bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the mechanism of the polymerization of ϵ‐caprolactam. II. The polymerization in the presence of water
Authors: Hermans P. H. , Heikens D. , Van Velden P. F. 
Published: April 2003

AbstractKinetic runs were performed at two temperatures with ϵ‐caprolactam–water mixtures containing from 5 to 10 mole‐% of water. The concentrations of unconverted lactam x and endgroups c were determined, and in some cases also the concentration of aminocaproic acid u1 and the quantity of cyclic oligomers formed. The concentration of water w and that of the amide groups in linear molecules were calculated from the boundary conditions. In the evaluation of the kinetics of the reaction, which run towards an equilibrium state, values of the equilibrium constants from previous determinations were used. The course of c can be satisfactorily fitted in with the picture of hydrolysis of the lactam, followed by polycondensation. The former starts off as an uncatalyzed reaction between lactam and water but is soon dominated by hydrolysis catalyzed by endgroups. The quantity of lactam thus converted appears to be only a small fraction of the total lactam conversion. If it is assumed that the bulk of lactam disappears through a reaction with rate proportional to xc2, satisfactory fit with the experiments is obtained. This reaction is interpreted as an endgroup catalyzed polyaddition, i.e., an addition of lactam onto an endgroup of a linear molecule catalyzed by another endgroup. From the determinations of aminocaproic acid concentration u1, confirmatory evidence can also be derived that conversion of this linear monomer is for the major part due to an endgroup catalyzed reaction with lactam of a rate proportional to xu1c and with a rate constant of the same magnitude as that pertaining in the general polyaddition reaction. It is argued that the existence of polyaddition also requires transamidation reactions between linear molecules in which one chain with its endgroup reacts with an amide group of a second chain under formation of two other chains of different lengths. This reaction will tend to produce random chain lengths and will thus accelerate the attainment of a normal Flory‐Schulz MW distribution in the reaction product. The rate of formation of cyclic oligomers during polymerization is also in line with the assumption that these substances are mainly produced by a transmidation reaction of a chain endgroup with an amide group of the same chain, rather than by cyclic condensation of a chain of the required length. A survey of rate constants is given. There is general agreement with those given by Wiloth.
Physico‐chemical study of an antigen‐antibody interaction (preliminary light transmission and light scattering investigations)
Authors: Kratohvil J. , Ajduković Dj. , Muić N. 
Published: April 2003

AbstractThe interaction of Ammodytes viper venom and the corresponding antivenin was followed by light transmission and light scattering measurements. The influence of the ratio of the venom/antivenin concentrations, of the ionic strength and pH of the reacting solution, and the kinetics of the reaction were investigated. The precipitation curve (turbidity versus venom/antivenin ratio) was of the flocculation type and showed a maximum. This maximum corresponded to the neutralization point as revealed through the measurement of the haemolytic activity of venom and antitoxic potency of antivenin. Sodium chloride, sodium sulfate, and ammonium sulfate inhibited the precipitation reaction. The rate of the reaction decreased with increasing concentrations of the salts. The turbidity versus pH curve showed a flat maximum in pH range 5 to 8. The reaction was almost completely retarded at the pH below 4 and above 10. The weight‐average molecular weight of venom, as determined by light scattering, was 28,000, of the antivenin (pepsin‐digested) 54,000, and of the venom‐antivenin aggregates from 120,000 to 3,100,000, depending on the venom/antivenin ratio.
Diffusion and viscosity measurements on macromolecules in solution
Authors: Rossi C. , Bianchi U. , Magnasco V. 
Published: April 2003

AbstractIn a previous paper we gave evidence for the validity of the Einstein‐Stokes law for determining molecular dimensions from the diffusion coefficient. In this work, we report on measurements on some polyoxyethylenes in water and on low molecular weight polystyrenes in benzene. The possibility of obtaining exact information regarding the molecular dimensions and the interactions with the solvent have been stated. In high polymers, the dimensions are considerably influenced by the molecular expansion coefficient, α; as a result of this, in studying structural properties of the molecules in solution, the measurements must be carried out in ideal solvents. We have developed a method based on viscometric measurements, which makes possible determination of the composition of the ideal mixture for a given temperature, where such a mixture consists of two components, of which one is a good solvent, and the other is a precipitating agent (non‐solvent). Such measurements have been made on 11 fractions of polystyrene from which it has been possible to determine the expansion coefficient α and the dimensions of the unperturbed molecules at 34°C.
Schwermetall‐Komplexe der Polysaccharidformazane
Authors: Mester L. 
Published: April 2003

AbstractDie mit perjodsäure, Ozon, bzw. Bichromat oxydierten Polysaccharide (z.B. Cellulose, Stärke, Dextrin, Dextran, Xylan) liefern nach Kondensation mit Phenylhydrazin, mit Diazoniumverbindungen intensiv rote Formazane. Diese Polysaccharidformazane ergeben mit Schwermetallsalzen farbige Metallkomplexe. Im Falle der einfachen Formazane, bilden sich die Komplexverbindungen im allgemeinen aus zwei Molekülen Formazan und einem Molekül Metallsalz. Wenn aber in dem Formazanmolekül Hydroxyloder Carboxylgruppen vorhanden sind, nehmen auch diese an der Komplex‐bildung teil; es entstehen dann meist koordinativ ungesättigte Komplexverbindungen, in denen sich je ein Molekül der beiden Komponenten vereinigt. Beim Studium der Polysaccharidformazankomplexe diente das einfache D‐Galakto‐diphenylformazan als Modellsubstanz, an welchem dasselbe Prinzip der Komplexbildung zu beobachten ist. Bei den Metallkomplexen der Polysaccharidformazane sind die Resultate nicht immer so eindeutig, doch kann deren Struktur auch im Sinne der obigen Formeln interpretiert werden. Die Uranylkomplexe der Polysaccharidformazane zeigen an den elektronenmikroskopischen Aufnahmen einen starken Schattungseffekt, so dass hier die Polysaccharide mit ausgeprägten schwarzen Tönen zum Vorschein kommen. Die Resultate lassen hoffen, dass auf dieser Grundlage eine Methode zur Polysaccharidforschung entwickelt werden kann.
Investigation of polymerization mechanisms by means of molecular weight distributions of reaction products
Authors: Bresler S. E. 
Published: April 2003

AbstractThe study of MWD functions gives insight into the mechanism of polymerization and polycondensation reactions. Especially all kinds of side reactions, by altering the already formed macromolecules, give characteristic changes in the MWD. Some special cases are discussed. For polycondensation products, two types of MWD are found. In the early stages of the reaction before the monomer has been consumed, broad distribution curves of the Flory shape are observed. In the later stages, after the polymer has been heated, quite narrow distributions of the Gaussian type are found. The theoretical explanation involves consideration of scission and macromolecular combination reactions, which result in random interchange of monomer units among macromolecules. For products of addition polymerization of dienes in the presence of a catalytic agent butyllithium, exceedingly narrow distribution functions are observed, the polymer being almost homogeneous. This is the result of simultaneous initiation and further growth of all the chains at the same rate during the entire reaction period without termination. For radical polymerization, sometimes simple unimodal, broad distribution curves are found and the termination constants (recombination and disproportionation rates) can be calculated from the curves. In special cases, however, the distribution functions are complicated and consist of many sharp maxima. It is suggested that secondary reactions of chain scission and macroradical recombination occur, which results in a sharpening of the MWD. Subsequent crosslinking of macromolecules from such sharpened distributions gives doubling, tripling, etc. of average molecular weights. This is the explanation for the polymodal sharpened distribution curves observed.
The effects of shape in streaming birefringence of polymer solutions
Authors: Frisman E. V. , Tsvetkov V. N. 
Published: April 2003

AbstractIn this paper are presented new results obtained during further experimental and theoretical investigations of the form effect in the dynamic double refraction of polymers in solution. The use of the dumbbell theory of W. Kuhn for flexible chains in solution and of the optical modle of an equivalent ellipsoid for the macromolecule, permits the formulation of a theory of flow birefringence which takes account of the form effect for a wide range of shear rates. The conclusions of this theory are compared with new experimental data obtained in a study of polystyrene and p‐tert‐butylphenylmethacrylate in different solvents. In the range of low shear rates and concentrations, the theory is found to be in a good accord with experimental results. On the contrary, the study of the double refraction of several polystyrene fractions in dioxane in a wide range of shear rates and concentrations shows that macromolecules are less deformable in the flow than it follows from the dumbbell theory for ideally flexible chains. A new phenomenon was discovered experimentally—an anomalous dependence of the orientation angle on the shear rate of flow in the range of shear stresses at which the birefringence changes its sign because of compensation of the positive shape effect by the negative intrinsic anisotropy effect. Investigation of the concentration dependence of flow birefringence shows that this dependence is due to two causes—the hydrodynamic and optical interaction of the molecules. The optical interaction is characteristic only for those solutions in which the form effect takes place. A simple theory of concentration dependence of the form effect is proposed which is in good accordance with experimental data.
Polyamides non saturées et leurs copolymères
Authors: Mihail R. , Bittman S. , Rizea A. 
Published: April 2003

AbstractOn sait que, par la copolymérisation d'un polyester non saturé avec un monomère contenant de I'azote dans la molecule, par exemple, le triallylcyanurate, on obtient des produits supérieurs du point de vue de la résistance mécaiiique aux températures éevées. On a escompté l'obtention des mêmes propriété, par la présence des atomes d'azote, non pas dans le composant de liaison entre les chaînes d'un polycondensat, mais dans ces chaînea mbmes. Dans ce but, on a fait une série d'expériences préliminaires, où la chaîne de polyester non saturé a été remplacée par des chatnes depolyamide non saturée. Pour établir les caractéristiques générales de formation et de copolymérisation des polyamides non saturées, on a choisi, parmi le grand nombre de polyamides non saturées qui peuvent étre; considérCes du point de vue thborique, le pol∼éthylhnediamino‐maléate. On a ¨︂ les propriétés de cette polyamide, du point de vue de sa solubilité dans divers sol‐ vants et de la compatibilite avec certains monomhres. On a tenté la copolymérisation de la polyamide non saturee avec du nitrile acrylique et de l'allylamine aussi bien A la température ambiante (20–25°C), qu'à une température plus é1evée (100–120°C), soub pression normale et sous pression 1égbrement plus élevée par initiation avec des peroxydes et par addition d'accé1érateurs pour les durcissements A froid. Parmi les nouvelles propriBtés observées, on peut mentionner la capacite de la polyamide non saturee de servir d'une manibre efficace d'agent de durcissement pour les resines Bpoxy, et I'aptitude du copolymbre avec le nitrile acrylique (allylamine) à être utilisé comme échangeur d'ions.
The alkali‐catalyzed polymerization of caprolactam
Authors: Saunders J. 
Published: April 2003

AbstractAn attempt has been made to combine the advantages of the rapid, base‐catalyzed addition polymerization of caprolactam with the more stable molecular weight distribution given by the much slower polycondensation process. This aim has been achieved by polymerizing the monomer in the presence of sodium hydroxide or carbonate and, at a later stage, introducing a small amount of a second agent which promotes hydrolysis or segment interchange reactions and which thus accelerates the chain length re‐distribution of the polymer. The polymerization and molecular weight re‐equilibration steps can be conveniently conducted as two distinct, consecutive batch processes or can be operated on a continuous basis. The practical, industrial significance of these results is discussed. Suitable agents promoting the re‐distribution reactions include water, 6.6 nylon salt, aminocaproic acid, acetic acid, and n‐butyl alcohol. All experiments were carried out at 250°C. under a nitrogen atmosphere and the course of the reaction was followed by measurement of the rate of change of the water‐soluble content of the polymer, and of its end group concentrations, solution viscosity and, in part, turbidity titrations of the water‐extracted products. An observation incidental to the main aim of this work was that the polycaproamide, after washing with water, contained an excess of free amine end groups over carboxyl terminal units. No chain branching was detectable from solution viscosity or infrared spectral investigations, and the polymer was free from sodium. Similar end group effects have been previously described by Dutch and German workers.
Synthesis of new polymers with inorganic chains of molecules
Authors: Andrianov K. A. , Zhdanov A. A. 
Published: April 2003

AbstractA synthesis of polyorganosiloxanes is based on attaching organic groups to inorganic silicon‐oxygen chains structurally corresponding to the quartz molecules. The extension of this idea to skeletons composed of silicon, oxygen, and metals, and corresponding structurally to the silicates, led to the synthesis of new polymers containing chains such as
magnified image
called polyorganometalosiloxanes. Further development of the idea of attaching organic groups to mineral chains, especially the use of the groups R3SiO—, allowed the inclusion even of elements which do not form stable bonds with carbon. This paper presents some results of our research on the formation of new polymers with mineral chain molecules containing atoms of aluminum, titanium, phosphorus, and oxygen. The reactions leading to the formation of aluminosiloxanes are expressed by the following schematic equations:
magnified image
Titanosiloxanes are formed as follows:
magnified image
Similarly mixed phosphoaluminosiloxane polymers are prepared:
magnified image
Thus carbon and silicon are no longer the only important elements forming polymer chains. Such elements as aluminum, titanium, phosphorus, and many others belonging to the second, third, fourth, and fifth groups of the Periodic System can be used in the synthesis of polymers. The method of organically enveloping inorganic skeletons makes it possible to change the properties of the compounds within wide limits. Silicates, corundum, and inorganic polytitanates are familiar as hard, brittle compounds, insoluble in organic solvents. If now, while preserving the polymer chains typical of these inorganic molecules, we surround them by organic groups, we obtain synthetic polymers with properties markedly different from those of their inorganic analogs. At a certain stage these polymers become soluble in organic solvents, form films typical for organic polymers, and show plasticity. The organic radicals surrounding the inorganic chains increase the flexibility of the molecular chains and confer the elastic properties of typical organic macromolecular compounds on these polymers.
Hydrolysis of methylethoxydisilylmethanes
Authors: Pao‐Jen Wang , Yu‐Jue Zeng , Chih‐Tang Huang , I Lin 
Published: April 2003

AbstractHydrolysis of monomers of the type (I) should give polymers with the skeleton SiCSiO, which might possess better properties than siloxanes. The monomers were prepared by the action of methylmagnesium bromide on hexaethoxydisilylmethane. From mono‐ up to pentamethylethoxydisilylmethanes were obtained, the symmetrically substituted and even‐numbered methyl compounds being obtained in preferential yields.Hydrolysis of these five monomers gave interesting results. The strong tendency of ring formation reduced their functionality and thus gave less chance to form crosslinks. While pentamethylmonoethoxydisilylmethane gave the normal product (II), tetramethyldiethoxydisilylmethane gave a ring dimer (III), which, although closely analogous to cyclosiloxane D4, resisted all attempts at ring opening to give a linear polymer. The trifunctional trimethyl compound gave an oil of the type (IV), consisting of rings connected into a chain by oxygen atoms. Dimethyltetraethoxydisilylmethane, although tetrafunctional, gave, on hydrolysis, a highly crystalline compound with a cage structure (V). Only the pentafunctional monomer, monomethylpentaethoxydisilylmethane, gave an insoluble infusible powder of high stability.Co‐hydrolysis of the monomers gave fused ring compounds; dimethyltetraethoxydisilylmethane and tetramethyldiethoxydisilylmethane, when hydrolyzed together, gave a compound of formula (VI).
magnified image
Einfluss verschiedener strahlen auf stärke
Authors: Samec M. , von Kosovinc I. , Reuschl H. 
Published: April 2003

AbstractZusammenfassend können wir feststellen, dass der Ultraschall in erster Linie eine Zertrümmerung der Makromolekule bedingt, dass die Ultraviolettbestrahlung neben einer solchen Peptisation auch hydrolytische und oxydative Vorgänge hervorruft, dass aber in beiden Fällen, der Phosphor in seiner organischen Bindung verbleibt. Im Gegensatz hietz lässt die Gammastrahlung anfangs die organischen Molekeln intakt, ihre erste Wirkung spielt sich an der Phosphorbindung ab. Diese Feststellung scheint uns für ein Verständnis der durch Nuklearstrahlung ausgelösten Schädigungen komplizierter organischen Substanzen sehr wertvoll zu sein. Wir finden ja in vielen lebenswichtigen Verbindungen veresterte Phosphorsäure vor und können nach den beschriebenen Versuchen erwarten, dass auch in diesen die Phosphorsäure abgespalten wird, bevor noch irgend eine andere fassbare Schädigungen festzustellen ist.
A light scattering study of the interaction of sodium desoxyribonucleate with horse serum albumin
Authors: Sokol F. 
Published: April 2003

AbstractThe properties of soluble complexes formed in acetate buffer solutions from sodium desoxyribonucleate and serum albumin have been studied by a light scattering method. It has been established that the molecular weight, size, and shape of the complexes formed are influenced by pH, ionic strength, and the proportions and total concentration of the components. At ionic strength 0.04 and about ‐a 1:1 weight ratio of the components, no binding of albumin by nucleate has been observed at pH higher than 6.0. With continuously decreasing pH, an increasing number of albumin molecules is bound by individual nucleate molecules; this causes stretching of the nucleate molecules and an increase in the excluded volume. At pH 5.5 crosslinking begins. This causes the nucleate molecules to shrink. The concentration of non‐bound albumin becomes negligible, and forces of attraction act between the complex particles in solution. With further lowering of the pH, the molecular weight of the complex increases until, at pH 5.1, precipitation of the complex occurs. Qualitatively, the same picture is obtained if we follow the influence of ionic strength at pH 5.3 and the weight ratio of the components. The formation of the complex begins at an ionic strength below 0.20, and crosslinking and complex precipitation occur at ionic strengths of 0.06 and 0.02, respectively. The lowering of the nucleate to albumin ratio has an effect similar to that of lowering of pH or ionic strength. The molecular weight, size, and shape of the complex are stable only in a limited concentration range. At too high concentrations, complex precipitation occurs, and at too low concentrations, there is dissociation of the complex. Ultraviolet absorption measurements indicate that purine and pyrimidine bases of nucleate do not participate in the binding of albumin. It is assumed that albumin is attached to the nucleate by electrostatic forces between positively charged groups of protein and negatively charged phosphate groups of nucleate only.
Cold‐drawing of glass‐like and crystalline polymers
Authors: Lazurkin J. S. 
Published: April 2003

AbstractSolid polymers—both glass‐like and crystalline—can be cold‐drawn. In addition to studies of the specific aspects of this process in individual cases, as governed by structural features, the development of a theory of cold‐drawing requires an investigation of the general laws of this process. According to the experimental conditions used, cold‐drawing may be carried out either isothermally (at low rates of drawing and with good heat dispersion) or non‐isothermally. A number of specific features of the non‐isothermal process may be explained by a temperature increase in the stressed region; this has in fact been done in published work on this subject. However, the basic features of this phenomenon persist, as has been shown experimentally, in the isothermal cold‐drawing of both glass‐like and crystalline polymers. These features include: (a) the possibility of cold‐drawing, with large residual deformations; (b) the character of the stress—deformation curves; (c) a displacement at the beginning, and a homogeneous or inhomogeneous stretching over the further course of the cold‐drawing (both possibilities being realized in either type of polymer—glass‐like or crystalline); (d) the effect of temperature and the rate of drawing on the initial stress σB. These phenomena must be interpreted in a way which does not involve the assumption of a temperature rise. The values of σB depends on the rate of drawing v, this dependence being expressed by the relation σB = A + B log v, valid for both glass‐like and crystalline polymers. The two types differ only in the value of the constant B, which is lower for crystalline polymers (polyethylene, polyamide, crystalline silicone rubber) than for glass‐like polymers (polyvinyl chloride, amorphous silicone rubber, polymethyl methacrylate, butadiene‐acrylonitrile copolymer, etc.). Crystalline and glass‐like polymers differ in their mechanisms of cold‐drawing. Crystalline polymers, as is well known, undergo recrystallization on deformation; in either type, however, there is a rupture of intermolecular bonds by stresses. Hence follows the kinetic, relaxational character of cold‐drawing. The dependence of σB on the temperature and rate of drawing may be explained on the assumption that the activation energy of the molecular rearrangement is decreased with increasing stresses. Uniform isothermal stretchig is, generally speaking, unstable. The fact that it may be realized in practice, and also the stabilization of the block in non‐uniform drawing, makes it necessary to assume that the mechanical relaxation properties of the polymer change on orientation.