bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer association. I. Osmotic pressure of solutions of mixed acidic and basic polymers
Authors: Morawetz H. , Gobran R. H. 
Published: April 2003

AbstractMethyl methacrylate was copolymerized with small amounts of methacrylic acid or dimethylaminoethyl methacrylate. The molecular weight of the basic copolymer calculated from osmotic pressure data in butanone and benzene gave consistent results. The molecular weight of the acidic copolymer was obtained from osmotic pressures of pyridine solutions, but in butanone and particularly in benzene strong molecular association was observed. Osmotic pressures of mixtures of the two copolymers in butanone at 30.2 and 50.1 and in benzene at 49.7°C. were determined. The reduced osmotic pressure plots were linear but indicated the persistence of molecular associations to the highest dilutions at which osmotic pressures could be measured. A thermodynamic analysis of the data showed that under certain conditions the activity of one or the other polymer component decreases with increasing concentration of the mixture.
Refractive indices of polythenes with different degrees of branching
Authors: Baccaredda M. , Schiavinato G. 
Published: April 2003

AbstractRefractive indices of five polythene samples, previously studied by Bryant and Franta and by Muthana and Mark, who determined their densities, degrees of branching, osmotic molecular weights and μ‐values in xylene solutions, have been measured by the immersion method in suitable liquid mixtures. Powdered samples have been prepared from xylene solutions by cooling and by evaporation of the solvent under identical conditions. They appear, under the microscope, as transparent radial and weakly birefringent spherulites; refractive index values are higher than those of the amorphous polythene and decrease as the degree of branching increases. The refractive index lowering is to be ascribed to the change both of the molecular structure (branching) and of the ratio between the amount of amorphous and of crystalline material, the latter strictly depending on the former when samples are prepared under identical conditions. Measurement of the refractive index may therefore be suitable for the empirical determination of the degree of branching in polythenes; it seems to be simpler and more significant than the measurement of the density, the latter also being affected by relatively large microvoids, while the refractive index may be affected only by those microvoids the sizes of which are not larger than the wave length of the light used. Refractive index measurement may also be suitable for the determination of the degree of branching and of the degree of crystallinity in other polymeric substances.
Interaction between polyelectrolytes and heteropolar precipitates
Authors: Težak Božo , Kratohvil Stanka 
Published: April 2003

AbstractThe interactions of some polyelectrolytes (anionic–gum arabic, agar; ampholytic–gelatin) with silver bromide sol in statu nascendi were studied. It was found that there are analogous phenomena to those encountered with usual hydrophobic sols. The polyelectrolyte effects on hydrophobic systems were treated in a manner usual for simple electrolytes. The appearance of the typical coagulation curves with maximum is used for the characterization of various systems: hydrophobic colloid–polyelectrolyte–electrolyte. Depending upon the position of the system on “stabilizing” or “sensitizing” side of this maximum (sometimes of minimum), there is a very pronounced difference of the polyelectrolyte action on the coagulation value of simple electrolyte. Thus, on the “stabilizing” side, the “reverse” antagonism was found, which is explained as a result of the dominating polyelectrolyte adsorption effect.
A dielectric study of a carboxymethylcellulose in aqueous solution
Authors: Allgén Lars‐Göran , Roswall Siw 
Published: April 2003

AbstractA carboxymethylcellulose sodium salt (CMC) with about 50% of the glucose units substituted, has been studied dielectrically by the “ellipsoid method” at various wave lengths. Aqueous solutions containing 0.1–0.0025 g./100 ml. were investigated. Dielectric increments of 2–9 dielectric constant units were obtained for these solutions. The calculated increment per gram per liter was not constant but increased considerably at the lowest concentrations, indicating the prevalence of polar molecules or aggregates at the lowest concentrations, whereas less polar aggregates dominate at higher concentrations (more than 0.01% solutions). At the lowest concentration studied, 0.0023%, the increment per gram per liter was about 120, corresponding to a molar increment of about 55,000,000. Dielectric dispersion curves were obtained which approached theoretical Debye dispersions, indicating that the CMC molecules are rather rigid. The dispersion curves were displaced toward shorter wave lengths with increasing concentration, probably due to the strong molecular interaction. At the lowest concentration a relaxation time of 4.6 × 10−7 sec. was calculated for the CMC molecule. This corresponds to a rotation of the molecules about their long axes in the electric field. An average molecular weight of about 460,000 was calculated for the CMC molecules, or polar aggregates, in very dilute aqueous solution. The electric moment of CMC was estimated to be about 1000 Debye units. In contrast to CMC, the uncharged polysaccharides dextran and ethyloxyethylcellulose did not show any deviation of the dielectric constant values from that of the pure solvent, when investigated in 0.5% aqueous solutions at various wave lengths. It was concluded that the dielectric properties of CMC are very similar to those of other polyelectrolytes studied–such as desoxyribonucleic acid, nucleohistone, and hyaluronic acid.
Separation of neutral proteins on ion‐exchange resins
Authors: Boardman N. K. , Partridge S. M. 
Published: April 2003

AbstractThe effect of pH of buffer on the adsorption of cytochrome C on the ion exchange resin IRC 50 has been studied in detail and the information gained has been used to predict conditions for the separation of neutral proteins such as the hemoglobins. The behavior of a protein on the resin is markedly different from that of ampholytes of low molecular weight such as the basic amino acids. The basic amino acids are desorbed as the pH falls below 5 due to suppression of the ionization of the resin carboxyl groups, but the adsorption of protein is greatly increased under acidic conditions. It is suggested that this is due to a large increase in secondary short‐range forces.Sheep fetal CO hemoglobin has been separated from bovine CO hemoglobin and bovine CO hemoglobin from bovine methemoglobin. The eluting buffer was citrate of pH 5.81 and 5.92, respectively, and Na+ concentration 0.34 g. ions per liter. In initial experiments, heavy losses of the CO hemoglobins occurred which was most probably due, to a large extent, to the formation of methemoglobin. To obtain good yields, it is necessary to work at a temperature near 0°C. and to use freshly prepared proteins.
La courbe de titration de l'insuline et de ses fractions
Authors: Fredericq Eugene 
Published: April 2003

AbstractOn a mesuré au moyen d'une électrode de verre les courbes d'électrotitration de l'insuline cristalline dans KCl 0,1 N, depuis pH 2 jusque pH 11. Dans la région alcaline les courbes ne sont pas réversibles. La solubilité de l'insuline entre pH 7 et pH 9 augmente beaucoup lorsque la protéine a été préalablement dissoute en milieu acide ou alcalin. Les quantités d'ions H libérées dépendent aussi du traitement subi antérieurement.On a séparé l'insuline en deux fractions suivant leur solubilité à pH 8. La fraction la plus soluble a une courbe de titration réversible en milieu homogène; dans le domaine d'insolubilité de l'insuline (pH 4 à 6,5), la courbe dépend du sens de la titration. La fraction la moins soluble révèle un nombre inférieur de groupes titrables en milieu alcalin. Ce nombre augmente par séjour à pH supérieur à 10. Les changements survenus dans les groupes dissociables ont été interprétés comme indiquant la présence de liaisons spéciales dans lesquelles seraient impliqués des groupes phénoliques et des groupes imidazole.On a calculé des courbes de titration suivant la théorie classique et suivant la théorie de Debye‐Hückel. On a pu rendre compte des résultats expérimentaux en assignant une seule constante de titration aux groupes de měme espèce déduits de l'analyse chimique, sauf pour les groupes phénoliques. La théorie des interactions électrostatiques permet d'interpréter ces faits. Elle fournit des valeurs de pK′0 en bon accord avec les données obtenues avec d'autres protéines. Les pK′0 sont respectivement de 6,6, 7,8, 9,9 et 10,0 pour les groupes imidazole, α‐aminé, phénolique et ε‐aminé.En utilisant comme solvant du dioxane à 40% dans une solution aqueuse 0,4 N en KCl, on a pu maintenir l'insuline en solution dans tout le domaine de pH. La courbe de titration a été mesurée dans ce milieu et interprétée théoriquement par l'effet de l'abaissement de la constante diélectrique sur les constantes de titration.
Interaction of vegetable tannins with polyamides as proof of the dominant function of the peptide bond of collagen for its binding of tannins
Authors: Gustavson K. H. 
Published: April 2003

AbstractThe irreversible fixation of vegetable tannins (mimosa) by collagen and esterified collagen, as well as by a hydrated polyamide, has been investigated. The polyamide possesses a marked affinity for the vegetable tannins and binds them irreversibly, proving that the peptide linkages function as binding sites for vegetable tannins. This fixation is independent of pH value of the system in the pH range 2–8. The same independence is shown in the fixation of tannins by collagen from solutions containing sodium chloride which prevents the swelling of collagen. The typical fixation curve of vegetable tannins by intact collagen is highly pH‐dependent. In this instance the tannin fixation is directly related to the degree of swelling of collagen as a function of the pH value of the system. This is due to the fact that the degree of swelling of the protein governs the number of coordination‐active peptide bonds present in collagen for the fixation of tannins. Esterified collagen, in which the major part of the potential hydrogen binding sites are free to react, fixes large amounts of tannins independently of the hydrogen‐ion concentration of the system in the pH range 2–7. The rapid drop in fixation of tannins at pH values >8 is due to the ionization of phenolic groups, leaving fewer hydrogen bonds available on the tannin molecule. Evidence is presented in support of the view that the main reaction of polyphenolic tannins of the major type represented by mimosa tannins consists in coordination of a polyphenolic molecule to peptide bonds of adjacent protein chains, probably by means of hydrogen bonds. This multipoint attachment will explain the stabilization of the protein lattice effected by the tanning agent.
Application of an integrator in the calculation of diffusion coefficients from plotted diffusion curves: Theory and practice, including an estimation of the accuracy of the method illustrated also by the calculation of a set of known Gaussian curves
Authors: Jensen Robert 
Published: April 2003

AbstractThe formulas used for calculation of diffusion coefficients in free diffusion are stated. The calculations request the 0th, first, and second moments of the curve to be calculated. This is usually made by calculation of moments of segments of the figure between the curve and the base line, followed by summation.It is proposed to replace this rather laborious procedure by the use of an integrator. A survey is given on the theoretical background and the principles for such instruments. Some equations are stated for the type of instrument used in these investigations. From these equations it is possible, by inserting the values in the formulas used for the calculation of diffusion coefficients, to express the latter for a certain curve as a function of the rotation of the three integration rolls in the instrument. The relative influence on the final result for these integration rolls is considered. For one of the rolls this can be shown to be insignificant, when the moment axis is chosen very near the central axis of the curve. Our experience has shown the standard error in a normal measurement to be 2 × 10−3 and 3 × 10−3 of a revolution for the two other integration rolls. Some curves are given which show the requests one must put on the relative number of rotations for these rolls to make certain that the relative standard error, introduced by the integrator, will not exceed certain values on the final result. The curves are drawn for values from 2 to 0.1%.From a known Gaussian distribution a set of diffusion curves is drawn. The diffusion coefficient is calculated from these curves both by the usual method and by the integrator. The results obtained by the integrator compare well with those by the usual method if the peaks are not drawn too narrow.
Two‐dimensional electrophoresis on paper
Authors: Dicastro Gino 
Published: April 2003

AbstractWith a view to finding a better method of separating the different components during electrophoresis on paper, we have carried out the electrophoresis in two dimensions, first flowing the current in one direction and then at right angles to that direction. For this purpose we used square paper sheets between two glass plates of the same dimensions. The electrical behavior of the material to be analyzed was tested before electrophoresis, so that it was possible in each instance to establish the duration and the different electrical characteristics of the two periods of electrophoresis and also the best initial position for placing the material. The experiments show that the components are found along a straight line, the position of which is determined in the plane by the characteristics and time flow of the current during the two phases of the process. Referring to the initial position of the material, each individual component is to be found at the extremity of the hypotenuse of a right angled triangle, the other sides of which are formed by the paths made by the substance in the two different phases of the process. The obvious advantage of the two‐dimensional electrophoresis on paper is that it is possible to trace, on the same sheet of paper, the path taken by the different components under two different electrical conditions.
Degradation of vinyl polymers in solution
Authors: Tasset G. , Smets G. 
Published: April 2003

AbstractThe degradation of high polymers was studied in dilute solution (1%) in the presence of an equivalent amount of benzoyl peroxide in a temperature range from 65 to 100°C.The reaction was followed dynamically by a viscometric method, and from a static point of view by determining the polydispersity of the samples after degradation, and also by spectrophotometric measurements. The viscometric method allows examination of the influence of the polymer concentration, of the degree of polymerization, of the initiator concentration, of the temperature, and of the chemical structure of the polymer on the rate of degradation. These rate constants were obtained under the same experimental conditions, and permit the classification of the polymers in the following decreasing order: polychloroacrylate, polymethyl methacrylate, and polystyrene. Under the same conditions, polyvinyl chloride and acetate are stable and not affected. These results are discussed as a function of the lability of some atoms present in the polymeric chain and as a function of the relative stability of the intermediate radicals produced during the reaction. Statically, the degradation was followed by determining the variation of polydispersity before and after degradation in the case of a sample of polymethyl methacrylate. On the other side, ultraviolet spectrophotometry shows the presence of monomer by degradation of a polystyrene sample; this spectrophotometric method also allows proof of the microreversibility of the polymerization process. The use of this technique makes it necessary to carry out the experiments under experimental conditions that differ from the preceding ones (lauroyl peroxide, and chloroform as solvent).
The lactam‐amino acid equilibria for ethylpyrrolidone and polyvinylpyrrolidone
Authors: Frank H. P. 
Published: April 2003

AbstractThe lactam‐amino acid equilibria of N‐ethylpyrrolidone and poly‐N‐vinylpyrrolidone were studied in dilute aqueous solutions and in n‐butanol at 100°C. and compared with earlier investigations of similar systems. It was found that with in the intermediate pH range the lactam is the predominant form. Below and above certain critical acid and alkaline pH values increasing amounts of amino acid will be formed. It has been shown that these critical pH values are closely related to pK1 and pK2 of the corresponding amino acid. The polymeric lactam PVP is more resistant against hydrolysis than the low molecular lactams. This effect is due to the polyampholyte character of the polymeric amino acid formed in the course of the hydrolysis reaction.
Polyvinylpyrrolidone. I. Distribution of molecular weights: Experimental methods and applications
Authors: Campbell H. , Kane P. O. , Ottewill Ingrid G. 
Published: April 2003

AbstractA method is described for determining the distribution of molecular weights of polyvinylpyrrolidone (P.V.P.) by measurement of the turbidity produced in aqueous solution by varying concentrations of sodium sulfate. Using this method, the acetone‐water method of fractionation is shown to be unsound due to inhomogeneity of the fractions obtained. This latter method is, however, of value in the preparation of P.V.P. of narrow molecular weight ranges by repeated fractionation. The distributions of molecular weights of typical samples of P.V.P. used in the plasma substitute, Plasmosan, are given. Less than 5% by weight of the molecules possess a molecular weight greater than 100,000. The reproducibility and stability to autoclaving of this polymer are shown to be satisfactory.
An approach to the solution of structure problems of organic chain polymers
Authors: Bjørnhaug A. , Ellefsen Ø. , Tønnesen B. A. 
Published: April 2003

AbstractA radial distribution method for interpreting diffuse x‐ray diagrams of liquids has been utilized and further developed for an approach to the solution of structural problems of unoriented specimens of chain polymer substances. The principles of the technique have been given. Experimental distribution curves, indicating the atomic distance distributions have been calculated for the following chain polymers: polyvinyl acetate, polyvinyl alcohol, polystyrene, polyhexamethylene adipamide, polymethyl methacrylate, regenerated cellulose, and alginic acid. For the structure interpretation some of the experimental distribution curves are directly compared with theoretical distribution curves calculated from the atomic distances in measured out structure models, which have been built up on a scale of 1 A. equal to 10 cm. by means of a molecular model building set. From the results obtained, the technique seems to be well suited for structure investigations of unoriented samples of polymer substances.
The electrostatic free energy of polyelectrolyte solutions. II. Fully stretched macromolecules
Authors: Lifson S. , Katchalsky A. 
Published: April 2003

Abstract(1) The electrostatic internal energy of a solution of rodlike, ionized polymolecules is calculated by an integration which makes use of the molecular potentials evaluated previously. (2) The electrostatic free energy is calculated by a charging process for which the reference state is a discharged solution of the same concentration as that of the charged solution. (3) A series of graphs is presented for the numerical evaluation of the internal and free energies of salt‐free polyelectrolyte solutions as a function of concentration, degree of ionization, and temperature. (4) The osmotic pressure of stretched polyelectrolytes is calculated from the free energy expression. The calculated osmotic coefficients are practically independent of molecular weight and polyelectrolyte concentration, and are determined by the degree of ionization. A comparison with the measurements of Kern on salt‐free polyacrylic acid at higher degrees of ionization (for which the macromolecules are stretched) gives a very satisfactory agreement. (5) An expression for the light scattering by polyelectrolyte solutions is derived from the equation for osmotic pressure and discussed briefly.
Polyampholytes
Authors: Katchalsky A. , Miller Israel R. 
Published: April 2003

AbstractSix amphoteric copolymers of different composition of 2‐vinylpyridine and methacrylic acid were investigated. The specific viscosities of the copolymer solutions exhibit a pronounced minimum at the isoelectric point and the spectrometric titration of the pyridinium groups shows a pronounced jump in pH at the isoelectric degree of ionization. A theory of the polyampholyte behavior, based on the shape changes of the macromolecules and the field energy of the ionized groups, is developed and compares satisfactorily with the experimental results. The theory permits inter alia the evaluation of the intrinsic dissociation constants of the monomeric units and the determination of the isoelectric points from copolymer composition.
Dissociation of weak polymeric acids and bases
Authors: Katchalsky A. , Shavit N. , Eisenberg H. 
Published: April 2003

AbstractThe electrolytic dissociation of several polymeric acids and bases in aqueous solutions has been investigated. The potentiometric behavior is well described by the following equations, For polyacids:

and for polybases:

pK0 is the intrinsic dissociation constant of the monomeric unit, α and β are the degrees of ionization of the polyacid and the polybase respectively, ψ0 is the electrostatic surface potential of the polyion. It is shown that ψ0 is equal to (1/ϵ) (δFe/δv) for polyacids and (1/ϵ) (δFe/δζ) for polybases where Fe is the electrostatic energy of the polyion and v or ζ the number of negative or positive ionized groups respectively. Equations for the calcualtion of ψ0 in the cases of randamly kinked and stretched polyelectrolytes are given and discussed. As the potential ψ0 can be obtained independently from electrophoretic measurements, the above equations correlate potentiometry and electrophoresis. The potentials of polymethacrylate ions were calculated from theory and obtained from electrophoretic and potentiometric measurements. The potentials obtained by the three methods agree within 3% thus justifying the use of the combined potentiometric and electrophoretic measurements for the evaluation of pK0. Application of this method to the potentiometric analysis of pectic acids gave good agreement with experiment and lead to pK0 = 3.40. Combined potentiometric‐electrophoretic analysis for polyaspartic acid gave pK0 = 3.53 and for polylsine pK0 = 10.44.
Effect of detergent on the polymerization of allyl acetate
Authors: Meehan E. J. , Kolthoff I. M. , Carr E. M. 
Published: April 2003

AbstractThe persulfate‐initiated polymerization of allyl acetate has been studied at 70°C. in the absence and in the presence of sodium lauryl sulfate. In the absence of the detergent a polymer of molecular weight about 800 is formed from initially homogeneous reaction mixtures at an initial rate approximately proportional to concentration of persulfate and approximately independent of concentration of monomer. The ratio of the initial rates of disappearance of allyl acetate and persulfate is about 14, corresponding to the ratio calculated from the molecular weight. With a separate phase of monomer the molecular weight is about 1000. The addition of the detergent does not increase the rate of initiation or affect the molecular weight of the polymer formed in innitially homogeneous media, although the rate of polymerization is increased somewhat. With a separate phase of monomer the polymer formed in the presence of detergent has a molecular weight of about 1300.