bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study on orientation effects in polyethylene in the light of crystalline texture
Authors: Hay I. L. , Kawai T. , Keller A. 
Published: September 2014

AbstractA comprehensive study of the molecular orientation and crystalline texture (the latter by low‐angle x‐ray diffraction supplemented by swelling measurements) in doubly oriented polyethylene on consecutive stages of heat annealing has allowed a picture of the structure and reorientation processes to be outlined. Thus even a drawn and rolled branched polyethylene is found to contain lamellae having {h0l}s basal planes with obliquities of 35–45°, in close analogy to those found in crystals grown from dilute solution and extracted from unoriented bulk linear polyethylenes. The initial ranges of the relaxation can be described by consecutive interlamellar and intralamellar slips activated by a rubber elastic compression. The cohesion between the lamellae opposing this is also found to be partially rubber elastic, and it is demonstrated that the resultant of the two elastic forces can be shifted by physical and chemical means. The individuality of the lamellae—requiring an appreciable amount of chain folding—is borne out. The possibility of producing macroscopic single‐crystal analogs is also demonstrated.
Anisotropy and structure in uniaxially stretched amorphous high polymers
Authors: Hennig Jürgen 
Published: September 2014

AbstractWhen an amorphous polymer is stretched uniaxially, the chain molecules are oriented along the stretching direction. Orientation causes an anisotropy of the macroscopic physical properties with rotational symmetry about the stretching direction. The phenomenological treatment of the properties exhibited by a uniaxially oriented polymer follows mathematical methods known from crystal physics. Earlier data on anisotropy of linear thermal expansion, thermal conductivity, and linear compressibility for PVC are quantitatively explained with the aid of a known distribution function. The complete set of the five elastic compliances of hot‐stretched PVC are experimentally determined as function of stretch up to 180%. The correspondent compliances for the perfectly oriented material are calculated yielding, e.g., 5 × 1010 dynes/cm.2 for the Young's modulus along the chains. Finally, the lengths of the statistical segments in natural rubber and polychloroprene are evaluated from thermal conductivity measurements on these substances in the strained state. As is expected the polyisoprene chains prove to be considerably more flexible than those of polychloroprene.
ESR studies on transient free radicals during redox polymerization of some monomers
Authors: Fischer Hanns , Giacometti Giovanni 
Published: September 2014

AbstractBy application of a flow system, ESR spectra of transient free radicals are obtained during liquid‐phase polymerization initiated by ·CH3. The coupling constants of the radicals are discussed with respect to previous findings with \documentclass{article}\pagestyle{empty}\begin{document}$ \[{\rm HO}^ \bullet \] $\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ \[{\rm NH}_2 \] $\end{document}, and ·CH2OH initiation. Some differences in the reactions of acrylic acid with HO· and ·CH3 are also reported. In total, the results strongly support the usual assumptions on reaction schemes of radical polymerization.
Graft copolymerization in aqueous dispersion of acrylic acid on olefin copolymer
Authors: Severini F. , Pegoraro M. , Tavazzani C. , Aurello G. 
Published: September 2014

AbstractThe polymerization of acrylic acid dissolved in an aqueous latex of an ethylene–propylene copolymer in the presence of benzoyl peroxide leads predominantly to the formation of graft copolymers. The amount of acrylic acid transformed into grafted chains is very high and can reach 80% of the starting monomer. Studies were made of the influence of reaction variables (temperature, initial concentration of acrylic acid and of benzoyl peroxide, concentration of the olefin copolymer in the latex used) upon the conversion rate of the monomer in a grafted polymer. Besides benzoyl peroxide, different initiators have been examined and compared. A fractionation method of the reaction crude is described, leading to the separation of the graft copolymer from the other products present. A reaction mechanism is proposed.
Rheological behavior of dilute polymer solutions in a general velocity field
Authors: Takserman‐Krozer R. 
Published: September 2014

AbstractThe rheological equation of state (constitutive equation) and the average rate of dissipation of energy flow are calculated for dilute solutions of flexible chain macromolecules. It is shown that such solutions may be considered as nonlinear viscoelastic fluids, the parameters of the equation of state being determined by the structural characteristics of the system: relaxation times τi and internal viscosity ρi. It is shown that in a general case the stress tensor is asymmetric; the antisymmetric part vanishes for systems with zero internal viscosity (ideally flexible chains). On the basis of structural data it is shown that the rheological equation of state may be linearized when the stress tensor is referred to the actual structure of the system. For the general case (ρi > 0, chains with limited flexibility) the average rate of dissipation of energy in the flowing system depends on the asymmetric part of the stress tensor as well as on the symmetric part.
Molecular structures of some low molecular weight model compounds with conformational features similar to those of high molecular weight compounds
Authors: Corradini P. , Ganis P. , Pedone C. , Sirigu A. , Temussi P. A. 
Published: September 2014

AbstractAn x‐ray study has been made of several alkylated dicarboxylic acids. The presence of atomic groupings similar to those in high molecular weight compounds has furnished interesting information about some structural features of high molecular weight compounds which cannot be directly established in the study of their structure. An interesting indication has been grasped about the non‐equivalence of the valence angles on CH2 and on CH(CH3. On this basis, the internal rotation angles, which characterize the conformation of isotactic and syndiotactic polypropylene and of the alternating crystalline copolymer ethylene–butene‐2‐cis, have been recalculated.
Study of aromatic sulfide polymers: Poly(2,5‐thienylene sulfide)
Authors: Jones K. , Moodie I. M. 
Published: September 2014

AbstractTwo methods of synthesis of poly(2,5‐thienylene sulfide) have been developed. The first of these is based on the uncatalyzed condensation of thiophene with sulfur chlorides and the second on the self‐condensation of 2‐chloro‐5‐thiophene thiol promoted by cuprous oxide in dimethylformamide. The polymers obtained by both methods are linear in structure and probably of low molecular weight. The polymer decomposes at 250–260°C. in air and under nitrogen. A study of molecular models suggests that steric hindrance may play an important part in the low thermal resistance of poly(2,5‐thienylene sulfide). Comparisons are drawn with the analogous poly(phenylene sulfide).
Charge interactions and association in polyelectrolyte solutions. I. Some general remarks
Authors: Mandel M. 
Published: September 2014

AbstractSome aspects of charge interactions in polyelectrolyte systems as compared with ordinary electrolyte solutions are discussed. It is shown that two different kinds of association between counterions and polyions may be expected. These are distinguished as “physical” and “chemical” association, the difference being due to the exact nature of the interaction which is involved. The shortcomings of the usual theoretical treatments are emphasized, although no theoretical calculation is presented. Some experimental results are quoted to demonstrate the existence of different types of association. The necessity of not relying on one experimental method when investigating association phenomena in a given polyelectrolyte–counterion system is stressed.
Die Chemische Umsetzung des PVC mit Nucleophilen Reagentien
Authors: Wolkóber Zoltán , Varga Iraida 
Published: September 2014

AbstractPVC in DMF gelöst, zeigt aromatischen Aminen, Aminoalkoholen bzw. aliphatischen Aminen gegenüber eine unterschiedliche Reaktionsbereitschaft, Substitutions‐ und Eliminierungsrenktionen erfolgen. Ein Aminüberschuss verschiebt die Reaktion in das SN‐Gebiet. Die geringste Reaktionsgeschwindigkeit wurde mit aromatischen Aminen festgestellt. Die Reaktionsgeschwindigkeit ist hoch bei Äthanolaminderivaten, am höchsten bei aliphatischen primären Aminen. Der Substitutionsgrad der Amine spielt eine bedeutend grössere Rolle als die pKa‐Werte. Unter den aliphatischen Aminen zeigen die quaternären Derivate die höchste Reaktionsgeschwindigkeit, innerhalb einiger Stunden gehen als in DMF zu 50% eine E′‐Reaktion mit dem PVC ein. Die Reaktionsbereitschaft der primären Amine liegt bedeutend niedriger, die der sekundären und tertiären sinkt weiter. Das Molekulargewicht des eingesetzten Alkohols beeinflusst bedeutend die Dehydrochlorierung des PVC durch Alkalialkoholate. Die höchste Dehydrochlorierungsgeschwindigkeit ergibt sich in Propylalkohol. Bei gleichem Molekulargewicht entscheidet die Konfiguration des Alkohols. Am langsamsten verläuft die Dehydrochlorierung bei Gegenwart von n‐Primäralkoholen.
Investigation of the hydrodynamic behavior of diene polymers and copolymers in ideal mixed solvents
Authors: Poddubnyi I. Ya. , Grechanovskii V. A. , Podalinskii A. V. 
Published: September 2014

AbstractThe hydrodynamic behavior of a number of diene polymers and copolymers (including cis‐1,4‐polybutadiene, cis‐1,4‐polyisoprene, butadiene–styrene, and butadiene–acrylonitrile copolymers) has been investigated in suitable mixed τ solvents. The relations of the basic hydrodynamic parameters, namely, the sedimentation constant, the diffusion coefficient, and the intrinsic viscosity, to molecular weight have been established, and may be used in calculating molecular weight distributions of the polymers investigated. For all polymer–solvent τ systems investigated the values of the parameter ϕ⅓P−1 are shown to be considerably lower than those predicted by theory. For all systems mentioned a distinct dependence of sedimentation and diffusion constants on concentration has been established. The experimentally observed regularities are interpreted on the assumption that the hydrodynamic interaction between macromolecules in sedimentation and diffusion processes affects the magnitude of the translational friction coefficient of the macromolecules. The effect of this dependence of sedimentation and diffusion constants on concentration is shown to decrease as the compactness of the macromolecular coils is increased, i.e., when the “specific dimensions” of the macromolecules \documentclass{article}\pagestyle{empty}\begin{document}$ \[\overline {r^2 } /M \] $\end{document}, in a given solvent are decreased.
The effect of the chain length on the optical activity of the helical polymers
Authors: Aslanyan V. M. 
Published: September 2014

AbstractThe theoretical interpretation data for optical activity of helical oligomers and for partly helixed polymeric chains require answers to the following questions: (1) How many monomeric units must each helical part contain so that its contribution to the optical rotation should be such as that of the same number of monomers in the infinite helix chain? (2) What role does the monomeric unit play at the ends of the helix section? (3) How far does the close interaction in the helix extend? The aim of this work is to answer these questions. The macromolecules crystallized in the helices were investigated. Cases were studied where only neighbor or neighbor and nearest nonneighbor monomeric units are interacted. It is shown that the contribution of the monomeric units in the helical section, consisting of twelve units to the optical rotation, practically coincides with that in the infinite helix.
The diffusion process in swelling ion exchanger beads
Authors: Dickel G. , Richter K. 
Published: September 2014

AbstractDiffusion coefficients were evaluated from kinetic measurements on an ion exchanger by means of an equation of diffusion for swelling ion exchanger beads. It follows that the true diffusion coefficient changes with the ionic composition in such a way that it is smallest for the almost pure H form (DH) and greatest for the pure K form (DK). For the total change HR + K → KR + H of the pure H form to the K form the diffusion coefficient therefore must run from DH to DK. It is shown that one can describe the entire diffusion process with the constant DK value with the exception of a negligible induction period. On the other hand, one can describe the entire backward exchange process with the constant DH value. Therefore, the fact already found—that one can describe the exchange processes with constant but different diffusion coefficient for forward and backward reaction—is theoretically founded.
Méthode Graphique de Boltzmann pour la Détermination du Coéfficient de Diffusion de Translation
Authors: Soulie L. 
Published: September 2014

AbstractBoltzmann has examined the solution of the equation with diffusion partial derivatives, the so‐called second Fick's equations when the translation diffusion coefficientDis a function of the concentration. In a particular initial concentration distribution he presents an integral solution of which one limit is infinite; the other limit containsx/√t, wherexis the distance from the initial separation surface andtthe time after the start of the diffusion. The concentration should therefore depend only on the variablex/√t. On the basis of theoretical considerations and experimental controls it is shown thatDis not a function only ofx/√t.
Étude des Complexes Polymères Dérivés du Tétracyanoéthylène
Authors: Rougée M. , André C. 
Published: September 2014

AbstractSeveral polymer complexes of tetracyanoethylene (TCNE) and nickel acetyl acetonate have been prepared, taking special care for the purification and separation methods of the compounds which are obtained. The compounds are probably characterized by a conjugated double bonds system, as shown by infrared analysis and by the data of electric and magnetic measurements (RPE). The composition of the samples does not agree with a polyphthalocyanine type structure nor with that of a radical anion salt (TCNE−)2 · Ni+2, but corresponds to a TCNE/Ni ratio equal to 1. It is not yet possible to define the structure with accuracy, and other results will be necessary for this purpose. The properties of these compounds depend markedly on the condition of their preparation; the comparison with previous data is therefore delicate.
Stress birefringence and optical anisotropy of macromolecules in swollen polymers
Authors: Tsvetkov V. N. , Grishchenko A. E. 
Published: September 2014

AbstractStress birefringence of several polymers swollen in various solvents was experimentally investigated. Gels of polystyrene (PS), natural rubber (NR), polydimethylsiloxane (PDMS), cyanoethylacetylcellulose (CEAC), and cyanoethyltritylcellulose (CETC) were studied over a wide range of degrees of swelling from dilute solutions to concentrated gels. In all systems where the increment of polymer–solvent index of refraction dn/dc differs from zero the form effect in stress birefringence is observed to be proportional to (dn/dc)2 in accordance with the theory. The dependence of stress birefringence on the concentration of a polymer allows us to determine the relative roles of macro‐ and microform anisotropy in the total stress birefringence. For rigid chains of cellulose esters at all concentrations form birefringence appears to be a microform effect. For flexible chain molecules of synthetic polymers, the microform effect plays the principal part at high concentrations. According to theoretical predictions the magnitude of the microform effect for cellulose derivatives is many times greater than for flexible polymers. In both cases the form effect is caused neither by micelles nor by macroheterogeneities in gels, but is molecular in nature. Its magnitude depends on the segmental mass of the molecular chain. The use of the microform effect theory with experimental data obtained on stress birefringence of gels permits the determination of the masses of molecular segments Ms for all the polymers investigated. Values Ms thus obtained agree with segmental dimensions determined by viscometry and light‐scattering methods.
Crystal structure of isotactic poly (vinyl methyl ether)
Authors: Corradini P. , Bassi I. W. 
Published: September 2014

AbstractThe crystal structure of isotactic poly(vinyl methyl ether) has been defined on the basis of x‐ray fiber spectra. Isotactic poly(vinyl methyl ether) crystallizes in a rhombohedral unit cell whose constants referred to hexagonal axes are: a = b = 16.25 ± 0.15 A., c = 6.50 ± 0.05 A. (chain axis) Z = 18, dcalc. = 1.168 g./cm.3. Probable space group \documentclass{article}\pagestyle{empty}\begin{document}$ \[R\overline 3 \] $\end{document}. Themagnified imagemonomeric units repeat along a threefold helix. Atomic positions were deduced by trial and error. Right‐handed and left‐handed macromolecules are contained in the unit cell and each macromolecule is surrounded by three enantiomorphous, anticlined macromolecules. The internal rotation angles around the CC bonds, defined with respect to the main chain bonds, have been found to be 280° and 160° for the right‐handed helix (the macromolecule is growing anticlockwise) and 80° and 200° for the enantiomorphous macromolecule. A comparison between the packing of the macromolecules of isotactic poly(vinyl methyl ether), of isotactic poly‐α‐butene (modification 1), and of other isotactic polymers is carried out.
Investigation of the ∈‐caprolactam polymerization process in the presence of hydrazine derivatives
Authors: Grekov A. P. , Yanchevsky V. A. , Kornev K. A. , Sukhorukova S. A. 
Published: September 2014

AbstractThe caprolactam polymerization process in the presence of the hydrazine derivatives has been investigated. During polymerization of ∈‐caprolactam in the presence of these initiators an induction period was observed in all cases due to formation of the product of the interaction of caprolactam with the initiator. The induction period and the molecular weight were ascertained to decrease with increase in the initiator's content. The initiator penetrates into macromolecular chain and thus regulates its molecular weight. The reaction rate was shown to be proportional to the square root of the initiator concentration. The given process obeys the kinetic regularities of a reversible first order reaction with respect to the monomer concentration and it agrees with the Arrhenius equation. On the basis of this investigation the scheme of the process was suggested and the constants of the initiation and the chain growth rate were calculated.
Study of crosslink formation by partial conversion properties. III. Copolymerization of styrene with polyethylene fumarates
Authors: Burnett G. M. , Pearson J. M. , Smith J. D. B. 
Published: September 2014

AbstractThe copolymerization of polyethylene fumarate and styrene has been investigated in dilute solution in dioxan at 60°C. by using partial conversion molecular weight to follow the reaction. Reactivity ratios have been measured, and the effects of reactant concentration on these ratios are discussed. The results are interpreted in terms of the relative contributions of inter‐ and intramolecular crosslinking reactions to the system.
Influence de la Morphologie a L'état Solide des Constituants des Copolymères Greffés sur leur Comportement Physicomecanique. Système Polyacrylate d'éthyle et Copolymère Styrolène–Anhydride Maléique
Authors: Agostini M. , Lebel P. 
Published: September 2014

AbstractSimilarly to most graft polymers, the system examined in this study presents in the solid state two phases, each of which can be spread out or entangled. If the spreaded compound is present in sufficient proportion, it forms the continuous phase and its nature determines the macroscopic properties of the graft copolymer. The graft copolymers were prepared using the preozonizations technique with backbone and graft being alternatively ethyl polyacrylate (PAE) and a styrene‐maleic anhydride copolymer (PSAM). The phases separation is taken in evidence with the electron microscope. The influence of the nature of the continuous phase on the chemical properties is shown by dynamometric measurements. The differential thermal analysis shows that there is no ship of the glass transition temperatures (Tg) with respect to those of both homopolymers, but that the entropy changes at the transition are function of the spreading out of the polymer chains. Dielectric relaxation measurements show an absorption identical to that of the α relaxation of PAE. In a graft copolymer where PSAM is the continuous phase and therefore appears to be rigid, the entangled chains of PAE of the discontinuous phase possess a higher mobility than when they form the continuous phase.
Crystallization kinetics of polycarbonates. I
Authors: Turska Eligia , Przygocki WĐAdysđaw , Masđowski Marian 
Published: September 2014

AbstractResearch on the kinetics of crystallization of polycarbonates based on bisphenol A at 190°C. has been carried out on six polydisperse samples. It was found that the process of crystallization, after a long period of induction, follows a course which can be described by the classical equation of Avrami. The final amounts of crystallization are small, ranging from 18 to 28%. Crystallization kinetics of polycarbonates depends on molecular weight and on the previous treatment of the polymer.
Role of free volume changes in polymer solution thermodynamics
Authors: Patterson D. 
Published: September 2014

AbstractThe thermodynamic effect of free volume changes in mixing is treated with the use of the corresponding states theory of Prigogine and collaborators. The interaction parameters χ1, κ1, ψ1 and their concentration dependences are derived. Each parameter contains two terms. The first is due to differences in cohesive energy and sizes between segments of polymer and solvent: the second or “structural” contribution is due principally to the difference in chain lengths between polymer and solvent. The structural effect gives a large value of χ1 ∼ 0.4 for a polymer with a chemically identical short oligomer as solvent. A minimum but nonzero value of χ1 occurs for a solvent with higher cohesive energy than between polymer segments. At high temperatures a lower critical solution temperature must occur due to the increase of the solvent configurational heat capacity to infinity as the solvent vapor‐liquid critical point is approached, the heat and entropy of dilution becoming negative. At ordinary temperatures χ and κ increase with polymer concentration. The solubility parameter approach is compared; particular polymer liquid models used by Prigogine and by Flory are briefly discussed. χ1 as calculated for natural rubber and a variety of solvents and fair agreement is obtained with published values.