bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation on the system nitrocellulose‐acetone
Authors: Münster Arnold 
Published: April 2003

AbstractNitrocellulose prepared from heterogeneously degraded cotton and technical rayon pulp has been divided into different fractions by adding water to the acetone solution. The osmotic pressure and the viscosity of each acetone solution at various concentrations have been measured. Within a range of concentration of 1.5 to 10 grams per liter the reduced osmotic pressure shows a linear dependence on the concentration. The molecular weight values obtained are in the range 26,000 to 2,500,000. The value of the virial coefficient B in the osmotic pressure equation depends on the molecular weight. With increased molecular weight the value of B decreases, at first strongly, later more slowly. This fact, which has also been observed on polystyrenes by Outer, Carr, and Zimm (measurements of light scattering), cannot be explained by the Flory‐Huggins theory. It depends on the flexibility of the threadlike molecules. An equation is given showing the relationship between B and M in satisfactory agreement with the experimental data. This equation contains as a parameter the length of a statistical chain element (Kuhn's theory), as obtained by viscosity measurements. Schulz stated that the entropy of dilution of the system nitrocellulose‐acetone differs but little from the ideal value. Consequently the positive excess term calculated for the athermal solution has to be compensated by a further negative term deriving from the solvation. Until now calculations of the solvation only supplied positive terms. Yet, a negative term is obtained, considering the fact that the bond of the acetone molecules with the nitrocellulose is fixing the orientation of the acetone molecule in a much stronger way than it would be in pure acetone. The statistical mechanical calculation shows that this model gives satisfactory results. The measurements of the viscosity cannot be represented by the Huggins theory. The plotting of ηsp./c against c gives curves the slope of which strongly increases with the molecular weight. The molecular weight being rather high, no linear relationship can be reached in plotting ηsp./c against ηsp. The intrinsic viscosity therefore had to be determined by graphic extrapolating. These values are used to find the relationship between intrinsic viscosity and molecular weight, and for the quantitative testing of the Kirkwood‐Riseman theory. The Staudinger formula cannot be applied for higher degrees of polymerization. The Kirkwood‐Riseman theory is confirmed for degrees of polymerization down to n ≈ 200. Below this value systematic discrepancies occur, the reasons for which are discussed. The measurements seem to demonstrate that there are small but characteristic differences between the molecular parameters of cotton cellulose and wood pulp.
Effects of hampered draining of solvent on the translatory and rotatory motion of statistically coiled long‐chain molecules in solution. Part II. Rotatory motion, viscosity, and flow birefringence
Authors: Kuhn Hans , Kuhn Werner 
Published: April 2003

AbstractIn Part I the translational resistance of the random coil was discussed. In the two limiting cases of the freely draining and the completely nondraining coil a theoretical treatment was given, while for intermediate draining conditions an experimental method, involving large‐scale models of the molecules, was shown to be available. The same treatment is now extended to deal with the analogous case of the hydrodynamic rotational resistance of the random coil. It is on this characteristic resistance that the intrinsic viscosity and the flow birefringence of solutions of chain molecules principally depend.magnified imageExpressions are found for the viscosity index [η], the orientation index [ω], and the birefringence index [n], respectively. In these formulas Z is the degree of polymerization while the parameters aη, aη, aη, and brot are independent of Z. These parameters are, however, functions of the length Am of the preferential statistical chain element and the hydrodynamic thickness dh of the chain. an also includes the anisotropy of polarizability of the statistical chain element. It is seen moreover that [ω] (in contrast to [η] and [η]) also depends on the shape resistance of the chain (i.e., on the resistance which the chain inherently offers to a rapid change in configuration).
Structure of copolymers from polymerization of ethylene of polyvinyl acetate
Authors: Roland J. R. , Richards L. M. 
Published: April 2003

AbstractThe formation of “grafted” vinyl copolymers by polymerizing one monomer in the presence of a preformed vinyl polymer has been extended to a new monomer‐polymer combination and one point of attachment of the lateral (grafted) polymer chain has been shown precisely. When ethylene was polymerized in the presence of polyvinyl acetate under a variety of conditions, modified polyvinyl acetates having lateral polyethylene chains were formed. Alkaline methanolysis of such modified polymers yielded mixtures of long‐chain fatty acids and ethylene‐modified polyvinyl alcohols (which were inseparable from any unmodified polyvinyl alcohol that may have been present). The hydrolysis to long‐chain acids shows that polyvinyl acetate acts as a chain transfer agent and that one point of lateral growth of polyethylene chains is the CH3 in the acetoxy group of polyvinyl acetate. The second hydrolysis product, the ethylene‐modified polyvinyl alcohol, shows that chain transfer, and subsequent growth of polyethylene chains, can also occur on the chain carbons of polyvinyl acetate. Oxidation of the ethylene‐modified polyvinyl alcohols yielded a mixture of oxalic acid and long‐chain fatty acids. At the low ethylene pressures studied (300 to 1200 p.s.i.) only traces to small amounts of low molecular weight polyethylene waxes were formed.
An investigation by light scattering of the state of aggregation of amylose in aqueous solutions
Authors: Paschall Eugene F. , Foster Joseph F. 
Published: April 2003

AbstractAqueous alkali has been assumed to be a good solvent for amylose, and has been used as a medium for physicochemical studies on this polymer. It is shown that there is a slow but substantial reduction in the turbidity of normal KOH solutions of amylose, even in the almost total absence of oxygen. More significantly there is a corresponding, but much more rapid, drop in turbidity in neutral solutions (pH 6.5–7.0). At pH 4.0 the turbidities are, in general, constant for up to at least 30 days. The results are interpreted on the basis of aggregates, which evidently must be of a very special type and are termed “native” aggregates. It is suggested that these may consist of amylose in essentially the helical configuration. The properties of these aggregates are in strong contrast to those of the retrograded aggregates. In the form of the first type of aggregate the amylose will not retrograde, at room temperature, without undergoing first a drop in turbidity suggesting that the transition from the “native” to the retrograded aggregate passes through the molecular state. The native aggregates are stabilized toward both disaggregation and retrogradation by pretreatment with iodine. Disaggregation is accompanied by a drop in relative viscosity. Some of the implications of these unexpected observations are pointed out.
Branching mechanisms in the polymerization of vinyl acetate
Authors: Wheeler O. L. , Lavin E. , Crozier R. N. 
Published: April 2003

AbstractA mechanism is proposed for branch formation in polyvinyl acetate. A simplified kinetic analysis gives the degree of branching in terms of six rate constant ratios. Four of these ratios were determined with satisfactory accuracy by very slow photopolymerization of highly purified vinyl acetate at 70°C. to different degrees of conversion. The polymers were believed to be near the maximum molecular weight obtainable at that temperature. Number‐average degrees of polymerization were estimated by quantitative determination of the double bond end groups. The correlation between these values and intrinsic viscosities was in good agreement with published osmotic and viscosity measurements. A fifth ratio was estimated less accurately by viscosity measurements on the polymers after alcoholysis and acetylation. A rough estimation of the sixth ratio was based on a cross‐linking experiment. These ratios were used to accurately predict the degradation on hydrolysis of a series of low molecular weight polymers. Calculations showed greater branching occurs in a single kettle continuous process than in the simple batch process.
Intrinsic viscosity–molecular weight relation for polymethyl methacrylate: Effect of size distribution
Authors: Baysal Bahattin , Tobolsky Arthur V. 
Published: April 2003

AbstractPolymethyl methacrylate samples were prepared by bulk polymerization at 60° initiated by benzoyl peroxide and 2‐azobisisobutyronitrile. Osmotic measurements and intrinsic viscosities were made in chloroform solutions at 20°, using unfractionated polymers of varying number‐average molecular weights. The relation between number‐average degree of polymerization and intrinsic viscosity was obtained and compared with reported relationships for fractionated polymers under the same conditions. Inferences were drawn regarding the size distribution in the unfractionated polymers.
Studies in continuous polymerization
Authors: Wall F. T. , Delbecq C. J. , Florin R. E. 
Published: April 2003

AbstractThe theory of continuous polymerization processes has been developed in a form that permits experimental verification. Under selected experimental conditions it has been found possible to predict the asymptotic, or steady state, conversion without recourse to any assumptions concerning the kinetic order of the polymerization reaction. The theory has been compared with results obtained for the continuous solution polymerization of styrene. Emulsion copolymerization of styrene and methyl methacrylate was carried out by a continuous process in the range 35–55°C. These polymerizations were extended over periods up to 48 hours and with the steady state conversions varying between 35 and 85%. The observation that the conversion passes through a maximum and then decreases somewhat to the steady state value has been found to fit in well with Harkins' picture of emulsion polymerization. A method for obtaining a composition fractionation of styrene‐methyl methacrylate copolymer was developed. Batch and continuous emulsion copolymers (obtained at 77% conversion) were fractionated by this method and it was established that the continuously prepared copolymer was compositionally more homogeneous than the other in spite of the complexity of emulsion polymerizations.
Mastication of rubber, I. Mechanism of plasticizing by cold mastication
Authors: Pike M. , Watson W. F. 
Published: April 2003

AbstractA mechanism is proposed for the degradation of natural rubber by the cold mastication process. The rubber hydrocarbon is considered to be ruptured into free radicals by the deformation of the rubber. These recombine, or react with oxygen or other suitable reactant, and thereafter do not necessarily recombine. Experimental evidence supporting this mechanism is reported, mainly the masticating or rubber in an atmosphere of nitrogen after incorporation of substances likely to interact with the radical ends of the ruptured chains. Forty‐seven substances functioning in this way are listed. A more detailed study has been carried out with one of these, benzoquinone, varying separately concentration, time of mastication, temperature, and mean chain length of rubber. A similar mechanism is shown to apply to the synthetic rubbers tested. The probable chemical reactions occuring and the correlation of cold mastication with other freeradical systems are discussed. The role of oxygen in cold mastication is considered in detail. The possible significance and practical application of the work is suggested.
Some relationships between organosilicon compounds and analogous carbon compounds
Authors: Gilman Henry , Dunn G. E. 
Published: April 2003

AbstractRelationships between organic compounds of silicon and carbon are based, in large part, upon the facts that the two elements have the same normal covalence and bonding orbitals, but different atomic weights, covalent radii, electronegativity, and maximum covalence. Similarities are most noticeable in the physical properties; and differences, in the chemical properties of analogous compounds of the two elements. One of the most outstanding chemical differences is seen in the high reactivity of bonds between silicon and electronegative elements when compared with similar bonds to carbon. The silicon halides are much more readily hydrolyzed than are analogous carbon halides, and the two types may hydrolyze by different mechanisms. In the hydrolysis of carbon of carbon halides the importance of bond breaking almost always equals, and frequently far exceeds, that of bond making. In the hydrolysis of silicon halides, however, exactly the reverse is true. The greater size of the silicon atom is illustrated by the case of formation of such compounds as tetraphenylsilane and hexaphenyldisilane, but the unreactivity of silicon compounds containing α‐substituted groups shows that steric interference between groups attached to silicon does occur. Well‐authenticated compounds containing silicon‐silicon or silicon‐carbon double bonds are unknown, and evidence that resonance contributions from such structures are small is found in the facts that siliconium ions are not formed from triarylsilanols by acid, hexaaryldisilanes do not dissociate into free radicals, and the retarding effect of the p‐dimethylamino group is less in the hydrolysis of triarylsilanes than in the hydrolysis of ethyl benzoates.
Normal and cross‐linked polystyrene. II. Viscosity behavior of polystyrene cross‐linked in emulsion polymerization
Authors: Cragg L. H. , Manson J. A. 
Published: April 2003

AbstractBy emulsion polymerization at 55°C., samples of styrene‐divinylbenzene copolymer were prepared, whose content of divinylbenzene varied from 0 to 0.150%. Measurements of intrinsic viscosity and of the slope constants β and k′ were made, at 25.0°C. in butanone and in benzene, of these samples and of fractions obtained from them by fractional precipitation. In both solvents the intrinsic viscosity of unfractionated polymer was at a maximum at a divinylbenzene content of about 0.005% and k′ was at a maximum at about 0.10%. Since the gel point was also in the neighborhood of 0.10%, it is concluded that a maximum in k′ is a better indication of the gel point than a maximum in [η]. As with linear polymers, [η] was smaller and k′ larger in the poorer solvent. For the higher fractions of a given lightly cross‐linked sample, k′ increased with increasing intrinsic viscosity, deviating progressively more from the value (0.40 in butanone) characteristic of the low fractions and of linear polystyrene. This progressive deviation appeared to begin at an intrisic viscosity which for different samples decreased with increasing proportion of divinylbenzene. These effects are accounted for qualitatively in termas of Baker's “microgel” concept and the effects of the two solvents on the dissolved molecules and dispersed microgel particles.
Studies concerned with the structure of collagen. II. Stress‐strain behavior of thermally contracted collagen
Authors: Wiederhorn Norman M. , Reardon Gerald V. 
Published: April 2003

AbstractThermally contracted collagen, when swollen in appropriate media, obeys rubber elasticity theory. On the basis of the measurements which were made, it was possible to establish that the material behaves as if it were a network polymer crosslinked by covalent bonds. However, the chemical nature of these crosslinks is not known. The molecular weight of the chain between points of crosslinking is approximately 55,000. This corresponds to the molecular weight calculated for collagen from x‐ray data (60,600), assuming the c axis of the unit cell to be the characteristic 625 A. spacing.
Abrasion of rubber by a needle
Authors: Schallamach A. 
Published: April 2003

AbstractA detailed study has been made of the scratches produced by a needle on natural rubber vulcanizates of different composition. The surface damage brought about in this way depends markedly on the nature of the rubber. In particular, the traces on unloaded vulcanizates are discontinuous whereas the traces on carbon loaded rubbers of the tire tread type are continuous. It has been found possible to explain the results qualitatively by reference to hardness, friction, and tear resistance of the vulcanizates.
Butadiene popcorn polymer
Authors: Miller G. H. , Alumbaugh R. L. , Brotherton R. J. 
Published: April 2003

AbstractUsing a direct weight method, the rate of butadiene polymer growth has been found to be logarithmic with time and proportional to the initial mass of polymer seed present providing active polymer seeds are used. When solutions of potassium sulfide (0.005 and 0.0025 g. per ml.) were added to butadiene, the growth of popcorn polymer in the vapor phase was greatly inhibited. The final weights of 0.100 g. initial polymer seeds were 0.205 and 0.389 g. after 29.6 and 30.5 days at 60°C. respectively, for the two sulfide concentrations. This is to be compared with a normal growth of 2.85 g. after 13.5 days at 60° for a non‐sulfided test. Water does not inhibit popcorn polymer growth and may possibly accelerate it. The activity of the popcorn seeds for spontaneous growth in the presence of monomer depends on the seed generation or extent to which the seeds have grown. The growth activity of a definite mass of polymer increases with continued seed growth until a point is reached where there is a structural change from popcorn‐like to more glassy‐like polymer. The latter has lower growth activity. It is believed that the effect of variation of activity with seed generation is independent of peroxide content and that these tests were performed with peroxide‐free seeds.
Treatment of osmotic pressure data
Authors: Krigbaum W. R. , Flory P. J. 
Published: April 2003

AbstractIn applying the quadratic form π/c = (π/c)0[1 + Γ2c + Γ3c2] to osmotic pressure of dilute polymer solutions, the use of a third coefficient (Γ3), which is related semitheoreti‐cally to the second (Γ2), is to be recommended over the use of unrestricted coefficients, both from the standpoint of expediency and of accuracy in the values so obtained for the intercept (π/c)0. and the initial slope (π/c)0Γ2.
The radical distribution functions of electrically charged macromolecules in solution
Authors: Kirkwood John G. , Mazur Jacob 
Published: April 2003

AbstractRepresentative radial distribution functions of electrically charged spherical macromolecules, interacting with a screened Coulomb potential, in electrolytic solutions, are determined by means of the statistical mechanical theory of distribution functions in fluid mixtures. At high concentrations locally ordered clusters, characteristic of liquid structure, are established. The degree of local order in the clusters increases with the magnitude of the double layer potential and decreases with increasing ionic strength of the solution.
Formation des alcali‐celluloses en milieu hydroalcoolique
Authors: Legrand C. , Grund A. 
Published: April 2003

AbstractLes mélanges eau‐alcool‐soude constituent des milieux qui favorisent, à un haut degré, la formation des composés sodés de la cellulose. La Na II‐cellulose, par exemple, quiexige la concentration sodique 8 N, en solution aqueuse, se forme à la concentration 2 N dans le mélange eau‐alcool‐éthylique. La nature de l'alcool possède une influence sur la fixation de la soude. Les faits observés fournissent une voie de recherches en ce qui concerne l'analyse du phénomène de la fixation sodique.
Interpretation des diagrammes de diffusion des rayons X par des systemes denses de particules
Authors: Fournet G. 
Published: April 2003

AbstractL'article est à peu prèb uniquement consacré aux cas des fluides (solutions de macromolécules par exemple). Il est montré qu'il est nécessaire de conuaître plusieurs courbes de répartition de l'intensité du rayonuement diffusé en fonction de l'angle, relatives à plusieurs concentration de la matière, pour obtenir le rayon de giration des macromolécules et des renseignements sur leur potentiel d'interaction.
Spectral studies of polyvinylpyrrolidone (PVP)
Authors: Oster Gerald 
Published: April 2003

AbstractPolyvinylpyrrolidone (PVP) shows ultraviolet maxima which may be attributed to the presence of pyrrolidone rings and to unreacted vinyl groups. The spectrum is considerably altered at extreme values of pH. Complex formation between PVP and molecular iodine was examined by following alterations in spectra of the iodine. Dyes bound to PVP show altered spectral and photochemical properties from that of the free dye.
Über ein neues differentialrefraktometer
Authors: Schulz G. V. , Bodmann O. , Cantow H.‐J. 
Published: April 2003

AbstractEs wird ein Differentialrefraktometer beschrieben das gegenüber den bisherigen Instrumenten eine um eine Zehnerpotenz gesteigerte Genauigkeit dadurch erreicht, dass es den Abstand der durch Beugung unscharfen Spaltabbildungen photometrisch aus markanten Kurvenpunkten bestimmen lässt. Das Gerät ist experimentell wie rechnerisch exakt kalibrierbar. Es erlaubt die Bestimmung der Dispersion von Brechungsindexdifferenzen. Kontrollmessungen an wässrigen Rohrzuckerlösungen ergeben gute Uebereinstimmung mit den Werten des National Bureau of Standards.
Bestimmung des durchmessers geknäuelter fadenmoleküle aus lichtzersträuung und viskositätszahl: Untersuchungen an polymethylmethacrylaten
Authors: Schulz G. V. , Cantow H.‐J. , Meyerhoff G. 
Published: April 2003

AbstractSur une serie de palyméthacrylates de méthyl fractionnés des mesures de la diffusion lumineuse (en fonction de I'angle et de la longeur d'onde) on été faites, puis la constante de diffusion, la constante de sédimentation dans I'ultrazentrifugeuse et la viscosité intrinshque [η] ont été déterminés. Les poids moléculaires et les diamètres des chaînes souples sont en concordance d'après ces méthodes. La dépendance des diametres des chaines sonples d,l du poids molkculaire est un peu plus forte que d'aprh la loi de Kuhn (dst ≃ M0.6). L'influence de cette decouverte sur la fonction de la diffusion lumineuse de mihe que sur l'equation de la viscosite de Kirkwood et Riseman est étudiée.
Extreme ultraviolet absorption spectra of various polymers
Authors: Klevens H. B. 
Published: April 2003

AbstractThe extreme ultraviolet absorption spectra between 1700–3000 A of a series of monomers and polymers show that, in addition to absorption due to the presence of chromophores such as phenyl rings and residual double bonds, other factors such as light scattering, orientation or polarization effects, and interaction, both intermolecular and intramolecular, are important in the observed spectra. In polymers such as polystyrene and polybutadiene, the effect due to scattering becomes appreciable (about 20–30%) at about 1700 A but the other factors do not appear to be important. In proteins, the absorption at short wavelengths is seen to be a function of absorbing chromophores as well as of residual double bond character of the polypeptide chain, of light scattering, and orientation or polarization and intramolecular effects. In other polyelectrolytes, such as polyvinylpyridinium chloride, changes in the 2000 A transition indicate that there is a degree of orientation and/or molecular interaction of the aromatic groups in these polymers.