bluuebunny/crossref_metadata_2025_split huggingface dataset:
Étude éxpérimentale de la Conductivité en Courant continu des Composés macromoléculaires
Authors: Yu L. T. , Borredon M. S. , Jozefowicz M. , Belorgey G. , Buvet R. 
Published: September 2014

AbstractLors des études de conductivité en courant continu, en fonction de la température, effectuées sur des composés macromoléculaires dopés par des substances gazeuses, il est nécessaire de s'assurer que le taux de dope du matériau constituant l'éprouvette de mesure reste constant pendant toute la durée des mesures. On décrit un dispositif expérimental de conditionnement de l'éprouvette de mesure permettant le maintien à une valeur constante du taux d'hydratation d'un polymère hydrophile, lorsque la température varie. Les résultats relatifs aux polyamides, au polyacrylonitrile, et aux sulfates d'éméraldine obtenus avec l'aide de ce dispositif sont reproductibles avec une bonne précision; ces résultats montrent que l'eau absorbée a une influence prédominante sur la valeur de la conductivité de ces polymères. Dans le cas des sulfates d'éméraldine hydratés on montre que la conductivité est sans ambiguïté d'origine électronique; néanmoins l'influence de l'eau est considérable. On en conclut que le fait que l'eau absorbée ait une influence sur la conductivité d'un polymère hydrophile ne saurait constituer une preuve excluant le caractère électronique de celle‐ci.
Paramagnétisme de Complexes à Transfert de Charge Macromoléculaires
Authors: Andre J. J. , Weill G. 
Published: September 2014

AbstractOn a étudié comparativement la résonance paramagnétique électronique des complexes d'éthyldiméthylaniline et de polydiméthylaminostyrène avec le chloranile à l'état solide et dans des solvants de polarité différente. Le polymère et l'élément de répétition donnent des signaux peu différents (valeur de g, largeur de raie, saturation). Cette identité permet néanmoins de préciser l'origine moléculaire du paramagnétisme à l'exclusion de défauts de réseau. L'exaltation du signal par irradiation optique révèle qu'il doit être dû à la paire d'ions‐radicaux dont le temps de recombinaison est de l'ordre de 10−4 sec. L'influence du solvant peut jouer soit sur la fraction ionique à l'état fondamental, soit sur l'énergie relative des niveaux singulet, biradical et triplet de la paire d'ions‐radicaux.
Relations entre Indice de Fluidite à Chaud, Viscosité à l'État Fondu, Viscosité Intrinsèque et Température pour le Poly(éthylène Térèphtalate) et pour un Poly(éthylène Térèphtalate) Partiellement Modifié
Authors: Manaresi P. , Giachetti E. , De Fornasari E. 
Published: September 2014

AbstractMethods for the determination of melt index and melt viscosity of poly(ethylene terephtalate) (PET) were performed. Measurements of melt index at different temperatures and of melt and intrinsic viscosity were carried out on laboratory samples. Relations have been obtained and theoretically interpreted among the above parameters. These relations allowed us to utilize melt index data in order to estimate melt viscosities and molecular sizes of PET. Melt indexes were found to be inversely proportional to newtonian melt viscosities. The relations among intrinsic viscosity, melt viscosity, and melt index, respectively, were found to be linear in a log‐log plot. The effect of temperature on melt index values was found to agree with the Andrade equation. The energy of activation of the viscous flow was calculated and showed a slight dependance on molecular weight.Measurements were also carried out on an adipic acid–terephtalic acid–ethylene glycol copolymer. It was possible also in this case to obtain relations among the above parameters which were similar to the ones obtained for PET. However, the melt viscosity of the copolymer was always lower than the one of PET at the same intrinsic viscosity. This effect was attributed to an increase in chain flexibility.
Mechanismus und Kinetik der Poly‐∈‐caprolactam‐Bildung unter Berücksichtigung von Amidin‐Zwischenstufe
Authors: Csürös Z. , Bertalan Gy. , Nagy J. , Trézl L. , Körösi J. 
Published: September 2014

AbstractThe most important reaction of the polycaprolactame formation is the lactame addition under ring opening on the end groups. This reaction, in accordance with Körösi's data, is composed of two consecutive steps: the condensation of and ∈‐caprolactame, forming amidine salt and water reaction products and, the hydrolysis of amidine salt. To find if, amidin formation is a general part of cationic polycaprolactame formation, research work has been carried out in two directions:
Oligomer studies. Equimolar mixture of caprolactame and of n‐butylamine HCl, has been studied to obtain amidine salt intermediate in the oligomer mixture. The formed amidine salt, N‐[1‐aza‐cycloheptene‐(1)‐yl‐(2)]‐butylamin. HCl has been identified by thin‐layer chromatography. Some additional chemicals, such as phosphorpentoxide, increase the quantity of amidine salt in the fusion. Other additional agents, however, such as water of some acids, can cause it to decrease or disappear completely.
Kinetic studies. The stability of the amidine salt had been investigated, aqueous solution of N‐[1‐aza‐cycloheptene‐(1)‐yl‐(2)]‐butylamin. HCl having been used as initiator. According to our supposition, the amidine salt reacts with water in two directions. groups necessary for polymer‐formation are formed in the course of these reactions. The products of the reaction are butylamine‐HCl and caprolactame, as well as N‐(∈‐amino caproyl)‐butylamine HCl. 1 mole active end group is formed from 1 mole of amidine salt and 1 mole of water. In other words, concerning water content, 1 mole of butylamine. HCl corresponds to 1 mole of amidine salt + 1 mole of water. It could be verified that the mixture of butylamidine. HCl and water initiates the same lactame transformation as the corresponding amount of butylamin. HCl, if more than 1 mole % has been taken. It could be shown that the velocity constant of the amidine formation is less, or much less, than that of the amidine hydrolysis. Considering an amidine intermediate stage in the formation of polycaprolactame released by water or by proton acids, we consider the deduct ion of a new and unified kinetic as probable.
Optically active vinyl polymers. XIV. Stereoselective and stereoelective polymerization of racemic α‐olefins
Authors: Pino Piero , Ciardelli Francesco , Montagnoli Giorgio 
Published: September 2014

AbstractPolymers of racemic 4‐methyl‐1‐hexene, 3‐methyl‐1‐pentene, and 3,7‐dimethyl‐1‐octene have been separated in fractions having optical activity of opposite sign by adsorption chromatography on highly crystalline poly‐(S)‐3‐methyl‐1‐pentene. It is shown that the observed prevalence of S or R monomeric units in the optically active polymers thus obtained cannot be explained on the basis of a model of a purely statistical copolymer of the two monomeric antipodes. This conclusion is confirmed by the fact that at‐acticpoly‐(R)(S)‐4‐methyl‐1‐hexene, obtained by hydrogenation of poly‐(R)(S)‐4‐methyl‐1‐hexyne prepared with a substantially soluble catalyst, has not been separated in fractions having optical activity of opposite sign in the adopted experimental conditions. The reported results prove that the stereospecific polymerization of the above‐cited racemic α‐olefins by heterogeneous catalysts is stereoselective, giving rise to macromolecules formed prevailingly by one single monomeric antipode. On the basis of the experimental results obtained in the stereoselective and stereoelective polymerization of racemic α‐olefins, the structure of the catalytic centers of the heterogeneous catalysts for the stereospecific polymerization of α‐olefins is discussed.
Optically active vinyl polymers. XV. The optical activity in hydrocarbon solution of poly[(s)‐1‐methyl propyl]vinyl ether and of poly[(s)‐2‐methyl butyl] vinyl ether
Authors: Pino Piero , Lorenzi Gian Paolo , Chiellini Emo 
Published: September 2014

AbstractThe molar rotatory power in hydrocarbon solution of poly[(S)‐1‐methyl propyl]vinyl ether (I) is far higher than that of poly[(S)‐2‐methyl butyl]vinyl ether (II). With increasing temperature, the molar rotatory power of (I) decreases greatly, whereas that of (II) increases very slightly. The comparison of O.R.D. of (I) and (II) in the absence of complexing agents and in the presence of Al(i‐C4H9)3 with that of low molecular weight model compounds has allowed some reasonable hypotheses to be drawn which explain, at least in part, the different behavior shown by the two polymers, and suggest that the relationships between optical activity and polymer structure are qualitatively the same in polyvinyl ethers and poly‐α‐olefins. The change of rotation of polyvinyl ethers by complexation with Al(iC4H9)3 is qualitatively consistent with the behavior of the low molecular weight models and, at least in the case of (II), dependent on polymer stereo‐regularity.
Molecular weight distributions from turbidimetric titrations
Authors: Bryce W. A. J. , Meldrum I. G. 
Published: September 2014

AbstractThe molecular weight distribution of the products of the reaction between polystyryl potassium and 1,3,5 tri[bromomethyl] benzene was determined by turbidimetric technique. For the system chloroform–ethanol–polystyrene (anionic) the solubility S of a species of molecular weight M at a volume fraction γ of nonsolvent is given by the expressionmagnified image
The polymerization of chloroprene. III. Characteristics of the initiation process in thermal polymerization
Authors: Billingham N. C. , Leeming P. A. , Lehrle R. S. , Robb J. C. 
Published: September 2014

AbstractThe observed activation energy for the thermal polymerization is shown to be the same as that for the simple dimerization reaction. This provides additional support for our conclusion that the latter process is controlling the rate of the thermal polymerization, which proceeds by consecutive reactions where the initial formation of dimers is followed by their subsequent polymerization. Present experiments further suggest that traces of peroxide are responsible for the initiation of this so‐called thermal polymerization, and the results indicate limits within which the “thermal” rate is controlled as above. Conventional free‐radical initiators are unable to initiate the polymerization of dimers, but with this exception the system displays several features characteristic of a free‐radical process, e.g., in its behavior toward inhibitors and UV irradiation. Kinetic measurements on initiated monomer systems suggest specific initiation of the monomer itself, and incidentally illustrate that there is surprisingly little cross‐propagation of dimers. The implications of the results are discussed.
Alkyl derivatives of pyrocatechol as stabilizers in γ‐irradiated polypropylene
Authors: Nechitailo N. A. , Sanin P. I. , Polak L. S. , Pospisil J. 
Published: September 2014

AbstractStudies were conducted of the stabilizing effect of dialkyl derivatives of pyrocatechol types I–III and 2‐alkoxyphenol types IV and V in polypropylene irradiated under vacuum with a dose of 110 or 228 Mrad. It was found that some derivatives, particularly those containing a bulky tertiary butyl group in o the position to the hydroxyl group, retard the destruction of the polymer and formation of crosslinks, protecting at the same time irradiated polypropylene against subsequent oxidation. In the studied series of pyrocatechol derivatives the structural dependencies are well visible although the interpretation of results is probably also affected by the direct action of γ‐radiation on the stabilizers.
A route to sulfur—nitrogen polymers containing eight‐membered rings
Authors: Heal H. G. , Kane J. 
Published: September 2014

AbstractThe condensation of disulfur dichloride with any one of the three positional isomers of hexasulfur diimide gives rise to linear polymers in which eight‐membered sulfur–nitrogen rings derived from the diimide are coupled together by S2 groups. From the 1,5‐diimide a single homologous series arises; we have isolated its first four members. Rings derived from the 1,3‐diimide can couple cis‐ or trans‐ to one another; we have isolated cis‐ and trans‐forms of the two‐ring coupling product and observed their spontaneous interconversion. Rings of the 1,4‐diimide are optically asymmetric; we have isolated diastereoisomers of the corresponding two‐ring coupling product, and a mixture of isomers of the three‐ring homolog.
Molecular motions in poly‐α‐methylstyrene
Authors: Baccaredda Mario , Butta Enzo , Frosini Vittorio , Magagnini Pierluigi , Andruzzi Fulvio 
Published: September 2014

AbstractDynamic mechanical properties (sound velocity and damping factor) have been determined in poly‐α‐methylstyrene in the temperature range from 60 to 470°K., at frequencies in the range 103 ÷ 106 Hz. Two high dissipation regions are found in the damping‐temperature curves: one, at temperatures below Tg, characterized by a loss peak at about 140°K., and another, at temperatures above Tg (405°K.), characterized by a very rapid increase of losses with increasing temperatures. The loss peak at low temperature (δ) is probably due to rotational motions of the phenyl rings in the side chain; the corresponding activation energy is about 4000 cal.‐mole−1, much higher then that of polystyrene, because of the sterical hindrance of CH3 in the α position. A δ transition is also found in other vinyl polymers containing aromatic groups as side chains: by plotting the logarithm of the activation energy as a function of the reciprocal maximum damping temperature, determined in different polymers, points nearly lying on a straight line are obtained. The main transition is associated with cooperative motions of chain segments. Practically no difference is found between the dynamic mechanical properties of atactic and syndiotactic samples of poly‐α‐methylstyrene.
Effect of structure and thermal prehistory on molecular order and relaxation properties of rubberlike polymers at low temperatures
Authors: Bartenew G. M. , Zelenev Yu. V. 
Published: September 2014

AbstractThe effect of thermal prehistory on relaxation mechanical and dielectrical properties of rubberlike polymers has been studied by varying the conditions of heating and cooling of the specimens. The annealing of specimens by slowly cooling heated specimens, as well as amorphization, which occurs when heated specimens are cooled rapidly, results in a marked change in the dependence of dynamic characteristics in the glassy and the viscoelastic state on temperature and frequency. Annealing and amorphization of specimens alter the temperature interval in which deformation is dependent on frequency affect the magnitude of the dynamic modulus at constant frequency over a wide temperature range, and also result in a non‐uniform variation of the modulus difference at the maximum and minimum external frequencies.The shape of the maxima of mechanical losses in the low‐temperature principal and auxiliary relaxation regions observed in the case of annealed and amorphized specimens is different from that of the initial rubber. Since variations in the thermal prehistory cause no alteration in the molecular structure of rubbers, the phenomena observed can be attributed only to rearrangement of supramolecular structures.Variations in thermal prehistory exert no effect on the shape of the maxima of dipoleelastic dielectric losses because changes occur only in the mobility of segments with polar side groups, whereas the motion of supramolecular structures is absent. Density of the space network and the type of vulcanization (heat vulcanization at elevated temperature or radiation vulcanization at 20°C.) likewise influence the molecular order in rubberlike polymers and the dependence of the mechanical loss factor on temperature.
Synthesis and polymerization studies of some N‐alkylol acrylamides. II. Polymerization and copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole
Authors: Jedliński Z. , Paprotny J. 
Published: September 2014

AbstractA study has been made of the radical polymerization and copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole with styrene at 60°C. This monomer homopolymerizes easily in water solution, yielding polymers of high molecular weight, but at high conversion crosslinking occurs. A further detailed kinetic investigation in dimethylformamide resulted in values for the overall rate of polymerization that were comparable to values for other acryl monomers. For copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole (M1) with styrene (M2) in dimethylformamide solution, the reactivity ratios r1 = 0.47 and r2 = 1.29 were obtained.
Polymerization of unsaturated methyl‐α‐d‐glucopyranoside acetals. I
Authors: Jedliński Zbigniew , Maślinska‐Solich Jolanta 
Published: September 2014

AbstractThe effectiveness of several cationic initiators for the polymerization of 4,6‐acrylidene‐methyl‐α,d‐glucopyranoside has been examined. The most effective initiators found for polymerization acrylidene‐methyl‐α,d‐glucopyranoside are cationic catalysts. Some properties of new polymers were investigated. Moreover some oligomeric acetals of methyl‐α,d‐glucopyranoside and acrolein have been separated and their structures have been proposed.
Radiation effects in polypropylene and ethylene–propylene copolymers
Authors: Odian George , Lamparella Don , Canamare Joseph 
Published: September 2014

AbstractThe effect of radiation on various propylene and ethylene–propylene copolymers has been followed by observing the gel fraction as a function of radiation dose. The G (crosslink) and β/α values were calculated from the solubility data and are discussed in terms of the polymer composition. Allyl methacrylate was found to greatly increase the efficiency of radiation crosslinking of both polypropylene and an ethylene–propylene copolymer.
Polymerization of α‐methylstyrene by naphthylsodium
Authors: Podolsky A. F. , Korotkov A. A. 
Published: September 2014

AbstractThe kinetics of the polymerization of α‐methylstyrene by naphthylsodium at −78°C. in tetrahydrofuran has been studied for elucidating the mechanism of the polymerization. The experimental relationships obtained are accounted for by an assumption that the polymerization proceeds by the “coordination” mechanism and 4 elementary reactions take place: (1) generation of the active centers of polymerization; (2) chain propagation; (3) chain termination; (4) reaction of chain propagation upon the organometal compounds formed as a result of the termination reaction (upon the “living” polymers).This latter reaction proceeds without termination. In solving kinetic equations reduced time φ = ∫0τ m · dτ is introduced here m is the monomer concentration and τ is the time. The apparent values of the constants of elementary reactions are determined from the dependence of the number‐average degree of polymerization \documentclass{article}\pagestyle{empty}\begin{document}$ \[\bar p\] $\end{document} on the initial catalyst concentration n0 and from the dependence of conversion X on reduced time φ. The coincidence of the expected relationship X = F(τ,φ) with those experimentally found was traced with an electronic computer over all the range of X values. Equations are derived for the dependence of the polymerization rate upon the initial concentration of the catalyst and for the molecular weight distribution of the polymer. Experimental points appear to agree with the calculated data. The curve of the molecular weight distribution has 2 maxima.
Studies on the kinetics of polyesterification
Authors: Vancso‐Szmercsányi I. , Makay‐Bödi E. 
Published: September 2014

AbstractThe polyesterification reaction in relation to proton catalysis was studied. The polycondensation reactions of maleic, fumaric, phthalic, succinic, adipic, and sebacic acids with various glycols were studied in the melt without catalysts. The results were classified into two groups. In the first group belong those reactions which proceed in the initial stage at a considerably greater rate than in the main stage, which kinetically is second order. The reactions of acids with greatly differing first and second dissociation constants, and with a high first dissociation constant, belong into this group. Acids with a relatively small difference between their first and second dissociation constants and a lower first dissociation constant belong in the second group. A reaction order of 2.5 was obtained for these acids. To provide evidence for a correlation between the auto‐catalytic effect and the dissociation constant, maleic and fumaric acids were esterified with methyl alcohol both with and without a foreign acid catalyst.
Solid state polymerization of several monomers by vacuum ultraviolet rays
Authors: Tabata Yoneho , Kadoi Hajime , Oshima Keichi 
Published: September 2014

AbstractSolid state polymerization of acrylonitrile and acetylene initiated by a vacuum ultraviolet radiation (Xenon resonance line, 8.44 e. v.) has been studied at low temperatures in a range of −100 to −196°C. The color of polymers obtained ranged from nearly white to brownish yellow. It was found from infrared spectra of the polymers that the structure of the polyacrylonitriles obtained by vacuum ultraviolet irradiation is quite different from that of the polyacrylonitriles obtained by γ‐rays or accelerated electrons irradiation. In the polymers obtained by γ‐rays, the nitrile groups remain unreacted but in the case of vacuum ultraviolet the number of unreacted nitrile groups decreases with decreasing polymerization temperature. It may be concluded that in the case of vacuum ultraviolet irradiation the polymerization reaction takes place both in nitrile and vinyl groups, and thus the ring is formed by an intramolecular linkage. The apparent activation energy was obtained from the initial rate as 3.1 kcal./mole (−100 to −130°C.) and 0.06 kcal./mole (−130 to −196°C.). The quantum yield in the polymerization at −196°C. was estimated to be about 0.2 and the G value was about 2. G value in γ‐ray‐initiated polymerization at −196°C. was 102 ∼ 103. The extreme differences between the G values may be attributed to the energy differences of radiations for the initiation reaction.
Mechanismus der Dreidimensionalen Polymerisation von Glykolmethacrylaten
Authors: Kopeček J. , Jokl J. , Lím D. 
Published: September 2014

AbstractThe three‐dimensional, homogeneous, and heterogeneous polymerizations in systems monoglycol or diglycol monomethacrylate–dimethacrylates of glycols in various solvents were studied dilatometrically. The network density and the content of pendant vinyl groups were determined at various conversions. The influence of physical crosslinks formed by hydrophobic crosslinking agents was estimated by the comparison with copolymers of diglycol monomethacrylate–methyl methacrylate. By correlation of kinetics of polymerization with the three‐dimensional network formation, it was possible to characterize the polymerizing systems within the whole range of conversion.
On the charge carriers mobility in polymers
Authors: Kryszewski M. , Szymański A. , Światek J. 
Published: September 2014

AbstractIn the case of polymers a direct determination of charge carriers mobility based on Hall constant measurements is impossible. Therefore, the theory of space charge‐limited current, which enables charge carriers mobility calculation, was applied. Transient space charge‐limited currents were investigated in thin films (13–150 μ) of polyvinyl chloride and of copolymer of acrylonitrile with 2‐vinylpyridine. Measurements were carried out at room temperature. The calculated mobility of charge carriers is within 10−3 to 10−4 cm.2/v. sec.