bluuebunny/crossref_metadata_2025 huggingface dataset:
Some properties of enzymatically produced polynucleotides
Authors: Steiner R. F. , Beers R. F.
Published: April 2003

Polymers of adenylic and uridylic acids have been prepared from the monomers by the action of an enzyme isolated from the bacteria M. lysodéikticus. Polyadenylic acid has been found to undergo an interesting structural change in the vicinity of pH 6. This is reflected by a marked contraction of the molecule, as observed by light scattering and sedimentation, and a pronounced drop in ultraviolet extinction at λ = 257 mµ. The structural and optical transitions may be eliminated by formaldehyde treatment or by the addition of calcium ions. By direct titration it has been found that these effects reflect the titration of the adenine group and probably its subsequent electrostatic pairing with a negatively charged phosphate. The molecular interaction of polyadenylic and polyuridylic acids to form a stable complex has also been studied. It has been found that the interaction is blocked by: (1) the binding of a hydrogen ion by the 6‐amino group of adenine, (2) formaldehyde blocking of the 6‐amino group of adenine, and (3) ionization of the hydroxyl group of the pyrimidine ring of uridine.
On the mechanism of the polymerization of ϵ‐caprolactam. I. The polymerization initiated by ϵ‐aminocaproic acid
Authors: Kruissink Ch. A. , van der Want G. M. , Staverman A. J.
Published: April 2003

In this first‐paper of a series of publications on the mechanism of the polymerization of ϵ‐caprolactam (CL), an investigation of the kinetics of the polymerization initiated by ϵ‐aminocaproic acid (ACA) is reported. Experiments were performed at 254°C. for three different initial ratios (ACA/CL)0:0.05, 0.022, and 0.011 mole/mole. The concentration (x) of unconverted CL and that of end groups (c) were determined by extraction with water at room temperature and by potentiometric titration, respectively. The method of kinetic evaluation consists in the direct checking of rate equations making use of the quantities dx/dt and dc/dt which were determined graphically from the curves of x and c versus time. In this way tedious integration procedures are avoided and the testing of rather different mechanisms is much easier. Moreover, it is not necessary to make the assumption of constant rate coefficients which, of course, will seldom apply. Thus the inadequacy of the “polycondensation mechanism” has been proved for every time instant separately, although accidentally the rate constant of the main reaction is fairly constant. In this polycondensation mechanism it is assumed that polymer formation can take place only by polycondensation of ACA, the supply of which is provided for by the reaction of CL with water formed in the process of polycondensation. It turns out that even when the rate of hydrolysis of CL is so high that the polycondensation reaction is rate determining, this latter rate is to small by a factor of 10 or more to account for the rate of CL conversion observed. It is shown that this difficulty can be overcome only by incorporating a third reaction in the mechanism, a reaction which must provide for the main consumption of CL. We have assumed this reaction to be a reversible polyaddition reaction, i.e., a reaction in which CL is added to one of the end groups of the polymer molecules. The rate constant for this reaction derived from the experiments appears to be in good agreement with the value derived from the experiments on the polymerization of CL initiated with water.
Polymerisation radiochimique de l'acrylonitrile quelques observations sur le post‐effet
Authors: Bensasson R. , Bernas A.
Published: April 2003

Nos expériencea ont porté sur l'irradiation par les rayons γ du 60Co (4 r/mn < I < 400 r/mn) du monomhre acrylonitrile qui donne lieu à un post‐effet très important quand la polymérisation est conduite en milieu précipitant. La rbaction, pendant et aprhs irradiation, a été suivie par dilatométrie et à la température de 20°C, sauf pour les déter‐ minations des énergies d'activation. Les résultats suivants ont été obtenus: Vitesse du post‐effet: La vitesse décroft continument au cows du temps. A 20°C, sa valeur initiale (V0)pp, ne semble pas dépendre du taux de radio‐conversion et paraît équivalente à la vitesse globale de radiopolymérisation. Le taux de post‐polymérisation (AM/M),,, pour un temps donné, augmente avec la quantité de polymhre formé au cours de l'irra‐ diation. Pour un taux de radioconversion donné, et des durées de post‐effet assez longues, (ΔM/M)pp peut s'écrire sous la forme:

L'Bnergie globale d'activation E i de la radiopolymérisation semble varier avec la température:

Si la radiopolymerisation est conduite à. 20°C, et le post‐effet observé à 40, 50, 60°C, l'énergie d'activation relative aux vitesses initiales semble très élée: de l'ordre de 35 kcal/mole. Viscosités des solutions ak polyacrylonitriles (PAN) : Si on compare le comportement dans le diméthylformamide de polyacrylonitriles P1. pour lesquels le post‐effet ne s'est pas développé, et de polyacrylonitriles P2 qui ont subi une post‐poly‐ mbrisation, on constate: (I) que P2 est moins facilement soluble que P1; (2) que P2 correspond à un indice de viscosite limite inferieur à celui de P1 et que la pente de la droite ηsp/c = [η] + [η]Kc est plus grande pour P2 que pour P1. Ces dernibres observa‐ tions sugghrent que la post‐polymérisation conduit tl la formation de chaînes branchés.
A study of diffusion in polymer solutions by the use of the polarization interferometer
Authors: Tsvetkov V. N. , Klenin S. I.
Published: April 2003

The use of the polarization interferometer and the further perfection of the experimental technique makes possible the measurement of diffusion coefficients between solutions whose concentrations differ by less than 10−4 g./cm.3 These circumstances permit the direct measurement of the differential diffusion coefficient, D, corresponding to the given concentration c. The concentration dependence of the diffusion coefficient obtained for fractions of polystyrene in the region of not too small concentrations agrees well with the concentration dependence of the scattering of light in the same samples. In the region of low concentrations, the curve of the dependence D = D(c) has a horizontal section which cannot be described by the formulas usually used. In the region of concentrations, where the dependence D = D(c) may be considered as a rectilinear one, it is shown experimentally that the integral coefficient of diffusion between solutions whose concentrations differ by c1–c2 is equal to the mean of two differential diffusion coefficients, D1 and D2, where D1 = D(c1) and D2 = D(c2). In that region of concentrations, the integral diffusion curve shows a marked asymmetry, which agrees with the concentration dependence of the differential diffusion coefficient. The measurement of the diffusion coefficient D in dilute solutions of fractions of a series of polymers shows that the value of D is inversely proportional to the radii of the high polymer molecules calculated from viscosity and from light scattering data. The value of the empirical constant was determined, which permits the determination of the radius of the molecules from the measured values of the diffusion coefficient.
Polymerization of aromatic and heterocyclic vinyl compounds
Authors: Koton M. M.
Published: April 2003

The polymerization of vinyl derivatives of naphthalene and of the heterocyclic series containing the atoms of nitrogen, oxygen and sulfur has been investigated. It is proved that an increase in the number of condensed rings in the radicals replacing the hydrogen atoms in the ethylene molecule, as well as the introduction of heteroatoms (nitrogen, oxygen, sulfur) into these radicals increase the polymerization ability of the above compounds.
Inhibited thermal polymerization of styrene. Kinetics of copolymerization of quinones with styrene
Authors: Tüdös F.
Published: April 2003

In research on the kinetics of the inhibition of the thermal polymerization of styrene, we came to the conclusion that quinones participate not only in the inhibition reaction but also in the copolymerization. We carried out the derivation of the basic kinetic equations of the process in two ways: (1) Using the usual simplifying assumptions of the theory of copolymerization (Melville‐Watson method) and (2) using the stationary state method. The kinetic equations derived by the second method transform under certain conditions to the corresponding equations of simple inhibition, while the equations from the first method lead to contradictions. On the basis of the kinetic analysis it was found that the inhibition period during copolymerization of the inhibitor does not increase linearly within increasing concentration of the inhibitor, and that on the curve of conversion versus time there is an inflection point if the concentration of inhibitor is higher than a certain value. The curve of initial polymerization velocity against concentration of inhibitor has a minimum at a certain concentration (“inhibition optimum”). Experiments carried out with p‐benzoquinone at 90, 105, 120, and 135°C. completely agree with what has been stated above. At the lower temperatures, except for a slight shortening of the inhibition period, no significant indications of copolymerization are apparent; the course of these experiments is well described by the equation of simple inhibition. At 120 and 135°C. copolymerization occurs to a marked extent and is well characterized by the equations derived by the second method. Finally, from the temperature dependence of the appropriate velocity constants, we determined the activation energy of the inhibition reaction (4.3 kcal./mol.) and the activation energy of copolymerization of quinone (9.4 kcal./mole).
Kritische betrachtungen zur bestimmung der uneinheitlichkeit von polyamiden
Authors: Griehl W. , Lückert H.
Published: April 2003

Die von verschiedenen Autoren durch Zerlegen von Nylon 6 in 8 bis 10 Fraktionen erhaltenen differentiellen Verteilungskurven zeigen eine grössere Einheitlichkeit des Polymers, als es der Flory‐Schulz‐Verteilung entspricht. Im System Kresol‐Benzin wurden nach der Zweiphasenmethode sowohl unstabilisierte als auch mit Essigsäure stabilisierte Polykondensate aus ϵ‐Caprolactam in 63 bzw. 33 Fraktionen zerlegt. Die integralen Verteilungskurven sowie die aus den Fraktionierergebnissen berechneten Werte für die Uneinheitlichkeit stimmen innerhalb der dieser Methode eigenen Fehlergrenzen mit der Theorie von Flory‐Schulz in demselben Masse überein, wie die von Taylor für das Polyamid Nylon 6–6 gefundenen Ergebnisse. Trotzdem erscheint ein exakter experimenteller Beweis für die Flory‐Schulz‐Verteilung mit Hilfe von Fraktionierungen weder beim Nylon 6–6 noch beim Nylon 6 möglich zu sein. Die Gründe hierfür wurden ausführlich erörtert und diskutiert. Ein zuverlässiger Beweis kann jedoch dadurch erbracht werden, dass man Endgruppenbestimmungen sowie Viskositätsmessungen an Fraktionen einerseits und nichtfraktionierten Proben andererseits durchführt und damit das Verhältnis M̄v : M̄n bestimmt. Im Bereich mittlerer Molekulargewichte wurde auf diese Weise ein gut mit der Theorie übereinstimmender Wert von 1,82 gefunden. Schliesslich konnte nachgewiesen werden, dass auch über eine längere Zeit kondensierte Produkte ihre Molekulargewichtsverteilung nicht ändern.
Zur kinetik der polyesterbildung durch umesterung
Authors: Griehl W. , Schnock Günther
Published: April 2003

Nach eingehender Untersuchung der sogenanten Vorkondensation bei der Polyäthylenterephthalatbildung bezüglich des Katalysatoreinflusses, der Reaktionskinetik usw, wird die als Umesterung verlaufende Polyesterbildung studiert. Der Reaktionsverlauf wird durch Viskositätsmessungen verfolgt und es ergibt sich erwartungsgemäss wie bei der “Vorkondensation” eine Reaktion erster Ordnung.
Kinetics of the reactions of thiourea with formaldehyde. Reactions in alkaline media
Authors: Dušek Karel
Published: April 2003

The kinetics of formation and dissociation of mono‐ and dimethylolthiourea were studied as well as the equilibria among the constituents in alkaline and neutral solutions. The polarographic determination of free formaldehyde and the determination of the reacting constituents by paper chromatography were used as analytical methods. A generally valid relation for equilibrium with a polyfunctional compound, to which formaldehyde is added, was derived and used to calculate both the equilibrium constants for the case of thiourea. The equilibrium constants found do not depend on pH. It was found from the temperature dependence of the equilibrium constant that the formation of monomethylolthiourea is an exothermal reaction. The possibility of formation of tri‐ and tetramethylolthiourea was discussed. Ways of simplifying the complex kinetic scheme were found which are suitable for calculation of the rate constants. The rate constants of formation and dissociation of mono‐ and dimethylolthiourea are directly proportional to the concentration of hydroxyl ions in the alkaline region and depend only slightly on the concentration of buffer. The reaction of thiourea with formaldehyde was found to be more rapid than the reaction of urea with formaldehyde in this region. By a graphical solution in which the known rate constants were used, the time dependence was found for the concentrations of all the constituents. The polarographic study of the reaction of thiourea with formaldehyde in strongly alkaline media of Chasanov and Lynch was discussed.
Alkaline polymerization of caprolactam. IV. Equilibrium and degradation with alkaline polymers of caprolactam
Authors: Králíček Jar. , Šebenda J.
Published: April 2003

The change in the intrinsic viscosity brought about by heating samples of alkalipolymerized polycaprolactam to 220–250°C. for extended periods has been investigated. The polymer samples were obtained by the catalytic action of the sodium salt of caprolactam. The experimental results shows that the intrinsic viscosity of the polymer decreases over the course of about 50 hours, but remains constant after this time. The equilibrium value of the intrinsic viscosity depends on the concentration of the catalyst and on the temperature. The viscosity drop at the beginning of the period of heating is due to the change of the original very unstable broad molecular weight distribution to the equilibrium distribution. Only basic groups, but no carboxyl groups, were detected. The concentration of basic groups remains constant, within the limits of experimental error, over the period required to reach the final value of the intrinsic viscosity.
Synthesis of some new esters and ethers of cellulose and examination of their properties
Authors: Rogovin Z. A.
Published: April 2003

A new method has been devised for the synthesis of normal esters of cellulose and carbonic acid by reaction of cellulose alcoholate and methyl chlorocarbonate:
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A normal ester of cellulose with monothiocarbonic acid has been prepared analogously as follows:
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A disulfide has been prepared by oxidation of the sodium salt of the thioester with iodine:
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A comparison was made of the stabilities toward various reagents of cellulose esters of carbonic, normal thiocarbonic, and dithiocarbonic acid and also of the acid and neutral esters of cellulose and monothiocarbonic acid. It was found that the stabilities of the esters toward acids and bases as well as to light and heat very considerably with the nature of the acid grouping introduced. A method has been worked out for the synthesis of phenyl esters of cellulose by the reaction of sodium phenoxide with p‐toluenesulfonylesters of cellulose:

A phenyl ester of cellulose (γ = 70–80) has been prepared and its properties investigated. It was shown that by this procedure the phenyl group is introduced into position 6.
Über den mechanochemischen abbau von zellstoff durch schwingmahlung
Authors: Grohn H.
Published: April 2003

1. Geschwindigkeit und Grad des mechanochemischen Abbaus von wasserhaltigem Sulfitzellstoff sind von den mechanischen Bedingungen der Schwingmahlung abhängig. Nach einer Mahldauer von 900 Stunden wurde ein DP‐Wert von 11 (Viskositätszahl) bzw. 7 (Reduktionsvermögen) erreicht. 2. Der lineare Anstieg der Cu‐Zahlen mit dem viskosimetrisch ermittelten Spaltungsgrad berechtigt zu dem Schluss, dass der mechanische Abbau von wasserhaltigem Zellstoff im wesentlichen als mechanisch aktivierte Hydrolyse verläuft. 3. Die Wasserlöslichkeit der Mahlprodukte steigt mit fallendem DP erst langsam, dann schnell bis auf etwa 90% an. Demnach erfolgt die mechanische Bindungsspaltung nicht von den Ketteneden her, sondern vorzugsweise zwischen mittleren Kettengliedern. 4. Die bisher unbeachtet gebliebene grosse Wasserlöslichkeit mechanisch abgebauter Zellulose erklärt ihre gute Rekristallisierbarkeit. Nur der wasserunlösliche Anteil, der von dem Abbau den höchsten Kristallinitätsgrad besass, wird nach dem Herauslösen aller aus den weniger orientierten Anteilen enstandenen niedermolekularen Abbauprodukte rekristallisiert.
Dielectric studies of the methacrylate series. III. Poly‐n‐hexyl methacrylate. IV. Poly‐n‐octyl methacrylate
Authors: Strella S. , Chinai S. N.
Published: April 2003

The complex dielectric constant of a pure molecular weight fraction of poly‐n‐hexyl methacrylate and of poly‐n‐octyl methacrylate was determined over a frequency range of 30 to 3 × 105 cycles/sec. and a temperature range of −66 to 106°C. and −61 to 81°C., respectively. The data indicate the presence of two transition regions, with the transitions being further apart with increasing side chain length. Examination of the data showed that superposition was not possible using the usual superposition schemes.
On the reversibility of the acid denaturation of sodium desoxyribose nucleate
Authors: Geiduschek E. Peter
Published: April 2003

The current disagreement as to whether the acid denaturation of DNA produces reversible or irreversible changes of macromolecular configuration can be resolved by paying proper attention to the temperature dependence of the denaturation process. Light scattering measurements have been made on a sample of sodium desoxyribosenucleate taken to pH 2.6 and reneutralized at 0 and 25°C. in 0.1 M NaCl. Whereas the material, acid treated at 25°C., is irreversibly collapsed (radius of gyration = 1370 A., molecular weight unchanged), 0°C. titration leaves the size of the DNA molecule unchanged (ρ = 2800 A.). Viscosity measurements at 0°C. and pH 2.6 show that at this pH the DNA is nearly as fully extended as in neutral solution ([η] = 40 dl./g. compared to 63 dl./g. in neutral aqueous salt solution). However, collapse occurs at pH 2.6 between 0 and 25°C., and this thermal denaturation at pH 2.6 is irreversible. The light scattering properties of acid‐denatured DNA are interpreted in terms of a more heterogeneous distribution of macromolecular configurations than in the native material.
Peroxide crosslinked carbon black polyethylene compositions
Authors: Dannenberg Eli M. , Jordan Merrill E. , Cole Harvey M.
Published: April 2003

Polyethylene containing large quantities of carbon black can be crosslinked by a chemical free radical mechanism utilizing the thermal decomposition of dicumyl peroxide as the source of free radicals. Crosslinking in the presence of different types of blacks was studied in a liquid paraffin model system. The information obtained from this study provides a logical basis for speculation on the mechanism of crosslinking of carbon‐black‐loaded polyethylene compositions. Evidence is presented that the grade of carbon black is an important factor and that the course of the peroxide decomposition is largely determined by the chemical nature of the carbon surface. Carbon blacks having a highly oxygenated surface cause an ionic decomposition which is not effective for crosslinking, while those of low oxygen content allow the decomposition to follow a free radical mechanism which results in the crosslinking of polyethylene. Marked changes in the physical characteristics of the polymer are brought about as a result of pigmentation and subsequent crosslinking. Such compositions display a surprising degree of flexibility and strength over a wide range of temperatures. Moreover, significant strength is observed at temperatures above the crystalline melting point of the polymer. These improved properties are attributed to the reinforcing ability of the carbon black and the crosslinked network of polymer chains.
Structure and photochemical behavior of nucleic acids and related components
Authors: Shugar D. , Wierzchowski K. L.
Published: April 2003

A study has been made of the photochemical behavior at 2537 A. of the following substances: 2′‐, 3′‐, 5′‐, and cyclic 2′:3′‐cytidylic acids and various preparations of apurinic, ribonucleic, and deaminated ribonucleic acids. The behavior of all the cytidylic acids is qualitatively similar, the photoproduct exhibiting a new maximum at 2360 A. The reaction can be reversed completely in the dark by heating, acidification, or addition of alkai. The 5′‐cytidylic acid differs quanlitatively from the other cytidylic acids in that the quantum yield is lower, as is also the extinction of the new maximum. These results are in agreement with previous findings and support the suggestion that there is hydrogen bonding in cytosine nucleosides and nucleotides between the pyrimidine 2‐carbonyl and the 5′‐sugar hydroxyl which influences the photochemical reaction. The results indicate also the possible existence of weaker bonds involving the 2′‐ and 3′‐hydroxyls. The irradiation of apurinic and ribonucleic acids is accompanied by a decrease in extinction of the principal absorption maximum and very little change below 2400 A. If the decrease of the principal absorption maximum does not exceed 50% as a result of photolysis, then it is subsequently possible to restore about 50% of this decrease by heating a few minutes at 70–90°C. The quantum yield for photolysis of apurinic acid is of the same order of magnitude as for 2′‐ and 3′‐cytidine nucleotides; for ribonucleic acid it is lower. For deaminated ribonucleic acid, the reaction is not reversible. The photochemical behavior of nucleic acids is discussed from the point of view of the photochemistry of uracil and cytosine nucleotides, as well as the relation of the results to the phenomenon of photoreactivation.
The orientation of the crystalline and amorphous regions in polyethylene film
Authors: Holmes D. R. , Palmer R. P.
Published: April 2003

The orientation in the crystalline and amorphous regions of a series of polyethylene films prepared by the tubular films extrusion process has been studied by a combination of x‐ray diffraction and optical methods. All of these films show a relaxation orientation differing both from the fully relaxed type of orientation previously proposed by the authors, and from the more complicated type of orientation suggested by Keller. In all films there is cylindrical symmetry about the machine direction and the b‐axes of the crystallites are preferentially oriented in the plane perpendicular to this direction. The preferred directions of the a and c crystallite axes depend both on the extrusion conditions and on the nature of the polymer; at low blow‐up ratios and high haul of speeds the c axes tend to lie more nearly parallel to the machine direction, but as the blow‐up ratios is increased and the haul‐off speed decreased rotation of the crystallites about their b axes occurs, and eventually the a axes tend to lie more nearly parallel to the machine direction. Both the preferred crystallite orientation and its angular distribution have been measured for a large number of films made from various ethylene polymers, and a linear relation between a function of the orientation angle and the optical birefringence has been established. As the c axes tilt away from the machine direction towards the plane perpendicular to this direction the birefringence steadily decreases, and eventually becomes negative. An expression is given for the birefringence of such a cylindrically symmetrical array of crystallites tilted to various angles, and is used to predict the orientation at which the crystallite birefringence contribution will be zero and also the extreme values of the crystalline birefringence contribution in the fully drawn and fully relaxed conditions. By comparing the theoretical and experimental relations between crystallite orientation and birefringence, it has been deduced that in these films the amorphous material appears to provide a nearly constant small positive contribution to the birefringence irrespective of the birefringence contribution of the crystallite regions; this means that in the negatively birefringent films some of the molecules in the amorphous regions are crossed with respect to those in the crystalline regions. When allowance is made for this amorphous contribution, crystallinities calculated from the extrapolated observed and theoretical extreme values of the birefringence are in reasonable agreement with the x‐ray measured crystallinity of 45%. The mechanism resulting in the formation of this unusual orientation is considered in reference to the manufacturing process.
Stabilization of viscose rayon by heat treatment
Authors: Kanamaru Kisou , Tokita Noboru , Noyama Susumu
Published: April 2003

Viscose fibers preswollen by treatment with very dilute sulfuric acid solutions of various concentrations (pH 2.4–5.1) were heat treated at various temperatures (60–200°C.). The effects of the heat treatment were considered from the measurements of: (1) The transition modulus of elasticity and other constants of a three‐parameter model for viscoelasticity, as well as the dynamic modulus of elasticity. (2) The breaking strength as well as elongation. (3) The percentage crystallinity. (4) The amount of water absorbed. Thus it was concluded that the effects of heat treatments of stabilizing viscose rayon, as exhibited by the above‐mentioned properties of the fibers, make their most prominent appearance in the range of pH optimal for the maximal hydration of regenerated cellulose, that is, pH = 3.0–5.0 of the acid bath, in which the fibers are soaked and swollen, and in the range of the temperature for the heat treatment near, or just above, the glass transition temperature of cellulose hydrate, i.e., at 60–70°C. where the acid‐bath‐treated fibers are heat treated. From the results of these measurements and also from the characteristic features of x‐ray diagrams qualitatively observed, it was considered that the heat treatment affects mainly the more disordered (amorphous) regions so that the more ordered regions are newly developed at the expense of the former.
Electrophoresis of polyelectrolyte in salt solutions
Authors: Nagasawa Mitsuru , Soda Atsuhiko , Kagawa Ikumi
Published: April 2003

Some measurements of the electrophoretic velocity were carried out on sodium polyvinyl alcohol sulfates. The intrinsic mobility of the polyion in sodium chloride solutions was obtained by extrapolating the values at various polymer concentrations. The extrapolating value at the zero polymer concentration was the same for both descending and ascending boundaries. The mobility of polyion vs. sodium chloride concentration curve thus obtained showed the following features. (a) At zero NaCl concentration the mobility of polyion quite agrees with the mobility of the monomer acid. (b) In the limit of sufficiently concentrated NaCl solution, the mobility also approaches the mobility of the monomer acid. (c) In the intermediate state between these two limits, measured mobilities of polyion are always larger than the mobility of the monomer acid. Accordingly, there is a maximum of the mobility at a certain NaCl concentration. These experimental results were analyzed in terms of the theory of Hermans and Fujita on the electrophoresis of coiled polyelectrolyte, and it was found that their theory gives a satisfactory (at least qualitatively) explanation of our experimental data.
Fractionation of polyethylene
Authors: Francis P. S. , Cooke R. C. , Elliott J. H.
Published: April 2003

The relatively rapid Desreux technique for polymer fractionation has been modified and applied to both linear and highly branched polyethylenes. The polymer is precipitated from p‐xylene solution onto a sand column by cooling from 127° to room temperature. After removal of solvent, the column temperature is again raised to 127° and fractions are eluted, using p‐xylene‐ethylene glycol monoethyl ether mixtures of increasing solvent power. Approximately 15 fractions are obtained and polymer recovery is essentially quantitative. The reproducibility of the integral distribution curves is within ±2% for a cumulative weight‐% of 85 or higher. In certain cases difficulty has been encountered in resolving the less soluble portion of the sample. The selective nature of the system is indicated by the fact that the reduced specific viscosities of the highest and lowest molecular weight fractions are generally in the ratio of 50 or higher.
Rupture of rubber. V. Cut growth in natural rubber vulcanizates
Authors: Thomas A. G.
Published: April 2003

Cut growth in natural rubber gum vulcanizates has been studied using both steady and repeated loading. The results have been expressed in terms of the concept of the energy for tearing that has been put forward previously. With cut growth under repeated loading the tip, initially smooth, becomes rough and the rate of growth simultaneously decreases markedly to a final steady value. Some consequences of this roughening have been discussed. Measurements of cut growth under repeated loading have also been made using two different types of test piece. A rupture criterion, which has been previously proposed, predicts a definite relationship between the behavior of the two test pieces, and this has been confirmed experimentally.
Structure of drawn polyethylene terephthalate
Authors: Dulmage W. J. , Geddes A. L.
Published: April 2003

Measurements of birefringence, infrared dichrosim, and x‐ray diffraction have been made on crystallized and uncrystallized polyethylene terephthalate films stretched up to 500%. The results show that, at high elongations, stretching induces high linear orientation of the chain molecules parallel to the direction of stretch. In the uncrystallized samples, a biaxial orientation in which the plane of the molecules tends to be parallel to the plane of the film can be detected in the x‐ray diffraction patterns and from the birefringence measurements. This higher orientation, as well as the usual linear orientation, is enhanced by crystallization, owing to directional crystal growth on oriented crystal nuclei which develop during the stretching operation. At low extension, pronounced tipping of the crystalline regions occurs during crystallization. As a result, the preferred direction for the fiber axis of the crystallites varies from a direction approximately perpendicular to the direction of stretch at low extension, to a direction almost parallel to the direction of stretch at the highest extensions.
Infrared spectra of high polymers. VII. Polyacrylonitrile
Authors: Liang C. Y. , Krimm S.
Published: April 2003

The infrared spectrum of polyacrylonitrile has been obtained in the extended region of 70 to 3200 cm.−1 Polarized measurements were made on stretched and rolled specimens in the range of 350 to 3200 cm.−1. An analysis of the spectrum has been made on the basis of an atactic chain configuration, and has been shown to be in agreement with the observed data. Detailed assignments are proposed for all of the absorption bands in the spectrum, being aided by previous studies of high polymer spectra and by approximate normal frequency calculations for the nitrile group.
Copolymers of vinyl alcohol and vinyl stearate
Authors: Jordan Edmund F. , Palm William E. , Swern Daniel , Witnauer Lee P. , Port William S.
Published: April 2003

Copolymers of vinyl formate containing various amounts of vinyl stearate were prepared by mass polymerization at 30°C. in the presence of small amounts of isopropanol. A study of the molecular weights and the viscosity properties of these copolymers indicated that they have high degrees of polymerization and are little branched. A study of the x‐ray diffraction patterns of the copolymers of vinyl alcohol and vinyl stearate indicated that the alcohol and stearate segments crystallize in separate lattices. The tensile strength of vinyl alcohol copolymers decreased as the vinyl stearate content increased and as their water content increased. When the samples were dried or were oriented, their tensile strengths increased. Copolymers of vinyl alcohol containing as little as 1.5 mole‐% of vinyl stearate had greatly improved resistance to water and were insoluble in water at 98°C.
Deformation of networks by detachment and formation of crosslinks
Authors: Oosawa Fumio
Published: April 2003

This paper is concerned with problems relating to dimensional changes in networks of long chain polymers caused by detachment and formation of crosslinks. Particular attention is paid to the dependency of the dimensional change caused by detachment of crosslink on the conditions at which the crosslinks were formed. A network having crosslinks formed under a given tension is elongated by detachment of these crosslinks under a tension higher than that at crosslink formation and is contracted by detachment under a lower tension. Similar results are obtained for the deformation caused by detachment of crosslinks formed under shear stress. The increment of configurational entropy produced by detaching a crosslink depends on both the state of the network at the time of crosslink formation and the state at which the crosslink is detached. In a network having many crosslinks formed in various states of deformation, when the attractive energy between polymers forming linkages is gradually decreased under a constant tension, the crosslinks are detached successively, and it can be expected that the network first contracts and then elongates. In swollen networks, the detachment of crosslinks always brings about the extension of volume, and the critical tension at which the deformation in the direction of tension caused by the detachment is changed from elongation to contraction is increased with decreasing number of crosslinks remaining. While, in networks containing no solvents, the formation of crosslinks does not produce any deformation directly, formation of crosslinks in swollen networks can produce contraction directly. By assuming that polymer chains with a given degree of orientation are distributed densely and uniformly in networks at the moment of crosslink formation, we obtain these results. The validity of this assumption is briefly examined. The theoretical results obtained in this paper are found to be useful for analyzing the behavior of living muscle and muscle models in various stages.
Acid hydrolysis and molecular weights of various corn amylopectin and glycogen
Authors: Erlander Stig R. , French Dexter
Published: April 2003

Amylopectin samples were obtained from mature and immature sweet, dent, and waxy varieties of corn starch samples by dispersing the starch samples with either 6 M LiBr or bufered amyl alcohol solutions. The degree of branching, molecular weights, and radii of gyration were obtained on these amylopectins. The results were explained assuming that Erlander's proposed mechanism for the synthesis of starch from glycogen is valid. The corn amylopectins and an immature sweet corn glycogen sample obtained from Schoch were hydrolyzed at a pH of 4.2 at the refluxing temperature. Samples were taken at various time intervals. The values of Mw obtained from these samples showed that glycogen and amylopectin behave as randomly formed polymers. The rates of hydrolysis obtained in these studies indicate that the large molecules in all corn endosperm amylopectins and glycogens exist in chemical aggregates of four. These chemical aggregates do not appreciably influence the statistical size distribution of the amylopectin and glycogen molecules. A comparison of the properties of a sweet corn glycogen sample and an immature sweet corn amylopectin sample indicates strongly that glycogen is a precursor to starch.
Crystalline modifications of cellulose. Part III. The derivation and preliminary study of possible crystal structures
Authors: Jones D. W.
Published: April 2003

Scale models are described for a stereochemical study of the cellulose chain assuming standard armchair β‐glucose residues crystallizing in space‐group P21. Infrared evidence about the hydrogen bonding and intensity data for the strongest equatorial and meridional x‐ray reflections are utilized in assessing the validity of many models. The structures published by Meyer and Misch and by other workers do not comply with the criteria thus set up. Some fully hydrogen bonded structures, which are likely to form the basis of the most highly ordered regions in cellulose I and II, are discussed.
A thermistor method of determining the rate constant for the copolymerization of vinyl acetate and methyl methacrylate
Authors: Suzuki M. , Miyama H. , Fujimoto S.
Published: April 2003

The authors have tried to measure the overall rate for the copolymerization of vinyl acetate and methyl methacrylate at various monomer ratios and by use of a thermistor method to obtain the absolute rate of “crossed” chain termination. Although an assumed value was used for the heat of copolymerization to convert the rate of temperature rise into the rate of copolymerization, the agreement between the assumed and analytical values of this conversion factor was satisfactory. By substituting our results into Walling's equation, ϕ = 170 was obtained. Moreover, the use of the values of termination constants for vinyl acetate obtained previously and those for methyl methacrylate measured by Melville et al. led to a value of 1 × 1010 for the absolute rate of “crossed” chain termination at 24°C.
The problem of osmometer membranes partially permeable to the solute
Authors: Tung L. H.
Published: April 2003

The problem of measuring osmotic pressure with membranes partially permeable to the solute has been treated from a kinetic point of view. The results show that, under favorable conditions, the method of extrapolation to zero‐time pressure gives values reasonably close to the true osmotic pressure of the starting solution. When the diffusion of the solute through the membrane becomes excessive, such an extrapolation will not be valid. The importance of choosing a fast osmometer has been demonstrated.
Preparation and properties of polybenzylidene
Authors: Bawn C. E. H. , Ledwith A. , Matthies P.
Published: April 2003

Polybenzylidene was prepared by the decomposition of phenyldiazomethane in the presence of boron trifluoride etherate as catalyst. The polymerization was carried out in toluene at −80°C., and polymer having a degree of polymerization of 30–35 was obtained in 80–85% yield. Examination of the infrared spectrum confirmed the “pendent” polybenzylidene structure, which is to be expected by analogy with the formation of other polyalkylidenes from the corresponding diazoalkanes. The infrared spectrum and melting point of polybenzylidene were found to be very different from those of polybenzyl‐type polymers in accordance with the dissimilarity in their structures. A mechanism is proposed involving the step‐wise growth of a boron‐alkyl chain, and it is shown that alcohols retard the polymerization.
Polymers and copolymers of hydronopyl acrylate
Authors: Marvel C. S. , Schwen Roland , Hobson R. W. , Coleman R. J.
Published: April 2003

Hydronopyl acrylate has been synthesized by direct esterification of the alcohol with acrylic acid. Its homopolymer and a variety of copolymers, terpolymers, and a tetrapolymer have been prepared and their properties determined. The terpolymer containing equal weights of the acrylate, butadiene, and acrylonitrile is a good oil‐resistant rubber with a gum tensile strength double that of a 31% acrylonitrile‐69% butadiene copolymer. These properties were obtained at the expense of good low temperature properties. Some evidence has been obtained that hydronopyl acrylate polymerized in the presence of vinyl chloride gives a compatible mixture of polymer which can be milled satisfactorily.
Microgel: An idealized polymer molecule
Authors: Shashoua Victor E. , Beaman Ralph G.
Published: April 2003

Pure microgels (i.e., those free from any linear or branched admixed polymers) were prepared by an emulsion polymerization process. The products were characterized by ultracentrifuge measurements. The best crosslinking agent for acrylonitrile microgels was found to be N,N′‐methylene bisacrylamide, while divinylbenzene gave the best styrene and methyl acrylate microgels. A study of the viscosity of microgel solutions vs. concentration showed that there was a sudden transition from a low viscosity to a high viscosity at a characteristic gel point, G, dependent upon the degree of crosslinking. For monodisperse systems, this coincides with the point where hexagonal close packing of the swollen spherical microgel particles occurs. The following equations relating the gel point and intrinsic viscosity of a microgel were found to apply: [η] = (0.025/ρ)S and (G/ρ)S = π/3√2, where S is a swelling factor which is equal to the ratio of swollen to dry volume and ρ is the density of the dry microgels. The above relationships were developed by considering microgels as swollen Einstein spheres. Evidence is presented to support the equations by some light scattering and viscosity measurements. The Flory equation relating swelling factor, polymer‐solvent interaction parameter, and degree of crosslinking was successfully applied to microgel solutions. A simple empirical equation, found to correlate the intrinsic viscosity [η] with the mole ratio of crosslinking agent, x for the microgels, was [η] = K(1/x) + 0.025/ρ where K is a constant.
Studies on the low pressure polymerization of ethylene using catalysts containing sodium alkyls
Authors: Zilkha Albert , Calderon Nissim , Frankel Max
Published: April 2003

The low pressure polymerization of ethylene with the use of catalysts prepared from various sodium alkyls and titanium tetrachloride was studied. Catalysts prepared from amylsodium were very active over a wide range of molar ratios of amylsodium to titanium tetrachloride (2–50); the activity decreased sharply with lower molar ratios. Rate of polymerization was found to decrease sharply, probably as a result of fusing of polyethylene particles to the catalyst surface during polymerization. Up to a pressure of about three atmospheres, the polymerization gave better yields with increase in pressure, but no increase in rate was observed on using higher pressures. Yields increased also with lowering of temperature; 0°C. gave the best yields. Molecular weight determinations showed that the polyethylenes produced had high molecular weights which did not vary over a wide range. With butylsodium, catalysts similar to those with amylsodium were formed; they showed a smaller optimum range (5–9) of molar ratios of alkyl sodium to titanium tetrachloride. Catalysts prepared from phenylsodium were much weaker, and the optimum molar ratio of phenylsodium to titanium tetrachloride, contrary to the other sodium alkyls, was found to lie at much lower molar ratios of alkyl sodium to titanium tetrachloride. Polymerizations were, in the case of phenylsodium, accompanied by an induction effect. Preliminary studies on the preparation of catalysts for the low pressure polymerization of ethylene in the presence of cyclopentadienylsodium and titanium tetrachloride were as yet not successful.
The pyrolysis of dimethylpolysiloxanes
Authors: Lewis Charles W.
Published: April 2003

The pyrolysis of linear dimethylpolysiloxanes was investigated by weight loss studies in vacuum over the temperature range 360–540°C. Rate maxima were observed at 14–16% weight loss; these were attributed to the presence of ionizable impurities in the polymer molecules.
Interaction between particles suspended in solutions of macromolecules
Authors: Asakura Sho , Oosawa Fumio
Published: April 2003

An attractive force appears between particles suspended in solutions of macromolecules when there is neither direct interaction between two particles nor energetic interaction between particles and solute macromolecules. The magnitude of this force is of the order of the osmotic pressure of the solution of macromolecules and the range is of the order of the diameter of macromolecules. This force is calculated as a function of concentration, shape, and charge of macromolecules, and it is shown that it becomes stronger in solutions of chain macromolecules or of macromolecules of dissymmetrical shape than in solutions of rigid spherical macromolecules at the same net concentration. If macromolecules have charge, the force can be greatly intensified. In every case numerical estimation is made, and it is found that actually this kind of force can have a remarkable influence on the state of suspended particles. Numerical examples of the critical concentration of particles at their macroscopic aggregation are given. Finally a short description is added on the effect of energetic interaction between particles and macromolecules.
A study of graft copolymers. II. Viscosity and light‐scattering measurements
Authors: Manson J. A. , Cragg L. H.
Published: April 2003

Measurements of intrinsic viscosity and light scattering were made on fractions of polymers prepared by the redox polymerization of styrene in the presence of oxidized polystyrene or copolymers of skyrene and 4‐vinylcyclohexene‐1. For comparison, similar measurements were made on fractions of linear polystyrene. The conclusion that branching had taken place by graft polymerization was confirmed. Values found for the intrinsic viscosity, the molecular size, and the second virial coefficient were generally lower for fractions of the graft polymers than for fractions of linear polystyrene of the same molecular weight. It was also observed that fractionation of the graft polymers took place with respect to molecular size, not molecular weight, and that the most highly branched fractions were the most soluble. A comparison of experimental values of the branching ratio g with values calculated for a model having linear branches equally spaced along a backbone chain indicates that the graft polymers contain up to at least 6 branches per molecule. Values of Huggins' k′ for these branched molecules did not differ significantly from those for linear polystyrene (0.30 < k′ < 0.40). It is concluded that though k′ is sensitive to bushy branching, it is not measurably affected by the presence in the polymers of a few linear branches per molecule.
The degradation of polymer molecules in solution under the influence of ultrasonic waves. Part II. The rate equation and the limiting degree of polymerization
Authors: Allen P. E. M. , Burnett G. M. , Hastings G. W. , Melville H. W. , Ovenall D. W.
Published: April 2003

The breaking of polymer bonds in solutions of polystyrene, polyvinyl acetate, and polymethyl methacrylate in benzene and toluene while under the influence of ultrasonic irradiation has been studied by following the consumption of a radical scavenger, α,α′‐diphenyl‐β‐picryl hydrazyl added to the solution. The results are consistent with the rate equation proposed in an earlier paper, dBi/dt = k(Pi – Pe)ni and its relevant solutions, where dBi/dt, Pi and ni are, respectively, the rate of breakage of bonds, the degree of polymerization, and the number of molecules of the ith species, and where Pe is the limiting degree of polymerization, k is a constant, characteristic of the system and dependent on the weight concentration of the solution. Earlier literature is discussed and, in one case, the results are found to be more consistent with the above equation than with the forms: dB/dt = k(P ‐ Pe) and dB/dt = k log P/Pe. Values of Pe found by extrapolation are 1700, 2000 and 2800, respectively, for polystyrene, polyvinyl acetate, and polymethyl methacrylate. The various values of Pe for these systems to be found in the literature are discussed.