bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellulose derivative‐solvent interaction
Authors: Moore W. R. , Epstein J. A. , Brown A. M. , Tidswell B. M. 
Published: April 2003

AbstractOsmotic pressure, initial phase separation, and viscosity results are presented for dilute solutions of cellulose nitrate, cellulose acetate, and ethyl cellulose, using polymers of similar molecular weight and degree of substitution. A fairly wide range of solvents has been used in each case. Osmotic pressure results suggest molecular dispersion of polymer in most solvents but there is evidence for association of ethyl cellulose in aromatic hydrocarbons. Values of the Huggins μ are obtained and, for systems involving cellulose nitrate and ethyl cellulose in homologous series of ketones and acetates, seem to fall to a minimum and then increase on ascent of each series. It is suggested that the heat term in μ should include an exothermic contribution arising from solvation in addition to an endothermic contribution resulting from mixing of solvated polymer and solvent. It is tentatively suggested that, in a homologous series of solvents, the entropy and exothermic contributions may not vary much and that the variation of μ may arise from varying endothermic contributions. The volumes of hexane required to cause initial phase separation of the nitrate and acetate from solution increase with solvent power, as estimated from μ, but with ethyl cellulose the volumes tend to decrease. It is suggested that solvated polymer may separate from solutions involving polar solvents and, making certain assumptions, estimates are made of the solubility parameters of the polymers separating. Those for cellulose nitrate vary markedly with solvent. The variation of solubility parameter with solvent is less with cellulose acetate and ethyl cellulose but in the latter case values for polymer separating from polar solvents are less than from nonpolar. Comparison of these estimated solubility parameters with those of the solvents and hexane suggests that the volumes of hexane required to cause initial phase separation will only serve as measures of solvent power if the solubility parameters of solvents and precipitant all lie on the same side of that of the polymer separating. This seems to be so for cellulose acetate and possibly the nitrate but not for ethyl cellulose. Comparison of viscosity parameters and values of μ suggests that in certain cases both [η] and the initial slope of the plot of ηsp/c against c increase with solvent power. Other suggested viscosity measures of solvent power do not seem to be generally applicable. Some variation of chain configuration with solvent seems probable. Solvation, solvent type and association of polymer may also affect the viscosities of dilute solutions of cellulose derivatives.
Osmometry with membranes permeable to solute
Authors: Staverman A. J. , Pals D. T. F. , Kruissink Ch. A. 
Published: April 2003

AbstractSimultaneous measurements of osmotic pressure and permeation of solute have been made for a nonfractionated polystyrene with a number of membranes of widely different permeability. It is shown that, even after many days, no real equilibrium is reached in an osmometer with a membrane permeable to part of the polymer. The theory of equilibria in such osmometers is developed and shows that, in first approximation, the distribution of permeating solute over the two osmometer cells is not affected by the presence of nonpermeating solute. In second approximation, this distribution is affected indeed, but in this approximation the osmotic pressure is not affected by this unequal distribution. Some short‐time experiments also show that when the number of permeated molecules is negligible (t → 0) the contribution of a molecular species to the osmotic pressure is less than the value given by equilibrium thermodynamics if the membrane is not completely impermeable to that molecular species. This phenomenon is in accordance with the theory of permeability of membranes based upon nonequilibrium thermodynamics.
Velocity of dissolution of polystyrene
Authors: Ueberreiter K. , Asmussen F. 
Published: April 2003

AbstractSix polystyrene fractions of molecular weights ranging from 1,300 to 250,000 were dissolved in amyl acetate a t various temperatures. The velocity of dissolution was measured by the increase in the refractive index. An assumption was made to describe the experimental results, namely, that the adhesive layer on the surface of solid polystyrene in solvent consists of macromolecular coils the diameter of which can be calculated by Flory's formula. Comparison of the value of the exponent A (from MA) obtained from viscosity measurements with the value calculated from the velocity of dissolution shows excellent agreement. The temperature dependence of the velocity of dissolution is dependent also on the diffusion process of the solvent molecules into the polymer. The expression for this diffusion derived by considering it, as usual, as a rate process, can be introduced into the equation for the velocity of dissolution. The resulting equation accurately describes the experimental results. The velocity of dissolution is different above and below the glass temperature of the polymer. It is possible to use the velocity of dissolution for a determination of molecular weight if the constant of the apparatus has been found by means of a standard sample of known molecular weight. This method helps in the difficult range of molecular weights from 5,000–40,000, where it is very sensitive, whereas other methods are not.
Diffusion de la lumière par des solutions de molécules en chaînes soumises à un champ électrique
Authors: Wippler C. 
Published: April 2003

AbstractDans le but de déterminer la portée pratique de l'étude de la lumière diffusée par des particules soumises à un champ d'orientation, nous avons établi les équations permettant de relier la variation de l'intensité diffusée aux caractéristiques moléculaires en fonction du champ d'orientation. Nous donnons tout d'abord les premiers termes du développement en série de ces équations dans le cas où la forme des particules et la nature du champ d'orientation sont quelconques. Puis, nous donnons l'expression complète de la fonction de répartition de l'intensité lumineuse dans le cas où le champ d'orientation est un champ électrique et où les molécules sont assimilables à des pelotes de Gauss. Les résultats de cette analyse théorique suggèrent une méthode expérimentale simple qui permet de caractériser la rigidité des molécules. Après une brève description de l'appareillage utilisé, nous citons, comme exemple d'applications, les expériences faites sur un échantillon de poly‐DL‐phénylalanine. En solution dans le benzène ces molécules se comportent comme des chaǐnes de Gauss flexibles. A partir des résultats expérimentaux il est possible de calculer, entre autres grandeurs physiques, la valeur du moment électrique porté par ses chaǐnons. Du point de vue pratique, le choix d'un champ électrique limite les applications aux molécules en chaǐnes porteuses d'un moment électrique. Cette restriction tomberait si l'on remplaçait le champ électrique par un champ hydrodynamique.
Group association equilibria in isolated polymer coils
Authors: Morawetz Herbert 
Published: April 2003

AbstractWhen two or more groups attached to a single chain molecule participate in the formation of an association complex, the equilibrium for complex formation in dilute polymer solution depends on the local concentrations in the swollen polymer coil rather than on the stoichiometric concentration in the bulk of the solution. The theory of intramolecular group association is developed using two models. In the first, the interacting groups are evenly spaced along the polymer chain and the probabilities of their association are governed by Kuhn's statistics of chain configuration. In the second model, every segment of the chain has the same probability of carrying an interacting group and the Kuhn statistics are applied only to large rings, the probability of small ring formation being governed by steric factors. The predictions of the theory are in agreement with the extent of carboxyl association in dilute solutions of seven styrene‐methacrylic acid copolymers, measured by infrared spectroscopy. The chelation of cations in dilute polyelectrolyte solution also involves the participation of groups attached to a single macromolecule, but the interpretation of experimental data requires that the electrostatic free energy of complex formation be taken into account. Spectroscopic evidence shows that in copper(II) binding to poly(methacrylic acid) or poly(N, ε‐methacrylyllysine) higher complexes are formed than in solutions of simple carboxylic acids or α‐amino acids, respectively. Dialysis equilibrium studies indicate that, in the concentration range 4.7 × 10−3 to 15.6 × 10−3 N poly(acrylic acid), the polymer coils act independently of each other in chelating small amounts of copper(II), while the copper (II) affinity of poly(methacrylic acid) molecules drops off with rising polyacid concentration.
Solution behavior of chemically synthesized polyglucoses
Authors: Mora P. T. 
Published: April 2003

AbstractThe solution behavior of polyglucoses prepared by the acid catalyzed polycondensation of Pacsu and Mora is discussed. According to this method glucose enters the polycondensation through the hemiacetal hydroxyl joining any of the other hydroxyls of a second glucose unit. Branching occurs up to the functionality of glucose but infinite network is not formed since the branching probability can only approach but never reach unity. The resulting polyglucose is a highly branched spherical molecule, readily soluble in water. Each polyglucose molecule contains one unreacted glucosidic hydroxyl in accordance with the suggested polycondensation scheme, as the agreement between osmotic and reducing end group number‐average molecular weights indicate. The intrinsic viscosity is very low ([η] = 0.08 at Mw 100,000) and increases only slightly with the weight‐average molecular weight, suggesting that the molecule is highly branched: a double logarithmic plot of [η] against Mw has a downward curvature and does not follow the straight line with a slope of 0.50, valid for linear molecules. Periodate oxidation data indicate that fractionation occurs not only by molecular weight but also by the extent of branching, and the lower molecular weight products appear to have relatively less branching.
A simple theory of thermodynamic properties of polyelectrolyte solutions
Authors: Oosawa Fumio 
Published: April 2003

AbstractThe osmotic coefficient and the activity coefficient of polyelectrolyte solutions were calculated by applying the relation of the chemical equilibrium between counterions retained in the apparent volume of polyelectrolyte molecules and those free from molecules. The relation of these coefficients to the concentration of polyelectrolytes depends on the shape of molecules and thus the qualitative difference observed in the behavior of the coefficients of different polyelectrolytes can be explained. The effect of valencies of ions was studied. In a mixture of counterions, all ions of the larger valency are bound by polyelectrolyte molecules when the density of ionized groups on molecules is larger than a certain value determined by the mixing ratio of counterions. The swelling force of polyelectrolyte gels was obtained by a similar method. A new formula is presented in which the osmotic force of counterions retained by chains plays an important role. the anisotropy of the swelling force of gels with oriented chains is attributable to the anisotropy of this osmotic force.
Potentiometric titration of polyacrylic and polymethacrylic acids with alkali metal and quaternary ammonium bases
Authors: Gregor Harry P. , Frederick Michael 
Published: April 2003

AbstractLithium ions, and, to a lesser extent, the sodium ions are bound by polyacrylic acid, as evidenced by pH titrations of polyacrylic acid in dilute (0.01 M) solutions of the alkali metal bases and solutions of their corresponding salts. The formation constant for the binding of lithium to polyacrylic acid was found to be 1.9. When dilute solutions of polyacrylic and polymethacrylic acids were titrated with quaternary ammonium bases, the polyacids became progressively weaker with increasing size of the counterion. These phenomena suggest that the counterions are largely held in close proximity to the polyanion chain, with distances of approach comparable to the sum of the ionic radii. Titrations of these acids with a mixture of a large and small cation also served to point up the increased chain potential in the presence of large cations. All of these effects are absent with the analogous low molecular weight acids.
Viscometric and conductometric titrations of polymethacrylic acid with alkali metal and quaternary ammonium bases
Authors: Gregor Harry P. , Gold Daniel H. , Frederick Michael 
Published: April 2003

AbstractThe reduced specific viscosity of polymethacrylic acid increased with counterion size at the same degree of neutralization for the cations: sodium < tetramethylammonium < tetraethylammonium < tetrapropylammonium < tetrabutylammonium. The increase on going from sodium to tetrapropylammonium at 50–70% neutralization was 20–25% for 0.003–0.01 M polymer, about 4% in 0.001 M solutions. These data indicate that a significant fraction of even large counterions are close to the chain. Conductometric titrations showed that the equivalent conductance of the polyanion was about 40 for most of the salts studied and at low values of α. The binding of counterions based upon the assumption that this value was constant over α led to values which were in reasonable agreement with those determined by Wall using transport experiments.
Theory of the effect of counterion size upon titration behavior of polycarboxylic acids
Authors: Kagawa Ikumi , Gregor Harry P. 
Published: April 2003

AbstractThe effect of the ionic radius of counterions has been introduced into the dissociation theory of polyelectrolytes, using the familiar rod‐like model. Increments in the average dissociation constant pKa and slope n for polyacrylic acid with increasing size of the gegenion have been calculated and compared with data using potassium and some tetraalkylammonium hydroxides. Good agreement is encountered. The effects of changes in concentration of the polyacid and of the presence of neutral salt are also considered.
Sur la notion de l'activité dans les solutions colloïdales
Authors: Dobry‐Duclaux A. 
Published: April 2003

AbstractSur diverses solutions colloïdales de polyélectrolytes globulaires ou filiformes j'ai mesuré, à diverses concentrations, la conductivité électrique, la vitesse de migration des particules et de leur ions compensateurs (counterions), ainsi que l'activité électrométrique de ces derniers. La vitesse de migration et le coefficient d'activité des ions compensateurs augmentent par dilution pour atteindre les valeurs des ions dans les solutions salines ordinaires. J'assimile la particule colloïdale réelle à une particule fictive équivalente qui est libre dans son mouvement et entourée par des ions compensateurs également libres. J'admets que l'influence des interactions électrostatiques est la měme sur la mobilité et sur l'activité; ainsi le nombre d'ions compensateurs “libres” est donné par l'activité. Cette hypothèse donne des résultat conformes à l'expérience. Elle permet de calculer la conductivité d'une solution colloïdale et de prévoir le sens et la grandeur de la vitesse de migration des ions compensateurs à partir des données d'activité. Elle donne pour le nombre de charges de la particule colloïdale des chiffres concordants quel que soit le mode de calcul: à partir de la vitesse de migration, de la conductivité ou de l'activité, contrairement à la méthode usuelle qui conduit à des chiffres discordants. Les résultats expérimentaux concernant la vitesse de migration ont été comparés avec les valeurs calculées d'après la théorie d'Overbeek, basée sur le freinage électrophorétique. Aux concentrations très faibles, l'accord entre les valeurs calculées et observées est bon. Aux concentrations plus fortes, les vitesses théoriques sont trop faibles.
Some statistical problems concerning linear macromolecules
Authors: Hill Terrell L. 
Published: April 2003

AbstractThe matrix method which has been employed in the theory of ferromagnetism is potentially very useful in treating statistical problems concerning linear macromolecules with repeating units. The method is reviewed briefly and applied to seven illustrative problems (two of which are not worked out completely). Six of these involve ion binding or titration curves of polyelectrolytes and one has to do with the question of imperfections (missing hydrogen bonds) in the α‐helix.
A dielectric study of sodium alginate in aqueous solution
Authors: Allgén L.‐G. , Roswall Siw 
Published: April 2003

AbstractSpecimens of sodium alginate have been investigated dielectrically in aqueous solution at low concentrations. The effect on the dielectric increment and dispersion of concentration of polyions and counterions, isoionic dilution, degree of polymerization and degree of neutralization of polyions, and the dielectric constant of the solvent has been studied mainly. Qualitative interpretation of the data in accordance with the present polyelectrolyte theory as Maxwell‐Wagner or Debye‐Falkenhagen effects has been attempted.
Surface chemistry of synthetic electrolytic polypeptides
Authors: Isemura Toshizo , Hamaguchi Kozo , Ikeda Shoichi 
Published: April 2003

AbstractThe copolypeptide of L‐lysine, L‐leucine, and L‐glutamic acid, and that of DL‐lysine, DL‐phenylalanine, and DL‐glutamic acid were studied by surface pressure and surface viscosity measurement. The relationships between ionization and monolayer properties were thoroughly studied. The monolayer of poly‐L‐glutamic acid was also investigated. These polyelectrolytic monolayers were affected by pH of the substrate and the concentration of salt in it. The monolayer behavior could be interpreted in terms of effective free charges and the number of salt linkages. The two‐dimensional Donnan equilibrium was applied to the polyelectrolyte monolayer. The derived relation is formally identical to that derived by Davies from an entirely different point of view.
Potentiometric titration of polyelectrolyte gels
Authors: Michaeli I. , Katchalsky A. 
Published: April 2003

AbstractThe dependence of the degree of ionization of highly swollen, crosslinked polyelectrolyte gels (immersed in salt solution) on the pH of the external equilibrium solution was investigated. A potentiometric equation was derived theoretically, comprising an ideal term, a Donnan term, and a term due to polyelectrolyte electrostatic interactions. Measurements were carried out with polymethacrylate gels in solution of LiCl, NaCl, or KCl. No difference in behavior was found with the different cations, and the observed dependence of the titration curves on ionic strength, degree of crosslinking, and degree of swelling was satisfactorily accounted for by the theory.
Sur le comportement physico‐chimique des solutions d'acide désoxyribonucléique du phage D4 de salmonella enteritidis
Authors: Barbu E. , Basset J. , Joly M. , Wahl R. 
Published: April 2003

AbstractL'acide desoxyribonucléique est extrait du phage D4 par différentes techniques: compression, chaffage, alcalinisation, etc. Les solutions aqueuses correspondantes sont étudiées, en fonction de divers facteurs physiques (concentration, pression, température, pH, force ionique...) par viscosité, par biréfringence d'écoulement et par absorption UV. L'activité biologique des phages au cours des différents traitements est également déterminée. Toutes les solutions étudiées sont fortement polydispersées. Pour chacune d'elles on a déterminé la longueur des particules d'ADN les plus fréquentes, leur anisotropie optique et leur taux de polydispersion. Les résultats obtenus sont comparés à ceux relatifs à l'ADN du thymus de veau. La question de la compatibilité des dimensions des particules du phage et de celles beaucoup plus grandes des particules de l'ADN libéré est discutée et une interprétation est proposée en vue de lever les contradictions apparentes.
Études physico‐chimiques sur deux catégories d'acides désoxyribonucléiques
Authors: Pouyet J. , Weill G. 
Published: April 2003

AbstractL'examen des viscosités intrinsèques d'échantillons de DNA en fonction de la masse permet de mettre en évidence deux catégories d'acides thymonucléiques. On a étudié systématiquement le coefficient d'extinction molaire à 2 590 å et montré qu'il existe également und différence sur εp entre les deux catégories. Il n'y a pas de différence de comportement vis‐à‐vis de la dégradation ou de la dénaturation thermique, ni de variation systématique dans les données analytiques. On donne deux mécanismes possibles permettant d'interprěter les deux catégories.
Des études physico‐chimiques les plus récentes sur l'amidon
Authors: Samec M. 
Published: April 2003

AbstractLes amidons de plantes différentes et de leurs fractions donnent après leur dissolution et leur dessication des images très diverses dans le microscope électronique. Elles se différencient aussi dans leur spectre infrarouge et surtout dans le domaine d'absorption qui correspond aux groupes d'atomes qui contiennent de l'oxygène. Dans ce domaine d'absorption, les processus de vieillissement deviennent perceptibles eux aussi. Les spectres infrarouges des films d'amidons désséchés laissent conclure à des liaisons d'hydrogène très importantes. Des phénomènes de vieillissement peuvent s'observer également à l'aide du spectre ultra‐violet, surtout dans un milieu alcalin.
Cupriethylenediamine and cuprammonium hydroxide as solvents in molecular fractionation of cellulose
Authors: Sihtola Hannes , Kaila Ermo , Laamanen Lauri 
Published: April 2003

AbstractThe possibilities of using cupriethylenediamine (or cuprammonium hydroxide) solution as solvent in molecular fractionation of cellulose was investigated. From the results the following conclusions could be drawn. (1) A real fractionation based on different dissolving power of cuene or cuoxam solutions of different copper concentration seems not to be possible. The results of such fractionations presented in the literature seem rather to be due to a fractionation on the basis of the accessibility. A clear relationship seems to exist between molar concentration of the excess copper in solution and, respectively, per cent dissolved substance and [η] value of the undissolved substance. (2) Precipitation of cellulose from a cuene solution by means of an acid does not bring about a fractionation according to chain length. (3) Fractionation takes place according to chain length when the precipitation of cellulose from a cuene solution is carried out by means of organic liquids, among which propanol has proved to be the most suitable one. In this case the precipitation is caused by decrease of the degree of solvation of the cellulose‐cuene complex. (4) Fractionation can be brought about by raising the temperature of a propanolcontaining cuene solution of cellulose. (5) Considering the depolymerization of cellulose in cuene and cuoxam solutions these solvents cannot be regarded as suitable for determination of the chain length distribution of cellulose.