bluuebunny/crossref_metadata_2025_split huggingface dataset:
Der Ringöffnungsmechanismus des Diäthylenglykolformals bei der kationischen Polymerisation
Authors: Weichert D. 
Published: September 2014

AbstractWährend der Untersuchung polymerisierbarer zyklischer Formale beschäftigten wir uns mit dem Problem der Ringöffnung des Diäthylenglykolformals. Aus der Struktur dieses Formals folgt, dass zwei Sauerstoffatome der Formalgruppe und ein Äthersauerstoff Oxoniumkomplexe bilden können. Natürlich war es theoretisch möglich, für den Formalsauerstoff eine höhere Reaktivität vorauszusagen, da das benachbarte Sauerstoffatom als Elektroacceptor das Karbeniumkation begünstigt. Obgleich der Formalrest besonders begünstigt für die Ringöffnung ist, sollen andere Mechanismen, z. B. zwischen dem benachbarten C‐Atom des Diäthylenglykolteils und des Formalsauerstoffs, diskutiert werden. Unter Berücksichtigung der Strukturen, die sich von verschiedenen Mechanismen ableiten, und bei Ausdehnung dieser theoretischen Modelle auf kombinierte würde schliesslich eine Abweichung von der klassischen Formalstruktur ergeben. Da in einigen Fällen neue Ätherbindungen geknüpft würden, müssten sich neue Verbindungen neben den erwarteten Diäthylenglykol und CH2O, wie z. B. Tri‐, Tetra‐ und Monoäthylenglykol nach der Azidolyse bilden. Es wurde versucht, den Äthylenglykolgehalt mit Hilfe der hochempfindlichen und spezifischen Perjodatmethode zu bestimmen. Innerhalb der Genauigkeit dieser Methode konnte kein Äthylenglykol in den Hydrolysaten entdeckt werden. Die Gaschromatographie ergab nur Diäthylenglykol im hydrolysierten Polyformal. Das gleiche Ergebnis ergab die fraktionierte Destillation. Unter Berücksichtigung dieser Ergebnisse konnten drei Ringöffnungstypen verworfen werden, so dass nur noch die Ringöffnung zwischen dem Sauerstoff und der Methylengruppe des Formalrestes postuliert wird.
Helix—Coil transition in some helical macromolecules
Authors: Gupta V. D. , Gupta A. K. 
Published: September 2014

AbstractA statistical thermodynamic approach based on the application of the Ising model for ferromagnetism is outlined to explain the phase transition in isolated single‐stranded helical macromolecules. The transition is characterized by the degree of helicity and the lengths of uninterrupted helical and random‐coil regions. The theoretical predictions for the temperature dependence of helicity in case of poly‐l‐lysine and poly(l‐glutamic acid) are compared with the experimental results of Applequist and Doty and Doty, Yang, and others. The application of the theory to the crystalline–amorphous transition in polyethylene and polypropylene is also suggested and some preliminary results are reported.
Casting of transparent polyacrylonitrile
Authors: Oplatka Avraham , Konigsbuch Mordechai , Shavit Nehemia 
Published: September 2014

AbstractThe bulk polymerization of acrylonitrile (AN) has been reported to give a white precipitate which then solidifies to a hard opaque aggregation of polymer particles. Contrary to the bulk polymerization of, say, methyl methacrylate, that of AN cannot therefore be considered as a cast polymerization process. We have found that by using catalytic amounts of mercury nitrates as initiators, the white slurry obtained during the early stages of the polymerization was transformed spontaneously, at higher degrees of conversion, into a transparent material which acquired the shape of the mold. The glass, contrary to the transparent gels obtained by Salomon,7 who used high concentrations of AgNO3 in AN, does not lose its transparency in water and is thus a real transparent plastic like poly(methyl methacrylate). The work was extended to examine the polymerization of AN by other mercury salts as well as by the salts of a number of other cations. Various properties of the new plastic obtained with Hg(NO3)2 were determined and compared with those of ordinary powdery PAN. Essentially, at the molecular level, the polymers do not seem to differ, and the difference in light transmission is ascribed to a difference in physical states. A qualitative mechanism for glass formation is suggested.
Chain conformation and crystal structure of the α‐polymorphic form of poly(dimethyl ketene)
Authors: Bassi I. W. , Ganis P. , Temussi P. A. 
Published: September 2014

AbstractThe chain structure of the two polymorphic forms of poly(dimethyl ketene) has been determined with the aid of internal energy calculations, theoretical characterization of polymer chain geometry, and finally by a complete x‐ray analysis. In the α form, a chain conformation containing a glide‐plane has been found, which along with the value of the identity period of the structural unit (4.4 A.) requires the structural unit to be composed of two monomeric units. An AB3AC3 conformation has been assigned and subsequently confirmed by the determination of the crystalline structure.
Zur Lichtstreuung an Lösungen verzweigter Makromoleküle. III. Verschiedene Verzweigungsmodelle
Authors: Dautzenberg H. , Ruscher Ch. 
Published: September 2014

AbstractWährend bisher nur Näherungen für die Lichtstreufunktionen von verschieden verzweigten Kettenmolekülen beschrieben worden sind, werden von uns nunmehr die exakten Streufunktionen berechnet, und zwar für das Kamm‐Modell, das Kaskaden‐Modell mit 1, 2 und 3 Verzweigungsstufen und das Stern‐Modell.
Investigation of the kinetics and mechanism of radiochemical and photochemical grafting of acrylonitrile from the gaseous phase to polyamide fibers
Authors: Kachan A. A. , Chervyatsova L. L. , Kornyev K. A. , Mertvichenko E. F. , Gnyp N. P. 
Published: September 2014

AbstractGrafting from the vapor phase of acrylonitrile, vinyl acetate, vinylpyridine, and isoprene to polyamide fibers was effected by radiation and photochemical initiation. The absence of a homopolymer in vapor‐phase grafted polymerization made it possible to take its kinetics continuously during the reaction in adsorption vessels with the aid of MacBen scales. Dependences of the reaction rate on the radiation dose, monomer vapor pressure, duration of experiment, and temperature are obtained. The basic kinetic peculiarities of the process are studied on a model reaction of grafted polymerization of acrylonitrile on capron fiber. Grafting is shown to occur chiefly according to an “impact” mechanism. The observed negative temperature coefficient of the reaction is due chiefly to the decay of free radicals. Values are obtained on the increment rate and chain scission constants at 22, 40, and 60°C., and the corresponding activation energy values. The quantum yield of free radical formation on capron is calculated for a wavelength of 2537 A. (G = 1.7 × 10−5). The results of the calculation of G are compared with those obtained by measuring the ESR spectra.
On radiochemical crosslinking of polyolefins in the presence of sulfur monochloride
Authors: Kachan A. A. , Chervyatsova L. L. , Kaurkova G. K. 
Published: September 2014

AbstractIt was found that in the presence of sulfur monochloride the gamma radiation dose may be considerably reduced during the radiochemical crosslinking of polyolefins. Thus, in the case of polyethylene practically complete crosslinking is attained with a dose of 0.1 Mrad, i.e., by three orders lower than with ordinarily used radiation doses. Sulfur monochloride was introduced from the vapor phase, which made it possible to apply S2Cl2 uniformly on the polymer, to control strictly the quantity of introduced substance, and to reduce its consumption sharply. Some peculiarities of the mechanism of the action of sulfur monochloride in the process of radiochemical crosslinking of polyethylene are clarified. It is shown that in polyethylene crosslinking occurs chiefly on bonds of the monosulfide type. The value of the radiochemical yield of cross‐bond formation was 1.25 × 103.
Détermination de la Structure des Poly‐2,3‐Diméthyl‐1,3 Butadiènes par Résonance Magnétique Nucléaire et Spectrographie Infrarouge
Authors: Assioma François , Marchal Jean , Schue François , Friedmann Gilbert , Maillard Alfred 
Published: September 2014

AbstractWith the shifts observed on the frequencies corresponding to the symetric absorption band of the CH3 groups, it has been possible to make a complete analysis of the microstructure of the poly‐2,3 dimethyl‐1,3 butadienes by IR spectroscopy. We have determined the δs CH3 frequencies for the three possible modes of addition and the corresponding absorbtivities, by mean of polymers all 1,4 cis, all 1,4 trans, and polymers with approximately 50% of 1.2 addition. The quantitative determination of this addition has been made at 888 cm.−1, corresponding to the out‐of‐plane deformation of the two hydrogen on the double band CC in the isopropenyl group. The results are in good agreement with those of NMR analysis.
Cyclo‐ and cyclized diene polymers. VII. cyclopolymerization of 2,3‐dimethylbutadiene‐1,3 and infrared spectra of poly(2,3‐dimethylbutadiene‐1,3)
Authors: Gaylord Norman G. , Kössler Ivo 
Published: September 2014

Abstract2,3‐Dimethylbutadiene‐1,3 was polymerized with cationic and Ziegler type catalysts and by radical polymerization. Polymers with linear and cyclic structure and copolymers with the dimer of 2,3‐dimethylbutadiene‐1,3 were obtained. The structure of the polymers was determined by infrared spectra.
Conformation and flexibility of some polypeptides in solution
Authors: Tsvetkov V. N. , Shtennikova I. N. , Skazka V. S. , Rjumtsev E. I. 
Published: September 2014

AbstractThe flow and electric birefringence of a number of poly‐γ‐benzyl‐l‐glutamate (PBLG) fractions in dichloroethane and m‐cresol have been studied. Molecular weights (0.4–3.4 × 105) of the fractions are determined from measurements of diffusion and sedimentation of solutions. The hydrodynamic, optical, and electrical data obtained are used for quantitative evaluation of molecular conformation and flexibility. From the experimental dependence of molecular optical anisotropy on molecular weight, an apparent persistence length a = 1200 A. is calculated for the PBLG chain. This value is obtained by using both the intrinsic anisotropy of molecules and their microform anisotropy. A similar value, a = 1100 A., is also obtained from the dependence of diffusion and sedimentation coefficients on molecular weight. The value a = 700 A. determined from the dependence of dipole moment upon molecular weight appears to be considerably lower. This means that orientation processes of polar PBLG molecules in mechanical and electrical fields should not be considered identical and that a marked difference exists in the correlation of molecular chain segments with the phenomena of flow and electrical birefringence.
Stereospecific polymerization of butadiene with cyclopentadienyl and carbonyl VIII group metal complexes
Authors: Babitskii B. D. , Kormer V. A. , Lapuk I. M. , Skoblikova V. I. 
Published: September 2014

AbstractButadiene polymerization with carbonyl and cyclopentadienyl nickel complexes combined with Lewis acids has been investigated. The microstructure of polybutadiene obtained is shown to be influenced by the nature of metal in π‐complex and independent of Lewis acid metal. In all cases polymers produced are mainly of 1,4 structure. Catalysts prepared by the reaction of nickel carbonyl with Lewis acids in aromatic hydrocarbons are arene nickel complexes. The activity of these catalysts is found to be dependent on the lability of arene–metal bond. It is suggested that there exists a genetic relation between catalyst systems studied and π‐allylic nickel complexes, which is supported by the same influence of the nature of halogen on polybutadiene microstructure.
Polycondensats Linéaires Obtenus à Partir de Monomères Triaziniques
Authors: Audebert Roland , Néel Jean 
Published: September 2014

AbstractDichlorotriazinic monomers prepared by the reaction of cyanuric chloride with an amine or a Grignard reagent are polycondensed with bisphenols as well as with diamines. Linear polymers thus obtained an analyzed and identified and their physical constants have been determined. Particularly, their behaviour towards heat, solubility, molecular weight, cristallinity and IR absorption spectra have been examined.
The aging of some pigmented polymeric films
Authors: Skledar Š. 
Published: September 2014

AbstractPigmented films based on different polymers and their blends have been prepared on pine‐wood and low‐carbon steel substrates, and exposed in laboratory and out‐of‐doors. In the high humidity cabinet, films based on pentaerythritol alkyd modified with 65% linseed oil and applied to a pine‐wood surface, deteriorated by blistering, except those pigmented with titanium dioxide. A blend of the same medium with stabilized chlorinated rubber showed good resistance to degradation in high humidity conditions as well as in marine and industrial environments. In the latter system, especially the combined pigmentations zinc oxide/rutile behaved very well on aging. However, in linseed oil varnish, the combined pigmentation zinc oxide/rutile/basic lead carbonate protected the exposed films very well. The rutile modification of titanium dioxide protects a polymeric film by absorbing ultraviolet light which would otherwise damage it. Also, zinc oxide indicates complete absorption of the shorter wavelengths, and basic lead carbonate transmits much more ultraviolet light. Nevertheless, lead and zinc soap formation with free acids might affect various film properties in the above pigment combination. The highest retention of whiteness was exhibited by the film samples exposed to a marine environment, and the lowest by those exposed to an industrial atmosphere.
The effect of crosslink structure on the tensile strength and oxygen absorption characteristics of natural rubber vulcanizates
Authors: Lal Joginder 
Published: September 2014

AbstractThe chemical nature of crosslinks in natural rubber–sulfur‐diphenylguanidine vulcanizates was modified by reaction with triphenylphosphine under nitrogen to determine the effect of this change on tensile strength and oxygen absorption characteristics of the vulcanizates. The vulcanizates were characterized by organically combined sulfur and polysulfidic sulfur. Polysulfidic crosslinks, i.e., crosslinks containing three or more sulfur atoms in the crosslink, were found not to be essential for the attainment of high tensile strength in these vulcanizates. Data for the samples which had lost significant amounts of polysulfidic crosslinks by reaction with triphenylphosphine fitted the tensile strength versus 300% modulus curve for the control samples.Vulcanizates which had been reacted with triphenylphosphine for 16 days at 80°C., had lost 95–99.6% of their polysulfidic sulfur. These triphenylphosphine‐reacted vulcanizates exhibited significantly lower rates of oxygen absorption at 100°C. as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.
The models of the denaturation of globular proteins. III. The intramolecular β‐structure coil transitions in poly‐S‐carbobenzoxymethyl‐l‐cysteine
Authors: Anufrieva E. V. , Birshtein T. M. , Bolotina I. A. , Burshtein L. L. , Eskin V. E. , Frolov V. I. , Illarionova N. G. , Kalikhevich V. I. , Korotkina O. Z. , Mitin Yu. V. , Ptitsyn O. B. , Purkinas A. V. , Volchek B. Z. 
Published: September 2014

AbstractConformational transitions in synthetic poly‐S‐carbobenzoxymethyl‐l‐cysteine (PCBMC) have been investigated in order to model the processes of the denaturation of globular proteins. The solutions of some samples of PCBMC in the mixtures of nonpolar solvents (dichloroethylene, chloroform) with highly polar solvents (dichloroacetic or trifluoroacetic acids) have been studied by viscosimetric, polarimetric, spectroscopic, and dielectric methods, as well as by light scattering and electronic microscopy. Intrinsic viscosity and levorotation increase sharply when solvent breaking hydrogen bonds are added in the narrow range of the solvent composition, the molecular weight (measured by light scattering) remaining constant. It means that intramolecular cooperative conformational transition occurs in the PCBMC molecules. The dispersion of optical activity shows the absence of the helical structures in PCBMC molecules for any solvent composition. Infrared spectra show that the PCBMC molecules possess β‐structure in inert solvents and in films; and viscometric and polarimetric data suggest that this structure is an intramolecular one and corresponds to the compact shape of the PCBMC molecules in solution. The compact structure of PCBMC molecules in nonpolar solvents is also confirmed by dielectric data. The experimental results permit us to draw the conclusion that cooperative conformational transition involving intramolecular β‐structure statistical coil occurs in PCBMC when solvent breaking hydrogen bonds are added. The position and the degree of sharpness of the transition do not depend on the molecular weight of the sample in the interval investigated (from 15,000 to 91,000). The “plate” model of the intramolecular β‐structure has been proposed which does not contradict the results of the electron microscopic study. An assumption is made that owing to the two dimensional character of the intramolecular cross‐β‐structure its melting occurs in accordance with the “all‐or‐none” principle.
Thermal polymerization of trimeric phosphonitrilic chloride
Authors: Colclough R. O. , Gee Geoffrey 
Published: September 2014

AbstractTrimeric phosphonitrilic chloride, when purified by a sequence of operations involving recrystallization, refluxing at 130°C. over barium oxide in an atmosphere of dry nitrogen, passage of the vapor at 130°C. over phosphorus pentoxide, followed by repeated sublimation with degassing in a high‐vacuum, all‐glass apparatus, polymerizes only very slowly at 300°C., and polymerization is sharply accelerated on admission of dry oxygen. Crude trimer, which was purified by only a single vacuum sublimation, polymerized relatively rapidly at 270°C. The conversion–time curve for the highly purified trimer shows a continuously accelerating rate of polymerization up to high conversion at 320 and 340°C.
Étude des Propriétés Catalytiques des Composés d'Insertion des Metaux Alcalins dans le Graphite
Authors: Golé J. , Stein C. 
Published: September 2014

AbstractThe lamellar compounds of alkali metals and graphite were tested as polymerization initiators of vinyl monomers. Cinetic studies of the styrene—C32K system showed that the rate of polymerization was directly proportional to the initiator concentration and to the three‐halves power of the monomer concentration. The activation energy of styrene was found to be 19 kcal./mole. These initiators lead to very high molecular weights (\documentclass{article}\pagestyle{empty}\begin{document}$ \[\bar M_w &gt; 10^7 \] $\end{document} > 107 for polystyrene). A mechanism of polymerization based on our experiments is proposed.
The relationship of performance characteristics to basic parameters of polymers. I. A collaborative study of polystyrene using torsion pendulum and impact methods
Authors: Jones T. T. 
Published: September 2014

AbstractIn July, 1963, a working party of I.U.P.A.C. was set up to consider collaborative investigations in the general area indicated by the main title of this paper, and joint studies were started with three polymers: polystyrene, polyvinyl chloride, and polyethylene. This paper gives an account of the work done to date with polystyrene. The paper shows the detailed torsion pendulum results of six laboratories with the use of the same toughened polystyrene. The significance of frequency of vibration in raising the temperature of maximum damping of the rubbery component is clearly brought out and the degree of agreement shown between laboratories is good. A smaller number of collaborators made impact strength and torsion pendulum studies over a range of temperatures on polystyrene and another toughened polystyrene. The dependence of the brittle–tough transition temperature on estimated rate of elongation of the breaking filament is correlated with the dependence of the temperature of maximum damping of the rubbery component on frequency.
Mechanism of anionic polymerization of acrylates and methacrylates
Authors: Báča J. , Lochmann L. , Jůzl K. , Čoupek J. , Lím D. 
Published: September 2014

AbstractThe mechanism of anionic polymerization of acrylates and methacrylates was studied by differential thermometry. The course of the temperature curves after the addition of the initiator to the monomer was analyzed. As initiator, organolithium and sodium compounds as well as lithium, sodium, and potassium tert. alkoxides were used. It was found that in case of methacrylates the lifetime of growing chains is according to the type of the initiator and monomer from seconds to about 1 min. In the case of lithium alkoxide, formation of active centers is a relatively slow process, different from potassium alkoxide, where the whole process resembles polymerization by organometallic compounds. Sodium alkoxide initiator evidently causes a very complicated process. After the region of acceleration is reached, polymerization resembles potassium alkoxide initiation. In the case of lithium compounds the high isotactic portion depends on the alkoxide present, whereas with sodium compounds, atactic polymer is normally obtained. Potassium alkoxide leads to slightly increased syndiotactic portion.
Graft copolymerization via polymeric initiators
Authors: Reynolds G. E. J. 
Published: September 2014

AbstractPoly(styrene‐alt‐maleic anhydride) was prepared by polymerization in benzene, a nonsolvent for the product, and from it partial peresters were prepared in acetone solution, with t‐butyl hydroperoxide and pyridine used as catalyst. The partial peresters were used to initiate methyl methacrylate polymerization by a thermal mechanism in homogeneous solution in acetone, and both homopolymer and graft copolymer were formed. Acrylonitrile was polymerized in aqueous solution by a redox mechanism, and here graft copolymer was produced, but there was no evidence of homopolymer. Parallel polymerizations with poly(styrene‐alt‐maleic anhydride) showed that this had no initiating activity in either system. With methyl methacrylate polymerization thermally initiated with t‐butyl hydroperoxide in the presence of poly(styrene‐alt‐maleic anhydride), grafting by transfer was shown to be substantially less than grafting produced via perester polymers.
Étude par Diffusion de la Lumière de Films de Polystyrène Isotactique
Authors: Picot C. , Weill G. , Benoit H. 
Published: September 2014

AbstractLight scattering by isotactic polystyrene films has been studied by a photographic technique. By changing the refractive index of the surrounding of the spherulites, it has been shown that only the anisotropic disk model explains the light scattering photographs. The modification of the light‐scattering patterns during an isothermal crystallization has been interpreted as an effect of the variation of the surrounding of the spherulites. The spherulites dimensions can be measured by this technique and experimental measurements of the radial growth of the spherulites are in good agreement with optic microscopic measurements.