bluuebunny/crossref_metadata_2025_split huggingface dataset:
Denaturation of plant proteins. I
Authors: Jirgensons B. 
Published: April 2003

AbstractBy denaturation of potato albumin by pyridine or by heat the viscosity increases; simultaneously the capability of the denatured protein t o reduce iodine increases, which, according to Anson, is due to the liberation of SH groups. A similar increase of viscosity was observed by the conversion of legumin into a water‐soluble modification, and further by heating the solution of this protein; the volume of iodine required for oxidation of the denatured protein is greater than that of the native legumin. This denatured protein can be reconverted into its native state, whereupon the reducing capacity again decreases. Several fractions of green pen and horse bean legumin were denatured by urea and it was found that the viscosity and the reducing capacity thereby increase. In the case of legumelin the viscosity is low but the reducing power high; this indicates that legumelin is a degradation product having globular molecules.
Beiträge zur kinetik der indenpolymerisation. VII. Die beschleunigung der indenpolymerisation durch die oxypolymeren des indens
Authors: Gutmann V. 
Published: April 2003

AbstractPolymere Oxydationsprodukte des Indens verhalten sich in Bezug auf Polymerisationsreaktionen wie typische Peroxyde. Ihre verhältnismässig hohe Stabilität bedingt eine relative geringe Reaktionsbeschleunigung, wobei Bruchstücke des zerfallenden Peroxyds in die polymere Molekel eintreten.
Adhesion of high polymers to cellulose. Influence of structure, polarity, and tack temperature
Authors: McLaren A. D. 
Published: April 2003

AbstractIt has been demonstrated that the adhesion of high polymers to cellulose is a function of tack temperatures and dielectric constants, ϵ, of the polymers and of dipole moments, μ, of polar groups. A plot of tack temperature versus mirror image force, μ1μ2/,of copolymers gives an area of adhesion bounded by a tack temperature of 100% and mirror image forces of 0.7 and 1.3 and opening toward lower tack temperatures. Outside of the area polymers do not adhere well to cellulose. By coating polymers on cellulose pretreated with Werner chromium complexes of acids bearing polar groups, it has been found that adhesion is a specific function of the polar groups within the polymer and on the modilied cellulose. Adhesion is strongest with approximately equal dipole moment substituents on the modified cellulose and in the copolymers.
Refractometric determination of second‐order transition temperatures in polymers. IV. Butadiene‐acrylonitrile copolymers
Authors: Wiley Richard H. , Brauer G. M. 
Published: April 2003

AbstractThe second‐order transition temperatures (Tm) for foruteen commercially available butadiene‐acrylonitrile copolymers with 18–50% acrylonitrile have been determined refractometrically and found to be somewhat lower than the corresponding brittle temperatrues (Tb). The data show a linear relation between Tm and acrylonitrile content.
Depolarization of light scattered from dilute macromolecular solutions. II. Experimental results
Authors: Doty Paul , Stein S. J. 
Published: April 2003

AbstractDepolarization measurements on solutions of polystyrene, polyvinyl chloride, polyvinyl acetate, polvdieblorostyrene, and tobacco mosaic virus have been made in order to examine various aspects of the qualitative theory proposed in the foregoing paper. In the case of the polymers the variation Of Ph and p, with concentration and solvent ability have been verified. The value of P, for tobacco mosaic virus is quite small as expected, and the value of ph for different virus preparations increases with decreasing molecular length as predicted.
Temperature dependence of copolymerization
Authors: Goldfinger G. , Steidlitz M. 
Published: April 2003

AbstractCopolymerization rate constant ratios have been determined as a function of temperature for the monomer pairs: styrene‐acrylonitrile and dichlorostyrene‐acrylonitrile. The temperature dependence, which represents the difference of the activation energies of the respective addition reactions, is of the magnitude expected, except for the styrene‐dichlorostyrene system.
Relation of intrinsic viscosity of polymer solutions to degree of polymerization and temperature
Authors: Sadron Charles 
Published: April 2003

AbstractThe fundamental basis of our work is the application of statistics involving both the energy of interaction between solute and solvent molecules and the effect of steric hindrances: the statistics of freely rotating chains (sometimes called the statistics of Kuhn) are a special limiting case. Using this we can show that in the law [η] = KNα the coefficient is a function of N having a value close to 2 for small values of N, and approaching on first approximation a value of 0.5 when N increases infinitely. This statistical method has the advantage of permitting an approach to the important problem of the variation of the intrinsic viscosity as a function of the temperature T. The behavior of intrinsic viscosity with degree of polymerization and temperature as predicted by the theory check with experiment, and, in the case of the hemipolystyrenes, it has been possible to obtain very satisfactory quantitative verification. In view of numerous experiments which show that, at a given temperature, the limiting value of α for very large N is greater than 0.5, we have altered the theory of the equivalent particle accordingly. As a basis for the change the concept of porosity is examined with several other concepts, and it is shown that it is likely to apply only with reservations when the molecular structure of the solvent is taken into account.
La vitesse de propagation des ultra‐sons dans les macromolecules
Authors: Natta G. , Baccaredda M. 
Published: April 2003

AbstractIl est montré que le rapport entre la vitesse de propagation des ultra‐sons et la densité (u/p) des polymères est fonction de la forme des molécules. En particulier on trouve: (1) dans les composés à chaîne rigide paraffinique non ramifiée, ce rapport à la température de 20° s'accroît sensiblement avec le poids moléculaire de 1.67 pour les hydrocarbures du poids moléculaire bas à 1.92 pour le polythène à poids moléculaire élevé; (2) dans les composés ramifiés ayant des groupes méthyliques ou éthyliques, ce rapport est pratiquement constant pour tous les composés examinés jusqu'au poids moléculaire 15.000; (3) dans les composés linéaires contenants des groupes latéraux de dimensions plus grandes (p.e., phényliques ou oxybutyliques), ce rapport est plus petit pour les hauts polymères que pour les composés à poids moléculaire bas; (4) en général la compressibilité est plus élevé pour les polymères avec des ramifications fréquentes et longues que pour les polymères peu ou pas du tout ramifiés.
Titration potentiometrique de la viscose. II
Authors: Herrent P. , Jnoff G. 
Published: April 2003

AbstractEn cherchant à interpréter la courbe expérimentale de la titration potentiométrique de la viscose par l'AgNO3, 0.1 N, on a découvert que les composés sulfurés de la viscose devaient se trouver sous la forme “ortho.” Ceci a permis de proposer une nouvelle théorie du mürissement de la viscose.
Thermal degradation of polystyrene. Part I
Authors: Jellinek H. H. G. 
Published: April 2003

AbstractThe decrease of the limiting viscosities of unfractionated and fractionated polystyrene with time has been studied over a range of temperatures from 248 to 340°C. in vacuo. Distribution curves of several degraded samples have been determined. It has been established that the theory of random breaking of links is not applicable in the case of polystyrene. Three major deviations from the random theory have been found. The experimental results have been evaluated employing the weak link theory. The mechanisms proposed account satisfactorily for the deviations from the random theory, and give a fair representation of the experimental results, only the experimental distribution curves still showing deviations from those predicted by theory. The elementary steps for the degradation in vacuo have been discussed and the role of oxygen during polymerization has been indicated.
Thermal degradation of polystyrene and polyethylene. Part III
Authors: Jellinek H. H. G. 
Published: April 2003

AbstractAn apparatus has been constructed which enables one to follow continuously the formation of monomer during degradation in vacuum. Experimental results are presented on the degradation of fractionated and unfractionated polystyrene over a range of temperatures from 340–400°C. in vacuum. A mechanism has been proposed which accounts satisfactorily for the apparent zero‐order reaction and for the dependence of the rate of degradation on chain length. This mechanism allows one to estimate relative number average molecular weights and the number of weak points per original chain. The influence of a platinum surface on degradation has been indicated. The degradation of poly‐alpha‐methylstyrene has been investigated over a range of temperatures from 281 to 363°C. in vacuum. The mechanism of the degradation of branched polymer chains has been discussed. The degradation of cross‐linked polystyrene containing various amount of m‐divinylbenzene has been studied at 364°C. in vacuum. The reaction shows long induction periods depending on the amount of m‐divinylbenzene and on the presence of benzoyl peroxide during polymerization. The degradation of polyethylene shows this polymer to be more heat resistant than polystyrene. Various grades of different average molecular weight have been investigated over a range of temperatures from 375 to 436°C. in vacuum. The energy of activation has been found dependent on chain length. A mechanism has been suggested to account for the observed experimental results.
Polyelectrolytes. IV. Conductance of n‐butyl bromide addition compounds of 4‐vinylpyridine‐styrene copolymers in nitromethane‐dioxane mixtures
Authors: Cathers George I. , Fuoss Raymond M. 
Published: April 2003

AbstractThe conductance of a series of salts made by the addition of n‐butyl bromide to 4‐vinylpyridine‐styrene copolymers (1.5 to 90 mole per cent vinylpyridine) has been measured in dioxane (ϵ′ = 2.2), ethylene dichloride (ϵ′ = 10.2), and a series of nitromethane‐dioxane mixtures (16.0 ≤ ϵ′ ≤ 39.4). Three independent arguments deduced from the data show that ionic association under the influence of interionic electrostatic forces must occur in solutions of polyelectrolytes in such a way that a certain average fraction of the counter ions accompany the large polycation and contribute nothing to conductance. First, the conductance at fixed copolymer composition and fixed salt concentration decreases with decreasing dielectric constant of the solvent medium. Second, at a given counter ion concentration in a given solvent, the conductance decreases with increasing pyridonium content of the chain. Third, for a given salt and solvent, the conductance decreases with increasing salt concentration at a rate much slower than that characteristic of simple electrolytes.
Ionic polymerization of mono‐olefinic hydrocarbons at low temperatures. A review of proposed mechanisms
Authors: Heiligmann Randall G. 
Published: April 2003

AbstractThe mechanism presented constitute proposals made in attempts to portray the role that electrophilic halides play in catalyzing the polymerization of unsaturated hydrocarbons. All of these halides require the presence of a Friedel‐Crafts catalyst in the reaction mixture and differ primarily in the interpretation of what constitutes the active factor in the initiation, propagation, and cessation steps. Mechanisms involving a thermal activation and dehydrohalogenation are discussed briefly and rejected as rather improbable. On the other hand, mechanisms involving a cationoid complex intermediate and a carbonium ion are extensively reviewed, especially in light of the recent findings of British investigators regarding the function of the so‐called third component or cocatalyst. Attention is called to the rather marked specificity of reactions involving water or other polar cocatalysts, and, in addition, it is pointed out that, although cocatalysts appear to be necessary prerequisities for activation in a number of cases, the phenomenon is not a general one, since systems exist in which proton‐supplying cocatalysts have not been proved necessary to initiate growth. To date, no single mechanism seems to satisfy all of the qualitative observations and known data. It is intended that the present discussion summarize available facts in terms of possible mechanisms, and, in addition, evaluate their plausibility in the light of present knowledge.
Copolymers of 1,3‐butadiene and 2,3‐dimethyl‐1,3‐butadiene
Authors: Marvel C. S. , Williams Jack L. R. 
Published: April 2003

AbstractSome experiments on the polymerization of 2,3‐dimethyl‐1,3‐butadiene and its copolymerization with butadiene are reported. This monomer requires very little modifier as compared to butadiene.
Osmometry of high polymer solutions. I. Osmometer and membranes
Authors: Masson C. R. , Melville H. W. 
Published: April 2003

AbstractThe construction of a thermostated osmometer of the Fuoss‐Mead pattern is described. The technique of preparation of bacterial cellulose membranes for osmotic measurements on high polymer systems is given. The permeability of such membranes may be controlled by growth to a thickness of 4‐5 mm., drying in contact with a stainless steel surface, and reswelling in water or alcohol‐water mixtures. The degree of reswelling required to give membranes suitable for use with polymers of a range of molecular weights is given. The factors affecting the behaviour of the membranes in the osmometer are discussed.
Osmometry of high polymer solutions. II. Osmotic measurements using bacterial cellulose membranes
Authors: Masson C. R. , Melville H. W. 
Published: April 2003

AbstractBacterial cellulose membranes have been used successfully to measure the osmotic pressures of a number of high polymer‐solvent systems. The dynamic method of Fuoss and Mead has been used in most cases, but for polyvinylxylene in benzene the rate curves are not symmetrical since the solvent passes through the membrane faster from the solution side. The molecular weight values for two polyvinyl acetates agree well with the calculated kinetic values, and for polyethyl sebacate the value obtained agrees with that found by endgroup titration. Values of the Huggins “constant” μ are given for various systems.
Dependence of tensile strength of vulcanized rubber on degree of cross‐linking
Authors: Flory Paul J. , Rabjohn Norman , Shaffer Marcia C. 
Published: April 2003

AbstractTensile strengths of natural rubber samples quantitatively crosslinked with decamethylene dis‐methyl azodicarboxylate have been determined. The proportion of the azo vulcanizing agent was varied 80‐fold, the fraction p of cross‐linked units in the products ranging from 0.10x 10−2 to 8.0 x 10−2. In spite of the small dimensions of the test specimen (cross section 0.10 in. by about 0.005 in.), the average error for a single observation is similar to that obtained in conventional testing procedures applied to specimens vulcanized with sulfur and accelerators. Deviations from the mean for 262 tests on 15 different cures are well represented by a Gaussian error function; a slight intimation of skewness is evident only at the extremities of the distribution of deviations. These results are incompatible with the commonly held view that rupture of the sample takes place at the “weakest link” in the series of flaws inevitably occurring along the specimen. It would appear that the ability to withstand tensile stress (applied in a specified manner) is an inherent characteristic of the bulk material. The rapid increase in tensile strength with the degree of crosslinking p for small values of this quantity is consistent with the conclusion, previously reached in the investigation of the physical properties of butyl rubber (6) that the tensile strength is directly related to the fraction of the structure which is permanently oriented by stretching. At higher degrees of cross‐linking (at ρ x 100 = 1.0 to 1.5, depending on the molecular weight of the rubber) the tensile strength passes through a maximum and then declines steadily to quite low values for higher ρ's. This adverse effect of higher degrees of cross‐linking is believed to result from the diminished elongation at which crystallization sets in and, hence, the smaller fraction of the network elements sufficiently oriented to participate in crystallite formation. Modification of up to 7% of the isoprene units of the rubber with the monofunctional compound, ethyl azodicarboxylate, depresses the tensile strength of the disazo vulcanized rubber relatively little. Evidently, the limited extent to which these modified (or copolymer) chains may enter into crystallization is adequate to bring about high tensile strength. Lack of direct correlation between modulus and tensile strength for rubbers vulcanized with various sulfur‐accelerator combinations can only be explained by assuming that conventional vulcanization processes are accompanied to varying degrees by chain scission reactions. When vulcanized rubber is “over‐cured,” or heat aged, chain scission becomes excessive.
Denaturation of plant proteins. II. Increase of viscosity and reducing capability (estimated by titration with iodine) associated with denaturation
Authors: Jirgensons B. 
Published: April 2003

AbstractLegumin of green peas and horse beans was dissolved in solutions of several salts and the viscosity and reducing capability of these solutions was determined. The amounts of iodine required for titration (reducing capability) are dependent on the pH of the solution and on the temperature; between pH 5.0 to 5.8 and +5° to +25° the titration values are almost constant. By comparing several neutral salts it was found that in the cases of sodium chloride, potassium bromide, potassium iodide, calcium chloride and magnesium nitrate the reducing capability and intrinsic viscosity of legumin both are low; however, in the case of potassium thiocyanate both values are high. No denaturation takes place in solutions containing 2‐30% ethyl‐ or propylic alcohol and calcium chloride or like salts. Sodium salicylate causes denaturation; the intrinsic viscosity and reducing capability of legumin in these solutions is high. Sodium dodecylbenzene sulfonate has a strong peptizing action on legumin and denaturates it. After a mild deamination of legumin with nitrous acid only slight differences in viscosity and reducing capability could be observed. The solutions containing much propylic alcohol and salt grew in time more and more viscous, if the concentration of legumin was high, but remained of the same viscosity when the concentration of legumin was low. It was concluded that in these cases the high viscosity of legumin is due not to unfolding of the compact coils of native legumin, but to the interaction of the particles with the molecules of the solvent and to subsequent structuration. Loosening and transformation in more elongated particles may be assumed in the cases with thiocyanate, salicylate, and the detergent.
Copolymerization. VII. Relative rates of addition of various monomers in copolymerization
Authors: Chapin Earl C. , Ham George E. , Mills Charles L. 
Published: April 2003

AbstractInformation concerning monomer reactivity in copolymerization has been obtained for thirteen copolymerization systems. The influence of substituents and chain length in vinyl polymerization is discussed in the light of this and preceding data. Unsaturated acid behavior in copolymerizations is discussed for the first time.
Reactivity of fibrous cellulose
Authors: Meller Alexander 
Published: April 2003

AbstractBy applying hydrochloric acid solution at different temperatures to various fibrous cellulose samples and following the per cent loss in weight with time, hydrolysis‐time curves have been obtained. These plots have been resolved into a straight line and a curve, representing the rate of removal of difficultly and easily removable components, respectively. Under the experimental conditions applied, the ratedetermining reaction in the removal of the difficultly accessible components from the fibers is essentially a kinetically zero‐order reaction. This was borne out by the results of hydrolyses of hydrocellulose preparations. Within the experimental range the temperature coefficient of this rate is independent of the representative fibrous materials and is relatively high, corresponding to an energy of activation of 28‐29 kcal./mol. The easily and difficultly accessible regions, assessed by resolving the rate plots, are different with the same fibers, depending on the experimental conditions. The reactivity of both the easily and difficultly hydrolyzable constituents varies with different cellulose fibers. The complex nature of the kinetics of removal (hydrolysis) of the easily accessible components is discussed.
Copolymérisation de l'Anhydride Maléique avec Différents Monomères Vinyliques
Authors: De Wilde M. C. , Smets G. 
Published: April 2003

AbstractDie Mischpolymerisation von Maleinsaeure Anydrid mit verschiedenen Vinyl‐Verbindungen wie Methakrylsaeure, Methylester, Vinylchlorid, Vinylazetat und Isopropenylazetat wurde untersucht. Die Verhaeltnisse der Geschwindigkeits‐Konstanten r1 und r2 wurden fuer jeden dieser Faelle festgestellt. Die Mischpolymerisation mit Monomeren, die eine elektronreiche Doppelverbindung enthalten, zeichnet sich durch eine hohe Selektivitaet aus. In diesen Faellen koennen die Ergebnisse nicht gaenzlich durch das Alfrey‐Price Schema erklaert werden.
Untersuchung einer katalysierten leinölstandölkochung unter heranziehung der ultraviolettspektrographie (vergleich mit nichtkatalysierten prozessen)
Authors: Maschka A. , Mendl A. 
Published: April 2003

Abstract(1) Laboratoriumsmässige Leinölstandölkochungen mit und ohne Katalysator in Kohlensäureatmosphäre, sowie eine Leinölfirnis‐ und eine Leinölstandölfirniskochung werden untersucht. (2) Neben den üblichen Kennzahlen werden auch die Ultraviolettabsorptionsspektren der einzelnen Proben ermittelt und daraus die Mengen der intermediär auftretenden Systeme mit zweifach und dreifach konjugierten Doppelbindungen berechnet. (3) Diese Zwischenstoffkonzentrationskurven und die übrigen Kennzahlen stimmen für die beiden Standölkochungen und einen in der Literatur beschriebenen technischen Prozess qualitativ überein. Naturgemäss verläuft der katalysierte Vorgang viel rascher. (4) Aus den Ergebnissen wird der Schluss gezogen, dass die in der Literatur als wahrscheinlich hingestellte Reaktionsfolge (Konjugation der isolierten Doppelbindungen—intra—bzw. intermolekulare Polymerisation im Sinne einer Diensynthese nach Diels–Alder) auch beim katalysierten Prozess auftritt. Der Katalysator beschleunigt alle Teilreaktionen. (5) Es wird der Versuch gemacht, aus der Zunahme der Viskosität und der Jodzahlsenkung die Bedeutung der Umesterung für die Viskositäts (Molekulargewichts) zunahme abzuleiten.
Optische anisotropie und form von fadenmolekülen. I. Depolarisationsgrad der lichtzerstreuung von lösungen mit fadenmolekülen
Authors: Stuart H. A. , Peterlin A. 
Published: April 2003

AbstractEs wird der Depolarisationsgrad bei der molekularen Lichtzerstreuung von statistisch geknickten Fadenmolekülen in Abhängigkeit vom Polymerisationsgrade berechnet und die Giiltigkeitsgrenzen der Theorie näher diskutiert.
Titration potentiométrique de la viscose. III
Authors: Herrent P. , Jnoff G. 
Published: April 2003

AbstractEn combinant différentes méthodes d'analyse courantes à notre méthode de titration potentiométrique, nous avons pu tracer la courbe individuelle de la variation de la teneur de chacun des éléments constitutifs d'une viscose en fonction de la durée du mǔrissement de la viscose.