bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über vernetzungsgrad un Porosität makromolekularer stoffe
Authors: Mikes J. A. 
Published: April 2003

AbstractPolymere wurden hergestellt, die der bekannten Regel über den Zusammenhang zwischen Porosität und Vernetzeranteil nicht gehorchen. Mit inertem Zusatz polymerisieren Kettenbildner und vernetzende Monomere zu Kopolymeren, dessen Quellung, Hydratation, Diffusionskonstante, innere Oberfläche, Maschenweite, also Porosität den bekannten Daten nicht entsprechen. Die Porositätsunterschiede, die auf Veränderung des Vernetzeranteils entstehen, können mit inerten Zusatzstoffen bis in die entgegengesetzte Richtung verschoben werden. Ein Molekülsiebeffekt wurde an Ionenaustauscherharzen mit unverändertem Vernetzeranteil erzielt.
The problem of polymer coacervation
Authors: Broda Andrzej , Chodkowska Maria B. 
Published: April 2003

AbstractThe relation between concentration of polymer in the precipitated phase and the properties of the system are derived. This relation indicates that, for any polymer, a separation into two liquid phases which agrees with Kruyt's definition of coacervates can be obtained. It is suggested that it is not always correct to distinguish coacervation as a special phenomenon. The experimental results of investigation of the systems: ethanediol–water–phenol–polyamide and acetone–methanol–benzene–polystyrene are presented.
Über Phasentrennung bei kolloiden Lösungen makromolekularer gemische
Authors: Hunyar A. , Wiesner E. 
Published: April 2003

AbstractEs ist bekannt, dass Mischungen von Polymeren im selben Lösungsmittel in sehr vielen Fällen zur Phasentrennung neigen. Solche Lösungen sind immer kolloide Lösungen bei denen kolloide Bereiche verschiedener Konzentrationen der einzelnen Komponenten nebeneinander vorliegen. Diese kolloiden Bereiche vereinigen sich dann zu getrennten Phasen, wenn die bei der Vereinigung geleistete Arbeit die Oberflächenenergie der kolloiden Bereiche übertrifft. Durch Erhöhung der Oberflächenspannung des Lösungsmittels mit geeigneten Zusätzen zum Lösungsmittel für das Polymere oder Zusätze die nur einige der Polymeren zu lösen in der Lage sind oder solche Zusätze, die keine der Polymeren zu lösen in der Lage sind, die aber immer die Oberflächenspannung erhöhen, kann man erreichen, dass für längere Zeit die kolloiden Lösungsmittel stabil bleiben und keine Phasentrennung eintritt.
Influence de la charge des particules sur la viscosité des sols
Authors: Donnet J. B. 
Published: April 2003

AbstractDie experimentellen Tatsachen, über welche hier berichtet wird, scheinen zu zeigen, dass das viskosimetrische Verhalten eines Sols geladener Teilchen in zutreffender Weise durch die Theorie (sowohl die von Smoluchowsky als auch die von Booth, übrigens auch nur solange als es sich um die Berechnung von Änderungen und nicht von Absolutwerten handelt) beschrieben wird, sobald man sich mit der Variierung von Parametern zufrieden gibt, die wenig Einfluss auf die Ladung der Teilchen haben; im Gegensatz dazu scheint die Variierung der Ladung, selbst bei Änderungen, die in unserem Fall im Extremtwert einen Übergang von 143 zu 3570 Ladungen pro Teilchen ausmachen, praktisch keinen Einfluss auf die Viskosität zu haben. Ein direkter Beweis für diesen mangelnden Einfluss wird durch die Untersuchung einer Schwärze geliefert, bei welcher die Ladung direkt gemessen wird und die Viskosität konstant blieb, während Q von 810 auf 2260 Elemen tarladungen pro Teilchen anstieg. Dieses Verhalten steht im absoluten Widerspruch zu den Voraussagen der Theorie, die alle erwarten lassen, dass der Relaxationseffekt dem Coulomb'schen Gesetz gehorcht und dass die durch die Ladung bedingte Viskositätszunahme vom Quadrat der Ladung abhängt. Es tritt hier ein sehr wichtiges Problem auf; möglicher Weise ist unser Modell nicht geeignet den Einfluss der Ladung auf die Viskosität wiedergeben zu können, möglicherweise müssen auch die Hypothesen, die als Grundlage für die theoretischen Berechnungen gedient haben, einer Revision unterzogen werden. Da der stark anormale Charakter unserer Ergebnisse auf jeden Fall feststeht, würde es interessant sein, gleichartige Versuche an anderen Modellen auszutühren.
The degradation and denaturation of sodium deoxyribonucleate by γ‐rays
Authors: Peacocke A. R. , Preston B. N. 
Published: April 2003

AbstractAn earlier investigation of the effects of γ‐irradiation on aqueous solutions of sodium deoxyribonucleate showed that a plot of log [η] against log R (where [η] = intrinsic viscosity, R = radiation dosage) was linear at high R with a negative slope of 1.85. According to the theory of degradation of macromolecules, this slope should equal ( −α), where α is defined by [η] = KMα (K = constant, M = molecular weight). Determination by light scattering measurements of the M values of γ‐degraded nucleate samples has now shown that [η] = KM1.0; the slope of the log [η] against log R plot was therefore approximately twice that to be expected for random degradation of a single chain. Moreover, M−1 was a linear function of R2 over the whole range from R = 0 and this suggested that the initial nucleate had a random distribution of molecular weights. These observations consitute more positive evidence for the earlier proposal that the decrease in molecular weight of the double‐helical nucleate structure during γ‐irradiation was caused by two independent and approximately opposite breaks, one in each of the polynucleotide strands, and that the formation of such double breaks was proportional to R2. Heating ruptures these hydrogen bonds and, in accordance with the mechanism proposed, caused a relatively greater decrease in M the larger the previous radiation dosage (R). Titration at 25°C showed that γ‐irradiation ruptured the hydrogen bonds, although half of them were still present in the samples of lowest [η]. This change has now been re‐investigated by titrations at −0.75°C. which allow the determination of the reversible dissociation curves of the double helices and of the denatured form. The low temperature titrations showed that, unlike the main chain breakdown, the rupture of hydrogen bonds was non‐random, those linking adenine and cytosine being broken more easily than those linking guanine and cytosine.
A thermodynamic and kinetic study of the dissociation of arachin
Authors: Williams R. K. , Naismith W. E. F. , Tipper C. F. H. 
Published: April 2003

AbstractThe dissociation of arachin has been studied over a range of pH values, ionic strengths, temperatures, and protein concentrations and standard energy values have been calculated. The standard entropy changes and standard heat contents were found to be lower than would be expected and possible reasons for this are discussed. The Kc values varied on altering the protein concentration and are considered to be dependent on a function of the ratio of concentration to ionic strength.
Logarithmic thermal degradation of a silicone resin in air
Authors: Doyle Charles D. 
Published: April 2003

AbstractThe weight‐loss of a methyl‐phenyl silicone resin was determined over the temperature range from 135 to 240°C. and up to approximately 10% volatilization. Weight‐fraction volatilized varied linearly with the logarithm of time. The history of such logarithmic processes is reviewed briefly. The empirical rate‐equation is discussed in terms of the data. On the basis of a surface‐removal experiment, and on the basis of the chemistry of the degradation, a mechanism of Fickian diffusion is proposed, wherein the diffusion coefficient varies exponentially as the degree of crosslinking and shrinkage, while the concentration gradient of volatilizable molecules remains constant.
Molecular weight of ethyl cellulose by dielectric dispersion of solutions in solvents of low dielectric constants
Authors: Scherer Philip C. , Hawkins M. C. , Levi D. W. 
Published: April 2003

AbstractThe critical frequencies for ethyl cellulose solutions were determined by a “differential” bridge method in carbon tetrachloride, benzene, and toluene. Correlations between the critical frequency and degree of polymerization were found to be similar to those previously reported. Intrinsic viscosity data for ethyl cellulose in four solvents of low dielectric constant are also included.
Lithium‐initiated copolymerization of styrene and methyl methacrylate. II. A propagating radical‐ion
Authors: O'Driscoll K. F. , Tobolsky A. V. 
Published: April 2003

AbstractIt has been shown that lithium‐initiated copolymerization of styrene and methyl methacrylate yields an unusual copolymer since it contains appreciable quantities of styrene. The probable nature of this copolymer is discussed, and it is suggested that lithium may act as an electron exchange type of initiator.
Copolymerization of trialkyl aconitates with vinylidene chloride
Authors: Marvel C. S. , Mano Eloisa B. 
Published: April 2003

AbstractReactivity ratios for the copolymerization of trimethyl aconitate and vinylidene chloride have been determined. Some copolymers of vinylidene chloride with trimethyl, triethyl, and tri‐n‐butyl aconitate have been reported. The stabilizing effect of aconitic esters on the color of polyvinylidene chloride has been confirmed.
On certain peculiarities of the structure of fibrous proteins and polymers
Authors: Andreeva N. S. , Iveronova V. I. 
Published: April 2003

AbstractAnalysis is made of the system of parallel chain molecules which has a long‐range order in the arrangement of the structural units along the chains, and a short‐range order in the packing of molecules. A solution has been obtained of the problem of scattering x‐rays on such a system. Analysis of the correspodence between theoretical results and the results for certain fibrous proteins and polymers has been made. This analysis shows that in some parts of these substances there are regions where the parallel chains are arranged without any correlation to the packing of the units of neighboring chains.
Über zusammenhange zwischen dem vernetzungsgrad und der degradation von naturkautschuk
Authors: Tkáč A. , Kellö V. 
Published: April 2003

AbstractOxidation reactions, as followed by infrared spectrometry, may serve as a measure for judging the relative extent of oxidative degradation and crosslinking of two independent parallel reactions subsequent upon the primary destruction. Such information can be derived from a kinetic analysis of the processes taking place in the rubber as a result of the absorption of energy, using the expression w = (k/b) (1 − e−bη) (1 − η). Since in this equation k is proportional to the rate of chain branching (which leads predominantly to oxidation), and b is proportional to the rate of recombination of the radicals (leading to crosslinking), the total degree of crosslinking will increase with increasing values of b/k. This assumption has been verified experimentally for the thermal and photochemical ageing of rubber, both in the absence of additives and in the presence of sulfur, of vulcanizing mixtures, and of copper as a catalyst of oxidation. At increased temperatures and pressures (130°C., 3 atm.) in the absence of vulcanizing additives and in a nitrogen atmosphere, radicals of long life are formed; this leads to an increased rate of the subsequent oxidative degradation. The number of active centers formed, and hence the final extent of oxidation, is a function of the time of exposure to the increased temperature.
Adsorption of certain high polymers by carbon black in dilute solutions
Authors: Yurzhenko A. I. , Maleyev I. I. 
Published: April 2003

AbstractAdsorption experiments were made to determine the time required for a complete adsorption of certain highly molecular substances from solutions. Aluminum oxide was preliminarily subjected to hydrophobization by caproic acid. Samples of polystyrene, polyisoprene, and polyethers of acrylic and methacrylic acids, ranging from methyl to heptyl inclusive, were taken as objects of the experiments. In all cases the time required for a complete extraction of the substances from solution was shown to be directly proportional to square of the characteristic viscosity. “Bad” solvents take a shorter time to effect a complete adsorption. The investigation of adsorption of polyethers of acrylic and methacrylic acids has shown that the increase in the alcohol radical influences the velocity of the adsorption process as a whole in different ways. While the increase in the alcohol radical of the polyacrylic ethers reduces the time required for a practically complete adsorption of the substance, in the case of polyethers of methacrylic acid the reverse relation was observed. Hydrophobic aluminium oxide is shown to adsorb polymethyl acrylate from solution reversibly.
Polymerisationsauslösung durch hydroperoxyde
Authors: Schröder G. 
Published: April 2003

AbstractEs wird versucht, den Mechanismus der Radikalbildung aus organischen Hydroperoxyden in homogener Lösung aufzuklären. Die scheinbare Diskrepanz, dass die bekannte thermische Zersetzung von Hydroperoxyden in Lösung kinetisch nach der 1. Ordnung verläuft, dagegen die Katalyse der Autoxydation ungesättigter Verbindungen durch Hydroperoxyde in einer Reaktion 2. Ordnung erfolgt, wird diskutiert und durch eine Arbeitshypothese überwunden. Ihre experimentelle Nachprüfung durch dilatometrische Verfolgung von Polymerisationen lieferte kinetische Ergebnisse, die sich durch folgende einfache Annahmen deuten lassen: (1) Hydroperoxyde bilden in Gegenwart von Styrol freie Radikale nach der Gleichung:
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Styrol greift also in die Startreaktion ein. (2) In Methylmethacrylat und Vinylazetat bilden Hydroperoxyde Radikale nach der Gleichung:
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(3) Alkylperoxy‐Radikale (ROO·) bewirken einen zusätzlichen Kettenabbruch durch Reaktion mit Makroradikalen:
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The X‐ray diffraction, birefringence, and infrared dichroism of stretched polyethylene. II. Generalized uniaxial crystal orientation
Authors: Stein Richard S. 
Published: April 2003

AbstractA general method for describing the crystal orientation in a uniaxially oriented crystalline polymer is presented. It is shown that two orientation functions may be quantitatively evaluated from x‐ray diffraction data. The variation of these during mechanical and thermal treatment may be studied. These functions are sufficient to completely characterize the crystal contribution to birefringence and infrared dichrosim. By subtracting the crystal contribution from the total birefringence or dichroism, the amorphous orientation may be characterized.
The X‐ray diffraction, birefringence, and infrared dichroism of stretched polyethylene. III. Biaxial orientation
Authors: Stein Richard S. 
Published: April 2003

AbstractA set of functions for characterizing the crystal orientation in a biaxially oriented crystalline polymer is proposed. The additional orientation functions may be determined from a measurement of the variation of x‐ray intensity with tilt angle of a film. From these functions and those described in Part II, the crystal contribution to the birefringence and the infrared dichroism of normal and tilted films may be calculated.
Dielectric properties of polymonochlorotrifluoroethylene
Authors: Nakajima Tatsuji , Saito Shogo 
Published: April 2003

AbstractThe dielectric properties of three kinds of polymonochlorotrifluoroethylene having various degrees of crystallinity were studied. The measuring instruments by which the dielectric properties can be measured over a wide range of frequency are briefly described. The dielectric measurements for three samples are made over a frequency range 0.1 to 106 cycles/sec. and a temperature range of −50 to 140°C. The main conclusions from the experimental results are as follows. Two dielectric dispersions observed would be due to the polar groups in amorphous regions. At the melting temperature, the positions of the two dispersions would coincide with each other. The energies of activation for the two loss processes are 16.8 and 57.0 kcal., respectively. Interpreting from the variation of the magnitude of the dielectric dispersion with temperature, the glass transition temperature of this polymer extends over the wide range from −80 to 60°C. For the low temperature dispersion, the value of Cole‐Cole's parameter β has constant value of 0.3 below 20°C. and increases with temperature above 20°C.
The polymerization of acrylamide with chlorate–sulfite initiator
Authors: Suen T. J. , Jen Yun , Lockwood Janet V. 
Published: April 2003

AbstractAcrylamide was polymerized in aqueous solution with chlorate‐sulfite initiator under the following conditions: temperature, 15–75°C.; pH, 1.5–3.9; monomer concentration, 0.3–1.1 mole/liter; NaClO3 concentration, 0.26–2.1 × 10−4 mole/liter; and Na2‐SO3 concentration, 0.79–6.3 × 10−4 mole/liter. The weight‐average molecular weight of the polymers formed under these conditions is in the range of 1–3 × 106. It was found that up to 40–50% conversion, the following rate equation holds:

where Rp is the overall rate of polymerization, [M] the instantaneous monomer concentration at time t, and [M]0 the initial monomer concentration. At 50°C., K = 6.9 ± 0.9 l. mole−1 sec.−1 Activation energy within the temperature range studied was found to be 7.3 kcal./mole. The value of k/kt at 50°C. was estimated to be about 30 l. mole−1 sec.−1 The rate dependence on [M]5/2[M]−3/20 is explained by assuming that the polymer formed binds part of the remaining monomer. The presence of ferrous ions in the polymerization system increases the rate but decreases the molecular weight of the polymer formed. Up to 3.6 × 10−3 mole/l. of [Fe++], the rate is affected in such a manner that

Chromic ions tend to retard and nickel ions tend to accelerate the rate of polymerization. It was found that HSO3− is an effective chain transfer agent. Its chain transfer constant was estimated to be about 0.17.
Polyvinylacetophenone: Preparation, reactions, and depolymerization
Authors: Kenyon William O. , Waugh George P. 
Published: April 2003

AbstractPolyvinylacetophenone was made by the Friedel‐Crafts reaction of acetyl chloride or acetyl bromide on polystyrene, in carbon disulfide, using aluminum chloride. Similar reactions, using bromoacetyl bromide or chloroacetyl chloride, gave insoluble polyvinylphenacyl halides. A soluble, low‐molecular‐weight polyvinylphenacyl chloride was obtained using chloroacetyl chloride and monomeric styrene. Polyvinylphenacyl bromides of limited Solubility were obtained by direct bromination of polyvinylacetophenone. Vacuum pyrolysis of polyvinylacetophenone gave p‐vinylacetophenone monomer in good yield. At atmospheric pressure, the product was about half p‐vinylacetophenone and half p‐ethylacetophenone. At intermediate pressure, an intermediate proportion was obtained.
Polar effects in the copolymerization reactions of aconitic acid and some of its esters with nonpolar monomers
Authors: Orr R. J. , Williams H. Leverne 
Published: April 2003

AbstractStudies of the copolymerization of aconitic acid and some of its esters with nonpolar monomers indicate that electrostatic effects occur due to the acid hydrogen of the free acid. These changes are such that normal methods of interpretation of reaction data no longer apply. A method of interpretation, based on a treatment by Laidler and Landskroener, of the effect of dipole‐dipole interaction on the reaction rate is presented. This interpretation is tested with the experimental results available.
Solution properties of polyvinyl acetate
Authors: Cotten G. R. , Sirianni A. F. , Puddington I. E. 
Published: April 2003

AbstractThe depression of the vapor pressure over solutions of fractionated polyvinyl acetate in benzene and ethanol was studied using a differential manometer. The Huggins' equation was obeyed within the concentration range used, i.e., up to 10% solute concentration. The semiempirical constant μ was evaluated for different fractions and was found to vary with the average molecular weight of the polymer. The heat and entropy of dilution were calculated for one fraction in benzene solution, and the results are discussed in terms of the existing theories of high polymer solutions.
The permeation of water vapor through polyethylene
Authors: Klute C. H. , Franklin P. J. 
Published: April 2003

AbstractA critical survey of the literature has been made relative to the permeation of water vapor through films of polyethylene. For conventional polyethylene, reported values of permeability range from 0.015 to 0.074 gm. mm./m.2 day cm. Hg at 25°C. Reported activation energies range from 6,590 to 14,540 cal./mole°C. It appears that the highest activation energies are associated with the lowest permeability coefficients. Recent investigations of the permeability of intermediate and high‐density polyethylenes are not in agreement with one another The explanation is offered that part of the transport of water vapor through these materials occurs by Fickian diffusion through the amorphous fraction of the polymer and part occurs by passage through micropores in the polymer film. The expectation exists that a superior water‐vapor barrier could be developed using ultralinear, crystalline polyethylene of high molecular weight. However, an incisive experimental test of this supposition would first have to be concerned with a more complete characterization of polyethylene in the solid state than has heretofore been employed in diffusion and permeability studies.
Some light‐scattering evidence of critical concentration in dilute polymer solution
Authors: Bigelow C. C. , Cragg L. H. 
Published: April 2003

AbstractEvidence of a critical concentration effect in dilute polymer solution has been obtained from light‐scattering measurements in two ternary systems of the type polymer A–polymer B–solvent S. The root‐mean‐square end‐to‐end distance, (r2)1/2, of A was measured in a series of mixed solvents (B–S), differing from one another only in respect Of CB, the concentration of polymer B. The (r2)1/2 vs. CB curve exhibited a slight dip in the system polystyrene–polyvinyl acetate–benzene and a slight peak in the system polystyrene–polyvinyl acetate–butanone, at values of CB close to but not identical with the critical concentrations determined viscometrically for the same systems. The size, nature, and location of these light‐scattering critical concentration effects are briefly discussed in the light of similar but better established viscosity effects.
Details on the half‐life of polymeric free radicals
Authors: Gehman H. , Goldfinger G. , Kolczynski J. R. 
Published: April 2003

AbstractA model is presented that is based on the experimental conditions prevailing during photopolymerization in a free falling stream. When some simplifying assumptions are applied it is possible to correlate quantities which are potentially measurable, such as yield of reaction and number‐ and weight‐average molecular weights, with the spread of times elapsing between subsequent addition steps. In other words, the average time elapsed can be refined to a time distribution curve. In the model, the time elapsed between initiation and forcible termination is subdivided into t time elements. During each of these it is assumed that exactly one of the following must occur: the growth of the free radical to one larger by one monomer unit, natural termination without any change of size, or nothing. The sum of the probabilities of those events, called, respectively, s, f, and i, is, of course, exactly 1. Considering forcible termination of all polyradicals still surviving after t time elements, one can calculate size and weight distribution curves.
Friction constants of chain molecules with excluded volume
Authors: Stockmayer W. H. , Albrecht A. C. 
Published: April 2003

AbstractThe validity of the Flory‐Fox treatment of the friction constant is investigated for chains with excluded volume with the aid of theories due to Kirkwood and to Fixman. It is found that the effective hydrodynamic radius of a linear macromolecule is less affected by excluded volume than the radius of gyration, and hence that the Flory‐Fox number P should decrease slightly with increasing molecular weight or solvent power.