bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromatographic fractionation of sugar beet araban
Authors: Goodban A. E. , Owens H. S. 
Published: April 2003

AbstractCrude araban prepared from sugar beet pulp is not a pure araban, but yields appreciable amounts of galactose upon hydrolysis. In order to obtain galactose‐free araban this material was acetylated and fractionated by precipitation from acetone by the addition of petroleum ether. Arabinose content rose from 78 to 85%. Chromatographic fractionation on a charcoal column by elution with chloroform‐acetone mixtures resulted in an increase in purity from 89 to 95%. Optical rotation was the most sensitive indication of the progress of the fractionation, with the chromatographic fractionation resulting in a change from −102 to −124°. Specific viscosity measurements support the findings of Claesson that retention volume is related to molecular weight; the strength of adsorption increasing with molecular weight up to a maximum near a molecular weight of 10,000. Reported molecular weights for sugar beet araban have ranged from 5,700 to 10,000. An arabogalactan was found which is strongly adsorbed, and is not eluted by chloroform, but may be removed with pyridine. Total recovery from the column was 89%.
Action des pH acides sur la sérum albumine bovine en solution
Authors: Champagne M. 
Published: April 2003

AbstractOn a montré dans une publication précédente, que l'on pouvait définir un ellipsoïde équivalent à la molécule de sérum albumine en mesurant dans des conditions de pH et de forces ioniques définies: le coefficient de diffusion brownienne; la viscosité intrinsèque et la masse de la particule. Les mesures avaient été faites dans unintervalle de pH allant de 3,5 à 9. De forme sphérique au point isoionique, la molécule de sérum albumine s'allonge de part et d'autre et son volume diminue. Les modifications sont réversibles. Pour des pH inférieurs à 3,2 un trouble apparaît dans les solutions de sérum albumine. Nous avons pu l'identifier comme étant de nature lipidique. Nous avons précisé les conditions e'élimination totale de cette impureté. II est possible alors d'étudier les modifications subies par la sérum albumine à des pH très acides. Nous avons poussé l'étudej usqu'à pH 1,5 et montré en particulier que la reversibilité était encore totale à pH 1,97. Nous avons comparé parallèlement l'activité antigénique d'une sérum albumine portée à pH 2 et ramenée à pH neutre et celle de la sérum albumine native.
Viscometric investigation into the influence of pH and ionic strength on molecular shape of a structural muscle protein
Authors: Wassermann Albert 
Published: April 2003

AbstractAn attempt to explain some viscosity properties of actomyosin in terms of a reversible polymerization reaction cannot be reconciled with experimental results described in this paper. A consistent explanation of these experiments can be given if it is postulated that actomyosin, in dilute solution, is composed of flexible chains, the shape of which depends on pH and ionic strength of the solvent. The order of magnitude of the average distance between the chain ends of actomyosin molecules is estimated.
Dilatometric measurements on gels of cellulose tributyrate and cellulose nitrate
Authors: Vrancken M. N. , Ferry John D. 
Published: April 2003

AbstractGlass transition temperatures (Tg) and thermal expansion coefficients (α) above and below Tg have been determined for gels of cellulose tributyrate in dimethyl phthalate (weight fraction polymer, w2, of 0.20 and 0.43) and of cellulose nitrate in diethyl phthalate (w2 = 0.12 to 0.37). Below Tg, α increases with w2; above Tg, α decreases with increasing w2. In the tributyrate (w2 = 0.43) a second transition appears, as noted by Mandelkern and Flory for the undiluted polymer. By combining the Tg values with the coefficients of the WLF equation, the quantities fg and αf are calculated for the tributyrate gels. Here fg, interpreted as the relative free volume at Tg, is about 0.020; while αf, interpreted as the expansion coefficient of free volume relative to the total volume, is 4.8 × 10−4 deg.−1, approximately equal to the macroscopic change in α at Tg.
Polymers and group interaction. V. Reaction of diazomethane on polymethacroyl chloride
Authors: Rondou S. , Smets G. , De Wilde‐Delvaux M. C. 
Published: April 2003

AbstractIn order to follow the course of the Arndt‐Eistert reaction on a polymeric system, polymethacryol chloride has been reacted with diazomethane in dioxane solution using different molar ratios of diazomethane/acid chloride at different temperatures. The structure of the reaction products has been determined by chemical methods and by infrared spectrometry. The contents of acid chloride and diazoketone units have been evaluated from chlorine and nitrogen analyses, respectively; conductometric and potentiometric titrations allow determination of the percentages of ketene and pseudo‐acid groups. From these data it is concluded that the first reaction products of diazomethane on an acid chloride unit are diazoketone groups, as expected; however, the interaction of these primary groups with the neighboring acid chloride units yields principally β‐ketocycloketene functions. The presence of these groups and their content have been confirmed by a decarboxylation reaction effected by hydrolysis in acidic medium, during which carbon dioxide is evolved, while the acid content decreases and cyclic ketones are formed. Their presence has also been confirmed by oxidation with dilute nitric acid, which transforms the polymer into polymethacrylic acid. These results of decarboxylation and of oxidation are unreconcilable with the formation of the higher homolog of polymethacrylic acid, the polyisopropenylacetic acid, which would be the normal chainlengthening reaction product of the Arndt‐Eistert reaction. Infrared spectrometry shows, in the triple bond region, absorption bands at 4.65 and 4.73 μ, and, in the double bond region, bands at 5.55, 5.70, 5.80, and 6.10 μ. By comparison with the data in the literature, and especially with the spectrum of the glutaric bisdiazoketone, these different bands have been assigned and their relative intensities interpreted. The spectrometric results confirm the presence of diazoketone and β‐ketoketene groups; moreover, they show relatively low amounts of cyclopentanone rings and of ester functions.
Anomalous behavior of polymer solutions. I. Non‐Newtonian behavior of polyvinyl acetate solutions
Authors: Kapur S. L. , Gundiah S. 
Published: April 2003

AbstractThe viscosity behavior of dilute solutions of polyvinyl acetate fractions in benzene has been investigated at different shear rates and at two temperatures. The importance of the effect of shear on the various physical constants has been discussed. It is shown that the value of Huggins' constant k′ at zero shear is independent of molecular weight for a given polymer and is a fundamental property associated with the inherent character of the polymer chains and their interaction with the solvent at a particular temperature.
A study of the rates of denaturation of arachin and conarachin II
Authors: Naismith W. E. F. , Williams R. K. 
Published: April 2003

AbstractThe rates of denaturation of arachin and conarachin II with sodium hydroxide and guanidine hydrochloride have been studied. Arachin is more susceptible to denaturation with both reagents. The rates of denaturation of the two proteins with sodium hydroxide or guanidine hydrochloride are decreased by increasing the sodium chloride concentration. Arachin is changed by both denaturants to slowly sedimenting material by way of an intermediate sedimenting component, but no intermediate component has been observed with conarachin II. Whereas the rate of alkaline denaturation of both proteins is very sensitive to temperature changes, with guanidine hydrochloride the rate is not affected appreciably by changes in temperature. This would indicate that an appreciable activation energy is required for the alkaline denaturation. Confirmation of this is seen in that the alkaline denaturation is always completely irreversible whereas with guanidine hydrochloride some reversibility has been observed. Although there was no increase in rate with increase in protein concentration for either protein, in no case did the plot of log concentration vs. time give the straight line graph expected of a reaction which is first order with respect to protein concentration.
Molecular orbital theory of reactivity in ionic polymerizations
Authors: Yonezawa T. , Higashimura T. , Katagiri K. , Hayashi K. , Okamura S. , Fukui K. 
Published: April 2003

AbstractThe stabilization energy due to the conjugation taking place between a monomer and an ion in the transition state is calculated by the LCAO perturbation theory, in the same way in which the reactivity in radical copolymerization has previously been treated. In terms of this stabilization energy, the reactivity ratios of several monomer pairs in ionic copolymerization are satisfactorily interpreted. It is noted that, by the present method, both the radical and ionic copolymerization can be treated in a unified manner, whereas it is difficult in existing empirical methods. The positions of attack in polymer ions as well as in monomers, which are predicted by the frontier electron densities, are shown to agree well with experimental facts. The relative reactivities of vinyl monomers in ionic homopolymerization is also explained successfully by the magnitude of the localization energy computed by the LCAO method.
A fundamental investigation of adhesion. II. Method for measuring shrinkage stress in restrained gelatin films
Authors: Weatherwax Richard C. , Coleman Beverly , Tarkow Harold 
Published: April 2003

AbstractGelatin solutions shrink as water evaporates from the gel. If the shrinkage is prevented, tensile stresses develop. A technique is described for measuring the tensile stress developing in the plane of edge‐clamped gelatin films during drying. It is based on measurement of the elastic deformation of the film when stressed normally to the plane of the film. A stress of 4000 pounds per square inch was observed in a dried gelatin film. The reality of the stress was confirmed in a completely independent manner.
Physicochemical studies on starches. VII. The infrared absorption spectrum of the amylose‐iodine complex
Authors: Greenwood C. T. , Rossotti Hazel 
Published: April 2003

AbstractChanges in the infrared absorption spectrum of amylose on complex formation with iodine, bromine, and iodine cyanide vapor are consistent with the occurrence of halogen‐oxygen interaction in the solid complexes. The implications of these results are discussed in terms of the possible conformations of the glucopyranose rings and their relationships to the helical structure for amylose. It is suggested that the most probable conformation is a chair‐form in which only one substituent is axial to the plane of the ring.
The mechanism of protection by the deactivating effect
Authors: Bras Jean Le , Danjard Jean‐Claude , Boucher Madeleine 
Published: April 2003

AbstractThe mechanism of protection by the deactivating effect has been studied on the basis of data from continuous and discontinuous relaxation experiments on vulcanizates accelerated with mercaptobenzothiazol and with diphenylguanidine. It has been shown that the mechanism involves the formation of intermolecular crosslinks, which restore the damages due to the thermo‐oxidative ruptures in the vulcanizate network. These intermolecular crosslinks are formed by the free sulfur present in the vulcanizates under the influence of the deactivator, which acts as a slow accelerator, as has been proved by free sulfur determinations carried out during aging. The resistance of these crosslinks to the thermooxidative degradation is specific for the deactivator; this allows for interpretation of the more or less pronounced effect of the deactivator upon aging as a function of the nature of the accelerator used during vulcanization. This explanation of the deactivating mechanism gives not only a better understanding of the phenomena, but also presents new ideas for the general interpretation of aging of vulcanized rubber.
Non‐stationary state kinetic determination of polymer radical lifetimes
Authors: Funt B. Lionel , Collins Edward 
Published: April 2003

AbstractLifetimes of polymer radicals were determined by a direct flow technique. The variation of yield of polymer with the period between initiation by an ultraviolet source and destruction in an inhibitor solution was determined by spectrophotometric analysis. A swiftly falling stream of monomer was irradiated by a sharply focussed beam of intense ultraviolet radiation, and the time of radical growth was controlled by varying the distance of fall at a constant flow rate. The variation of yield of polymer with the time interval between photochemical initiation an destruction in an inhibitor solution was determined by spectrophotometric analysis of the polymer formed. A polished elliptical reflector was used, instead of the customary quartz lenses, with the source and stream at the foci of the ellipse. A water‐jacketed capillary was employed to eliminate spurious thermal initiation. Radical lifetimes of 0.24 seconds for styrene and 1.80 seconds for butyl acrylate were obtained. The data were compared with values calculated on the basis of non‐stationary state kinetics in a flow system.
Sulfostyrenes1. Reactivity ratios for the copolymerization of styrene with potassium p‐vinylbenzenesulfonate and with p‐sulfoamidostyrene
Authors: Wiley Richard H. , Trinler W. A. 
Published: April 2003

AbstractDetermination of the copolymerization reactivity ratios for the styrene/p‐sulfonamidostyrene and styrene/potassium p‐vinylbenzenesulfonate has given values of r1 = 0.24; r2 = 1.07 and r1 = 0; r2 = 0.56, respectively. Values for the salt copolymerizations are subject to considerable variations, presumably due to adsorption of the monomer on the precipitating copolymers. The significance of these data in determining the distribution of the ionic groups in copolymers derived from these monomer pairs is discussed.
Use of the second virial coefficient to estimate chain branching
Authors: Krigbaum W. R. , Trementozzi Q. A. 
Published: April 2003

AbstractBranching frequencies have been determined by dilute solution measurements through evaluation of the radius of gyration, either directly by light scattering or indirectly through the intrinsic viscosity. A third possibility is presented by the decrease in the second virial coefficient, A2, with branching. Through use of a semi‐empirical relation between A2 and [η], it is shown that a reasonable approximation over a wide range of branching frequencies should be furnished by:

where the quantities designated by an asterisk refer to the branched polymer, and the corresponding unmarked quantities to a linear polymer having the same molecular weight. The validity of the approximate relation between A2 and branching is confirmed using the data of Thurmond and Zimm for linear and branched polystyrene, and using data for linear and branched polyethylene presented here. This procedure should prove useful inasmuch as the molecular weight of a branched polymer must be determined by an absolute method, and the branching frequency can be estimated through the A/A2 ratio from these same data.
Molekulargewichtsverteilungen in Polykondensaten aus 2.6‐dioxymethyl‐4‐methylphenol (Polyoxybenzyläthern). Osmotische Molekulargewichtsbestimmungen unter einem Molekulargewicht von 20000 mit einem modifizierten Heppschen Osmometer
Authors: Kämmerer H. , Kern W. , Heuser G. 
Published: April 2003

Abstract2,6‐Dioxymethyl‐4‐methylphenol wird bei 130°C derart kondensiert, dass hierbei fast ausschliesslich Polyoxybenzyläther entstehen. Die Konstitution dieser Polyätherketten wird durch die quantitative Bestimmung der Spaltprodukte bei der Polykondensation und durch die Bromwerte der HBr‐Hydrolysate der Polykondensate bewiesen. Verhältnismässig hochmolekulare Polyoxybenzyläther lassen sich in Benzol als Losungs‐ und mit Petroläther als Fällungsmittel durch Fällringstitration in Fraktionen zerlegen, wobei jeder Fraktion eine Fällbarkeit γ* zugeordnet werden kann. Für diese Fraktionen gilt log M = a − b · γ* im Molekulargewichtsbereich von 2500 bis 20000. Die Molekulargewichte wurden mit einem Osmometer nach Owens und Immergut osmotisch twstimmt. Sind die Polyoxybenzyläther genügend hochmolekular, so können unter Vernachlässigen der Anteile mit Molekulargew‐icht unter 2500 (P = 17) integrale und differentielle Massenverteilungen ermittelt werden. Es lässt sich nicht eindeutig feststellen, ob oder wie stark die experimentell ermittelten von den statistischen Massenverteilungen abweichen.
Viscosités intrinseques de solutions de chaînes courtes
Authors: Sadron Charles , Rempp Paul 
Published: April 2003

AbstractLa relation entre la viscosité intrinsèque et la masse moléculaire de molécules à chaîne courte fait l'objet du présent travail. Une relation du type

rend compte des résultats expérimentaux dans le cas des polyoxyéthylhe glycols dans tout le domaine de masses moléculaires considéré. Par contre la viscosité intrinsèque des α,ω‐diméthoxy polyéthylèneglycols diffère de celle des polyoxyéthylène glycols correspondants de façon assez notable dans le domaine des masses moléculaires faibles. Le raccordement satisfaisant des courbes [η] = f(M) relatives aux deux séries de substances nous incite à admettre d'une façon générale, dans le domaine de masses moléculaires considéré, une loi de viscosité de la forme:

dans laquelle le premier terme est en rapport avec la nature chimique de la chaine et le deuxième résulte de ses configurations statistiques.
Branching in macromolecules of different synthetic rubbers
Authors: Poddubnyi I. Ya. , Ehrenburg E. G. 
Published: April 2003

AbstractFrom results of a study of the intrinsic viscosity and the dynamooptical properties of homogeneous polymer fraction solutions, the influence of the polymerization temperature on the degree of branching in various synthetic rubbers was determined. The dynamooptical method proved to be the most suitable for our purpose. It was found that the influence of the polymerization temperature on the degree of branching of rubber macromolecules prepared in the presence of sodium, potassium, and lithium depends largely on the metal employed. With sodium‐butadiene rubbers, even a considerable change in the temperature of polymerization has little influence on the degree of branching of the macromolecules. On the other hand, when potassium is used as the catalyst, an increase in the polymerization temperature leads to a marked increase of the degree of branching. A considerable increase in the degree of branching was also observed in high‐temperature, lithium‐catalyzed polymerization. A relatively small effect of temperature on the degree of branching was observed in the case of butadiene‐styrene copolymers obtained by free radical‐initiated emulsion polymerization. The determination of the intrinsic viscosity of polymer fractions of various molecular weights in an ideal (Θ) solvent permits a quantitative evaluation of the degree of branching by applying Flory's equation, as modified for the case of branched polymers. Such an evaluation was made for three samples of lithium‐isoprene polymers. For two samples which were found to be branched, it was discovered that one branch unit occurs for every ∼4000 monomer units.
Conductance of partially neutralized polymethacrylic and polyacrylic acids, using a polarization compensated twin cell
Authors: Eisenberg H. 
Published: April 2003

AbstractThe a.c. conductance of partially neutralized fractions of polyacrylic and polymethacrylic acids has been investigated in salt‐free solutions. Experimental variables included frequency (10 to 50,000 cycles), nature of counterions (potassium, sodium, and lithium), molecular weight, degree of ionization, concentration, and temperature. The use of a polarization compensated twin cell arrangement in frequency dispersion measurements is described.
Donor‐acceptor interactions in cationic polymerization. II. Influence of some bases on polymerization of isobutylene
Authors: Ambrož L. , Zlámal Z. 
Published: April 2003

AbstractAnalysis of literature data permits the conclusion that a close link exists between cocatalytic effects and inhibition in cationic polymerization. All compounds described as efficient co‐catalysts of isobutene polymerization, e.g., water, alcohols, acetic and trichloroacetic acid, can have inhibiting effects under other conditions. All these compounds can be considered as weak bases able to form a catalytic complex on interaction with aluminum trichloride. It was found that the dependence of the molecular weight of polyisobutene on the ratio of the concentration of the organic base to that of the aluminum trichloride exhibits a clear maximum at the molar ratio of 1:1. A number of simple compounds containing oxygen, sulfur, and nitrogen were investigated, e.g., alcohols, ethers, esters, aldehydes, ketones, mercaptans, hydrogen sulfide, ammonia, amines, and nitriles. The results obtained indicate that co‐catalytic activity is not limited to compounds with “active” hydrogen. In the case of acetic and chloroacetic acids, anomalous behavior was found. This is explained by acid‐base equilibria between these acids and aluminum trichloride in ethyl chloride solution.
Mutual solubility of polymers and properties of their mixtures
Authors: Slonimskiĭ G. L. 
Published: April 2003

AbstractHeats of mixing of polymers with each other have been measured, the behavior of the mixtures of solutions of various polymers has been studied, and the dependence of mechanical properties of polymer mixtures on the ratio of components has been investigated. It has been shown that mixing of polymers with each other is usually an endothermic process and, therefore, leads to formation of macroscopically homogenous, but actually microheterogenous, systems with an extremely high degree of dispersion. These microheterogenous polymer mixtures are formed because of the enormous viscosity of polymer mixtures, which prevents macroscopic separation into phases but does not hinder the considerable mobility of the segments of flexible chain molecules. It has been shown that the dependence of mechanical properties of microheterogenous polymer mixtures on the ratio of polymers in the mixture have sharp maxima or minima which cannot be found in the case of true polymers in polymer solutions. It has been found that the behavior of some polymer pairs is anomalous, in that exothermal mixing is supplemented by separation of the solution mixture into phases and by the appearance of maxima or minima in the dependences of the properties of polymer mixtures on the ratio of polymers in the mixture. This anomaly has been attributed to the effect of loose packing of the molecules of the polymers which show anomalous behavior. It has been shown that, in these systems, there necessarily exists a lower critical temperature of mixing whose value can be decreased by adding low‐molecular solvents to the loosely packed polymer. Attention has been drawn to the fact that, although mixing of amorphous polymers should be considered on a thermodynamic basis to be a mutual solution of two liquid phases, the large dimensions and the flexibility of polymer chain molecules require a critical revision of the possibility of formal application of the basis thermodynamic concepts and relations to a theoretical analysis of the behavior of polymer mixtures.