bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase relations in the ternary system atactic polystyrene‐atactic polypropylene‐toluene
Authors: Berek D. , Lath D. , Ďurďovič V. 
Published: June 2010

AbstractParameters of the phase equilibrium of the system atactic polypropylene‐atactic polystyrene‐toluene (volume of phases, molecular weight, and relative and total concentration of polymers in both phases) as a function of concentration of polymers and temperature have been studied. Considerable changes of the parameters were found in the vicinity of the point at which formation of one‐phase systems occurs. Limiting miscible concentrations and temperatures in which the system becomes homogeneous for various molecular weights of both polymers have been determined. On the basis of the Flory‐Huggins theory the polymer‐polymer interaction parameter α23 has been calculated from the parameters of the phase equilibria as well as from the critical parameters of the system. The value of the interaction parameter depends on the temperature and the concentrations of polymers in the system. From our results we can obtain a very approximate value of the interaction parameter [α23] for a homogeneous mixture of polypropylene‐polystyrene in the absence of solvent. This value could be a measure of the compatibility of a pair of polymers.
Polymerisation von oktamethylzyklotetrasiloxan mit thermolabilen katalysatoren
Authors: Laita Z. , Hložek P. , Buček B. , Jelinek M. 
Published: June 2010

AbstractLow molecular weight silanolates of tetramethylammonium hydroxide and tetrabutylphosphonium hydroxide have been prepared. The kinetics of octamethylcyclo‐tetrasiloxane polymerization induced by either of these bases was studied and the activation energies were determined. It was found that the activities of these catalysts were much greater than that of the potassium silanolate (about 50–150 times). Nevertheless the activation energies did not differ from those found for polymerizations catalyzed by alkali metal silanolates (19.5 kcal./mole). The polymerization rate of the octamethylcy‐clotetrasiloxane‐tetramethylammonium silanolate system is thus comparable to the polymerization rate of the potassium silanolate‐tetradecamethylcycloheptasiloxane system, which is the most reactive of the low molecular cyclic poly (dimethyl siloxanes). Also the decomposition of the silanolates of the onium compounds was studied. It was found that tetramethylammonium silanolate is more stable than the phosphonium compound, the half‐time of decomposition at 100°C. of the former being more than five times that of the latter. Activation energies of the decomposition were also different: 42 kcal./mole for the ammonium compound and 28.5 kcal./mole for the phosphonium compound. This corresponds to a different proposed mechanism of the reaction, as described by Ingold. The most striking feature is that the decomposition follows first‐order kinetics. By analogy with experiments performed by Ingold and his co‐workers, we expected the second‐order kinetics in this medium of low dielectric constant. The first‐order kinetics was found even if excess potassium silanolate was added at 120°C. The rate of decomposition remained unaffected, the half‐time of decomposition being 27 min. This agrees quite well with the value of 24 min. found at the same temperature in the absence of potassium silanolate.
Interpolymer transformations in polymer mixtures initiated by peroxides: The system polyethylene‐polyisobutylene‐dicumyl peroxide
Authors: Šimǔnková D. , Rado R. , Letz J. 
Published: June 2010

AbstractThe decomposition of dicumyl peroxide in polyethylene‐polyisobutylene mixtures initiates, along with the crosslinking of polyethylene and the degradation of polyiso‐butylene, the formation of an interpolymer as a consequence of the interpolymer combination of macroradicals. Analysis of the kinetics of these transformation processes involves obtaining data for the transformation of the individual polymers in toluene solution, verification of the derived quantitative relations for the model system polyethylene‐low molecular weight only polyisobutylene, and finally application of these relations to a mixture of high molecular weight polymers. On the basis of the obtained results, the physical import of the individual kinetic parameters is interpreted, and the values are compared for the two types of mixtures.
Untersuchungen über die verfärbung von polyacrylnitril. IV. Polymeranaloge umsetzungen an durch erhitzung verfärbtem polyacrylnitril
Authors: Fester W. 
Published: June 2010

AbstractUltraviolet and infrared spectroscopy indicated that the primary discoloration of polyacrylonitrile during heating was due to the formation of conjugated carbon double bonds. This conclusion was supported by hydrolysis experiments. In the polyacrylic acid obtained from polyacrylonitrile after heat treatment the C°C stretching band could not be observed in the infrared spectrum because of the wide carbonyl band; therefore poly(allyl alcohol) was prepared from the acrylic acid via poly(methyl acrylate). In the infrared spectrum of this deeply colored polymer a carbon‐carbon double bond frequency was found. Oxidative cleavage of the poly(acrylic acid) obtained from heat‐treated and discolored poly(acrylic acid) by KMnO4 yielded an amount of CO2 increasing with increasing discoloration of the polymer. This supports the presence of conjugated carbon double bonds in the poly(acrylic acid). On the basis of the reactions carried out on the polymers in this work the assumption seems justified that the primary discoloration of polyacrylonitrile is due to formation of a system of conjugated double bonds in the carbon chain rather than to hydrogenated naphthyridine rings.
Polymerization of isobutylene catalyzed by aluminum tribromide
Authors: Chmelíř M. , Marek M. , Wichterle O. 
Published: June 2010

AbstractSolution polymerization of isobutylene in heptane, catalyzed by aluminum tribromide, takes place at high rate even at low catalyst and monomer concentrations, without addition of water as cocatalyst. The overall rate of polymerization is of first order with respect to the monomer and of second order to the catalyst. The activation energy of the polymerization is practically zero within the temperature range investigated (‐60 to +20°C.). A value of −3.9 kcal. has been found for the “activation energy of degree of polymerization”; the extrapolated ceiling temperature is +131°C. Additions of water substantially decrease the rate of polymerization. The concentration of residual moisture in the polymerization apparatus was so low that no detectable isobutylene polymerization catalyzed by boron trifluoride or titanium tetrachloride was observed. Additions of water were necessary for polymerization in the presence of these two catalysts.
Photopolymerization of vinyl monomers initiated by pentaaminecobalt (III) complexes
Authors: Delzenne G. A. 
Published: June 2010

AbstractThe polymerization of acrylamide in aqueous solution can be initiated by free radicals formed during the irradiation of pentaaminecobalt(III) complexes with light of wavelengths corresponding to the charge transfer band of the initiators. The kinetics were studied for two different cobalt(III) complexes: the chloropurpureosalt [CoCl(NH3)5]‐Cl2 and the roseosalt [Co(H2O)(NH3)5](NO3)3. In both cases the dependence of the rate of polymerization on the initiator concentration indicates a termination reaction due to an oxidation of the growing chains by the metal complexes. The effect of the chloro complex on the photopolymerization rate of acrylamide initiated by riboflavine showed the same termination activity. A termination constant, kt = 1.5 × 103 liter/mole‐sec., could be calculated. The first‐order dependence of the rate of polymerization on the monomer concentration for the initiation by the chloro complex agrees with an internal charge transfer during the photochemical activation of the initiator. The second‐order dependence of the rate of polymerization on the monomer concentration for the initiation by the aquo complex can be attributed to a substitution of the coordinative bonded water by a monomer molecule. An electron transfer within the intermediate complex agrees with the observed initiation.
Regulation of molecular weights of polymers in emulsion
Authors: Dvořák E. , Hrabák F. 
Published: June 2010

AbstractDependence of the apparent transfer constant of diisopropyl xanthogen disulfide on the rate of emulsion copolymerization of butadiene with styrene was followed up in various emulsifiers. On the basis of data obtained the relation was derived between both the relative and apparent transfer constant and the rate of polymerization.
Changes of blood haptoglobin in acid media
Authors: Pavlíček Z. , Kalous V. 
Published: June 2010

AbstractThe behavior of blood haptoglobin, isolated from Cohn's fraction IV, has been studied in acid solutions. Titration curves, differential absorption spectra, and measurements of optical rotation indicated that in the region below pH 5.0 the haptoglobin molecule undergoes important structural changes. Haptoglobin with altered conformation is unable to bind hemoglobin, and for this reason it cannot be determined on the basis of its increased peroxidase activity.
Polymerization of acrylonitrile initiated by organomagnesium compounds
Authors: Erussalimskii B. L. , Kulevskaya I. V. , Masurek V. V. 
Published: June 2010

AbstractThe polymerization of AN at −75°C. in various systems with the participation of the organomagnesium compounds was studied. For the system AN–BuMgCI. Bu2O–toluene kinetic data are given and a reaction scheme including the deactivation of the catalyst is proposed. The initial period of the polymerization is characterized by first order with respect to the catalyst and second order with respect to the monomer. On the basis of: (a) the proportionality of the molecular weight of PAN to the conversion, (b) the independence of the polymer molecular weight on the catalyst concentration, and (c) narrow molecular weight distribution of the polymer obtained at relatively high conversion. the absence of the termination reactions of the growing chains is suggested. The maximum molecular weight of the polymer attained in the systems AN–RMgX–toluene was 435.000. The efficiency of the process in the hydrocarbon media increases sharply in the presence of catalytic quantities of dimethylformamide (DMF) and dimethyl sulfoxide. As it is shown for the system Bu3Mg2I–DMF–toluene, the interaction of the catalyst components at −75°C. leads only to the formation of a complex of the type RMgX DMF. The addition of RMgX to the carbonyl group of DMF can be observed only at a higher temperature.
Solid‐state radiation polymerization of triselenane to polyselenomethylene
Authors: Carazzolo Gianalvise , Mammi Mario 
Published: June 2010

AbstractTriselenane, the cyclic trimer of selenoformaldehyde (CH2Se)3, subjected to gamma irradiation, has been partially converted into crystalline polyselenomethylene (CH2Se)n, The solid‐state polymerization has been proved to take place in two directions, parallel to the two [hhO] and [hhO] diagonal axes in the ab plane of the trimer orthorhombic unit cell. The polymer crystal lattice is orthorhombic with a = 5.37 A. b = 9.03 A., c = 4.27 A., and space group P212121; the polymer chains are helicoidal with their axes parallel to c.
Elution fractionation of poly(vinyl chloride)
Authors: Garbuglio C. , Mula A. , Chinellato L. 
Published: June 2010

AbstractTwo samples of PVC of different stereoregularity were elation fractionated by using the eyclohexanone‐ethylene glycol system under various experimental conditions. Inversions of viscosity in the less soluble fractions were shown in some cases and were found to be related to crystallinity effects. They were eliminated by operating at high temperature and by precipitating the polymer on the support by rapid cooling of the solution. Some data are reported on the M.W.D. of the fractions which seem to indicate a satisfactory efficiency of the fractionation method used.
Optical investigation into the crystallization of polyolefines from dilute solutions
Authors: Scholte Th. G. 
Published: June 2010

AbstractWith the aid of a modified Sofica light‐scattering apparatus an investigation was carried out of the crystallization of polyolefines from dilute solutions in several solvents. The intensity of the light scattered at various angles was determined as a function of time in the initial period of crystallization. Both linear polyethylene and polypropylene in p‐xylene and in 1‐chloronaphthalene showed the formation of disk‐shaped crystals, which, after their formation, rapidly grew.
Luminescence spectra of impure molecules and polymer matrix structure
Authors: Egorov G. P. , Moisya E. G. 
Published: June 2010

AbstractLuminescence spectra of anthracene solutions in polyethylene matrices were studied for various solute concentrations at 77°K. The impurity spectrum appeared to be a summation of at least two spectra corresponding to different types of interstitial dispersion of anthracene in crystalline and amorpous regions of polyethylene. The sensitivity of impurity electronic spectra to structural effectson the polymer matrix (variation in crystallinity, quenching) was found to be high. This leads to the assumption that impurity electronic spectra may serve as an “indicator” of structural transformations in the polymer (this possibility is illustrated with the cold‐drawing of polyethylene). Also noted were unusually large energy spacings for electron transitions which occur with different interstitial arrangements of impurity in polyethylene. These result from specific intermolecular interactions within the crystalline and amorphous regions, and thus characterize the morphology of the polymer.
A study of structural changes taking place upon orientation and in the process of annealing oriented polymers
Authors: Zubov Yu. A. , Selikhova V. I. , Tsvankin D. Ya. , Markova G. S. , Kargin V. A. 
Published: June 2010

AbstractThe reversible character of the deformation of polyethylene films containing well‐defined spherulitic structures was shown by optical microscopy. The sizes of crystalline and defect (amorphous) regions were derived from theoretical calculations based on the data of small‐angle x‐ray diffraction. The specimens were obtained by annealing them in the stretched state. The dependence of the long period on the annealing temperature for oriented fibers of polyethylene, polycaproamide, and polypropylene was found. The possibility of irreversible and reversible structural changes was shown by means of a small‐angle x‐ray diffraction method.
Vibrational and NMR spectra and conformational analysis of stereoisomers of 2,4‐pentanediol, 2,4,6‐heptanetriol, and the corresponding acetates
Authors: Doskočilová D. , Štokr J. , Votavová E. , Schneider B. , Lím D. 
Published: June 2010

AbstractNMR and infrared spectra of pure stereoisomers of 2,4‐pentanediol, 2,4‐pentanedioldiacetate, 2,4,6‐heptanetriol, and 2,4,6‐heptanetrioltriacetate were measured in different solvents at several temperatures. The structure of rotational isomers was determined by analysis of the methylene proton band in NMR spectra and by analysis of vibrational spectra. From temperature changes of NMR and infrared spectra, conformational equilibria of various stereoisomers were determined. The consequences of the present findings for the interpretation of polymer spectra are discussed.
The kinetics and mechanism of thermal and thermal‐oxidative degradation of formaldehyde polymers
Authors: Dudina L. A. , Karmilova L. V. , Tryapitsyna E. N. , Enikolopyan N. S. 
Published: June 2010

AbstractThermal degradation processes are of great importance in the case of polyoxymethylene. Establishment of the mechanism of oxidative decomposition is particularly important, because it proceeds under conditions when depolymerization is predominant over oxidation. The basic kinetic regularities of thermal and thermal‐oxidative degradation of polyoxymethylenes have been determined, and differences have been observed; that depend on the chemical nature of endgroups. Thermal degradation proceeds as depolymerization with generation of active centers at the chain end for POM hydrate, and following the “random law” for end‐capped POM and copolymers. The “kinetic” chain is shorter than the “substance” one. Formaldehyde participates in chain transfer of POM degradation. A method has been proposed for determining the true activation energy of reactions that are more complicated due to heat transfer. The true E of POM for different end groups has been determined. The thermooxidative decomposition proceeds as depolymerization initiated by oxygen and follows the “random law.” Oxygen has an inhibiting effect by reacting with active centers of POM. The degradation rates and accumulation of formic acid depend on the nature of end groups, and HCOOH acts as an accelerator. The most probable sources of HCOOH were proposed, and the active centers of POM degradation are shown to be of a dual nature. The mechanism of degradation and some principles of stabilization are proposed.
Untersuchungen Über die Lineare Volumennachwirkung bei Amorphen Hochpolymeren
Authors: Goldbach G. , Rehage G. 
Published: June 2010

AbstractMeasurements of isothermal‐isobaric volume retardation occurring in atactic polystyrene after temperature and pressure jumps applied to the material are reported. The volume post‐effect could be measured at very small deviations from internal equilibrium and therefore linear retardation behavior was obtained. In this case, different kinetic theories give an exponential time dependence of volume deviation from the equilibrium value due to the presence of a single reatrdation time. This prediction was not corroborated by our experiments. It was found that the isothermal‐isobaric volume post‐effect could not be described, at least with styrene, by a single retardation time but that it was necessary to assume a retardation time distribution.
Grafting some polymers on a glass surface treated with titanium tetrachloride
Authors: Lipatova T. E. , Skorynina I. S. 
Published: June 2010

AbstractIt is shown that when polymerization of styrene, dimethacrylate(bistriethyleneglycol)‐phthalate and epoxy resin takes place in the presence of the glass fiber treated with TiCl4 or SnCl4, the grafting of polymers onto the glass surface proceeds. The amount of grafted polymer depends on the reaction temperature and conditions of treatment of the fiber. By means of polarography it was established that TiCl4 is firmly bonded with glass surface and, as a consequence, noticeable reinforcement of the fiber takes place. It is shown that due to inhomogeneity of the glass surface, grafting is realized in some separate places and grafted polymer is there in the form of little gammas of a size that changes from 2 to 14 μ. Some investigation of the peculiarities of grafting were also fulfilled and data on tensile strength of glass fiber before and after grafting some polymers in different conditions of treatment onto it were obtained. Grafting of styrene was also realized onto the surface of PVA film treated with TiCl4, as PVA can be considered a model of a glass fiber due to the existence of the surface OH groups of it. All these data enable us to conclude that OH groups of the glass forming some complexes with catalyst molecules are centers of grafting.
Some peculiarities of cationic polymerization of trioxane
Authors: Enikolopyan N. S. , Irzhak V. J. , Kravchuk I. P. , Plechova O. A. , Rakova G. V. , Romanov L. M. , Savushkina G. P. 
Published: June 2010

AbstractThe polymerization of trioxane in various solvents and in the presence of different catalysts has been investigated. Effect of the catalyst on the induction period was studied and the kinetic criterium for establishing the nature of the induction period was suggested. The maximal rate of polymerization is first order with respect to the catalyst concentration and of different high orders with respect to the monomer concentration, depending on the solvent. The polymer molecular weight is proportional to the extent of conversion, the slope being dependent on temperature. The explanation of this phenomenon involves reactions of chain transfer with scission occurring in these systems.
Superconductivity of organic polymers
Authors: Little William A. 
Published: June 2010

AbstractA recent suggestion that superconductivity might be able to occur in certain types of organic macromolecules at temperatures near room temperature will be discussed. A crude description of the microscopic theory of superconductivity will be given first and from this it will be argued why superconductivity should be able to occur in certain highly specific types of organic macromolecules. Why the transition temperature for the onset of superconductivity should be high compared to that of metallic superconductors will be discussed together with recent developments in the field.
Anisotropy of electrical conductivity in doubly oriented nylon 66
Authors: Seanor D. A. 
Published: June 2010

AbstractThe electrical conductivity of doubly oriented nylon 66 has been studied as a function of direction over the temperature range 23–150°C. Measurements were made (a) along the chain axes, (b) along the hydrogen‐bonded planes perpendicular to the chain axes, and (c) perpendicular to the hydrogen‐bonded planes. A complicated dependence of conductivity on pretreatment was found. In general the conductivity over the whole temperature range was anisotropic, being least along the chain axes and, after a number of thermal cycles, greatest along the hydrogen‐bonded planes perpendicular to the chain axes. Below 120°C. the activation energy of conductivity was also anisotropic. At temperatures higher than 120°C. the temperature dependence is isotropic. The anisotropy of the activation energy and conductivity are explained in terms of activated mobility and structural parameters. Water vapor had a pronounced effect on the conductivity. It lowered the activation energy of conductivity while increasing the overall conductivity in an anisotropic manner. The conductivity along the chain axes was again less than that parallel and perpendicular to the hydrogen‐bonded planes. The activation energy of conductivity along the chain axes was equal to that parallel to the hydrogen‐bonded planes. The increase in conductivity caused by the adsorption of water was greatest along the chain axes. Four factors may contribute to the observed effects: (a) increased dielectric constant, (b) increased carrier concentration, (c) increased charge carrier path length, and (d) plasticization.
Conductivity of iodine
Authors: Ham Joe S. 
Published: June 2010

AbstractAn anisotropy of the electrical conductivity is observed in single crystals of iodine both by direct electrical measurement (a.c. and d.c.) and by thermally generated noise. These observations are inconsistent with the much smaller anisotropy found by Simhony and co‐workers in the drift mobility unless one invokes a complex band structure or assumes that the light alters the properties of the crystal during the drift mobility measurements.
Crystallinity from thermal measurements
Authors: Dole Malcolm 
Published: June 2010

AbstractThe problems involved in the determination of the fraction of crystallinity by thermal measurements are discussed. It is shown that in certain cases specific heat measurements themselves can be used to estimate the fraction of crystallinity. In the case of specific heat data on single crystals of polyethylene obtained by Karasz and Hamblin the specific heats are a linear function of the reciprocal fold length and can be extrapolated to infinite fold length to obtain the specific heat of 100% crystalline polyethylene. This extrapolated value is compared with other estimates and is used to calculate the fraction of crystallinity of polyethylene of different forms. Within the experimental uncertainties it would appear that estimates of the crystallinity from calorimetric, x‐ray, dilatometric, and infrared measurements are all in substantial agreement.