bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation of composition of polyvinyl acetals to their physical properties. I. Acetals of saturated aliphatic aldehydes
Authors: Fitzhugh Andrew F. , Crozier Robert N.
Published: April 2003

Polyvinyl alcohol was condensed with straight and branched chain aldehydes (CnH2nO, n = 2 to 8) to varying degrees of completion. Measurements on resins and plasticized compositions included apparent modulus of elasticity at various temperatures, brittle temperature, tensile strength and elongation, and solubility. From these measurements it is concluded that: (1) Increasing degree of acetalization results in lowered transition temperature, lower stiffness at transition, narrower transition range, higher brittle temperature, decreased tensile strength, and shift in solubility toward solvents of lower dielectric constant. (2) Acetals of higher normal aldehydes have lower transition and brittle temperatures, lower tensile strength, and more limited solubility. (3) Branched chain aldehydes have higher transition and brittle temperatures than their normal isomers.
Absolute propagation rates in emulsion polymerization. III. Styrene and isoprene
Authors: Morton Maurice , Salatiello P. P. , Landfield H.
Published: April 2003

The study of the rate of polymerization per particle in emulsion systems has been extended to include the following monomers and initiator systems:

Monomer
Initiator System

Styrene
Persulfate

Styrene
CHP‐TETA

Isoprene
DIBHP‐TEPA

In all cases, linear rates of polymerization were obtained in the region where the number of particles can be considered as remaining constant (30–60% conversion). Furthermore, the addition of catalyst in this region did not affect the rate of polymerization, so that a rate per particle could be calculated. From the rates per particle, the following absolute propagation rates were calculated for styrene and isoprene, and are compared with values obtained for styrene from photoinitiation studies:

Monomer
Catalyst system
Eact.
A
kp at 60°C.

Styrene
Persulfate
7.4
4.1 × 107
277

Styrene
CHP‐TETA
8.4
3.3 × 107
221

Styrene
Photoinitiation
7.8
2.2 × 107
176

Isoprene
DIBHP‐TEPA
9.8
1.2 × 108
50
Nouvelle chambre de diffraction de rayons X pour les fibres
Authors: Legrand C.
Published: April 2003

Une chambre de diffraction de rayons X spécialement adaptée à l'étude des fibres et des hauts polymères a été construite. Conçue de façon à utiliser un rayonnement strictement monochromatique obtenu par réflexion sur un cristal de quartz courbé (méthode Guinier), elle permet deplacer l'échantillon dans une atmosphère contrôlée et à une température déterminée. Le film est isolé de “l'espace laboratoire” et est maintenu dans le vide. La qualité des diagrammes a été considérablement améliorée par cette technique.
The number‐average molecular weight of polythene
Authors: Harris Ivan
Published: April 2003

Direct determinations of the number average molecular weights of a variety of British and American polythenes have been made making use of two experimental techniques: (1) ebulliometry and (2) high temperature osmometry. An intrinsic viscosity‐molecular weight relation has also been obtained which covers the range 1.3 × 103 to 76 × 103 and includes representative samples of Alkathene. The Huggins constants k' and μ have been evaluated from viscosity and osmotic pressure data and their bearing on polythene structure discussed.
Réactions de condensation de formaldéhyde et d'urée
Authors: Smets G. , Borzee A.
Published: April 2003

The condensation reaction of urea and formaldehyde was studied in a molar ratio 1:1 and 1:2 of both components; the reaction always proceeds by a second‐order mechanism. These reactions were compared and found analogous to the condensations of pure mono‐ and dimethylolurea. In neutral medium, by measuring at 65, 75, and 85° the value obtained for the energy of activation was 21 kcal./mole for both reactions; the 1:2 ratio‐condensation reaction is nevertheless three times slower than the 1:1 condensation. In acidic medium, a pure acid catalytic effect was found to be true, and the rates of the reaction between pH 3 and pH 5 were proportional to the hydrogen‐ion concentration; the activation energy was evaluated at about 8–10 kcal. for the acidic condensation reaction. At higher pH values, both reactions, thermal and acid‐catalytic, occur together, and the exponent to the hydrogen‐ion concentration in the expression of the rate of condensation appears to be smaller than unity. Analytical determinations of the condensation products are given and a likely kinetic scheme for the reaction is indicated.
Solubility and fractionation of polyvinylpyrrolidone
Authors: Jirgensons B.
Published: April 2003

Polyvinylpyrrolidone (PVP) can be conveniently fractionated from water by successive precipitation with acetone, from chloroform with ether, or from ethanol with benzene. The major part (60–70%) of the common PVP has the intrinsic viscosity of 0.12–0.30. The fractions can be liberated from the low molecular components by extraction of the solid polymer with acetone. Precipitability with ammonium sulfate is a very convenient means of characterizing the fractions. The amount of ammonium sulfate needed to produce turbidity decreases with increasing mean molecular weight of the fractions, with the increasing concentration of the polymer, and with increasing temperature. The molar concentration of ammonium sulfate that produces turbidity is a linear function of the logarithm of the mean molecular weight of the fractions. The amount of ammonium sulfate which produces turbidity decreases linearly with increasing temperature.
Elastoviscous properties of polyisobutylene. V. The transition region
Authors: Tobolsky A. V. , McLoughlin J. R.
Published: April 2003

A discussion of the principles for the extension of the time scale for elastoviscous data by use of experimental information obtained at various temperatures is presented. A quantity k is defined such that stress relaxation curves at all temperatures are identical if plotted versus time divided by k(T). This function k(T) is compared with the function a(T) used by Ferry and by Fox and Flory for other viscoelastic data. In particular, k(T) for polyisobutylene is found to be identical (within experimental error) with a(T) obtained by Fox and Flory from viscosity measurements.

The complete composite relaxation curve Er,T(t) for polyisobutylene is constructed from data of Brown and Tobolsky and Andrews and Tobolsky. Er,T(t) is shown to have three regions: a “rubbery region,” and a “glassy region.” This conclusion is reinforced by comparison with data on polymethylmethacrylate. The “rubbery region” is molecular weight dependent, whereas the “transition region” is molecular weight independent and independent of the presence of a small concentration of cross links.

Simple empirical functions are given for Er,T(t) and the corresponding distributions of relaxation times are also presented.
Study of degradation of polystyrene by means of mass spectrometry
Authors: Achhammer B. G. , Reiney M. J. , Wall L. A. , Reinhart F. W.
Published: April 2003

The degradation of polystyrene by heat and ultraviolet radiant energy was followed by mass spectrometric analysis of the gaseous products evolved. Oxygen content, discoloration, and insolubility of the treated polymer were also investigated. The degradation of polystyrene involves two different processes: (1) the breakdown of thermolabile groups formed in the polymer prior to degradative treatment; this breakdown is caused by exposure to heat at 120°C. in vacuo and 115°C. in oxygen and to ultraviolet radiant energy at 120°C. in vacuo and 118°C. in oxygen; it is accompanied by the removal of residual materials such as solvent; and (2) the oxidation of the polymer caused by exposure to ultraviolet radiant energy in the presence of oxygen. The evolution of benzene, methyl ethyl ketone, dimethylbenzenes, and alcohols is associated with the first stage involving the breakdown of thermolabile groups and the removal of residual materials. Compounds such as formaldehyde, formic acid, and acetic acid are produced as a result of oxidation of the polymer. The oxygen content of the polymer was decreased from 0.33 to approximately 0.1 percent by heating at 120°C. in vacuo and at 115°C. in oxygen, and by exposure to ultraviolet radiant energy at 120°C. in vacuo. Ultraviolet treatment at 118°C. in oxygen for 250 hours quadrupled the original oxygen concentration. Discoloration of the polystyrene was definitely noted only on exposure to ultraviolet radiant energy in oxygen and is associated with oxidation of the polymer. The material became insoluble as a result of all heat and ultraviolet treatments. The amount of insoluble material increased with severity of exposure conditions.
Effect of the velocity gradient on intrinsic viscosity of polymers in solution
Authors: Peterlin A.
Published: April 2003

For a soft free‐draining coil that changes its shape quite easily in flow, intrinsic viscosity does not depend on velocity gradient. The deformation and extension of the coil in flow, which increases the contribution of the single molecule, is just compensated for by the decrease in number of molecules crossing the flow plane and thus actually contributing to the additional shear stress. The finite valence angle and the restricted rotation around the valence bond, however, not only extend but also stiffen the molecule. The completely stiff coils—an idealization that never occurs but is very suitable for computing purposes—are oriented in the flow without any alteration of their shapes and shape distribution. The intrinsic viscosity thereby decreases with increasing orientation. The effect is the more accessible the longer the molecule, the deviations from the initial viscosity at rest being proportional to the square of the gradient and the fourth power of the degree of polymerization. The real molecules are neither quite stiff nor completely soft. Thus their intrinsic viscosity ought to lie between the two limiting cases, the decrease with the gradient being smaller than for the stiff coils. Taking into account the hydrodynamic interaction of the chain elements, the gradient dependence cannot be computed precisely. Qualitative considerations yield an increased viscosity contribution with the stretching of the coils, since they become more permeable the more they are extended. Thus the intrinsic viscosity of quite soft molecules should increase with the gradient. In completely stiff coils, however, the partial solvent immobilization does not change the gradient dependence, on the whole, since the shapes and the shape distribution are unaltered by the flow, although the appearing of the effect is displaced to higher gradients, and the absolute value of the initial intrinsic viscosity is very markedly reduced. Experiments are too rare and not sufficiently precise to allow any reliable test of the theory. In most cases, the concentrations and the gradients are too high for an unambiguous extrapolation to infinite dilution and zero gradient viscosity. But they nevertheless seem to exclude the case of quite soft molecules and are not in contradiction with the general features of the theory.
Investigation on the system nitrocellulose‐acetone
Authors: Münster Arnold
Published: April 2003

Nitrocellulose 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

In 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 image

Expressions 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

The 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

Aqueous 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

A 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

Polymethyl 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

The 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

A 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

Relationships 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

By 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

Thermally 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.
Degradation of long chain molecules as a reverse polymerization process and degradation polymerization processes
Authors: Jellinek H. H. G.
Published: April 2003

Kinetic equations are derived, first for degradation of polymers as a reversal of polymerization processes and, second, for degradation polymerization processes ultimately leading to equilibria between monomer and polymer.
Abrasion of rubber by a needle
Authors: Schallamach A.
Published: April 2003

A 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

Using 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

In 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

Representative 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

Les 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

L'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

Polyvinylpyrrolidone (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

Es 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

Sur 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

The 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.
X‐Ray and light scattering by chain molecules in solution
Authors: Porod G.
Published: April 2003

Starting from Debyes theory the problem of x‐ray and visible light scattering of chain molecules in solution is shown to be essentially a problem of distance statistics. The exact calculation of the average \documentclass{article}\pagestyle{empty}\begin{document}$\overline {r^4 }$\end{document} is carried out for a simple model in order to characterize the distance distribution functions as to their width. On that basis a refined approximation of the scattering function is available. By a numerical example the essential features of the preliminary theory are corroborated. It is shown that the scattering function of a coiled chain molecule approaches asymptotically that of the corresponding rigid rod.
The distribution of polymer fractions
Authors: Sayre Edward V.
Published: April 2003

Systems which obey the Flory‐Scott equation are discussed, and it is shown that the molecular‐weight distribution of increasingly small fractions taken from a polymer solution of the same initial concentration becomes constant. Means of calculating this limiting distribution of an incipient fraction are presented, and it is shown that, in a practical sense, all fractions smaller than the order of one‐sixth the polymer present have nearly the same distribution. To obtain sharp fractions it is more efficacious to take a small number of cuts per stage and refractionate a number of times.
Viscometric detection of branching in polymers. II. Branching in poly(butadiene‐co‐styrene) as a function of polymerization temperature
Authors: Cragg L. H. , Fern G. R. H.
Published: April 2003

Samples of poly(butadiene‐co‐styrene)—all of charge ratio butadiene:styrene 72:28—were prepared in emulsion at 15, 30, 40, and 50°C. Essentially the same redox recipe was used for each, with slight modifications to produce in about the same time polymers of similar intrinsic vistex (1.9 to 2.0) at similar conversions (about 65%) well below the gel point. Each sample was fractionated by precipitation from 1% benzene solution with methanol, special pains being taken to obtain fractions of equal size (each around 5% of the original rubber in the sample fractionated). Careful measurements of the viscosity functions [η], β, and k′ for each fraction were made; with every sample except that prepared at the lowest temperature, the values of β and k′ were observed to deviate in the high molecular weight region from the “base value” common to lower fractions, the deviation starting at a lower molecular weight, and being greater at a given high molecular weight, the higher the temperature of polymerization. It is concluded that branching in a diene polymer of this type is repressed as the temperature of polymerization is decreased: the lower the temperature the higher is the molecular weight at which branching is detectable and the lower is the degree of branching at a given molecular weight. In the 15°C. rubber no branching was detectable at any molecular weight.
Hydratation de diverses formes polymorphes de la cellulose
Authors: Champetier G. , Legrand C.
Published: April 2003

X‐ray diffraction experiments confirm the data obtained by the blotting or centrifuging method, concerning the action of water which penetrates at different degrees in the regions of cellulose. Different forms of cellulose are more or less easily accessible. X‐rays only show variations of intensity for native cellulose, but the unit cells are changed for lattices II and IIIα; the transformations are still deeper for cellulose IIIβ. X‐ray diffraction does not permit determination of the stoichiometric ratios.
Diffusion of acetone into cellulose nitrate films and study of the accompanying orientation
Authors: Drechsel Paul , Hoard J. L. , Long F. A.
Published: April 2003

Studies have been made of sorption and desorption of acetone by films of cellulose nitrate (11 and 12% N) at 30°C. by following the weight of vapor takeup or loss as a function of time. The takeup‐time curves show marked inflections and plots of takeup versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt t$\end{document} are initially nonlinear for both sorption and desorption, indicating that Fick's law with the usual boundary conditions is not obeyed. The rate of vapor takeup is also considerably more rapid and different in character for films cast on glass than for films cast on mercury. A striking result is that for successive sorption‐desorption cycles the rate of sorption decreases markedly, e.g., by a factor of 16 for five cycles. Studies of the optical anisotropy of the films show that the orientation of the polymer molecules normal to the plane of the film is increased by the diffusion process and it is concluded that this accounts for the decreased rate for successive sorption‐desorption cycles and provides an explanation for the diffusion anomalies. A possible cause of this orientation is the observed anisotropic swelling combined with slow movement of the polymer segments.
Crystallization of polyethylene terephthalate
Authors: Cobbs W. H. , Burton R. L.
Published: April 2003

A method for following rapid crystallization in polymers using infrared absorption has been devised. The infrared absorption was correlated quantitatively with the density of polyethylene terephthalate for varying degrees of crystallinity and qualitatively with the change in x‐ray diffraction pattern on crystallization of this polymer. This technique has been applied to measure the crystallization–time curves of thin films of polyethylene terephthalate at intervals of 10°C. for temperatures between 120 and 240°C. Half‐times from these curves show a minimum near 190°C. The temperature dependence of the data is discussed in terms of the Volmer‐Becker‐Turnbull theory of nucleation in condensed systems. An activation energy of 20 kcal./mole for short‐range diffusion of chain segments is obtained from the temperature coefficient of the observed induction time. The data on the kinetics of the crystallization are compared with the results of an analysis of Avrami. A constant, A, was introduced into Avrami's equation to give:

A is the limiting volume fraction of crystalline material after a long time and was determined from density measurements. The crystallization was found to follow this equation from 2 through 90% transformation for temperatures from 120 to 180°C. Deviation appeared in the region below 10% transformation at higher temperatures. The value of k was interpreted as indicating plate‐like growth at crystallites from 120 to 180°C.
Rupture of rubber. I. Characteristic energy for tearing
Authors: Rivlin R. S. , Thomas A. G.
Published: April 2003

A criterion for tearing of test‐pieces cut from thin sheets of a natural rubber vulcanizate, similar in form to the Griffith criterion for spreading of a crack, is formulated. This criterion involves a characteristic energy for tearing which is independent of the shape of the test‐piece and of the disposition of the cut. It is shown how this characteristic energy can be found experimentally for a particular vulcanizate and used to predict the force required to tear test‐pieces of the vulcanizate.
Properties of dilute solutions of polymethylmethacrylate. II
Authors: Bischoff J. , Desreux V.
Published: April 2003

A discrepancy between the previously reported viscosity‐weight‐average molecular weight relationship obtained for fractionated polymethylmethacrylate in acetone and that given by Meyerhoff and Schulz is attributed to the great influence of small chemical inhomogeneities on the molecular dimensions in the poor solvent acetone. Light‐scattering results for the root‐mean‐square end‐to‐end distance R have been recalculated, taking into account a correction pointed out by Oth. It is shown that the results are in excellent agreement with the relation R3 = M[η] 2.1 × 1021 proposed by Flory and Fox, rather than the M1/2 dependence predicted for R by Kuhn.
Degradation of long chain molecules as a reverse polymerization process. Part II
Authors: Jellinek H. H. G.
Published: April 2003

A reverse polymerization process with random initiation has been calculated. Initial stages of various degradation processes have been considered and the initial rates of formation of monomer have been presented as a function of the total number of monomer units present in the system, the initial chain length, etc.
On the degradation of long chain molecules
Authors: Simha Robert
Published: April 2003

The general rate equations for free radical depolymerization previously developed are interpreted for the special case of terminal initiation and absence of transfer in view of recent work by others on the same subject. The discrepancies in the two sets of results are shown to arise from an invalid evaluation of the role of kinetic chain length in this recent analysis.
Benzoyl peroxide initiated polymerization kinetics of vinyl monomers in various solvents
Authors: Conix André , Smets G.
Published: April 2003

Initial rates of polymerization in the presence of benzoyl peroxide as initiator have been determined for methyl methacrylate, vinyl acetate, and vinyl chloride in order to determine the order of reaction with respect to the monomer concentration. In the case of methyl methacrylate, the order of reaction is 1 if benzene is used as solvent; with tert‐butylbenzene, the order of reaction is more complex, and can be interpreted by a “complex” formation mechanism (Mark‐Josefowitz) or by cage effect (Matheson). In the case of vinyl chloride and vinyl acetate in the presence, respectively, of ethyl chloride and ethyl acetate as solvent, the order of reaction has been evaluated to 3/2 vs. monomer concentration. On the contrary, addition of benzene, even in small quantities, produces a strong decrease in rate of polymerization in the case of vinyl acetate, and makes it illusory to determine the order of reaction at high monomer concentrations. Preliminary results using azo‐bis‐isobutyronitrile as initiator for vinyl acetate with benzene as solvent have shown that the considerable influence exerted by benzene in the previous case cannot be attributed to a difference of rate of decomposition of the peroxide only. The results are interpretd by the mechanism of chain‐transfer reactions on the solvent, with formation of radicals from which the relative stability is different from that of the growing chains.
Calibrage de la diffusion lumineuse
Authors: Oth A. , Oth J. , Desreux V.
Published: April 2003

Nous utilisons la méthode de transmission pour calibrer la diffusion lumineuse. Nous vérifions en utilisant des solutions d'indices de réfraction différents que la correction de réfraction est pratiquement n2 pour l'intensité diffusée, l'intensité incidente à travers la cellule devant être corrigée empiriquement pour une réfraction due à la légère divergence du faisceau primaire. A partir de ce calibrage, nous obtenons pour le rapport de Rayleigh du benzène à 20°C. et pour λ 4358 A. R = (48,4 ± 1,5)10−6 cm.−1. Pour les mesures de dissymétrie dans la cellule commerciale semioctogonale “Pyrocell,” nous montrons la présence de réflexions totales pour les solutions d'indice de réfraction ≥ 1,41, réflexions qui peuvent être éliminées aisément en plaçant un verre absorbant dansle fond de la cellule. D'autre part, nous calculons la correction à apporter à la dissymétrie du fait des réflexions de Fresnel quand le faisceau lumineux émerge normalement à la paroi de la cellule.
Copolymerization of isobutylene and styrene at low temperatures in the presence of friedel‐crafts catalysts
Authors: Rehner John , Zapp R. L. , Sparks W. J.
Published: April 2003

Isobutylene and styrene were copolymerized at low temperatures, in methyl chloride solution, in the presence of aluminum chloride. The temperature was varied from −30 to −94°C., and the monomer/solvent ratio, the ratio of monomers, and the catalyst concentration were varied over a considerable range. The copolymerization equation was found to be applicable to the data, and the reactivity ratios were determined for various experimental conditions. For an “open” system in which the volume steadily increases during the course of polymerization, it is shown that the copolymerization equation is formally identical to that of Mayo and Lewis, except that concentrations are replaced by amounts of the reacting species. The temperature coefficients of the reactivity ratios in the present system are compared with those for free‐radical systems; some important differences are noted. The reactivity ratios of isobutylene and styrene in the present system are greatly increased under conditions of turbulent agitation. A procedure for the compositional fractionation of the copolymers is described. The results are interpreted in terms of the copolymer chain structure; they appear to admit the postulate that the reactivity ratios and corresponding propagation rate constants are functions of chain length.