crosslinked just past the gel point, with only 32% gel fraction present. The crosslinking agent was sulfur. Complex shear compliances were measured over a frequency range from 0.1 to 1000 cps at temperatures from −70 to 30°C. with a Fitzgerald transducer and a Plazek torsion pendulum; and torsional creep measurements were made over time periods up to about three days. The creep data were converted to the corresponding dynamic viscoelastic functions at very low frequencies by conventional approximation methods. All data were reduced to 25°C. by shift factors calculated from a previously adopted equation of the WLF form. In the transition zone, the viscoelastic properties of linear samples were almost independent of molecular weight. The entanglement spacing, derived from the minimum in the loss tangent and the inflection in the storage compliance, was 130 to 160 chain atoms. The maximum in the retardation spectrum attributable to motions of individual network strands was closely similar to the corresponding maxima for more highly crosslinked vulcanizates previously studied, showing that even in the latter it is associated with entanglement network strands rather than strands between chemical crosslinks. For a linear sample with molecular weight 180,000, the retardation processes disappear at times beyond about 10 sec. at 25°C. With crosslinking short of the gel point (i.e., branching) the slow retardation processes are enormously increased and prolonged to longer times. With further crosslinking through the gel point and beyond, the slow retardation processes decrease progressively in magnitude. Qualitatively, this behavior resembles the sharp maximum in content of highly branched and aggregated molecular species which is predicted at the gel point by crosslinking statistics; but the slow processes (or low‐frequency losses) persist farther past the gel point than would be expected on this basis. The steady‐state compliances of the linear samples were smaller, but for a sample crosslinked short of the gel point were much larger, than the prediction of the Rouse theory modified for molecular weight distribution.
Multiple‐order light scattering from ringed spherulites
Authors: Clough Stuart B. , Stein Richard S. 
Published: April 2003

AbstractLight scattering from polymer films containing ringed spherulites may show multiple‐order intensity maxima directly related to the period of the banded structure. Calculations based on spherulite models where the angle of twist of lamellae ω varies linearly with radial distance predict only first‐order peaks. If the variation of ω is nonlinear, even though the ring spacing remains constant, higher‐order intensity maxima will result. Other sources of multiple‐order scattering are considered. It is concluded that for polyethylene the presence of multiple‐order scattering is due to non‐uniform twisting of the lamellae.
Structure–property relations of polyimide films
Authors: Wallach M. L. 
Published: April 2003

AbstractA series of well‐characterized polyamic acids from pyromellitic dianhydride and 4,4′‐diaminodiphenyl ether of systematically varied molecular weight and known molecular weight distribution were chemically converted to polyimide films under regulated conditions. The films were essentially noncrystalline, of moderate orientation, and soluble in concentrated sulfuric acid. The mechanical properties of the films varied sigmoidally with the solution properties of the precursor. Molecular weights were derived for the onset of mechanical strength and limiting property values are given. The relations between film properties and molecular structural parameters suggest that cyclization probably occurs here with little contribution from crosslinking, degradation, or other side reactions which would appreciably alter molecular weight and molecular weight distribution.
Morphology of cold‐drawn nylon 66
Authors: Crystal Richard G. , Hansen David 
Published: April 2003

AbstractA nylon 66 composed of uniformly sized spherulites approximately 50 μ in diameter was examined before and after cold drawing by light and electron microscopy of thin sections and by low‐angle x‐ray diffraction. Spherulites retained their identity through drawing, but the spherulites elongated less than the bulk specimen indicating that relative motion of spherulities must have occurred. The observation of dilations (0.3 μ long) at interspherulitic boundaries support this contention. The thin‐section electron micrographs indicated that the spherulites were composed of radiating lamellae approximately 95 A. thick. After drawing, the lamellae were preferentially oriented both parallel and perpendicular to the draw direction. Lamellae parallel to draw had thinned to approximately 70 A. While lamellae perpendicular to the draw had apparently thickened to 150 A. Three low‐angle x‐ray diffraction patterns yielded quantitative agreement with the electron‐micrograph data. The pattern form the undrawn nylon was a diffuse ring corresponding to a 95 A. spacing. On the drawn specimen, with the beam parallel to draw, a ring corresponding to the 150 A. spacing was obtained, while with the beam perpendicular to draw two arcs were recorded at spacings of 70 and 150 A. The drawing was done at room temperature and proceeded by neck formation and propagation, yielding a 4:1 draw ratio.
Upturn effect in the Non‐Newtonian intrinsic viscosity of polymer solutions. II. Polyisobutylene in polybutene oil
Authors: Bianchi U. , Peterlin A. 
Published: April 2003

AbstractWith an increasing gradient, the intrinsic viscosity of a high molecular weight polyisobutylene (M̄n = 7 × 106) in polybutene oil L.100 (ηs = 5 poise) first drops to a minimum and then rises again. The minimum occurs at β = M[η]0ηsG/NkT = 240, which is about ten times the value predicted by the dumbbell model. Such a shift to larger gradient is in good agreement with the more realistic necklace model of macromolecules in a good solvent. The increase of intrinsic viscosity after the minimum is nearly linear with the gradient and continues beyond the value at zero gradient. Experiments with capillaries of different length‐to‐diameter ratios yield identical flow curves so that one may exclude the possibility that the observed upturn is an artifact caused by end effects or time dependence of viscosity.
Depolymerization studies on polyacetaldehyde
Authors: Graessley W. W. , Nagasubramanian K. , Advani R. , Huetter D. F. 
Published: April 2003

AbstractDepolymerization of amorphous polyacetaldehyde has been studied by measurements of weight loss versus time for thin films of the polymer in vacuum. Temperatures ranged from 40 to 80°C. The samples were prepared by freezing or melting the monomer in contact with treated glass surfaces. Light scattering, osmometry, and intrinsic viscosity measurements were used to characterize the polymers. Depolymerization rates were between second and third order with respect to the unvolatilized fraction, and the activation energy was 26.3 kcal. Much of the evidence points toward a slow unzipping reaction at the chain ends, but the analysis seems to be complicated by structural variations among the samples.
Annealing experiments on drawn nylon 66 fibers
Authors: Dumbleton J. H. , Buchanan D. R. 
Published: April 2003

AbstractDrawn, nylon 66 yarns have been annealed in oil under relaxed conditions. Shrinkage and tensile modulus were measured and the yarns were examined by wide‐ and small‐ angle x‐ray diffraction. The results are similar to those obtained by Dismore and Statton, but there are significant differences. The data indicate a model for a drawn nylon 66 fiber in which substantial amounts of folds remain.
Development of gel permeation chromatography for polymer characterization. I. Operational variables
Authors: Boni K. A. , Sliemers F. A. , Stickney P. B. 
Published: April 2003

AbstractThe effects of operational variables on calibration of GPC are reported. Variables examined include (1) temperature and solvent changes, (2) sample concentration, (3) injection time, and (4) flow rate. Each of these variables significantly affected molecular weight averages calculated from GPC data. The causes and methods of minimizing the effects produced by the individual variables are discussed.
Crystallization kinetics of isotactic polystyrene. II. Influence of thermal history on number of nuclei
Authors: Boon J. , Challa G. , van Krevelen D. W. 
Published: April 2003

AbstractThe influence of various thermal pretreatments on the nucleation of isotactic polystyrene has been studied quantitatively by dilatometry. A distinction can be made between nuclei still present above the melting point (“resistant” nuclei) and nuclei created by severe supercooling (“induced” nuclei). The number of spherulites formed has been determined for different combinations of supercooling and crystallization temperatures. The results are interpreted in a satisfactory manner by assuming that in severe supercooling induced nuclei are created, which may grow into effective nuclei at higher temperatures. The crystallization of a severely supercooled polymer is completely governed by these induced nuclei, because they outnumber the resistant nuclei by some orders of magnitude. The number of induced nuclei can be decreased by purifying the polymer (removing catalyst residues). When cooled polymer is heated to temperatures just above the melting point, the induced nuclei are destroyed (“reversible melting”), so that only the resistant nuclei, which are few in number, remain. These resistant nuclei govern the crystallization behavior of a polymer which has not previously been cooled. Their number decreases on heating to temperatures far above the melting point.
Determination of melt viscosity as a function of hydrostatic pressure in an extrusion rheometer
Authors: Choi S. Y. 
Published: April 2003

AbstractPolymer melt viscosity was determined as a function of hydrostatic pressure in an extrusion rheometer. An extrusion rheometer consisting of a barrel and a capillary can be looked upon as two capillaries in series. The barrel itself was used as the main viscometer and several different capillaries having length/diameter ratios of 3.5–100 were used as pressure boosters. For a Phillips type polyethylene of 0.95 g/cc density and 0.4 melt index, the apparent viscosity at 190°C and 7.12 sec−1 was increased nearly fourfold as the average pressure in the barrel was raised from atmospheric to 24000 psi. With colored layers of polyethylene as tracers the flow pattern in the barrel was examined. The velocity profiles in the barrel were well developed and parabolic, and thus indicated regular laminar flow under these conditions.
Steady‐state distribution of water in cellulose acetate membrane
Authors: Rosenbaum S. , Cotton O. 
Published: April 2003

AbstractThe effect of hydrostatic pressure applied to a solution on one side of a membrane on the steady‐state concentration distribution of permeating solvent inside the membrane has been examined with a view to distinguishing between different mechanisms of permeation in reverse osmosis. The concentration gradients found experimentally in stacks of cellulose acetate films support the view that permeation takes place by diffusion in a nonporous membrane.
γ‐Ray‐induced copolymerization of carbon monoxide with cyclic ethers
Authors: Kagiya Tsutomu , Kondo Masatsune , Fukui Kenichi , Yokota Hisao 
Published: April 2003

AbstractThe γ‐ray copolymerization of carbon monoxide with cyclic ethers, such as ethylene oxide, phenyl glycidyl ether, 1,3‐dioxolane, 2‐vinyl‐1,3‐dioxolane, terahydrofuran, 1,4‐dioxane, and acetaldehyde was studied. A yellowish or brownish powdery copolymer was obtained in most of the cases examined. The infrared spectra showed that copolymers containing the ester structural unit were produced in the copolymerization with cyclic ethers which have no vinyl groups, and that a copolymer containing a ketone structure was produced from cyclic ether having vinyl group. It was found that the copolymer with ethylene oxide also had a β‐propiolactone ring structure at the chain end or the side chain. The copolymers were confirmed to be partially crystalline from the x‐ray diffraction diagrams. Further, a ring‐opening polymerizability of the cyclic ether by γ‐radiation was discussed. And it was found that as the bond dissociation energy between the carbon–oxygen linkage of the cyclic ether is small, the polymer yield both in the homopolymerization and copolymerization with carbon monoxide is high. A mechanism for the copolymerization is proposed on the basis of the results.
Effects of iron(III) chloro complexes on the polymerization of styrene
Authors: Dass N. N. , George M. H. 
Published: April 2003

AbstractThe polymerization of styrene initiated by 2,2′‐azobisisobutyronitrile has been studied in N,N‐dimethylformamide solution at 60°C in the presence of hexakis(N,N‐dimethylformamide) iron(III) tetrafluoroborate alone, and also in the presence of added lithium chloride. The presence of Fe(DMF)63+ ions in the polymerizing systems caused retardation, but iron(III) chloro complexes produced well defined inhibition periods. Velocity constants at 60°C for polystyryl radicals towards Fe(DMF)63+, Fe(DMF)5Cl2+, Fe(DMF)4Cl2+, and FeCl4− ions were calculated to be 847, 4.15 × 104, 6.55 × 104, and 3.14 × 104 l./mole‐sec, respectively. Values of the initiator efficiency f for most systems investigated ranged from 0.59 to 0.62.
Metal‐containing initiator systems. VI. Polymerization of butadiene with metal–organic halide systems
Authors: Otsu Takayuki , Yamaguchi Masami 
Published: April 2003

AbstractThe polymerization of butadiene with binary initiator systems consisting of some activated metals and organic halides was investigated at 60°C. From the results obtained, it was found that systems of reduced nickel and methyltrichlorosilane or dimethyldichlorosilane were most effective for the polymerization, and those of reduced nickel and carbon tetrachloride, benzyl chloride, benzyl bromide and benzoyl chloride, showed moderate activity. The polybutadienes obtained with these systems were observed to contain product of more than 80% cis‐1,4 microstructure. From detailed studies on the reduced nickel–methyltrichlorosilane system, these polymerization mechanisms were explained by the hypothesis that the initiation occurred through the reaction of the dissociated transition state complex with the monomer or with a trace amount of water, and then the propagation proceeded via a coordinated cationic mechanism. These systems did not show a good activity for the cis‐1,4 polymerization of isoprene.
Reactivity ratios for copolymerization of vinyl chloride with 2‐methylpentyl vinyl brassylate by computerized linearization
Authors: Chang Shu‐Pei , Miwa Thomas K. , Tallent William H. 
Published: April 2003

AbstractA computerized version of the Fineman‐Ross linearization procedure was used to determine reactivity ratios for copolymerization of vinyl chloride (monomer 1) and 2‐methylpentyl vinyl brassylate (monomer 2). From differential refractometry data for the products of low‐conversion copolymerization, the procedure gave r1 = 1.06 and r2 = 0.234. The ratios computed from chlorine contents of the same products were r1 = 1.10 and r2 = 0.239. The polarity factor (e2) and general monomer reactivity (Q2) calculated for monomer 2 from these ratios were, respectively, −0.95 to −0.98 and 0.032–0.033. The interquartile range for the copolymerization of a mixture of 60% monomer 1 and 40% monomer 2 was 1.4%. These values suggest that from suitable proportions of reactants, sufficiently homogeneous distribution of monomers can be achieved in copolymers of vinyl chloride and 2‐methylpentyl vinyl brassylate to offer the possibility of effective internal plasticization.
Polyimides having pendant hydroxy and acetoxy groups. II. Polyimides derived from bisaminoalcohols
Authors: Iwakura Yoshio , Kurita Keisuke , Hayano Fusakazu 
Published: April 2003

AbstractPolyamic acids were prepared from bisaminoalcohols and pyromellitic dianhydride. They were converted to polyimides having pendant hydroxy groups by heating them in toluene or xylene (ηinh = 0.22–0.34 dl/g). Treatment of these polyamic acids with a mixture of pyridine and acetic anhydride gave polyimides having pendant acetoxy groups (ηinh = 0.22–1.04 dl/g). These acetoxypolyimides were converted to hydroxypolyimides (ηinh = 0.20–0.81 dl/g) by an ester‐exchange reaction. Furthermore, the hydroxypolyimides were easily acetylated to give acetoxypolyimides.
Polymerization of acrylonitrile by V5+–lactic acid system in aqueous sulfuric acid
Authors: Saccubai S. , Santappa M. 
Published: April 2003

AbstractKinetics of polymerization of acrylonitrile by the redox system V5+–lactic acid in sulfuric acid at 20–35°C was studied. Oxidation of lactic acid by V5+ in the absence of monomer was also carried out under identical conditions. The rates of polymerization, V5+ disappearance and the chainlengths of polyacrylonitrile were measured. From the results it is concluded that the polymerization reaction is initiated by an organic free radical arising from the V5+–lactic acid reaction with termination by V5+ ions. Mutual termination of active polymer radicals does not appear to operate under the conditions studied. The various rate parameters were evaluated.
Salt effect in the base‐catalyzed polymerization of unsaturated amide compounds. IV. Polymerization of p‐vinylbenzamide in the presence of LiCl/N,N,N′,N′‐tetramethylethylenediamine
Authors: Asahara Tomohiko 
Published: April 2003

AbstractIn the presence of lithium chloride and N,N,N′,N′‐tetramethylethylenediamine, p‐vinylbenzamide was polymerized in basic media to form a polymer with structure consisting of units due to both proton transfer and vinyl type polymerization, whereas in the presence of the salt alone the monomer underwent exclusively vinyl type of polymerization to give a polystyrene derivative:
magnified image
Novel preparation of pure β‐TiCl3 and its use in isoprene polymerization
Authors: Smith G. H. , Perry D. C. 
Published: April 2003

AbstractTreatment of the reaction product of TiCl4, Al, AlCl3, and an aromatic compound with an ether and subsequently with TiCl4 yields very pure β‐TiCl3. This material, when treated with small amounts of aluminum trialkyls, is a very active catalyst for the stereospecific polymerization of isoprene. If the above reaction is stopped after the ether addition, before the addition of TiCl4, the product so obtained is largely TiCl2. Reaction variables in the preparation of TiCl3 are described as is the effect of various organoaluminum compounds as cocatalysts for polymerization.
Effects of metal salts on polymerization. VI. Photo and thermally catalyzed polymerization of N‐vinylimidazole in the presence of metal salts
Authors: Tazuke Shigeo , Okamura Seizo 
Published: April 2003

AbstractPolymerization of 2‐methyl‐1‐vinylimidazole (MVI) and 2‐ethyl‐1‐vinylimidazole (EVI) was found to be markedly photosensitized in the presence of oxidizing metal salts such as UO2(NO3)2, Ce(NH4)2(NO3)6, Hg(CH3COO)2, AgNO3; non‐oxidizing metal salts such as ZnII did not act as photosensitizers. The interaction of monomer with a metal salt is discussed on the basis of infrared and electronic spectroscopy. This photopolymerization is very specific with respect to the kind of monomer. The polymerization of noncomplexing monomer (styrene) is not photosensitized by these metal salts. Consequently, photosensitized electron transfer between monomer and metal salt via complex formation is considered to be the most probable initiation mechanism. Cupric acetate and sodium chlorolaurate, which have been reported as efficient initiators for the polymerization of vinylpyridine and N‐vinylcarbazole, respectively, act as linear terminators of growing radicals. The radical polymerizability of the zinc complex of MVI was studied by means of copolymerization with styrene. The reduction of the reactivity of MVI on complexing was explained by correlating with the spectroscopic observations. Because the polymerization system is heterogeneous, a detailed discussion was not possible.
Polybis(phosphinato)fluoroalanes
Authors: Schmidt Donald L. , Flagg Edward E. 
Published: April 2003

AbstractA new class of coordination polymers, polybis(phosphinato)fluoroalanes, [Al(F) (OPRR′O)2n], where R,R′ are alkyl, phenyl, or benzyl, was prepared and studied. The properties of these polymers are influenced by the phosphinate (R) substituents; polymers having n‐alkyl groups with more than five carbons are flexible and exhibit unusual hydrolytic stability. A polymer was obtained with a degree of polymerization of 104 by incorporating a 2:1 ratio of benzyl(n‐heptyl) and di‐n‐octyl phosphinate groups. The properties of the flexible materials are consistent with linear rather than highly crosslinked or network systems. Feasible structures are proposed for the polymers.