bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disulfide bridges and configuration of human serum albumin. Relationships between viscosity, optical rotatory dispersion and configuration
Authors: Jirgensons Bruno , Ikenaka Tokuji 
Published: April 2003

AbstractThe effect of oxidative and reductive cleavage of the disulfide brides of serun albumin on the viscosity, specific rotation, and rotatory dispersion was investigated. Human serum albumin was oxidized with performic acid at low temperature. Our data show that oxidized human serum albumin (OHA) prepared in this manner represents an unfolded polyelectrolyte. It could be shown that no peptide bonds were hydrolyzed during the oxidation, and that approximately 90 % of all SS‐bonds were oxidized to SO3H. From viscosity data (in 4M guanidine thiocyanate) it can be concluded that the SS bonds are important for partial folding, and that some of the SS‐bridges are linking distant parts of the polypeptide chain. This was ascertained also by cleaving the SS bridges by reduction and carboxymethylation. The reduced and carboxymethylated albumin exhibited similar optical rotation and viscosity behavior as the OHA. It was also established that the levorotation does not depend solely on the folding but also on the presence or absence of the SS bonds, i.e. cystine content. Finally, it was concluded that in the instance of human serum albumin the dispersion constant λo is a safer criterion for the estimation of configurational changes than the specific rotation.
Copolymérisation de la N‐vinyl‐2‐oxazolidinone
Authors: Hart R. , Timmerman D. 
Published: April 2003

AbstractLa N‐vinyl‐2‐oxazolidinone a été copolymérisée avec plusieurs monomères. Les paramètres r1 et r2 ont été calculés:

acétate de vinyle‐vinyloxazolidinone
r1 = 0.60, r2 = 1.50

chlorure de vinylidène‐vinyloxazolidinone
r1 = 1.35, r2 = 0.08

méthacrylate de méthyl‐vinyloxazolidinone
r1 = 6.00, r2 = 0.03

Les résultats sont interprétés en fonction du schéma d'ALFREY‐PRICE; la polarité e est de −0.8 et la réactivité Q de 0.07. Ces valeurs sont comparées à celles d'autres monomères N‐vinyliques.
Synthesis of polyanhydrides. II. New aromatic polyanhydrides with high melting points and fiber‐forming properties
Authors: Yoda Naoya 
Published: April 2003

AbstractNew aromatic polyanhydrides with high melting points and fiber‐forming properties containing aliphatic chain or aliphatic chain and ether linkage between aromatic nucleus and carboxyl group in the main chain have been prepared. Contrary to the polyanhydrides of aliphatic dibasic acid prepared by CAROTHERS, it has been shown that these polyanhydrides possess high melting points and relatively stable properties towards hydrolytic degradation.Introduction of methylene group of methylene group and ether linkage between aromatic nucleus and carboxyl function enhances the flexibility of molecular chains, lowers melting points and causes the accumulation of phenylene nucleus along the polymer chain to form regular molecular structure of closes packing.Thus, polyanhydride of 1,4‐bis‐carboxymethyl benzene having a melting point 152°C. was obtained, while the polyanhydride prepared from hydroquinone‐0,0′‐diacetic acid with acetic anhydride has a melting point 158°C., and both of them show film‐ and fiber‐forming properties and good hydrolytic stability. The crystallinity of the polyanhydrides increases by annealing the stretched fiber at 100°C. 2.2‐bis(4‐hydroxyphenyl)propane 0,0′‐diacetic acid was polymerized with acetic anhydride and gives a linear polyanhydride of the melting point 196–202°C. which possesses fiber‐forming properties. Polyanhydrides thus obtained show a good stability towards thermal and hydrolytic degradations. Furthermore, the influence of the molecular structure on the physical properties of these polymers was discussed.
Effects of esters, aldehydes and some impurities on the polymerization of vinyl acetate
Authors: Matsumoto M. , Ukida J. , Takayama G. , Eguchi T. , Mukumoto K. , Imai K. , Kazusa Y. , Maeda M. 
Published: April 2003

AbstractEffects of aliphatic esters, aldehydes and some impurities, as monovinyl and divinyl acetylene which exist normally in vinyl acetate, on the polymerization of vinyl acetate were studied. Esters and saturated aldehydes such as methyl acetate, ethyl acetate, isopropyl acetate and dimethyl oxalate etc. and acetaldehyde and butyraldehyde act only as transfer agent and the values of the transfer constants on these substances were determined. Unsaturated aldehyde such as crotonaldehyde and also benzaldehyde, and monovinyl and divinyl acetylene act as retarder. The several reaction constants relating the retarding effect were obtained.
Zur polymerisation und copolymerisation des natriumvinylsulfonats
Authors: Kern W. , Kalè V. V. , Scherhag B. 
Published: April 2003

AbstractNatriumvinylsulfonat (VS‐Na) zeigt in konzentrierten wäßrigen Lösungen eine ausgeprägte Polymerisationsneigung. Die Polymerisationsgeschwindigkeit und der erreichte Umsatz hängen stark von der Acidität der Lösungen ab. Es wurde gefunden, daß mit der Polymerisationsdauer und mit wachsendem Umsatz auch die Molekulargewichte der Polymerisate ansteigen. Wasserunlösliche oder nur begrenzt lösliche ungesättigte Verbindungen wie Styrol, Vinylacetat und andere können in Dimethylsulfoxyd in homogener Lösung mit VS‐Na copolymerisiert werden.
Alkali catalyzed phenol formaldehyde reaction – part II. Formation of dimethylol phenols
Authors: Gopalakrishna V. V. , Yeddanapalli L. M. 
Published: April 2003

AbstractThe kinetic study has been made of the sodium hydroxide‐catalyzed interaction of o‐ and p‐methylol phenols with formaldehyde to give dimethylol phenols. At 0.006 M NaOH and within less than 10% of the reaction, first order kinetic behaviour was obtained. The rate constant, at 80°C., for the formation of 2,4‐dimethylol phenol from p‐methylol phenol and formaldehyde, was found to be 1.17·10−5 sec−1 and the activation energy, 23.92 kcal/mole, whereas for formation of 2,6‐ and 2,4‐dimethylol phenols from o‐methylol phenol, the rate constants were respectively 0.55 and 1.11·10−5 sec −1, the corresponding activation energies being, 25.10 and 23.37 kcal/mole. In terms of these data and those present in Part I, the relative reactivites of the free ortho and para positions in phenol and substituted phenols are evaluated and shown to be, unlike those reported by FREEMAN et al.5, consistent among themselves and with theoretical requirements.
Intramolecular branching in polyvinyl acetate
Authors: Melville H. W. , Sewell P. R. 
Published: April 2003

AbstractThe polymerisation of vinyl acetate at various temperatures between+18°C. and −50°C. to various conversions has been carried out to obtain polymers with different degrees of branching. All polymer samples showed a fall in intrinsic viscosity after hydrolysis and reacetylation. This change is related to the amount of branching in the original polymer, but the relationship did not become clear for unfractionated material. One sample was fractionated, and the fractions studied by following the changes in intrinsic viscosity and osmotic molecular weight occurring on hydrolysis and reacetylation. The fractionated sample was made from radio‐active initiator, which enabled the number of catalyst‐fragments per molecule to be counted. An intramolecular branching mechanism is proposed to explain the incidence of branch points in molecules which are in effect linear.
The polymerisation of styrene by solid catalysts derived from the reaction of titanium IV compounds with grignard reagents
Authors: Allen P. E. M. , Harrod J. F. 
Published: April 2003

AbstractSolid catalysts, prepared by treating alkyl or aryl magnesium halides with titanium tetrachloride or butyl o‐titanate, polymerize styrene rapidly to amorphous low molecular weight (104–105) polymer. The energy of activation for the process is approximately 20 kcal/mole for all active catalysts. Kinetic evidence indicates that initiation and propagation proceed by insertion of monomer molecules at a metal‐carbon bond and that termination is spontaneous.If the catalysts are pre‐heated to 150°C., the polymer produced contains a substantial proportion of high molecular weight (ca. 5·106) crystalline material.
Untersuchungen über die emulsionspolymerisation des acroleins. Polymere acroleine. 15. Mitteilung
Authors: Cherdron Von Harald , Schulz Rolf C. , Kern Werner 
Published: April 2003

AbstractDie Polymerisation des Acroleins mit verschiedenen Emulgatortypen wird untersucht. Es zeigt sich, daß eine Lösung von Polyacrolein in wäßriger schwefliger Säure ein vorzüglicher Emulgator für die Emulsionspolymerisation von Acrolein mit Redox‐Systemen ist. An diesem System wird der Einfluß der Emulgatorkonzentration S, der Initiatorkonzentration ci, der Monomerkonzentration und der Temperatur geprüft. Man findet folgende Beziehungen: VBr ∼ S1/5; VBr ∼ c; und VBr ∼ M. Die experimentellen Ergebnisse werden mit den nach der Theorie von SMITH und EWART zu erwartenden verglichen und diskutiert.
Über die autoxydation von polyacrolein‐schwefligsäure‐lösungen und die eigenschaften wäßriger schwefeldioxyd‐freier polyacroleinlösungen. Polymere acroleine. 16. Mitteilung
Authors: Schulz Von Rolf C. , Löflund Irmela , Kern Werner 
Published: April 2003

AbstractPolyacroleine sind in Substanz nicht autoxydabel. Lösungen von Polyacroleinen in wäßriger schwefliger Säure nehmen in Gegenwart katalytischer Mengen von Schwermetallsalzen Sauerstoff auf. Dabei wird nur Schwefeldioxyd autoxydiert; die Polyacroleine bleiben in Lösung. Physikalische Eigenschaften und chemische Reaktionen dieser Lösungen werden beschrieben.
A light scattering instrument for molecular weight measurements
Authors: Ovenall D. W. , Peaker F. W. 
Published: April 2003

AbstractFurther developments in the design of a light scattering instrument are described. E.M.I. photomultipler tubes, which are stable and sensitive, are used. These tubes have a plane front window which is of considerable advantage when the absolute calibration of the instrument is considered. The use of a magnesium carbonate surface as a standard diffuse reflector is discussed and details of the performance of the instrument are given.
Melting points and heats of fusion of polymers and copolymers
Authors: Dole M. , Wunderlich B. 
Published: April 2003

AbstractTheoretical calculations indicate that the melting point of a linear polyethylene should be experimentally determinable within 0.1°C., that of a low density polyethylene within 1°C., that of a 80/20 copolyester within 2°C. copolyester within 2°C. and that of a 60/40 copolyester within 5°C. Heats of fusion of polyethylene and polyesters as estimated by diffeerent methods are in good agreement, but uncertainties still exist in the case of polyamides. It is shown that correlation of melting points with molar cohesion energies is misleading and without theoretical foundation. Eastimation of the absolute entropies of polyethylene, polyethylene sebacate and several polyamides gives results indicating that the high melting point of the polyamides is due to a low entropy of the liquid phase rather than to a high entropy of the solid phase as has hitherto been proposed. On the other hand the low melting point of the aliphatic polyesters results chiefly from a low heat of fusion, and not from a high entropy of fusion as has also been previously suggested.Two melting regions which can be observed in certain copolyesters result from melting of crystals formed under two conditions; namely, small crystals produced by random crystallization of nearest neighbours, “cold crystallization”, and crystals of equilibrium size produced under ideal thermodynamic conditions. Because of restrications to crystallization due to the decreasing numbers of long sequences of crystallizable units with decreasing mole fraction, it is doubtful if melting points of copolymers hitherto measured have any thermodynamic significance. Much more precise measurements of carefully annealed samples at high mole fractions will be required before heats of fusion of activity coefficients of crystallizable units can be calculated from melting point data.
Organic reactions on high polymers
Authors: Smets G. 
Published: April 2003

AbstractWhen organic high polymer reactions are compared to similar reactions carried out on low molecular weight compunds, some special characteristics become evident, which are directly related with the polymeric structure of the substances.These characteristics may be pointed out either from comparative kinetic measurements, either from the structural organic analysis of the reaction products.From kinetic point of view, a distinction must be made between mono‐and bifunctional reactions. For monofunctional reactions, the similarity of reaction kinetics between a polymeric molecule and its low molecular weight homologous compound is only disturbed if the electrical potential of the mecromolecule increases in the course of the reaction, or (and) if the shape of the molecule changes. Examples are given in the cases of vinyl pyrrolidone copolymers, polymethacrylamide and related polymers.As soon as the reaction becomes itself multifunctional, the differences are very important; intramolecular functional interaction very often become prevalent, and they are necessarily related with the internal structure and tacticity of the polymer molecule. Examples are given on copolymers of (meth)acrylic acid with methyl methacrylate and with acrylamide of different compositions, which confirm and complete some previous data of MORAWETZ. By the use of partially hydrolyzed polymethacrylic esters, the influence of the isotacticity, the syndiotacticity and atacticity has been demonstrated directly.From the organic and structural point of view the functionality of the reaction is also very important; the course of the reaction differ only from that of the low molecular compounds when the reaction is multifunctional. Sometimes interfunctional condensation occurs during the synthesis of the polymer, e.g. in the cases of polymethacrylamide, polyalpha‐chloroacrylic acid or during further transformation reactions of the polymer. Some apparently unexpected results are discussed and further explained. Sometimes the interaction may be concomitant with some chain degradation, as in the case of the FRIEDEL‐CRAFTS reactions applied to polyvinyl derivatives.The influence of the stereochemical composition of the polymeric chain is also illustrated with cyclization reactions on polyacrylic acids of different tacticity depending on their methods of synthesis.Reactions including peroxidic groups which determine the degradation phenomena as well as the grafting possibilities, were intentionally omitted.
Untersuchung der molekularen Relalxation in Polymeren mittels des dielektrischen Verfahrens
Authors: Michailow Von G. P. 
Published: April 2003

AbstractIm einleitenden Teil der Mitteilung werden die Hauptmerkmale der Erscheinung der molekularen Relaxatioin behandelt, die in Polymeren über die dielektrischen Verluste (tgδ) und die Polarisation (ε′) beobachtet wird. Es wird vorgeschlagen, diese Erscheinung in zwei Typen zu unterteilen; die Relaxation einzelner polarer Gruppen und die Relaxation der Makromoleküle in der Form von Segmenten.Es werden einige Ergebnisse angeführt, die es ermöglicht haben, die Besonderheiten eines jeden von diesen Prozessen zu begründen. An Hand der Untersuchung der Temperatur‐ und Frequenzabhängigkeit von tgδ und ε′ der Mischpolymerisate Methylmethacrylat‐Styrol und Styrol‐Methylacrylat wird der Einfluß des Kettenaufbaus auf die Dipolgruppenund die dipol‐elastische Relaxation gezeigt.Der Einfluß der Isomerie der polaren Gruppen auf beide Relaxatioinsprozesse wird am Beispiel von drei Homologen der Polymethylmethacrylat‐ und Polyvinylacetat‐Reiheuntersucht.Auf Grund der für tgδ = φ(T,f) gewonnenen Werte und der Werte effektiver Dipolmomente wird die Schlußfolgerung gezogen, daß im Falle der Dipolgruppen‐Relaxation die zwischenmolekulare und im Falle der dipol‐elastischen Relaxation ‐ die innermolekulare Wechselwirkung vorherrschend ist.
Some aspects of anionic polymerization.
Authors: Szwarg M. 
Published: April 2003

AbstractInitiation of anionic polymerization by negative ions is discussed in terms of acidbase reactions. The differences between a conventional acid‐base reaction and the initiation process are considered and elaborated on the basis of a few illuminating examples.The electron‐transfer initiation is described in greater detail. the course of the reaction following the formation of the monomeric radical‐ions is discussed; a distinction is made between primary dimerization, primary monomer addition, secondary electron transfer process, tetramerization and polymerization. Examples of these processes are quoted. Furthermore, some aspects of initation by alkali metals are examined.A tentative discussion is given of polymerization involving dipolar species and zwitterions.Modes of termination are discribed and the conditions required to prevent the termination are outlined. The consequences of the lack of termination are elaborated, namely: the establishment of equilibrium between monomer and “living” polymers, molecular weights and molecular weight distributions of the resulting polymers, the possibilities of intorduction of functional end groups, of formation of block polymers, etc.The problem of pseudo‐termination is discussed in terms of association, solvation, polymer chain configuration, etc. The effect of pseudo‐termination on the structure of the resulting polymer is considered.
Chemical properties of modified celluloses
Authors: Sihtola Hannes 
Published: April 2003

AbstractThis article deals with the chemical properties of some modification of cellulose prepared by means of oxidizing and reducing agents. After a survey of relevant publications, a description is given of work carried out at the Finnish Pulp and Paper Research Institute, and in particular the investigations made by VIRKOLA, as yet un‐published. The last mentioned investigations are primarily concerned with the “dialcohol cellulose” obtained by borohydride reduction of dialdehyde cellulose. The results obtained by VIRKOLA show, amongst other things, that dialcohol cellulose, contrary to what is the case with dealdehyde cellulose, is rather stable in an alkaline solution, but does not withstand the influence of acids. The report also includes a comparison between hydrolysis of the different modifications of cellulosein an acid and an alkaline medium. Finally, by means of molecular fractionation investigations, it has been proved that the reaction between periodate and cellulose does not take place at regular distances in the cellulose chin, and that a further oxidation with intensified influence of periodate occurs in the immediate neighbouhood of the chain units already oxidized.
Ergebnisse der Röntgenkleinwinkelstreuung bei der Bestimmung der Größe und Gestalt von Makromolekülen in Lösung
Authors: Kratky Von O. 
Published: April 2003

Abstract
1. Bei der kohärenten Streuung einer Welle an einer Partikel von vergleichbarer Größe tritt ein merklicher Abfall der Streuintensität mit zunehmendem Streuwinkel auf, der ein Ausdruck für die Größe des beugenden Teilchens ist. Denken wir uns bei festgehaltener Wellenlänge die Partikel mehr und mehr vergrößert (Röntgenwelle und Proteinmolekül), so schrumpft der Bereich merklicher Streuung zu entsprechend kleineren Winkeln zusammen: Röntgenkleinwinkelstreuung.
2. Die Streukurve korpuskularer Partikel zeigt in erster Näherung einen GAUSSschen Verlauf. Bei der Auftragung des Logarithmus der Intensität gegen das Quadrat ds Ablenkungswinkels erhält man daher in erster Näherung eine Gerade, aus deren Neigungstangente man den „Streumassenradius”︁ entnehmen kann.
3. Aus der Streuintensität beim Winkel Null ist das Molekulargewicht berechenbar. Für die Absolutbestimmung muß man allerdings die Intensität des Primärstrahls kennen. Es werden zwei experimentelle Verfahren zur genauen Ermittlung dieser Größe angegeben.
4. Der Vergleich von Molekulargewicht und Streumassenradius gestattet die Bestimmung der Anisotropie, frei vom Einfluß einer äußeren Solvatation. Eine Komplikation kann die innere Solvatation verursachen. Die Invariante nach POROD gestattet, das gleichmäßig erfüllte Volumen zu berechnen. Zur Festlegung der Gestalt ist die genaue Analyse der Streukurve notwendig.
5. Es werden experimentelle Beispiele für die Formbestimmung korpuskularerl Proteine besprochen.
6. Die Streukurve gelöster verknäuelter Fadenmoleküle zeigt einen Verlauf gemäß 1/ϑ2, der mit zunehmendem Winkel in einen 1/ϑ‐Verlauf übergeht. Es läßt sich zeigen, daß aus der Lage des Übergangsgebietes der beiden Bereiche direkt die Länge des statistischen Fadenelementes zu entnehmen ist. Über Versuche an Lösungen von Cellulosenitrat und Crěpe‐Kautschuk wird berichtet.
7. Von den Hinweisen auf die experimentelle Methodik sei besonders die Beschreibung eines Blendensystems erwähnt, das frei von schadlicher Streuung ist.
The photo‐initiated grafting of vinyl monomers to cellulose and other polymers using anthraquinone vat dyes
Authors: Geacintov N. , Stannett V. , Abrahamson E. W. 
Published: April 2003

AbstractUp to 300% of polyacrylonitrile and certain copolymers have been successfully grafted onto cellulose using a photosensitizer and visible or near ultraviolet light. The sensitizers used are photo‐tendering dyestuffs, in particular anthraquinone 2,7 disulfonic acid, sodium salt.The grafting which is accompanied by considerable homopolymerization is proportional to the area of the cellulose substrate and presumably is initiated at the surface. After a certain degree of grafting a definite maximum is reached. The effects of sensitizer and monomer concentrations are also reported, a maximum being shown in both cases.Unlike many radical initiated reactions the presence of oxygen does not decrease the rate of grafting and, in fact, appears to give enhanced rates.The results obtained with other polymers and monomers are described and a tentative reaction mechanism proposed.
Experiments with tritium in macromolecular chemistry. I. Assay of the isotope by gas counting of acetylene
Authors: Bevington J. C. , Eaves D. E. 
Published: April 2003

AbstractA method suitable for the assay of tritium in organic materials, such as high polymers, is described. The specimens are oxidized to water which is reacted wich calcium carbide to give acetylene; this gas is mixed with argon and used for the filling of a GEIGER counter. The procedure is quite simple, gives reliable results and can be used with small specimens giving about 10 mg. of water. It is possible to assay carbon‐14 and tritium in doublylabelled specimens.
Sedimentation, viscosity, and light scattering studies of human fibrinogen at various ionic strengths
Authors: Sowinski Raymond , Freling Vera , Koenig Virgil L. 
Published: April 2003

AbstractA study of two preparations of human fibrinogen revealed that ionic strength influences the sedimentation, viscosity, and light‐scattering properties. The changes occurring in solutions of NaCI at various ionic strengths are discussed in relation to shape, volume, hydration, and interaction of the protein molecules. The presence of impurities is critically assessed. Average molecular weight calculated from sedimentation‐viscosity data and light‐scattering determinations was found to be 269,000 ± 19,000.