bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of solution‐crystallized polypropylene
Authors: Morrow D. R. , Sauer J. A. , Woodward A. E. 
Published: September 2014

AbstractResults are presented of the structures obtained upon crystallization of polypropylene from dilute solutions in α‐chloronaphthalene. It is shown that under proper conditions of concentration and crystallization, isotactic polypropylene can be caused to grow in the form of lath‐shaped single‐crystal lamellae. Electron diffraction pictures of these lamellae indicate a monoclinic crystal structure. Crystals have been grown both from whole polymer and from sharp molecular weight fractions. When crystallization from dilute solutions (0.4–0.001 wt.‐%) is allowed to take place under ambient cooling conditions, the crystals formed are not well defined, but tend to be more ordered if fractions are used. When fractions are crystallized under constant temperature conditions (from 90 to 115°C.) the resulting structure formed tends to be a close‐packed interwoven array of individual elements. However, if whole polymer is used the aggregate has a more open weave structure and, upon deposition upon a carbon substrate, the elements making up the quadrites tend to collapse at the edges. Electron transmission and diffraction pictures show these elements to be single lamellar crystals of polypropylene with well‐defined edges and with thicknesses of the order of 125–150 A. Fracture of crystals by ultrasonic vibration leads to the presence of fibrils between the separated parts when the break is at right angles to the a direction, but to no fibrils when the break is parallel to this direction. These results suggest that the polypropylene chains are folded, and that the fold planes are parallel to the a crystallographic axis
The radiation‐induced polymerization of dienes with sulfur dioxide
Authors: Kearney J. J. , Stannett V. , Clark H. G. 
Published: September 2014

AbstractCopolymers of sulfur dioxide and butadiene, isoprene, 2,3‐dimethylbutadiene, and chloroprene were prepared by irradiation at low temperatures with remarkably high efficiency. The polymers were all insoluble in the monomer mixtures and therefore only limited kinetic data could be obtained. However, the following conclusions could be reached from the data. Isoprene, butadiene, and 2,3‐dimethylbutadiene all produced 1:1 copolymers with sulfur dioxide across a wide range of temperature and composition. At high sulfur dioxide contents the cyclic sulfones began to form. Chloroprene behaved differently in that copolymers containing considerably more than 50 mole‐% of chloroprene were obtained. Also, the infrared spectra revealed a considerable proportion of pendant vinyl groups as compared with the predominately 1,4 addition in the case of the other dienes studied. The isoprene and 2,3‐dimethylbutadiene polymers were found to be soluble in highly polar solvents containing dissolved salts. At lower temperatures the radiation caused concurrent degradation of the polymer. The compositions of isoprene, 2,3‐dimethylbutadiene and sulfur dioxide terpolymers were found to be unusually sensitive to the polymerization temperature. Thermal gravimetric analysis of the various polymers showed thermal stabilities in the order, 2,3‐dimethylbutadiene > isoprene and butadiene > chloroprene. A sample of tetramethylene polysulfone prepared chemically showed greatly enhanced thermal stability, catastrophic degradation beginning about 100°C. higher than the corresponding butadiene copolymer. Attempts to hydrogenate the diene copolymers were unsuccessful although the corresponding cyclic sulfones were hydrogenated successfully. The highly efficient radiation polymerizations are believed to be free radical in nature and to proceed via monomer complex function. The difficulty of chain termination between sulfonyl radicals is suggested as a reason for the very high yields and molecular weights obtained at low temperatures.
Model structures for vinyl polymers. III. Equilibrium tacticity of 2,4‐dimethylglutaric acid and 2,4,6‐tricarboxyheptane
Authors: Clark H. G. 
Published: September 2014

AbstractModel compounds of the general formula H(CH2CHX)nCH3 (where n = 2 and 3 and X = CO2H, CO2CH3, CO2C2H5, CO2CH(CH3)2 and CN) have been prepared. These compounds were brought to steric equilibrium by treatment with alkaline catalysts and the equilibrium concentrations measured by gas chromatography. The syndiotactic configuration is preferred over the isotactic in all cases. Steric factors are more important than polarity for the systems which were investigated. It is proposed that the equilibrium triad content of the high polymers is approximated by the equilibrium composition models where n = 3.
Kinetics of radical polymerization. XX. Energy transfer processes in liquid‐phase radical reactions
Authors: Tüdös Ferenc 
Published: September 2014

AbstractIn order to account for the significant stoichiometric anomalies observed in the course of investigations on inhibited radical polymerization, the author propounded the hot‐radical hypothesis, according to which the reaction heat released during the formation of the active centers can serve as a source of activation energy in the subsequent reactions. This hypothesis is based on the assumption that the relaxation (the vibrational deactivation of the hot radicals) is essentially a slow process. To control this assumption in a direct way, the author conducted experiments in which vibrationally excited radicals were produced by UV irradiation of the initiators. The primary hot radicals formed were added onto various unsaturated compounds and thus transformed into more stable radicals, the concentrations of which could be measured with the aid of the ESR method. A comparison of the steady concentrations of the intermediate radicals formed under the effects of thermal and hot radicals, respectively, permits the rate and the probability of the relaxation of the hot radicals to be determined.
The viscoelastic relaxation mechanism of inorganic polymers. III. The sodium polyphosphates
Authors: Eisenberg A. , Sasada T. 
Published: September 2014

AbstractThe sodium polyphosphates represent a class of materials in which the viscoelastic relaxation mechanism in the glass transition region (≈300°C.) could be either molecular flow or bond interchange. At room temperature in aqueous solution these polymers behave like the normal organic polymers in which only molecular flow is encountered, whereas in the melt at 65°C., bond interchange is known to occur. To elucidate which of these two mechanisms is responsible for the relaxation behavior of the polyphosphates, two studies were undertaken. In the first, the viscoelastic properties were investigated as a function of the chain length and of the nature of the terminal units. The results indicated that molecular flow was the mechanism responsible for the relaxation behavior. In the second study, radioactive low polymer was mixed with inactive high polymer, and the mixture separated chromatographically after heating. No evidence of interchange was found here either, confirming the result of the first study.
Dipole moments of stereoregular polymethyl methacrylate in solution
Authors: Roig A. , Horta A. 
Published: September 2014

AbstractThree samples of stereoregular PMMA were studied by calculating their dipole moment from the experimental data of dielectric constant, specific volume, and refractive index measured on PMMA solutions in toluene at several temperatures in the interval 20–90°C. The tacticity of the samples is investigated by NMR. Results show that the highest dipole moment corresponds to isotactic polymer. However, no exact relation between tacticity and μ can be found. It would be necessary to have further knowledge of the distribution of regular sequences in the chain and of its length, rather than the quantity of individual units given by NMR. Dependence with temperature shows a smooth variation.
Zur Theorie der Phasentrennung im Ternären System Polymer–Lösungsmittel—Fällungsmittel
Authors: Klein J. , Patat F. 
Published: September 2014

AbstractThe basis of the theoretical discussions of this paper is a number of experiments concerning (a) the composition of the coexisting phases formed during precipitation fractionation, (b) the dependence of the initial point of phase separation on polymer concentration and molecular weight distribution, and (c) the amount of precipitated polymer. A discussion of the thermodynamic equations shows that the divariant distribution–equilibrium as following from the assumption of a Nernst equilibrium of polymer distribution between two immiscible liquid phases can be excluded. The experimentally determined constancy of the phase composition—independent of the initial concentration of the solution—confirms the univariant behavior of the system as following from the statistical thermodynamic theory. Therefore the precipitation process has to be described as a separation process from homogenious phase by phase formation. Contrary to commonly accepted theoretical results however, the behavior of a polydisperse system is determined by the partial concentrations of the various degrees of polymerization forming the mixture. Discussing the molecular‐kinetic steps of the precipitation process, one can say that in the solution the polymer chain forms polymer–solvate molecules of definite composition. The nucleation process—naturally preceding the phase separation—can be understood as an association process by forming intermolecular polymer–polymer contacts between the solvate molecules. A molecular weight specific ability of association may explain the dependence of precipitation on the partial concentration of polymer. The question whether the structure of the gel phase has to be interpreted as polymer–solvate complex or as a kind of swollen network cannot be answered yet.
The limit phenomenon in copolymerization of tetrahydrofuran with propylene oxide
Authors: Korovina G. V. , Novikovs D. D. , Barzikina R. A. , Kuzaev A. Y. , Entelis S. G. 
Published: September 2014

AbstractIn this work the occurrence of the limit in the copolymerization of THF and PO in bulk on tetrahydrofuranate trifluoride borane was studied within a temperature range from −10 to 20°C. and BF3 concentrations from 0.05 to 0.5 mole‐%. Under all conditions studied the copolymer yield was no more than 80%, the yield decreasing with THF concentration in the initial mixture. Increase in the catalyst concentration, other conditions being equal, promotes the reaction to higher yields. The addition of either of the two comonomers in the terminated reaction zone does not change the limit value. The addition of 20 wt.‐% of epichlorhydrin relative to the initial THF–PO mixture in the terminated reaction zone promotes complete polymerization.
The mechanism of the formation and the constitution of flavonoid tannins
Authors: Weinges Klaus 
Published: September 2014

AbstractThe majority of the flavonoid tannins that occur in tanning woods very probably originate by acid‐catalyzed intermolecular condensation of hydroxyflavan‐3‐ols (“catechins”) and hydroxyflavan‐3,4‐diols (so‐called “leucoanthocyanidins”) without the participation of enzymes. The mechanism of the reaction and the stereoselectivity of the acid‐catalyzed intermolecular condensation of catechins are described. The mechanism for the formation of flavonoid tannins consists of a primary polymerization step and a secondary condensation with elimination of water. These two steps are illustrated by the condensation of the dicatechin IV and that of the anhydrodicatechin VII, VIII, or IX. It cannot yet be decided whether the dehydration step occurs after the addition of each new molecule of catechin to the growing tannin. For this reason, the constitution of the flavonoid tannins is best represented by a combination of the formulas VI and X.
Some regularities of butadiene polymerization initiated by the “cobalt” catalyst and role of π‐allylic systems in stereospecificity
Authors: Dolgoplosk B. A. , Tinyakova E. I. , Vinogradov P. A. , Parenago O. P. , Turov B. S. 
Published: September 2014

AbstractNucleophilic additives and potassium and sodium chlorides, complexing with alkyl aluminum chlorides, are shown to result in an increase in the 1,2 structure of polybutadiene and a sharp decrease in molecular weight and polymerization rate. Trialkyl aluminum behaves in a similar way. There exists a correlation between these effects and the reducing power of the system. A mechanism of the influence of various compounds on the polymerization process is proposed. A mechanism of the formation of 1,4 and 1,2 polymer units is discussed with respect to the role of π‐allylic systems in diene polymerization and the nonequivalence of carbon atoms bonded to metal atoms in π‐crotylic systems.
Determination of the isotacticity of polypropylene by infrared spectroscopy
Authors: Kotschkina A. , Grell M. 
Published: September 2014

AbstractA method for determining isotacticity of polypropylene is proposed, which is based on the measurement of the ratio of the optical density of the 1000 (isotactic) and 1460 cm.−1 (“internal” standard) bands (D1000:D1460). The method has been compared with the extraction method and the other infrared methods. It has been shown that the other infrared methods are unreliable, either because of the failure of the 975 cm.−1 band to behave as a true “internal” thickness band, or because of the wrong assignment of the isotactic band.
Fraktionierung von Polyacetalen
Authors: Grohn H. , Friedrich H. 
Published: September 2014

AbstractTwo apparatus are described which allow fractionation of polyacetales showing different molecular weight distributions with sufficient reproducibility. Results obtained by the discontinuous and continuous elution method are compared to those obtained by a modified solution fractionation method, originally devised by O. Fuchs. Within experimental error the three methods give the same mass distribution curve. An equation is proposed by means of which it is possible to calculate the variation of the concentration in the mixing vessel during a fractionation with the eluted volume. By changing certain parameters of the equation the variation of the concentration may be fitted to any molecular weight distribution.
Homogene Polymerization des Acrylnitrils in Anorganischen und Organischen Lösungsmitteln
Authors: Ulbricht Joachim 
Published: September 2014

AbstractThe homogeneous polymerization of acrylonitrile in anorganic (Mg(ClO4)2) aqueous salt solutions proceeds with greater rates and results in higher degrees of polymerization than in organic solvents. The rate dependence of the degree of polymerization has been determined. Calculation of the degree of polymerization has been performed, taking into consideration the termination by disproportionation and recombination, as well as the change in molecular weight distribution, provoked by transfer reactions. The ratio of the rate constants kt/kp2 is shown to decrease by a factor of 102 in organic salt solutions compared with that in dimethylformamide and dimethylacetamide, whereas the rate of initiation is only little changed in all the solvents investigated. Furthermore, the mean lifetimes of radicals have been determined by intermittent illumination and is shown to be lower in dimethylformamide than in dimethylsulfoxide, ethylene carbonate, and aqueous magnesium perchlorate solution, provided that the polymerization rate is the same. From that it follows that the propagation rate of acrylonitrile is equal in the organic solvents investigated, but increases by a factor of 107 in the salt solutions.
Highly unsaturated polymers of polyethynylpolyarene and polyazopolyarene series
Authors: Kotlyarevskii I. L. , Shvartsberg M. S. , Fisher L. B. , Zanina A. S. , Bardamova M. I. , Terpugova M. P. 
Published: September 2014

AbstractTwo new classes of highly unsaturated polymers—polyethynylpolyarenes and polyazopolyarenes are synthesized by oxidative polycondensation of polyethynylarenes in the first case and of aromatic diamines in the second one and investigated. The polymers have common formulas H[(CC)kAr(CC)k]nH and H2NArN(NArN)NArNH2 respectively. The polymers either keep the conjugation along the main chain or the conjugation is intentionally broken. This is attained by changing the structure of the arylenic part of the monomers. Depending on the structure, electrical properties of the polymers vary in a wide range. For example the conductivity at 20°C. varies from 10−2 to 10−20 ω−1 cm.−1. The temperature dependence of conductivity is σ = σ0 exp {−E/kT}. The activation energy is specially predetermined by the structure and can vary in the range of 0.1 to 4.7 e.v. Similarly magnetic, dielectric, catalytic and other properties and solubility can be changed by varying the structure.
Vibrational and NMR spectra and molecular structure of poly(vinyl chloride)
Authors: Schneider B. , Štokr J. , Doskočilová D. , Kolínský M. , Sýkora S. , Lím D. 
Published: September 2014

AbstractInfrared spectra of PVC in the region of CCl stretching vibrations and the β proton band in NMR spectra of PVC are interpreted, based on the analysis of infrared and NMR spectra of pure stereoisomers of 2,4‐dichloropentane and 2,4,6‐trichloroheptane. For the interpretation of infrared spectra, only the presence of conformations found to be stable in model compounds has been assumed. The combined evidence of NMR and infrared investigations indicates that interpretations can be found to describe PVC samples prepared by radical polymerization at +50°C. as atactic, and those prepared at −25°C. as about 60% syndiotactic.
Electronic properties of poly(azothiophenylenes), polymers with systems of conjugated bonds in the backbone chain
Authors: Poniński M. , Kryszewski M. 
Published: September 2014

AbstractIn the course of investigations of electron spectra of previously obtained four fractions of poly(azothiophenylenes) PATPh it was stated, that benzene rings form quinoic structures, and NN or NN groups and S atoms exist in the chain. On the basis of EPR studies the numbers 1016–1018 and 1019 spins/1 g. are obtained for different fractions and for that pyrolized at 625°C., respectively. The investigations concerning electric conductivity and thermal activation energy show that these polymers exhibit a rather poor conductivity. A tentative interpretation of the conductivity is suggested on the basis of discussion of different models of electron mechanism.
Radiolyse Oxydante du Polyoxyéthylèneglycol en Solution Chloroformique Diluée
Authors: Gugumus François , Marchal Jean 
Published: September 2014

AbstractThe radiation chemistry of polyethylene oxide in aerated chloroform solutions was studied by exposure to cobalt 60 gamma rays. The rate of chain scissions was determined by viscosity measurements. The rates of formation of formates and formals resulting from degradation were measured by IR spectroscopy and colorimetry. To interpret the results we propose a kinetical scheme based on monomolecular decomposition of peroxy macroradicals PO2 leading to a formate and an α‐alcoxyalcoxyl radical. As this radical can attack other polymer molecules or its own chain, the degradation is explained by means of the superposition of a random scission process and of a nonrandom one leading to products of low molecular weight.
Étude par Birefringence d'Écoulement et Viscosimétrie de Copolymères Greffés
Authors: Gramain Philippe , Leray Joseph , Benoit Henri 
Published: September 2014

AbstractTwo series of graft copolymers, polymethylmethacrylate—polystyrene (PMM–PS) and polydiphenylpropene—polystyrene (PDP–PS), have been investigated by streaming double refraction and by viscosimetry. The results obtained in bromoform, which cancels the form effect, show that the intrinsic anisotropy is positive for the PMM–PD type and negative for the PDP–PS type. Consequently, these two families of compounds have a different morphology in solution. The influence of the various structural factors, such as the number and length of the grafts, and the mass of the backbone, on the anisotropy of the macromolecule has been considered. For the PDP–PS type, we suggest a model with properties similar to those of a statistical coil and for the PMM–PS type, a model composed of a core of PMM surrounded by the PS.
Comparaison des Propriétés de Solutions de Poly‐2‐Vinylpyridines Atactiques et Isotactiques
Authors: Loucheux Claude , Czlonkowska Zofia 
Published: September 2014

AbstractWe have prepared an atactic polymer of 2‐vinylpyridine by bulk polymerization at 30°C. with azobisisobutyronitrile as the initiator. The fractionation furnishes seven fractions. In addition, we have obtained a series of isotactic poly‐2‐vinylpyridines by homogeneous phase polymerization with phenylmagnesium bromide as initiator. We have studied these polymers by viscosity and light scattering techniques. In solution in absolute ethanol and in dimethylformamide, the behavior of atactic polymers is quite usual and we have established the two relations:

On the other hand, in the same solvents, the isotactic polymers present an important polyelectrolyte effect. This effect disappears by adding soluble electrolytes in the solvents, and in these conditions it is possible to give the two relations:

For the atactic polymers, we have the relation:

We think that a small extent of quaternization of isotactic polymers is responsible for the effects observed.
Polymérisations Provoquées par le Calcium Metal
Authors: Parrod Jacques , Sinn Victor , François Bernard , Mayer Nicole 
Published: September 2014

AbstractIsoprene has been polymerized with calcium converted into powder. Three methods have been investigated to reduce the metal: evaporation of the ammoniacal solution, distillation in argon atmosphere, and grinding. The structure of the polymers has been studied.
Combinaisons Cristallisées des Polyoxyéthylènes et des Polyesters avec l'Urée et la Thiourée
Authors: Parrod Jacques , Kohler André , Hild Géradd , Mayer Roger 
Published: September 2014

AbstractUrea gives adducts with polyoxyethylenes, with polystyrene—polyoxyethylene block polymers, and with some polyesters. Three ways can be used to get them: one can shake powdered urea with the polymer solution, or grind the solid constituents, or mix them in homogeneous solution. The first procedure is described with some details. The main properties of these addition compounds, and their crystalline structure are reviewed.
Étude par Ultracentrifugation Analytique d'un Système Enzymatique Monomère—Polymère (Polyphénoloxydase)
Authors: Arnaud Y. 
Published: September 2014

AbstractPolyphénoloxydase (P.P.O.) is an enzyme responsible for the hydroxylation of monophenols to the ortho forms, and also the oxidation of these o‐diphenols to o‐quinones. It is a macromolecule biologically active in the form of a tetramer. In order to study “monomer—oligomer” transformations, we made use of an analytical ultracentrifugation method which enables the hydrodynamic constants and the weight of the macromolecule to be determined on preparations diluted to the physiological concentration level (μg./ml.)8 This method consists in following the P.P.O. sedimentation during ultracentrifugation, observing the transformation of diphenol into o‐quinone by ultraviolet absorption. Physical properties of an enzyme in the course of its action on the substrate are thus determined. This method insures the functional integrity of the molecule, and provides the best criterion of specificity. This study has enabled us to show various degrees of polymerization of this macromolecule, and to follow the influence of changes in its quaternary structure on its functional activity.