bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural studies of several helical polymers
Authors: Tadokoro Hiroyuki 
Published: June 2010

AbstractAn extension of Bunn's nomenclature of polymer conformation is given with several examples. The structures of polyethers expressed by a general formula [(CH2)mO]n with m = 1–4 are described and discussed with respect to the properties. Poly‐oxymethylene molecule has a helical structure which contains nine chemical units and five turns in the fiber identity period, and is the sequence of the internal rotation angle 78°13′. Detailed structure analysis of this polymer was made by the method of three‐dimensional Fourier synthesis. The diffraction data were measured on a highly ordered sample prepared from a single crystal of tetraoxymethylene by solid‐state radiation polymerization. It was deduced from the experimental results that the polyoxymethylene crystallite is composed of only one type of helix, either right‐handed or left‐handed. The poly(ethylene oxide) molecule is a loosely turned helix, and is a succession of nearly trans, trans, and gauche conformations. The structure of polytetrahydrofuran is essentially a planar zigzag. It has been also found quite recently that the third member, polyoxacyclobutane, has three types of crytalline modifications. One is planar zigzag, and the other two have longer fiber periods; T3GT3Ǧ and (T2G2)2 types. The structure of polyallene [CH2C(CH2)]n is also discussed; this polymer is a succession of nearly gauche conformations, the internal rotation angles being about 65°.
Mechanical properties and fine structure of drawn polymers
Authors: Takayanagi Motowo , Imada Kiyohisa , Kajiyama Tisato 
Published: June 2010

AbstractComplex moduli of oriented specimens of polyethylene (PE), polypropylene (PP), polyoxymethylene, polyethylene oxide), and polytetrahydrofuran were measured in sheet form as a function of direction. The dynamic tensile modulus (E′) along the stretched direction (0° direction) was found to be lower than that perpendicular to the stretched direction (90° direction) above the temperature of primary dispersion (αa) for all polymers cited above. Below the temperature of an dispersion the E′ value of 0° direction is higher than that of 90° direction as expected from the anisotropy of modulus of the crystal. This fact leads us to the model that the crystalline region (C) and this amorphous region (A) are arranged mainly in series along the stretched direction and at the same time the C region should be more or less continuous along the 90° direction. The actual drawn sample is composed of many microfibrils as proved ł y the x‐ray small‐angle scattering. Those conditions imposed on the model should be satisfied even when many microfibrils are bound together into a fiber. This picture agrees with the structural model of hot‐drawn PE presented by Hosemann after its slight modification. Effects of cold drawing on the anisotropy of modulus were also surveyed.
On the Structure and Properties of Polyamides. XXVII. The Mechanism of Water Sorption in Polyamides
Authors: Puffr R. , Šebenda J. 
Published: June 2010

AbstractThe sorption and the desorption isotherms of water are described for several crystalline polyamides (nylons 2, 3, 6, 7, 8, 11), amorphous polyamides (poly‐C‐methylcaprolactam, terpolymer of caprolactam, aminoheptanoic acid and aminoundecanoic acid) and model amides (N‐ethyl acetamide, Y‐ethyl butyramide, N‐butyl capronamide) at 27°C., with amides also at 40 and 55°C. On the basis of our own as well as reported data (on sorption isotherms, heat balance of sorption, sorption heats, infrared absorption, nuclear magnetic resonance, mechanical properties of polyamide‐water systems), we propose the following mechanism for the sorption of water in polyamides (capillary condensation is not considered): In nylon 6, three molecules of water are sorbed on two neighboring amide groups in an accessible region. The first molecule forms a double H‐bonds between the CO groups (firmly bound water) and the other two molecules form H‐bonds between the CO and the NH groups (loosely bound water). It turns out that even in nylons 2 to 6, water is probably sorbed by this mechanism whereas in nylons 8 to 12 only one molecule of water is sorbed on two amide groups, probably as a firmly bound water. Nylon 7 stands somewhere between the two groups.
Influence of Thermodynamic Quality of a Solvent upon Non‐Newtonian Viscosity of Poly(methyl Methacrylate) Solutions
Authors: Quadrat O. , Bohdanecký M. , Munk P. 
Published: June 2010

AbstractUnlike the monotonous decrease of both the reduced and intrinsic viscosity with the increase in shearing stress with polystyrene, polyisobutylene, and other polymers in thermodynamically good and poor solvents, the dependence of the viscosity on the shearing stress, with poly(methyl methacrylate) solutions in the vicinity of θ‐temperature, shows an anomalous course. Reduced viscosity at first decreases with the increase in shearing stress; at 50 to 150 dynes/cm.2 it reaches a minimum but thereafter rises. The effect disappears with infinite dilution. The increase of reduced viscosity with the increase in shearing stress is in connection with a great increase of the Huggins constant, which means a high molecular interaction. Since this behavior at θ temperature does not occur with other polymers, it seems to depend on the specific structure of poly(methyl methacrylate).
Diffusion in gels
Authors: Špaček P. , Kubín M. 
Published: June 2010

AbstractA new method for the determination of diffusion as well as partition coefficients of low molecular weight substances in membranes of polymers was developed, based on the solution of Fick's equation with appropriate boundary conditions (both concentrations variable). On its basis D and k of dilute (0.05%) KCl solutions in swollen hydrophilic gels of different porosity were determined. From the temperature dependence of diffusion coefficients the activation energy of the process was computed and a simple model describing the structure of the heterogeneous membrane was proposed. The diffusion coefficients strongly depend on the structure of the system investigated.
Viscoelastic properties of single crystal mats of some polymers and polymer crystal obtained by radiation‐induced solid‐state polymerization
Authors: Takayanagi Motowo , Imada Kiyohisa , Nagai Akihiko , Tatsumi Tetsujiro , Matsuo Takaaki 
Published: June 2010

AbstractMeasurements of the tensile dynamic viscoelasticity have been made in the temperature range from −170°C. to near the melting temperature at 110 cps on the single crystal mats of linear polyethylene with different lamella thickness and trans‐1,4‐polybutadiene, and the polymer crystal of polytetraoxane prepared by the radiationinduced solid‐state polymerization of tetraoxane. Under the conditions of measurements, the stress applied is almost perpendicular to the molecular axis for the single crystal mat and parallel to the molecular axis for the polytetraoxane crystal. The crystalline absorption of the single crystal mat of linear polyethylene shifted to the high temperature side and increased its intensity with increasing lamella thickness. The single crystal mat of trans‐1,4‐polybutadiene showed the comparatively large primary absorption, which was almost eliminated by heat treatment. This phenomenon may be caused by the existence of loose loops in the sample of single crystal. Various absorptions of polyoxymethylene such as the crystalline and the low temperature secondary absorption, which was remarkable in the single crystal mat, almost completely vanished for the polytetraoxane crystal, and outstanding constancy of the dynamic modulus was attained close to the melting temperature 190°C.
Crystallization and ordering processes in polyhydrocarbons with chemically irregular chains
Authors: Platé N. A. , Kheu Tran , Shibaev V. P. 
Published: June 2010

AbstractAn x‐ray, electron microscope, and mechanical properties study was carried out on polyethylene, isotactic polypropylene, and trans‐1,4‐polyisoprene (gutta‐percha) with different degrees of chemical irregularity made by halogenation reaction of these regular polymers. The gradual distortion of chemical regularity causes a change in crystalline lattice parameters, degeneration of crystalline spherulitic structure, and simplification of supermolecular structures of the polymers investigated. The introduction of chemical irregularity is analogous to supercooling of a crystalline polymer with suitable change of mechanical properties and morphological forms of structures. In the case of gutta‐percha, chlorination in films also favors the α to β transition within the crystalline state. It has been found that stretching of vulcanized samples of chlorogutta‐percha at temperatures above its melting point proceeds with an essential change in internal energy and increase of entropy. A supposition has been made about the structure peculiarities of chlorogutta‐percha which permit the appearance of such an effect. A total picture of change of different parameters and properties is given from the point of view of gradual transformation of the stereoregular polymer to an irregular amorphous one.
Cyclic polymerization of N‐dimethacrylamides
Authors: Sokolova T. A. , Rudkovskaya G. D. 
Published: June 2010

AbstractMonomer dimethacrylamides are polymerized on heating in bulk and in solution, yielding soluble and fusible polymers which contain practically no unsaturation. Similar polymers are obtained by partial thermal deamination of polymethacrylamides at 300°C. in vacuum. Infrared spectroscopy has shown that the polymers obtained by the polymerization of the monomer N‐substituted dimethacrylamides consist of fivermembered cycles (the region of carbonyl absorption 1700‐1790 cm.−1) linked by a bridge of two methylene groups. The polymers obtained by deamination of polymethacrylamides contain six‐membered cycles (carbonyl absorption in the range from 1680 to 1730 cm.−1) linked by one methylene group. This is confirmed by a comparison of the infrared spectra of the polymers and of model compounds: imides of succinic and glutaric acids. Dimethacrylamide is an exception, its polymerization yields a polymer consisting of 5‐membered cycles as well as 6‐membered ones. X‐ray analysis shows the polymer obtained by thermal deamination of polymethacrylamide to be oriented and highly crystalline. Some properties of the polymers obtained are described.
Kinetics and mechanism of acrylonitrile polymerization by p‐toluene sulfinic acid. I. Experimental
Authors: Amdur Shimon , Shavit Nehemia 
Published: June 2010

Abstractp‐Toluene sulfinic acid (TSA) of a high degree of purity, halide free and low p‐toluene sulfonic acid (TOSA) content, was prepared. A cooled‐capillary dilatometer was constructed for the study of the bulk heterogeneous polymerization up to high conversions. Acids were found to show both cocatalytic and inhibitory activities, depending on their type and concentration. The bulk polymerization of acrylonitrile (AN) by TSA shows the usual autoacceleration, which was found however to be depressed or even eliminated by the addition of TSOA and other acids. An autoacceleration phenomenon was found in the solution polymerization of AN at 60°C. by TSA alone. In this case the addition of small amounts of TSOA eliminated the autoacceleration. On addition of TSOA to samples of constant TSA concentration, in bulk or in solution, the initial rate increases, reaches a maximum, and then decreases. A decrease in rate was also observed in the azo‐initiated bulk polymerization on addition of TSA + TSOA. Increasing the concentration of TSOA or H3PO4 in the bulk polymerization, at constant TSA concentration, leads to a lowering of molecular weight. The order of the polymerization with respect to TSA was found to be between 1.1 and 1.5, depending on the TSOA concentration. The results are explained by an enhancement of the TSA initiation through its interaction with a proton, and the role of a TSA‐proton complex in a retardation mechanism.
Phase separation during the formation of three‐dimensional polymers
Authors: Dušek K. 
Published: June 2010

AbstractPhase separation during the formation of three‐dimensional polymers in the presence of inert diluents, by crosslinking of linear polymers, or by polymerization of multifunctional monomers, was treated under the assumption of thermodynamic equilibrium by using the Flory theory of swelling equilibria and rubber elasticity. The separation begins when the maximum swelling of the network in the diluent or diluent‐monomer mixture drops to the degree of dilution of the network; the two quantities remain equal even after separation of phases. The network formed in this way is a composite one. Relations have been derived for the dependence of composition and volume of the network phase upon initial conditions and degree of crosslinking or extent of polymerization. The results of calculations for binary and ternary model systems are discussed with respect to syneresis or formation of porous structures, as two possible modes of phase separation.
Rheo‐optical studies of high polymers. IX. A study of deformation process of low‐density polyethylene by simultaneous measurements of stress, strain, and infrared absorption
Authors: Onogi Shigeharu , Asada Tadahiro 
Published: June 2010

AbstractAs one of rheo‐optical methods to study the relation between structure and mechanical properties of high polymers, simultaneous measurement of the stress, strain, and IR absorption during the experiments involving stress relaxation and stretching at constant rate of strain has been developed. The IR absorbances measured with radiations, both unpolarized and polarized, for the crystalline bands near 725 cm. −1 of low‐density polyethylene can attain their equilibrium values in a time shorter than 1 sec. during the stress relaxation, being consistent with the results obtained by the dynamic birefringence method. In the case of stretching at a constant rate of strain, the orientation functions of crystallographic axes can be obtained as functions of strain from the dichroic ratio. The orientation function vs. strain curves and the corresponding stress‐strain curve for low‐density polyethylene film in the machine direction are divided into four regions according to the magnitude of strain. On the basis of comparison of these curves with each other and by employing the current model of folded chains, an interpretation has been given of the above four regions in the stress‐strain curve.
The pore structure of macroreticular ion exchange resins
Authors: Kun Kenneth A. , Kunin Robert 
Published: June 2010

AbstractA series of new cation and anion exchange resins differing entirely from conventional homogeneous (microreticular) gels and having a rigid macroporous structure similar to those of conventional adsorbents are characterized. These ion exchangers have been designated as macroreticular ion exchange resins. A detailed analysis is made of the pore structure of the resins including pore size distribution, surface area, and electron micrographs. From these data a model of the physical structure is presented. The relationship between the physical structure and utility of these ion exchange resins is developed for various areas of application, including catalysis, adsorption from nonpolar solvents, and the adsorption of large molecules such as peptides and proteins. The effect of hydration upon the pore structure of several of the macroreticular ion exchange resins is critically evaluated also. During the course of hydration, the gel portion hydrates first and this is followed by the filling of the macroreticular pores. From these data one is able to ascertain the pore structure not only in the anhydrous state but also in aqueous media.
Vinyl chloride polymerization initiated by the interaction of organoaluminum compounds and various agents
Authors: Minsker K. S. , Sangalov Yu. A. , Razuwayev G. A. 
Published: June 2010

AbstractInteractions of organic aluminum compounds and organic or inorganic halogen‐containing compounds (halogens, haloid alkyls, saturated or unsaturated chlorocarbons, metal halides, halogen anhydrides of organic acids) were used to polymerize vinyl chloride. Utilization of the foregoing reactions makes it possible to polymerize vinyl chloride at low temperatures (+20 to −50°C.). The polymerization process can be controlled by adjusting the reaction conditions of the initiating components. Furthermore, the combinations of organic titanium compounds and some of the previously mentioned chlorocarbons were also used as active initiators. The polymers which were synthesized possessed novel properties as well as those which are characteristic to poly(vinyl chloride).
A study of the formation of supermolecular order in polymeric solutions by means of low‐angle scattering of polarized light
Authors: Frenkel S. Ya. , Baranov V. G. , Volkov T. I. 
Published: June 2010

AbstractA relatively simple device is described for studies of phase transitions in polymer solutions and films by means of low‐angle scattering of polarized light. The device differs from that described by Stein. It functions as a horizontal polarizing microscope, as a photodiffractometer, and as a photometer. A study was carried out of the structure formation in concentrated solutions of poly‐γ‐benzyl‐L‐glutamate with Mw = 105 in dioxane. At room temperature and in the absence of external fields a successive development of several levels of supermolecular order is observed. The structure formation starts with the spherulitic phase characterized by a cross‐shaped diffraction pattern. During their progressive growth the spherulites fill the volume of the solution and finally begin to collapse. This changes the scattering pattern to a circular one. The mechanical instability of this phase and the thermodynamic advantage of a parallel packing of rodlike particles leads to the appearance of an orientational order in the system with a rhombic‐shaped scattering pattern. The structure formation is completed with the development of a highly ordered liquid crystalline (cholesteric) phase characterized by a specific pattern similar to the x‐ray diffraction patterns of oriented crystalline polymers. A detailed interpretation of rhombic scattering pattern is presented based on an analysis of polarized light scattering from a system of noncoherent scattering elements with the shape of a rectangular parallelepiped. Expressions are derived connecting the shape and the size of the scattering pattern with the dimensions of a single scattering element, and with the optical properties of this element and of the supporting medium. The spherulitic growth habit in isotactic polypropylene solutions when subjected to cooling also has been studied. At temperatures below 100°C. the spherulites appear and the rate of their growth is dependent on the thermal history of the solution. Kinetic curves are obtained showing the existence of a “kinetic memory” in the system which is manifested by a pronounced acceleration of growth of the structure when the fusioncrystallization cycles are repeated.
Studies on phenolic resins. VII. The preparation of a new type of self‐crosslinking phenolic resin and the reaction mechanism of the crosslinking
Authors: Kumanotani Ju , Yoshikawa Toshio , Kubo Etsuji , Kawanishi Isamu , Okamura Takeshi 
Published: June 2010

AbstractA new type of a phenolic self‐crosslinking resin was prepared by the oxidation of the hydroquinone–phenol formaldehyde resins with chloric acid. The chemical behaviors of the resin in the process of self‐curing occurred by heating were followed by DTA and the infrared spectral analysis. Some physical properties such as glass transition temperature and the extent of crosslinking were examined for the cured resins by the swinging beam method and the solvent extraction method, respectively, and the excellent thermal rigidity of the cured resins was compared with that of the conventional phenolic resins cured with hexamethylenetetramine. The radical reaction mechanism in the self‐crosslinking of the resin is proposed from the results obtained in the reactions of p‐benzo‐quinone with some model phenolic compounds and that obtained in the observation of ESR spectrum of the quinhydrone system.
Relations between crystalline structure and dielectric properties of polyethylene
Authors: Booij H. C. 
Published: June 2010

AbstractSlightly oxidized polyethylenes show dielectric loss factor–frequency curves exhibiting three maxima. The magnitude of the α‐maximum at low frequencies is proportional to the oxygen content and to the weight of crystalline material per cc. The frequency of this maximum is in general higher as the degree of branching of the polyethylene increases. The frequency of the α maximum of solutions of n‐ketones in polyethylenes decreases with the length of the ketone and increases with the degree of branching of the polyethylene. A theory was developed which quantitatively describes the frequency of this α maximum as a function of the temperature, the chain length of the ketone, the average crystalline density of the polyethylene, and a quantity which is related to the twist energy per unit length of the chain. This theory can be experimentally used in to find a value for the length of the molecules participating in the α process in oxidized polyethylenes. The values found are about equal to the crystallite lengths, or the lamella thicknesses, of the polyethylenes.
Fractionation of polymers by crystallization from solutions. II
Authors: Pennings A. J. 
Published: June 2010

AbstractThe fractionation of polyethylene and polypropylene is carried out by establishing equilibrium between a polymer solution and the solid polymer. This procedure involves crystallization kinetics, crystal morphology, surface effects, and the formation of solid solutions. If the solution is stirred, the polymer forms thin fibrous crystals which adhere to the stirrer as a loose fabric. The experimental data on the precipitation and extraction of polyethylene in various solvents and of polypropylene indicate that fractionation takes place in the low as well as in the high molecular weight range. The components with a very high molecular weight crystallize first. The method appears to be especially suitable for the separation of branched from linear polymers, atactic from isotactic stereoisomers, and mixtures of polymers which differ considerably in crystallization rate. Thus, 46% pure polypropylene, 7% rubber, 1% pure polyethylene, in addition to block copolymers varying in structure, could be isolated from an ethylene‐propylene block copolymer.
Procédé Amelioré de Fractionnement des Polymères sur Support Inerte (Polypropylène, Polyéthylène, chlorure de Polyvinyle)
Authors: Ferrier Jean 
Published: June 2010

AbstractA two‐stage process is described: the first, stage is a fractional precipitation, the second a fractional dissolution. Preciptiation is carried out in a column containing glass beads and functioning under a temperature gradient. The polymer is washed with a poor solvent and subsequently a continuous linearly programed dissolution by a solvent‐preciptiant system takes place at constant temperature. This procedure has been applied successfully to polypropylene, polyethylene, and poly(vinly chloride). Reproductible results have been obtained independent of tacticity and cristallinity in every case. The separation obtained is very satisfactory.