bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrinsic viscosity‐molecular weight relationships for dextran
Authors: Wales M. , Marshall P. A. , Weissberg S. G.
Published: April 2003

Intrinsic viscosities of dextrans of known branching ratio were measured in water formamide, and in a water‐methanol mixture at two temperatures. Weight‐average molecular weights (sedimentation equilibrium) ranged from 1.1 × 104 to 1.7 × 106. A model for the hydrolyzed dextran molecule was assumed. Using the methods of Zimm and Stockmayer, the g factor calculated from this model was compared with the g factor obtained from the intrinsic viscosity‐molecular weight data through the use of the Flory‐Fox theory (g = ratio of squares of radii of gyration of branched to unbranched polymer). The calculated branch lengths required to make consistent the g factors obtained by two different routes were of the same order of magnitude as those found by classical organic chemical methods for other dextran preparations. The intrinsic viscosity‐molecular weight relation at 25°C. in water for linear dextran was predicted from the data. It is suggested that investigations of branched polymers of known constitution be carried out by these methods.
Determination of the rheological properties of fluids by an electronic method
Authors: Thickens R. W.
Published: April 2003

It has long been known that a single point determination can not describe the rheological properties of a fluid. A new method applicable to nonconducting fluids with viscosities ranging from a few hundred to more than 15,000 poises is described. The method consists of a cup and ball in which the ball is forced into rather than pulled out of the cup. Viscosity is measured electronically as a function of the time required for the ball to move a predetermined distance under a given load. Shear rates are variable over very large ranges. Rheological studies were made of a blown castor oil, three polyisobutylenes, and a high viscosity polystyrene. In addition certain physical properties of polyisobutylenes are presented.
Diffusion moléculaire de la lumière: Les constantes de lord rayleigh des liquides étalons
Authors: Rousset A. , Lochet R.
Published: April 2003

Une revue des déterrninations des constantes de Rayleigh pour les liquides montre qu'un nombre appréciable de chercheurs différents arrivent è des réultats concordants en utilisant des m6thodes photographiques; ces rèultats sont considCablement plus bas que ceux de Carr et Zimm et que ceux prévus par la thérie. Le premier groupe de rbultats confirme des considérations thériques modifiées, mais ni ces réultats ni la dbtermination des poi& moléculahes n'apportent de confirmation de la valeur absolue de la constante de Rayleigh. Les auteurs recommandent l'adoption des valeurs déterminks photographiquement.
Infrared examination of various polyisoprenes
Authors: Richardson W. S. , Sacher A.
Published: April 2003

The infrared spectra of synthetic polyisoprenes have been used to obtain quantitative analyses for the various types of addition occurring in the polymers. It is found that the composition of polymers prepared in bulk and emulsion systems is, within experimental error, independent of specific catalyst and per cent conversion of monomer to polymer. The structure of these materials is affected by preparation temperature, increasing temperature leading to a slight increase in 3,4 addition and a large increase in cis 1,4 addition. Polymers prepared in solution with alfin and sodium catalysts show increased amounts of 3,4 addition at the expense of 1,4 addition. Polymers prepared with a cationic catalyst (BF3) are apparently not exclusively linear polyisoprenes.
Methacrylamide polymers and copolymers and their alkaline hydrolysis
Authors: Pinner S. H.
Published: April 2003

New evidence bearing on the resistance to hydrolysis of a portion of the amide groups in polymethacrylamide has been obtained through a study of methacrylic acid (M1) — methacrylamide (M2) copolymers. These copolymers were prepared in aqueous solution with potassium persulfate catalyst. The reactivity ratios were found to be approximately r1 = 2.0, r2 = 0.3. The ratio of accessible amide nitrogen to total nitrogen was determined for each copolymer and was found to vary from 62.3% for polymethacrylamide to 4.3% for a copolymer containing 4.2 mole % of the amide. Some calculations have been made based upon a semiquantitative statistical interpretation of the suggestion of Arcus that the hydrolysis of polymethacrylamide ceases as soon as each amide group is bordered by two carboxylic ion neighbors and the agreement between observed and calculated ratios offers good support for this theory. The actual mechanism of stabilization by the ion neighbors is still obscure but the chain‐stiffening effect of the α‐methyl groups is believed to play an important role.
Relation between stress relaxation and aging resistance of rubber vulcanizates. II. Effect of copper in various accelerated stocks
Authors: Pedersen H. Leth
Published: April 2003

Some details for the construction of a modulus balance and thermostat are discussed. A new dumbbell type is developed for aging tests. In four stocks containing different accelerators, the function of copper applied as stearate is investigated. In the case of Santocure, a comparatively high sensitivity is found, and the t1/2 (TB) value for aging at 70°C. represents a sensitive measure of the prooxygenic effect, whereas relaxation times at 121° showed a smaller but definite variation. With MBT boosted with DPG only a limited effect was observed. Conversely, for the thiurams, copper addition produced a marked antioxidant effect comparable with the retardation normally effected by 2PHR of ordinary antioxidants. 0.05% copper showed an antioxidant activity equivalent to the 2PHR antioxidant. Consistent results were obtained for aging, relaxation, and rate of oxidation. The factors of retardation as might be expected, however, are not quite comparable. The factor of retardation for copper alone is 4–8 units. The copper develops in the thiuram vulcanizates a strong brown color giving colored solutions upon extraction with acetone and iso‐octane. As the spectrophotometric determination of the colored complex is difficult, owing to the presence of the strong absorbing ZDC, the nature of the colored complex has not yet been ascertained, but it must somehow be responsible for the inverted action of copper found here.
The structure of branched polymers of diallyl phthalate
Authors: Simpson W. , Holt T. , Zetie R. J.
Published: April 2003

The complete characterization of a branched polymer involves many factors, the most difficult to assess being the average number of elementary linear portions, or branches, of which the polymer is composed, the degree of polymerization of the branches and the extent of cyclic structure formation. A method of analysis of branched polymers is proposed which should be applicable to polymers of any polyfunctional monomer the unsaturated groups of which are separated by saponifiable links. The method is based on the measurement of degree of polymerization and residual unsaturation of the polymer followed by saponification and determination of degree of polymerization of the resulting polymer, and involves the assumptions that branching in the polymer occurs only by the sharing of a monomer unit by two or more linear portions or branches depending on the number of double bonds in the monomer and also that the average degree of polymerization of the branches remains unchanged by the saponification treatment. Evidence from experiments on the saponification and re‐esterification of poly(allyl acetate) and poly(allyl benzoate) indicates, that, in the case of diallyl esters, the above conditions are satisfied. The technique was therefore applied to three polymers of diallyl phthalate, and in each case the average number of chains and degree of polymerization of the chains were estimated. Evidence of considerable extents of cyclic structure formation was found, each individual branch in the polymers consisting of approximately fourteen diallyl phthalate units, six of which are doubly reacted. It is suggested that the existence of extensive formation of cyclic structures may be partly responsible for the poor correlation of predicted with actual degrees of conversion at gelation in polymerizations involving multifunctional monomers.
Notes on the statistics of polymer chains
Authors: Ullman R. , Hermans J. J.
Published: April 2003

The configurations of flexible macromolecules are discussed with particular emphasis on some problems arising in the theory of the volume effect. The main points considered are: (1) the relationship between the Kuhn statistical chain element and the carbon bond length; (2) the assumption that a polymer chain is equivalent to a collection of independent beads normally distributed with respect to the center of gravity (“Gaussian gas” model); (3) the distribution of segments of a polymer chain with respect to the center of gravity; (4) the theory of the execluded volume for plane models of a polymer molecule; (5) the relationship between the excluded volume and the local density of polymer segments; (6) the influence of the solvent on the excluded volume; (7) polymer configurations and viscosity.
Redox recipes. IX. Alkaline nitroprusside‐hydroperoxide recipes
Authors: Kolthoff I. M. , Meehan E. J.
Published: April 2003

Redox recipes containing nitroprusside are described for the emulsion copolymerization of butadiene (75)‐styrene(25). Approximately 65% conversion is reached in 8 hours at 25° with a recipe containing 5 parts of fatty acid soap, 0.3 part of sodium nitroprusside dihydrate, 0.1 part of hydroxylamine hydrochloride, 0.1 part of diisopropylbenzene hydroperoxide, 0.5 part of n‐dodecyl mercaptan, and 0.5 part of potassium chloride per 180 parts of water and 100 parts of monomers. If alkali is added to the polymerization system the polymerization is accelerated markedly and the addition of 0.1 part of hydroxylamine does not affect the rate. Approximately 60% conversion is reached in 12 hours at 5°C. with a recipe similar to that given above, but without hydroxylamine, provided that the aqueous phase is 0.01 M in trisodium phosphate or alkali hydroxide. From the effect of various factors upon the rate of conversion it is postulated that in the low temperature recipe (with added alkali) the initiation occurs by RO · radicals:
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In the recipe without added alkali but with hydroxylamine hydrochloride the initiation apparently occurs by RS · radicals (RSH is mercaptan) formed by interaction of the oxidation product of nitroprusside with primary mercaptan.
Effect of nonterminal monomer units on the reactivity of polymeric free radicals
Authors: Barb W. G.
Published: April 2003

Certain abnormalities in the compositional relationship of styrene/maleic anhydride copolymers indicate that nonterminal monomer units in a polymer radical (principally the penultimate unit) can detectably influence radical reactivity, through electrostatic interactions with reacting monomer molecules. This effect should be particularly pronounced for monomers of type CHXCHX, where X is a dipole. Several examples from the literature are cited to show that abnormal dependences of copolymer composition on monomer concentration ratio can be explained along these lines. It is suggested that the recently observed variation of cross‐termination velocity coefficients with composition of the monomer mixture is attributable to a similar cause.
Copolymers of 2‐vinylpyridine, methyl acrylate, and dichlorostyrene: Polymerization and properties in solution
Authors: Aggarwal Sundar L. , Long F. A.
Published: April 2003

Copolymerization studies have been made on the three two‐component systems formed by the monomers methyl acrylate, 2‐vinylpyridine, and dichlorostyrene, and values of the monomer reactivity ratios were determined. Terpolymers were prepared from mixtures of these same monomers, and their compositions were compared with those predicted from the kinetic data for the copolymerizations. Measurements of dissymmetry of scattered light, molecular weight, and viscosity were made on solutions in acetic acid and in methyl ethyl ketone of a terpolymer containing 37 mole per cent methyl acrylate, 47 mole per cent 2‐vinylpyridine, and 16 mole per cent dichlorostyrene. The molecular weight of the terpolymer is essentially the same in the two solvents but the polymer chain is more extended in acetic acid than in methyl ethyl ketone. In nitromethane solutions of the terpolymer the ηsp/c values increase sharply with decreasing concentration. This increase is eliminated if the solutions also contain 0.01 mole per liter of a substituted quaternary ammonium iodide. These facts indicate that the polymer behaves as a polyelectrolyte in nitromethane, presumably because of reaction between the aci‐form of the solvent and the vinylpyridine groups.
Dielectric relaxation in a series of polyvinyl acetals
Authors: Sutherland T. H. , Funt B. L.
Published: April 2003

The dielectric properties of polyvinyl isobutyral, hexanal, and 2‐ethylhexanal have been investigated. Dielectric constants and loss factors were measured at eight frequencies between 50 and 100,000 cycles in the temperature range of 25 to 130°C. Free energies, entropies, and enthalpies of activation were calculated, using the absolute reaction rate theory. The results illustrate the effects of “internal plasticization.” With increasing complexity of the interchain substituent, the electrical relaxation time is lowered, and the free energy, entropy, and enthalpy of dielectric relaxation are also decreased. These changes offer a quantitative measure of the decrease in interchain forces. It was also noted that the normal aldehyde substituents exhibited greater plasticizing action than the branched chain secondary groups. The electrical transition temperatures were compared with independently determined softening and inflection temperatures. The electrical and mechanical determinations were in good agreement for identical samples of the polymers.
Study of the viscoelastic behavior and molecular weight distribution of polyisobutylene
Authors: Van Holde Kensal E. , Williams J. W.
Published: April 2003

A study is made of the behavior under constant shear stress of several carefully characterized samples of polyisobutylene. The materials used are whole polymers and fractions obtained from these by dractional precipitation. As a first step in the characterization, the intrinsic viscosity of each is determined. It is shown that the samples cover a molecular weight range from 1 × 105 to 1 × 106. To provide a more detailed characterization, sedimentation equilibrium experiments are performed with several of the polyisobutylenes. These experiments yield values of several average molecular weights for each polymer, from which data an approximation to the molecular weight distribution can be made. It is pointed out that the whole polymers of isobutylene are very polydisperse. The viscosity‐average molecular weights calculated from these experiments are in good agreement with the results of the intrinsic viscosity measurements. The viscoelastic behavior of some of these polymers is then studied by means of creep and recovery experiments. The melt viscosity is determined in two ways, from flow during creep and from the amount of nonrecoverable deformation after elastic recovery. The elastic recovery of the polyisobutylene samples is analyzed in some detail. A method for the reduction of data taken at several temperatures to a standard temperature, previously used for dynamic‐mechanical properties and stress relaxation data, is shown to be applicable to elastic recovery data. Furthermore, the results of creep and recovery experiments can be superimposed in favorable cases. The steady‐state elastic compliance is evaluated, and errors in its determination discussed. The results would seem to indicate that this quantity depends, at least in part, upon the degree of polydispersity of the polymer. This dependence appears to mask any direct variation with average molecular weight. Finally, it is shown that an average retardation time is directly proportional to the melt viscosity of the polymer.
Quantum‐mechanical discussion of the gas‐phase formation of quinonedimethide monomers
Authors: Hush N. S.
Published: April 2003

The formation of quinonedimethide monomers by pyrolysis of the corresponding dimethyl hydrocarbons has been described by Szwarc in a number of publications. Under certain conditions, the monomers so produced may polymerize to high molecular weight products which are of considerable interest. Some dimethylated hydrocarbons do not, however, appear to from monomers under these conditions, and the products of pyrolysis vary considerably with hydrocarbons of different structure. In this communication, the energetics of the various reactions leading to formation of radicals, quinonedimethide monomers, and products of their dimerization or disproportionation are briefly discussed theoretically. The kinetics of the most probable reaction sequences are discussed in the light of the energetic data, and it is shown that a number of features of results so far obtained can be understood in terms of this preliminary treatment. It is hoped that this approach will prove useful as a guide to the types of reactions to be expected for aromatic hydrocarbons of differing π‐electron structure.
Thermal degradation of vinyl polymers in solution. I. Degradation of polystyrene in naphthalene solution
Authors: Jellinek H. H. G. , Turner K. J.
Published: April 2003

The thermal degradation of polystyrene has been studied in naphthalene solutions in high vacuum. The rates of loss of weight have been determined over a range of temperatures from 350 to 380°C., and the energy of activation has been derived. Also the decrease in intrinsic viscosity with time and the loss of weight as function of polymer concentration have been investigated. The mechanism of degradation in naphthalene solution is similar to that of the thermal bulk degradation; it consists of an initial random chain scission process due to weak links, followed by a reverse polymerization process with chain end initiation.
X‐ray small angle scattering of ramie and rayons
Authors: Heikens D. , Hermans P. H. , Van Velden P. F. , Weidinger A.
Published: April 2003

The small angle scattering of ramie and of 25 highly oriented rayon samples of widely different prehistory has been examined in both the air‐dry and the water‐swollen condition with monochromatic radiation in a vacuum camera. All intensity curves are given. For some rayons the curves show distinct maxima or inflection points in either the swollen or the dry condition which seem to be indicative of the existence of a maximum of relatively low intensity superimposed on a normally descending small angle intensity curve. The Bragg spacing corresponding to these maxima lies close to 80 A. for the swollen and to 50 A. for the dry fibers. Other specimens either do not show these superimposed maxima or show only faint indications of their occurrence. The existence of maxima (particularly pronounced in Fortisan, Fiber G, Super Cordura, and Celanese K 36) seems to demonstrate that in some rayons a part of the fiber substance has a micellar structure of unexpectedly high regularity and with average interparticle distances given by the Bragg spacings indicated. The intensity curves of those swollen specimens which did not exhibit a maximum, when evaluated by the Guinier method for dilute systems, assuming parallel cylinders as the basic structure, yield figures between 35–55 A. for the diameter of the cylinders. Evaluation of the intensity curves according to an approximation suggested by Kratky (based on the picture of closely packed lamellae) points to the existence of a preferred spacing of the same order of magnitude (∼40 A.) for the dry and of ∼60 A. for the swollen fibers. No clear correlation between small angle scattering features and other known properties of the rayons has been detected.
A simple and inexpensive osmometer. The molecular weight of 1:3 vinyltoluene‐styrene copolymer fractions
Authors: Mock Richard A. , Marshall Charles A. , Floria V. Deane , Sanders John W.
Published: April 2003

A simple and inexpensive instrument for measuring the osmotic pressure of polymer solutions has been designed. It consists of two 1‐mm. I. D. Pyrex capillary tubes sealed into a flanged Pyrex sleeve, which is ground to fit snugly into a 19 × 60 mm. roundbased Alundum Thimble of medium porosity. A regenerated cellulose membrane is cast over the Alundum thimble, and the entire assembly is sealed in a test tube containing the polymer solution to be examined. This osmometer offers several unique advantages over others in current use. Its low cost and compact size permit inexpensive simultaneous measurement of many polymer solutions.

A 1:3 copolymer of vinyltoluene and styrene monomers was separated into 24 cuts by fractional precipitation. On the basis of viscosity data these cuts were combined into 14 fractions. They were in the order of decreasing molecular weight, and infrared analysis indicated a uniform distribution of the ring methyl groups among the fractions. These two observations demonstrate that introduction of methyl groups into the benzene rings of a polystyrene molecule does not influence the polymer solubility appreciably.

Osmotic molecular weights obtained with the Alundum thimble instruments and experimental limiting viscosity numbers gave values of 2.69 × 10−4 and 0.622 for K and α respectively in the Flory‐Staudinger relation [η] = KMα. These results compare favorably with reported values for polystyrene samples prepared under similar conditions.
The general theory of irreversible processes in solutions of macromolecules
Authors: Kirkwood John G.
Published: April 2003

The general theory of irreversible processes in solutions of macromolecules, previously formulated by the author, is reviewed. The theory is based upon the Oseen method for determining the perturbation in the hydrodynamic flow pattern produced by the frictional forces exerted by the macromolecule on the solvent, and on a generalized theory of Brownian motion in molecular configuration space. Applications of theory to viscoelastic behavior, flow birefringence, and the Kerr effect, and to dielectric dispersion are presented in outline.
Etude de la validité des lois fondamentales de la diffusion brownienne de translation et de rotation, de la viscosité et de la sedimentation des particules rigides de petites dimensions, en solution infiniment diluée
Authors: Donnet J. B.
Published: April 2003

Nous avons groupé dans cet article les principaux résultats d'un travail, dont le principe consiste à mesurer au microscope électronique les dimensions des particules colloïdales rigides utilisées comme modèles, puis à calculer à partir des dimensions la viscosité intrinsèque [η], les constantes de diffusion de translation Δ et de rotation D ainsi que la constante de sédimentation s. Ces paramètres calculés à l'aide des théories fondamentales sont ensuite comparés aux valeurs expérimentales mesurées par les techniques correspondantes et la comparaison des deux groupes de résultats doit permettre de juger de la validité des théories mises en jeu. Dans le calcul des valeurs théoriques nous avons tenu compte de la polydispersité et nous indiquons comment nous avons calculé les valeurs moyennes apparentes de \documentclass{article}\pagestyle{empty}\begin{document}$[\bar \eta ], {\rm \bar \Delta}, {\rm \bar D} $\end{document}. Les mesures de viscosité, de diffusion de translation et de sédimentation effectuées sur un sol de V2O5 donnent des résultats dont la comparaison avec les valeurs théoriques calculées à partir des dimensions n'est guère possible de manière quantitative en raison de l'imprécision de celles‐ci. Mais l'utilisation simultanée des valeurs expérimentales de [η], Δ, s, nous conduit à la conclusion que le sol de V2O5 se comporte comme un sol monodispersé d'ellipsoïdes de révolution rigides de 1692 Å de longueur et de 44 Å de diamètre, or 40,3% des particules de sol étudié ont pour dimensions 1607 Å de longueur et une section rectangulaire de 100 sur 50 Å. La détermination de D par birefringence d'écoulement conduit à un désaccord considérable avec la valeur calculée de D̄ et ce désaccord semble dǔ à la présence dans le solvant d'acides vanadiques qui perturbent l'orientation des bǎtonnets. L'étude d'un sol de virus de la mosaïque du tabac a donné un bon accord entre la valeur calculée D̄ = 205 c.g.s. ± 20% et la valeur mesurée D = 260 c.g.s. ± 20% ce qui constitue la première vérification expérimentale de la théorie de Peterlin et Stuart. Cette étude a permis de calculer l'indice de réfraction de la particule de V.M.T., on trouve n1 = 1,58, n2 = 1,59, ce qui corrobore les valeurs trouvées par d'autres employant des méthodes indirectes. Enfin l'étude d'un sol aqueux de noir de carbone a permis d'observer un accord convenable entre \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \Delta $\end{document} calculé = 1,10 · 10−7 c.g.s. ± 15% et Δ mesuré = 1,37 · 10−7 c.g.s. ± 10%, ce qui montre la validité de la loi de Stokes pour des sphères dont le diamètre est de l'ordre de 1 à 200 Å. Ce sol présente d'autre part de l'effet électro‐visqueux et la constante d'Einstein K = 2,5 est trouvée égale à K = 7,8 ± 0,5. On donne quelques résultats concernant l'étude de l'effet électro‐visqueux de ce sol.
Thermodynamic properties of polystyrene solutions
Authors: Bawn C. E. H. , Wajid M. A.
Published: April 2003

Measurements have been made of the osmotic pressure of polystyrene fractions in toluene and methyl ethyl ketone at 25, 50, and 55°. The results can be accurately represented by the equation:

The virial coefficients have been evaluated and it is shown in agreement with theory that A2αM−ε where ε = 0.15 or 0.33 according to method of derivation of A2. The results are compared, and shown to be in general agreement with other reported measurements. The heat of dilution of polystyrene in toluene and methyl ethyl ketone was determined from measurements of the temperature coefficient of the osmotic pressure. In the concentration range 3 to 9 × 10−3 g./cc. ΔH/ϕ where ϕ2 is the volume fraction of polymer was approximately zero in toluene and −20 ± 5 cal./mole in methyl ethyl ketone. In part III vapor pressure measurement of polystyrene fractions in acetone, chloroform, and propyl acetate solutions are summarized and the heat of dilution in these solvents derived. The results are discussed in relation to existing theories of the free energy and entropy of dilution of polymers and it is shown that the results cannot be explained in terms of theories based on the lattice model of solutions.
Solution properties of polystyrene prepared under high pressure
Authors: Trementozzi Q. A. , Buchdahl R.
Published: April 2003

The molecular weight, the size, and the second virial coefficient have been determined for a series of styrene polymers prepared under high pressure (0 to 4000 atmospheres) using light scattering techniques. The intrinsic viscosity–molecular weight relationship, the size–molecular weight relationship, and the magnitude of the second virial coefficient reveal no significant differences when compared to similar data of regular polystyrene. Structural differences due to the method of polymerization do not exist to the extent that they can be revealed by such measurements.
Effect of salts on the interaction of nucleic acid particles
Authors: Conway B. E. , Butler J. A. V.
Published: April 2003

The finding of Pouyet and Sadron that, at extreme dilutions of thymonucleic acid, the specific viscosity at low shear rates is either unaffected or only slightly affected by salts is confirmed with two samples prepared in different ways. The specific viscosity in these solutions increases considerably above the limiting value at very low concentrations and is then markedly sensitive to the presence of salts even at very small concentrations of the latter. The rapid increase of the specific viscosity with increasing concentration must be due to increasing interaction between the particles, and as these interactions are sensitive to small salt concentrations they must be electrostatic in nature. It is suggested that they arise from the Debye‐Hückel forces between the particles and their counter ions. When no added salt is present the counter ions can only complete their ion atmospheres by interacting with two of the polyelectrolyte particles and this will give rise to interactions between the particles, which will be greatly reduced by even small concentrations of added electrolytes. Interactions of this type will vary in strength according to the distances of the interacting charges and may be so weak that the shearing stresses can over come them. This will produce the high shear dependence observed in solutions of this kind. The differences between the behaviour of deoxyribonucleic acid and various synthetic polyelectrolytes which have been studied may arise from the fact that in the former the charges are carried by the “backbone” of the fiber and in the latter on side chains which are capable of rotation.
The preparation and properties of some gelatin fractions
Authors: Stainsby G. , Saunders P. R. , Ward A. G.
Published: April 2003

A method for fractionating gelatin based on the solubility behavior of gelatin/detergent complexes is described. The method is practical and convenient both for determining molecular weight distributions and for preparing gelatin fractions. It is shown that fractions of equal reduced viscosity, and hence molecular weight, derived from gelatins of similar isoelectric points may still differ in important respects, thus confirming the conclusions of Pouradier and Venet, who prepared fractions by a different method of fractionation. It is established that the rigidity of gels formed from the gelatin fractions is independent of molecular weight, at least at 5.5 g./100 ml. concentration. There is some indication that, for the lowest molecular weight fraction, a slight variation of rigidity with molecular weight is occurring. Some other structural feature, at present unidentified, must be associated with the mechanism of gel formation.
Ultracentrifuge studies with a synthetic boundary cell. I. General applications
Authors: Schachman H. K. , Harrington W. F.
Published: April 2003

This report presents some general applications of a new type of ultracentrifuge cell, called a synthetic boundary cell, in which a sharp, stable boundary is obtained by layering one solution over another more dense solution while the ultracentrifuge is in operation. Since such a boundary between a solvent and a dilute solution of a low molecular weight solute can be formed in the center of the cell, the complications encountered at the meniscus in conventional ultracentrifugation by the high diffusion and low sedimentation rate of the solute are obviated. By this technique the sedimentation velocity method has been extended to substances with molecular weights as low as 350. Sedimentation constants of a number of low molecular weight materials such as fraction A of insulin (molecular weight 3000), vitamin B12 (molecular weight about 1500), β‐dextrin (molecular weight 1134), and sucrose (molecular weight 342) have been determined. The cell has also been used to form a boundary between solutions of two different concentrations of the same macromolecule and differential sedimentation constants have been obtained. The relationship between these differential sedimentation constants and those obtained for either of the two solutions when studied alone is discussed. Application of the cell to the determination of hydrodynamic volumes of sedimenting components is described. Measurements are made of the backward flow of solvent by the use of an indicator boundary formed by layering a virus solution over another virus solution containing an additional component, such as sucrose or a protein, which acts as an indicator. In addition, the cell was used in a preliminary investigation of some fundamental problems in ultracentrifugation such as the sedimentation of slowly sedimenting materials in the presence of more rapidly sedimenting components, the analysis of equilibrium systems such as insulin and chymotrypsin, and the role of convection.
Ultracentrifugation of bacterial viruses
Authors: Putnam Frank W.
Published: April 2003

The bacteriophages (bacterial viruses) are the largest biologically active agents having known dimensions and particle morphology which have been prepared in a homogeneous state. Because all the bacteriophages have an appendage or “tail”, they offer an interesting system for study in the analytical ultracentrifuge in comparison of the results of direct and indirect methods for estimation of particle size and shape. The sedimentation behavior of phages T5, T6, and T7, all differing in size and morphology, has thus been investigated. Although, under certain conditions, the three viruses sediment with a single sharp boundary, T6 appears to undergo aggregation to form a dimer at neutral pH. The sedimentation rate of the phages is little affected by concentration and is uninfluenced by the centrifugal field, thus indicating the absence of interaction or of particle orientation due to the peculiar morphology. A comparison of estimates of the particle size and weight based on molecular‐kinetic constants, electron micrograph dimensions, and unit infectivity yields a good correlation among the results of the direct and indirect physical methods for the quasispherical particle of T7, satisfactory agreement for the large tadpole‐shaped particle of T6, but considerable discrepancy for the sperm‐shaped particle of T5. It is suggested that the dimensions of T5 based on early electron micrographs are in error. Despite their large size and unusual shape the bacteriophages are amenable to physicochemical study, and each type is as uniform in molecular‐kinetic properties as are molecular proteins.
New types of membranes for osmotic pressure measurements
Authors: Immergut E. H. , Rollin S. , Salkind A. , Mark H.
Published: April 2003

Semipermeable membranes used for osmotic pressure measurements are usually made from collodion or from regenerated cellulose or from other cellulosic materials. Such membranes are readily attacked by corrosive solvents, they are easily oxidized, and they can be used for only a few hours at high temperatures. To overcome these difficulties new noncellulosic membranes have been developed. The preparation of a polyvinyl butyral membrane and of a Kel‐F (polychlorotrifluoroethylene)membrane is described. The data for typical osmotic pressure measurements using the new membranes are presented. The Kel‐F membrane can be used for measurements in all common organic solvents as well as for solutions of cellulose in solvents such as cupriethylene diamine and cuprammonium hydroxide. It is also suitable for high‐temperature osmotic pressure measurements.
The synthesis of block copolymers in a flow system
Authors: Hicks J. A. , Melville H. W.
Published: April 2003

A selected monomer containing a photosensitizer flows along a capillary at a defined rate into a suitable receiver. Very high concentrations of free radicals (up to 10−4mole/l.) are produced at a selected point by focusing into it a large proportion of the radiation from a capillary are lamp. These polymer radicals grow to a chain length determined by the time spent subsequently in the capillary and it has been demonstrated by a utilization of the theory of the nonstationary phase in chain reactions that most of the radicals can be introduced into a second monomer contained in the receiver. That their continued growth in the new environment leads to the synthesis of block copolymer has been proved by examination of the ultraviolet spectra of the products.
A new method for the determination of the rate of initiation in radical polymerizations
Authors: Bevington J. C. , Bradbury J. H. , Burnett G. M.
Published: April 2003

In a radical polymerization in which initiation is solely by the addition of an initiator fragment to a monomer molecule, there must be in the polymer one combined initiator fragment for each kinetic chain; analysis of the polymer therefore can lead to a determination of the kinetic chain length. The rate of initiation is equal to the over‐all rate of polymerization divided by the kinetic chain length, and so it can be calculated. This new method for calculating rates of initiation is not subject to the uncertainties associated with older methods. Analysis for initiator fragments can be performed accurately if the initiator is labeled with a radioactive isotope; in the work described here C14‐α,α′‐azo‐bis‐isobutyronitrile was used. An essential requirement is that the polymer molecules of low molecular weight must not be lost during precipitation of the polymer. Tests are described showing that loss of low molecular weight materials is negligible in most cases and that even when the average molecular weight of the polymer is low and there is an appreciable loss a correction can be made. A correction can also be made for the consumption of initiator during the reaction. The results presented in this paper refer to the copolymerization of butyl acrylate and styrene in benzene solution at 60°. It is shown that for a given monomer mixture the rate of initiation is proportional to the concentration of initiator, and that for each initiator molecule decomposed approximately one reaction chain is started.
Synthesis and properties of a new polyether: Poly‐3,3‐bis(chloromethyl)‐1‐oxabutene
Authors: Farthing Alan C. , Reynolds R. J. William
Published: April 2003

3,3‐Bis(chloromethyl)oxacyclobutane may be polymerized in the presence of powerful electrophilic catalysts, e.g., boron trifluoride; minute traces of water are also necessary for polymerization to proceed. The resulting polyether, poly‐3,3‐bis(chloromethyl)‐oxabutene, is an inert, highly crystalline and insoluble polymer, m.p. 180°, capable of forming oriented films and fibers. The high crystallinity and strong interchain forces are reflected by the complete inconsistency of solution viscosity values measured at 100°. The molecular weights could only be compared by determining melt viscosity values.
Some aspects of the polymerization of fibrinogen
Authors: Ferry John D. , Katz Sidney , Tinoco Ignacio
Published: April 2003

The polymerization of activated fibrinogen takes place in two stages. First, the monomer units form intermediate polymers with twice the original cross‐section area and about eight times the original length. The polymers have been detected under a variety of conditions between pH 6.1 and 10. The polymerization geometry is believed to be lateral dimerization with a staggered configuration, determined by a pattern of electrical charges. The negatively charged groups, though unidentified, appear to be near histidine residues, as deduced from the dependence of polymerization on pH. The positively charged groups, from this and other evidence, appear to be α‐amino groups. Second, the intermediate polymers unite to form the strands of the fibrin network. This association appears to involve nonpolar groups, and the width of the final strands, unlike that of the intermediate polymer, depends markedly on the net charge as determined by the pH.
The role of free radicals in the degradation of high polymers by ultrasonics and by high‐speed stirring
Authors: Alexander P. , Fox M.
Published: April 2003

High molecular weight polymethacrylic acid in aqueous solution is rapidly broken down by ultrasonics (250 kc.). The rate of degradation varies as the shape of the molecule in solution is altered and is greatest when most asymmetric.

It is concluded that cavitation is essential for the breakdown of the polymer molecules and that the reaction proceeds by two mechanisms. The major part of the reaction is due to mechanical forces produced on the collapse of the cavity but chemical degradation by HO2 radicals also occurs. Polymerization experiments confirm that free radicals are formed during cavitation. The quantity of H2O2 formed by ultrasonics is much greater than the number of free radicals produced and a separate mechanism for its formation must be postulated. High‐speed propellers, e.g., in a “Waring Blendor,” bring about cavitation and degradation of polymethacrylic acid.
Alleged catalytic effect of hydrogen chloride on decomposition of PVC at high temperature
Authors: Arlman E. J.
Published: April 2003

Experiments are described made with the object of measuring the alleged catalytic effect of HCl on PVC decomposition. The conclusion is that this effect does not exist.
Thermal and oxidative decomposition of polyvinyl chloride
Authors: Arlman E. J.
Published: April 2003

An investigation into the kinetics and the mechanism of thermal and oxidative decomposition of polyvinyl chloride is reported. The rate of HCl evolution was measured in streams of nitrogen, air, and oxygen. The reaction is described as a chain reaction involving initiation (thermal and oxidative), propagation, and termination (spontaneous and oxidative). A Kinetic scheme is given representing the rate of HCl evolution as a function of the reaction constants of the step reactions. The results indicate that thermal decomposition starts at the end groups of the macromolecules, whereas oxygen initiates decomposition within the chain.
Herstellung und eigenschaften von polygalakturonsäureamiden
Authors: Solms J. , Deuel H.
Published: April 2003

Polygalakturonsäuremethylester verschiedener Veresterungsgrade können durch Behandlung mit flüssigem Ammoniak im Autoklaven bei 16°C. während 24 Stunden annähernd quantitativ in die entsprechenden Amide übergeführt werden. Die Amide sind in Wasser schwer löslich und ergeben Lösungen geringer Viskosität. Sie können aus ihren Lösungen durch Elektrolyte leicht koaguliert werden. Derivate mit einem Amidierungsgrad von über 70% sind wasserunlöslich. Mit steigendem Amidierungsgrad können eine Erhöhung der Stabilität gegenüber dem Enzym Polygalakturonase. sowie eine Zunahme der Geliertendenz festgestellt werden. Die Amide bilden keine festen Gele. Die Eigenschaften der Amide werden stark durch ihre Fähigkeit zur Bildung inter‐ und intramolekularer Wasserstoffbrücken beeinflusst.
Size and shape of droplets of demixing polymer solutions in a field of flow
Authors: Silberberg A. , Kuhn W.
Published: April 2003

The phases which are formed at, e.g., 22°C., when a solution containing, e.g., 1.1% polystyrene and 1.7% ethyl cellulose is made in benzene, are characterized by having a low interfacial tension (⋍10−3 erg/cm.2), which permits droplets of the one phase in the other to be easily deformed and disrupted in a field of flow. The size and shape of the droplets thus formed were determined by an optical method depending upon the statistical addition of the deflections suffered by a beam of light in its passage through the medium. It is found that at intermediate velocity gradients very small and extremely elongated droplets are stable and that, at a given temperature, the phase separation can be reversed by raising the velocity gradient above a definite value. A full discussion of the observations is given and it is shown in particular that the appearance of extremely elongated drops at certain velocity gradients is due to a stationary state equilibrium between processes causing the drops to break up and others causing them to recombine again. The superposition of break‐up and recombination is thus responsible for the existence in practice of inherently unstable drop shapes.
Theory of strong polyelectrolyte solutions. I. Coiled macro ions
Authors: Ōsawa Fumio , Imai Nobuhisa , Kagawa Ikumi
Published: April 2003

A new theory of strong polyelectrolyte solutions based upon the Poisson‐Boltzmann equation is presented. Assuming that the ratio of the effective charge of the macro ion to its original charge is very small, the Poisson‐Boltzmann equation is solved without adopting the Debye‐Hückel approximation. As a result of the calculation, the effective charge of the actual coiled macro ion with the strongly dissociative groups was found small enough to justify this assumption for the solutions of varying concentration over wide range. Moreover, the free energy, and consequently the chemical potential of the components, of the polyelectrolyte solution with or without simple salt are calculated. The idea of “ion fixation” is theoretically introduced as convenient for representing the state of the polyelectrolyte solution. The theoretical results obtained above are quantitatively compared with experimental data with very good agreement.
Preparation and properties of poly‐p‐xylylene
Authors: Corley Richard S. , Haas Howard C. , Kane Marshall W. , Livingston Daniel I.
Published: April 2003

The preparation of poly‐p‐xylylene, , in 24–26% yield, by pyrolysis of p‐xylene, is described in detail. The nature and amount of by‐products of the pyrolysis were determined. The physical appearance and the following properties and reactions of the polymer are described: x‐ray diffraction, crystallinity, optical constants, infrared absorption spectrum, degradation by autoxidation in solvents and by pyrolysis, dielectric constant and loss, sulfonation and chlorination. The significance of this data is discussed relative to an understanding of the mode of formation and the structure of the polymer.
Vinyltoluene‐styrene copolymer sulfonic acid. I. Viscous properties and ionic character in hydrochloric acid solutions
Authors: Mock Richard A. , Marshall Charles A.
Published: April 2003

Assuming complete dissociation of the mineral acid in dilute aqueous solutions of a 1:1 vinyltoluene‐styrene copolymer sulfonic acid and HCl, the degree of dissociation of the polyacid is apparently a constant independent of the concentration of either solute. On the basis of this result, it is likely that the polysulfonate chain initially contracts in such a manner with increasing HCl content of the solution that a maximum number of sulfonate groups remains on the surface of the coil. The variation of reduced viscosity (ηsp/c) with polyelectrolyte concentration c in the presence of a finite quantity of added “normal” electrolyte is determined mainly by the ratio of the counterions resulting from polyelectrolyte dissociation to the total counterion content of the solution. In regions of high dilution, where counterions from the polyelectrolyte are much less numerous than those from HCl, an apparently linear increase of reduced viscosity with increasing polymer concentration is observed. These data probably can be extrapolated to infinite dilution. Over the range of HCl concentrations 10−4 to 10−2 equivalent per liter the reciprocal square root of such extrapolated polysulfonic acid “limiting viscosity numbers” is proportional to the pH of the solvent. At the maxima of reduced viscosity plots the contribution of the polyelectrolyte to the hydrogen ion activity of the solution is half the contribution of the HCl: i.e., one third of the hydrogen ion activity is the result of polyelectrolyte dissociation. Moreover, the reduced viscosity at the maximum is directly proportional to the pH of the solvent. Curves of ηsp/c vs. c at high dilutions and constant pH are parabolas rather than straight lines. It is permissible to postulate rather convincingly from our data that the reduced viscosity curve of the polysulfonic acid in water possesses a maximum accurately indicated by the intercept of a Fuoss plot (cf. equation (7) in the text). The intercept of a Fuoss plot for any polyelectrolyte can have the significance of a limiting viscosity number only when measurements are made in a nonionizing solvent.
The microstructure of diene polymers. III. Polyisoprenes and polybutadienes prepared with cationic catalysts
Authors: Richardson W. S.
Published: April 2003

A number of polyisoprenes and polybutadienes have been prepared at temperatures between 30° and −78°C. using Friedel‐Crafts catalysts. Quantitative analyses for the various types of addition occurring in these polymers have been made from their infrared spectra. It has been found that the linear structures corresponding to 1,4; 1,2 and 3,4 addition are present in about the same ratios as in free radical type polymers. However, in the case of the polyisoprenes (and apparently also the polybutadienes) these structures account for only about 50 to 75% of the material present.