bluuebunny/crossref_metadata_2025 huggingface dataset:
Some chemical effects of ionizing radiations on nucleic acids and related compounds
Authors: Scholes G. , Ward J. F. , Weiss J. J.
Published: April 2003

The degradation of deoxyribonucleic acid (DNA) by irradiation of its aqueous solutions with ionizing radiations in the presence of oxygen has been discussed in terms of the reactions of free radicals (produced by the radiolytic decomposition of the water) with the different molecular entities of the macromolecule. It has been found that attack of the radicals on the purine and pyrimidine bases is a major effect of the irradiation, and it has been estimated that about 80% of the OH radicals attack the base components. In the presence of oxygen an important radiation‐induced reaction is the formation of peroxidic compounds from the pyrimidines. Breakage of the strands in the DNA helix is apparently due mainly to an attack of the radiation‐produced radicals on the sugar moieties which leads to a splitting of the phosphate ester linkages along the chains. The extent of attack which leads to breakage of internucleotide bonds, leading to the production of phosphomonoester groups, has been determined directly: the number of endgroups formed on irradiation with 200 k.v. x‐rays corresponds to a yield of G ⋍ 0.5 (endgroups/100 e.v.). Rupture of hydrogen bonds within the helix is a consequence of chemical changes in the polynucleotide chains; several hydrogen bonds can be broken following a single chemical event. The hyperchromic effect which is observed in the action of the radiations on nucleic acids in solutions has been investigated in some detail. It has been concluded that this effect is caused, in general, by environmental changes of the chromophoric groups of the purine and pyrimidine bases of the DNA, and is due to the change of the nature of the hydrogen bonding of the bases within the intact helix, where the bases of one strand are bonded to the bases of the complementary strand, to hydrogen bonding with water molecules when the latter have penetrated between the strands of the helix.
Some polyvinyl chloride resin systems containing epoxidized oil
Authors: Hopf P. P. , Sully B. Dudley
Published: April 2003

Rigid resin systems containing epoxidized vegetable oil are described. These systems in combination with PVC give products which are mechanically similar to rigid PVC, but have the additional property that they adhere to steel and glass.
Recherches sur les combinaisons d'insertion de macromolécules
Authors: Parrod J. , Kohler A.
Published: April 2003

Cet artirle présente certains résultats concernant l'absorption du polyoxyéthylèneglycol (POEG) par l'urBe, la thiourée et l'argile (bentonite Wyoming), en particulier l'extraction du POEG aux dépens de ses solutions benzéniques par ces trois absorbants, et la variations de viscosité de ces solutions par suite de l'absorption du soluté. Les résultats de l'absorption du POEG par l'uriée et la bentonite correspondent aux résultats classiques concernant l'absorption de petites molécules dans des cavités‐canaux de l'urée, en entre les couches de la bentonite; par contre dans le cas de la thiourée, la quantité de POEG absorbée est plus grande que la capacité d'absorption des cavités laisse prévoir. Nous avons observé dans ces trois cas qu'une solution polydispersée dans le benzène de POEG (préparée en mélangeant deux échantillons de POEG de poids moléculaire très différent) en contact avec de l'urée, la thiourée ou la bentonite, présente une viscosité intrinsèque qui décroît rapidement en cours d'absorption du soluté. Ce fait pourrait être le résultat d'un “ancrage” de la molécule absorbée, qui dépendrait de la longueur de la chaîne, les plus courtes chaînes restant en solution; un tel phénombne s'accorderait avec les résultats connus pour l'absorption de molècules parafiniques de petite taille par l'urée, à savoir que les parafines plus longues sont le plus fortementretenues. Si ce phénomène est confirmé et généralisé, une telle propriété de l'urhe, de la thiourée, de la bentonite et peut‐être d'autres absorbants, rendrait possible un test rapide et facile de la polydispersité d'un polymère, au moins d'un échantillon de POEG.
Polymer molecules involving coordination links in the crystals of cupric oxalate and related compounds
Authors: Kubo M. , Kishita M. , Kuroda Y.
Published: April 2003

Copper salts of α,ω‐dibasic acids, HOOC(CH2)n−2COOH, in which n = 2–10, show (cupric malonate excepted) abnormal magnetic moments, which are lower than the theoretical spin value (1.73 B.M.) for one free electron. (Therefore structures may be expected containing two copper atoms, as there are in cupric acetate monohydrate crystals) in cristalline cupric salts of α‐ω‐dicarboxylates which show subnormal magnetic moments. A nonplanar structure of oxalic radicals is confirmed experimentally as well by radiostructural analysis as by electron diffraction. These data indicate that cupric oxalate crystals have a dimeric structural network or polymeric molecules containing coordination links and do not behave as isolated molecules with one copper atom or as dimeric molecules, as do the crystals of cupric acetate monohydrate. Analogous network structures are possible for cupric salts of α‐ω‐dicarboxylic acids having an even number of carbon atoms, although the carbon chains may be bent more or less from their normal configurations; the Cu‐Cu links could also be simultaneously changed. Indeed, the magnetic moment of the copper salts of the even series increases with increasing length of carbon chains. For the malonate, the rotation of chains within the central carboxylic groups forbids the formation of such network structures. For the other acids of the odd series the flexibility of the carboxylic groups must take part in bringing two copper atoms together. Indeed, cupric malonate shows a normal magnetic moment as observed for most cupric derivatives, and the effective moment per copper atom in the cupric salts of the odd series decreases with increasing length of carbon chains of the acids until the curve of the magnetic moments of the dibasic acids of the even series practically coalesces with that of the odd series (above pimelic acid). These conclusions, which are based on the magnetic moment data of the polymeric structures of cupric salt crystals of α‐ω‐dicarboxylic acids, are also confirmed by infrared spectral data, especially by the variations of the CO stretching and the CH2 rotation bands. Analogous structures are also proposed for the abnormal magnetic moments observed for the cupric salts of rubeanic acid, thioxamide, and similar derivates.
High polymers and their intermediates in the phosphonitrilic halide system
Authors: Shaw R. A.
Published: April 2003

Polymers in the phosphonitrilic halide system are classified into addition and condensation polymers. Recent results bearing on the structure and mechanism of formation of “inorganic rubber” are discussed. Views on the structure of condensation polymers of a ceramic type are put forward, and the first phosphams with different but reproducible physical properties are reported. The stereochemistry of one of the most important intermediates, the cyclic trimer, is discussed in some detail.
Effect of heterogeneity on the second virial coefficient
Authors: Varadaiah V. V. , Rao V. S. R.
Published: April 2003

The values of the second virial coefficient A2, were determined by a light‐scattering method for polymethyl methacrylate mixed fractions in methyl ethyl ketone and ethyl acetate systems. It is shown that in a mixture of two components A2 is sensitive to the presence of the higher molecular weight component in a sample of a lower molecular weight, but not to the presence of a lower molecular weight component in a sample of higher molecular weight. This effect is found to be predominant in the good solvent (methyl ethyl ketone). The results obtained are in general agreement with those of Chien et al. but are in contrast with those of Elias.
Effect of intrachain and interchain interactions on the structures of crystalline regions in linear polymers
Authors: Huggins Maurice L.
Published: April 2003

In order to explain (1) the chain folding observed in single crystals of linear polyethylene and some other polymeric substances and in isolated molecules obtained from dilute solutions, (2) the twisted ribbon structure in polyethylene spherulites, (3) long x‐ray diffraction spacings in various polymers, and (4) the rotation of polarized light by single crystals of n‐paraffins, it is proposed that (1) intrachain forces produce slight departures from a planar zigzag structure of the carbon chain (or from a helical structure of simple multiplicity), (2) intrachain and interchain forces make these departures approximately uniform within each chain, and (3) when the total departure from the simpler structure reaches a limiting value, a sudden alteration in structure occurs.
On wave propagation in viscoelastic media
Authors: Davis J. L.
Published: April 2003

A mathematical analysis is made of the problem of wave propagation in a one‐dimensional bounded viscoelastic medium under prescribed boundary conditions. Closed form expressions are obtained for viscoelastic waves for the case of a relaxation function involving a single relaxation time. An expression for the phase velocity as a function of ratio of relaxation frequency to frequency of applied periodic displacement is obtained for the steady state part of the solution. The generalization to a relaxation function involving a finite number of relaxation times is discussed, and a method is sketched out for solving the more general integropartial differential equation of motion. Comments are made on the molecular interpretation of viscoelastic models.
A study of the ionic species present in ionic polymerizations. I. Styrene polymerization initiated by stannic chlorides
Authors: Metz Donald J.
Published: April 2003

The polymerization of styrene initiated by stannic chloride in the mixed solvent carbon tetrachloride‐ethylene dichloride was carried out between co‐axially mounted cylindrical electrodes. The dielectric loss of the polymerizing solution was measured in the frequency range of 104 to 107 cycles per second. The observed dependence of dissipation factor on frequency is interpreted as being indicative of conducting ions in the solution during the reaction. These ions are found only when both monomer and catalyst are present in the solution and not when one or the other is missing. The data also indicate that the concentration of the ions which contribute to the measured dielectric loss is not reduced to zero after completion of the reaction.
Relative activity of hexafluorobutadiene‐1,3 in polymerization and copolymerization reactions with other dienes
Authors: Klebanskiĭ A. L. , Timofeev O. A.
Published: April 2003

The effect of conjugation on the reactivity of perfluorinated diolefins has been little investigated. A characteristic representative of this class of compounds is hexafluorobutadiene, the activity of which in polymerization reactions is much less than that of tetrafluoroethylene. There is an inadequacy of published data on the polymerization of hexafluorobutadiene. We have investigated the conditions for the polymerization of this compound and have found that it takes place only in emulsions in the presence of a cationactive emulsifier in acid medium (pH 1–3) in the presence of a radical type of initiator. The effect of the basic parameters on the emulsion polymerization was investigated. The hexafluorobutadiene polymer obtained in emulsion, in contrast to the polytetrafluoroethylene, is characterized by a low melting point and little stability. It is insoluble in most organic solvents. To ascertain the relative activity of hexafluorobutadiene as compared with other dienic compounds a study was made of copolymerization with chloroprene, fluoroprene, and isoprene, both in emulsion and in solution, and the reactivity constants were determined. The monomer reactivity ratios of the systems are as follows. Chloroprene‐hexaflurobutadiene: r1 = r2 = 0.1; fluoroprene‐hexafluorobutadiene: r1 = 2.93, r2 = 0.24; isoprene‐hexafluorobutadiene: r1 = 1.19, r2 = 0.78. On the basis of the monomer reactivity ratios in the monomer‐hexafluorobutadiene systems and of reported data on the ratios for chloroprene‐fluoroprene and isoprene‐fluoroprene copolymerization, the relative reactivity of the monomers was calculated with respect to a common radical, the relative reactivity constant of the radical and its monomer being taken as unity. Chloroprene is 10 times more active than hexafluorobutadiene with respect to the radical of the latter; it is 8 times as reactive as isoprene and 2.4 times as reactive as fluoroprene. The results are in conformity with data on the separate polymerization of the monomers in emulsion. The considerable fall in activity of hexafluorobutadiene in polymerization and copolymerization reactions can probably be interpreted by localization of π‐electrons at the double‐bonded carbon atoms and weakening of the conjugation effect owing to a shift in electron density to the highly polar fluorine atom. Similar effects were observed for hexafluorobutadiene in diene synthesis.
Microtacticity of polymers and methods of its investigation
Authors: Birshteĭn T. M. , Gotlib Yu. Ya. , Ptitsyn O. B.
Published: April 2003

The microtacticity (degree of stereoregularity) of vinylic polymers with asymmetric side groups is determined by the competition between the stereospecific influence of the catalyst (if the polymerization is of a catalytic nature) and of the end of the growing chain. The stereospecific influence of the latter is due to the differences in the transition state energies corresponding to isotactic and syndiotactic addition. These differences are associated with van der Waals repulsion of the bulky side chains, determining also chain flexibility. The concept developed by the authors of the effect of chain flexibility on the physical properties of a polymer shows that an important part is played by the interaction not only between neighboring side groups but also between the nearest nonneighboring groups. This leads to dependence of the probability of isotactic or syndiotactic addition of the monomer on the manner of addition of the previous monomer, explaining the formation of stereoblock polymers the chains of which consist of alternate iso‐ and syndiotactic arrangements. A quantitative method of studying the effect of polymerization conditions on the microtactic state of the polymers should be based on physical properties depending directly on the probability of iso‐ and syndiotactic addition rather than on the stereoregularity of large regions (such as degree of crystallinity). A theory of the geometrical, electrical, and optical properties of macromolecules has been developed, predicting the relation between these properties and the microtactic state of the chain. The theory recently received experimental verification as to the sizes (Krigbaum, Carpenter, and Newman), dipole moments (Krigbaum and Roig) and optical anisotropy (Tsvetkov and Magarik) of isotactic and atactic polystyrene molecules. A method of investigating the microtacticity on the basis of determination of infrared dichroism in stereoisomeric polymers has also been proposed.
Une methode d'etude de la vitesse de la polymérisation à haute conversion
Authors: Kryszewski M. , Grosmanowa B.
Published: April 2003

La recherche des processus de polymérisation à des hauts degres de conversion n'est pas seulement importante pour la technologie mais est aussi intéressante au point de vue de l'élucidation des processus avec des radicaux libres en milieu non liquide. Une méthode a été développée pour des études de polymérisation à des hauts degrés de conversion. Cette méthode est basée sur la mesure du changement dans la vitesse de polarisation d'une solution de monomère contenant une petite quantité d'une substance fluorescente (si le monomère n'est pas fluorescent). Comme substance fluorescente il faudrait employer un produit qui n'influence pas la cinétique de la polymérisation. La concentration de la substance fluorescente est de l'ordre de 10−6 gr./cm.3. La fluorescence devrait être excitée avec de la lumière d'une telle longueur d'onde, qu'elle n'initie pas la polymérisation. L'appareil consiste en un récipient de polymérisation thermostaté et un montage permetant de mesurer la vitesse de polarisation de la lumière. Par la même technique (avec une petite modification) il est possible de mesurer l'intensité de fluorescence. En utilisant cette méthode, le cours entier de la polymérisation du méthacrylate de méthyle et de méthacrylate de butyle a été examiné. On a trouvé que la vitesse de réaction était constante pour un certain temps et qu'elle croissait alors très rapidement. L'accélération et le changement des constantes de vitesse ont été confirmés par les résultats d'autres auteurs.
Methods of synthesis of new polymer containing rings in the chains
Authors: Koton M. M.
Published: April 2003

Methods of obtaining new polymers with cycles in the chain possessing high softening point and high thermostability are described in this article.
Kinetics of formaldehyde polymerization
Authors: Macháček Z. , Mejzlĭk J. , Pác J.
Published: April 2003

Polymerization of formaldehyde was studied in diethyl ether solution at −58°C. Monomeric formaldehyde has been prepared through pyrolysis of carefully dried paraformaldehyde and purified by passage through liquid formaldehyde at its boiling point and subsequent condensation in a reservoir. A catalytic system consisting of n‐dibutylamine has been used. The course of polymerization was studied in a dilatometer provided with a stainless steel stirrer, since the polymer formed is insoluble in the reaction mixture. The components (i.e., liquid monomer, solvent, and catalyst solution) were measured into the dilatometer under dry nitrogen so as to form separate layers, one on top of the other. The polymerization reaction was started by mixing the contents. The rates of reaction were chosen so that the initial overall rate of reaction did not exceed 5% conversion per min. It was observed that at constant n‐dibutylamine concentration the overall rate of reaction increases with increasing water concentration, while the molecular weight as checked by viscometry practically did not change. The n‐dibutylamine‐water ratio lay in the range from 1:10 to 1:1000 at a formaldehyde concentration of 5 mole/l. With increasing n‐dibutylamine concentration (in the range from 2.5 to 14 μmole/l.) and at a constant concentration of water (3.5 mole/l.) the overall rate of reaction increases while the molecular weight does not change. The results obtained permit a study of dissociation equilibria of amines with water in nonaqueous media. The role played by water in the formation of the anion ‐OH (which initiates the polymerization) and the influence of the structure of the cation RxNHy+ on molecular termination or possibly transfer are discussed.
Study of some details of the mechanism of polymerization under the action of complex catalysts
Authors: Bresler S. E. , Mosevitskiĭ M. I. , Poddubnyi I. Ya. , Guan‐I Schi
Published: April 2003

To elucidate some details of the mechanism of isoprene polymerization by means of the complex catalyst TiCl4 + Al(i‐C4H9)3 an analysis has been made of the data on the molecular weight distribution of the polymers. A relation has been established between the heterogeneous character of the polymerization process and the degree of dispersity of the polymer. In particular, it has been shown that for very small catalyst particles polymerization proceeds slowly and is a nonstationary process. The molecular weight distribution of the polymers changes with time. On increasing the catalyst particle size above certain, critical dimensions required for carrying out heterogeneous catalysis, a stationary molecular weight distribution of the polymers sets in, remaining unchanged up to the end of the process. An investigation of the molecular weight distribution of the polymers obtained at various catalyst component ratios and various methods of addition to the monomer permitted a number of details of the chain termination mechanism in catalytic polymerization to be elucidated. Chain breaking has been shown to be not the result of reversible interaction of growing chains with the active centers on the surface.
Thermal stability of polydimethylsiloxane. I. Deactivation of basic active centers
Authors: Kučera M. , Láníková J.
Published: April 2003

The thermal stability of polydimethylsiloxane is determined by both the resistance of the siloxane chain to depolymerization and the resistance of the hydrocarbon side groups to various forms of degradation. Basic and acidic impurities present in the polymer promote depolymerization as well as degradation. Especially efficient in decreasing the thermal stability are the centers remaining “alive” in the polymer after completed polymerization.

The rates of depolymerization and degradation of unstabilized polydimethylsiloxane were measured and compared with those of polymers with active centers deactivated through the formation of complexes with CO2 and iodine. Also measured was the stability of a polymer prepared by using Bu4P(OH) as catalyst and containing only decomposition products of active centers. Inasmuch as high molecular weight polydimethylsiloxanes are seldom used alone, the authors have studied the ability of some oxides (commonly used as fillers) to form complexes with basic active centers and so to influence the thermal stability of polydimethylsiloxane.
Infrared spectra of crystalline and stereoregular polymers. III. Spectra of polypropylene and some deuterated polypropylenes in the region 650 to 1550 cm.−1
Authors: Liang C. Y. , Lytton M. R. , Boone C. J.
Published: April 2003

From an infrared study of partially deuterated polypropylenes, the spectrum of polypropylene was interpreted in the region 650 to 1550 cm.−1. It was found that the internal carbon‐hydrogen vibrational modes are associated with “group frequencies”. The A and E components of each of these modes have been observed at the same frequency. The external carbon‐hydrogen vibrational modes as well as the skeletal modes are complicated mixed modes which do not give rise to “group frequencies”. The A and E components of some of these mixed modes were found to split into different frequencies.
The copolymerization of 1,3‐butadiene with styrene by butyllithium initiation
Authors: Kuntz Irving
Published: April 2003

The homopolymerization of styrene (1M) by n‐butyllithium (0.006M) in n‐heptane at 30°C. is approximately six times faster than the homopolymerization of butadiene under the same conditions. In copolymerizations 1M in each monomer, butadiene is the more reactive comonomer. When 90% of the butadiene monomer has been converted to polymer, more than 80% of the styrene monomer present at the beginning of the reaction still remains. The initial copolymerization rate is the same as that observed in the polymerization of butadiene alone, and about 10 mole‐% styrene is incorporated into the copolymer initially produced. When the butadiene has all reacted a marked increase in polymerization rate is observed. The copolymer reactivity ratios for initial reaction appear to be 7 for butadiene and nearly 0 for styrene. When the copolymerization is carried out in the presence of concentrations of tetrahydrofuran similar to the concentration of butyllithium, increased polymerization rate is observed. Kinetic experiments indicate that the reaction is first‐order with respect to tetrahydrofuran. The amount of 1,2‐addition in the polybutadiene segments of the copolymer increased from the 7% observed in the absence of ether to 15 and 43% as the ratio of (THF)/(BuLi) was varied from 0.4–20. The copolymer initially produced contained 30 mole‐% styrene over this entire range of ether concentrations. The implications of these observations on the polymerization mechanism are discussed.
Dielectric dispersion of polar polymers
Authors: Bueche F.
Published: April 2003

A simple molecular theory is presented for the dielectric dispersion behavior of polar polymers. It is shown that the α dispersion involves movement of the chain backbone. The relaxation time for this dispersion is given by a relation of form τα = a2f0/4kt, where a, and f0 are, respectively, the jump distance and friction factor for a chain segment. Although the numberical factor in this relation will depend somewhat on the exact model used for the computation, the general form of the relation is independent of the model as long as the chain can be considered a statistical coil. If the dipole is not rigidly attached to the chain backbone, a second, β dispersion region will result. The causes of the broadening of the dispersions are discussed.
Polymerization of alkynes by ziegler‐type catalyst
Authors: Watson William H. , McMordie Warren C. , Lands Larry G.
Published: April 2003

A study has been made of the polymerization of acetylene, propyne, and butyne‐1 using aluminum triisobutyl, n‐butyllithium, or zinc diethyl in combination with titanium tetrachloride as catalyst. Optimum conditions for polymerization were determined by varying the catalyst composition. The major product was a black insoluble polymer whose spectrum indicates a high degree of conjugation. A small quantity of soluble low molecular weight polymer was also obtained. Reactions were run at atmospheric pressure and 21–62°C.
Properties of polyvinylidene fluoride. Part II. Infrared transmission of normal and thermally decomposed polymer
Authors: Wentink Tunis , Willwerth Lawrence J. , Phaneuf Jean P.
Published: April 2003

The infrared transmission of the plastic polyvinylidene fluoride has been measured. Normal and thermally decomposed samples were used. Bands yielding information on phase transitions and behavior during pyrolytic decomposition have been observed. The mechanism of thermal degradation is briefly discussed. Absorption coefficients of important bands have been evaluated.
A new synthetic elastomer based on a chlorophosphonated polyolefin. II. Effect of polyolefin structure on vulcanizate properties
Authors: Leonard E. C. , Loeb W. E. , Mason J. H. , Stenstrom J. A.
Published: April 2003

The paper describes the effect of ethylene‐propylene copolymer structure on the properties of vulcanized, chlorophosphonated ethylene–propylene copolymer. The crystallinity of copolymer has a marked effect on vulcanizate properties. The more crystalline the copolymer, the higher hysteresis values and permanent set are for the vulcanizate. The catalyst used for the copolymerization of ethylene and propylene affects crystallinity markedly, titanium trichloride as a catalyst component giving a more crystalline copolymer than does the use of vanadium salts. Copolymer molecular weight has an effect on vulcanizate tensile strength but no effect on heat stability, elongation, and hysteresis loss.
Crystal structure of polyketone (1:1 ethylene/carbon monoxide copolymer)
Authors: Chatani Yōzō , Takizawa Takeo , Murahashi Shunsuke , Sakata Yoshiaki , Nishimura Yasushi
Published: April 2003

The crystal structure of polyketone (1:1 ethylene/carbon monoxide copolymer) obtained by γ‐irradiation copolymerization of ethylene and carbon monoxide was determined by x‐ray diffraction. An orthorhombic unit cell was found, having space group D (Pnam) of dimensions a = 7.97, b = 4.76, c (fiber axis) = 7.57 A. The unit cell contains four repeating units (CH2CH2CHO). The main chain has a planar zigzag form. The side‐by‐side molecular packing is analogous to that of polyethylene, and CO groups arrange at two equivalent levels, z = 1/4 and 3/4. An apparent anisotropic thermal vibration of the molecule was recognized; i.e., the thermal vibration in the direction perpendicular to the fiber axis is about three times that along the fiber axis. Furthermore, from a preliminary investigation on polyketones having several mole ratios of ethylene and carbon monoxide, an interesting result was found: the larger the fraction of CO, the longer the a axis and the shorter the b axis.
Precipitation of polyelectrolytes by salts
Authors: Ikegami Akira , Imai Nobuhisa
Published: April 2003

Precipitation of poly(acrylic acid) by added salts has been investigated under various conditions. The PAA was neutralized to various degrees of ionization α by tetra‐n‐butyl ammonium hydroxide. The minimum salt concentration C̄s at which precipitation occurs was determined at various polymer concentration Cp, temperature T, and α. The amount of bound cations to polyions, the change in ion hydration, and the polymer expansion near C̄s were estimated by conductance, refractive index, and viscosity measurements, respectively. It is concluded that there are two kinds of precipitation; The L type which satisfies the relation C̄s ≐ αCp and occurs at high α due to cation binding to the polyions, and the H type in which C̄s is independent of Cp and which appears at low α with salts other than those having large ions. This classification of the precipitation is justified also by the C̄s – T relation; in the L type, C̄s is nearly independent of T, and in the H type C̄s increases with T. At intermediate α‐values pronounced specificities of salt ions are found in the precipitation; at α = 0.25, with Mg2+ the H type appears, while with Ba2+ or Ca2+ the L type appears, although all of these divalent cations are bound to polyions to the same degree. This is due to the difference in the hydration of the polyion‐cation complexes. In the L‐type the formation of cation bindings, such as salt bridge, makes the polymer hydrophobic, while in the H type highly concentrated salt ions render the polymer solution unstable by changing the arrangement of the water molecule.
Report on nomenclature dealing with steric regularity in high polymers
Authors: Huggins M. L. , Natta G. , Desreux V. , Mark H.
Published: April 2003

This report deals with the classification and naming of high polymers composed of molecules possessing steric regularity, and with related problems of nomenclature. It has been tentatively approved, for one year, by the Commission on Macromolecules of the International Union of Pure and Applied Chemistry.
Effect of gases on the electron spin resonance spectra of irradiated acrylamide and methacrylamide
Authors: Ueda Hisashi , Kuri Zen'Ichiro , Shida Shoji
Published: April 2003

The effects of various gases on irradiated acrylamide and methacrylamide were studied by ESR. The results are not the same with irradiated monomers and irradiated polymers. Nitrogen oxide and hydrogen sulfide are known as radical scavenger, but they act as radical transformers for these samples. In source and postirradiation reaction of polyacrylamide or polymethacrylamide with hydrogen sulfide give rise to broad spectra having a g factor of 2.0267 and the new radicals produced here are concluded to be of the RS. type.
Photolysis of poly‐α‐methylstyrene
Authors: Stokes Suzanne , Fox R. B.
Published: April 2003

The photodegradation of thin films of poly‐α‐methylstyrene by near ultraviolet radiation has been studied in vacuum at 27 and 115°C. Changes taking place during photolysis were followed by a determination of monomer formation by ultraviolet spectroscopy, residue molecular weight through a measurement of intrinsic viscosity, and volatile products by mass spectroscopy. Gross features of the photolysis include random chain scission in the polymer with subsequent depolymerization of the radicals formed to yield small amounts of monomer; the kinetic chain length is on the order of 15 in the temperature range studied. Quantum yields at 27°C. for chain scission and monomer formation are 1 × 10−3 and 7 × 10−3, respectively. At 115°C. the quantum yields are 2 × 10‐2 and 0.5. Small quantities of hydrogen, CO2, CO, and a number of hydrocarbons were liberated during irradiation. An approximate one‐to‐one correlation between the number of main chain scissions and CO2 + CO molecules evolved was found, suggesting the occurrence of chain scission at weak linkages involving oxygen.
Thermal conductivity of high polymers from −180°C. to 90°C.
Authors: Eiermann K. , Hellwege K.‐xH.
Published: April 2003

Systematic measurements of the thermal conductivity of plastics have been undertaken by various methods and checked against each other. Between −180 and +100°C. the thermal conductivity depends only slightly on the temperature. For instance, amorphous plastics and natural rubber show a break in the curve at the second‐order transition temperature. This break probably is connected with the break in the volume versus temperature curve. In stretched samples, the thermal conductivity was found to be larger when stretching was in a direction parallel than perpendicular to the chains. Partially crystalline plastics show a more complex behavior.
Equilibrium ultracentrifuge for molecular weight measurement
Authors: Beams J. W. , Boyle R. D. , Hexner P. E.
Published: April 2003

The magnetically supported vacuum‐type equilibrium ultracentrifuge previously described has been improved and used for the measurement of the molecular weights of a number of substances. The modifications include an electric motor drive which accelerates the rotor to operating speed. The rotor coasts freely during the sedimentation, and the operating speed may have any desired value from a few revolutions per second to the maximum safe speed of the rotor. Improvements have been made in the ultracentrifuge cell, and both white light and monocromatic light fringes can be used interchangeably in the interferometer. These modifications make possible the determination of the molecular weight quickly either without waiting for equilibrium to take place or after equilibrium has been established. The overall precision is the order of one part in a thousand for the centrifuge measurements themselves. Molecular weight data are given for a number of substances, including sucrose, ribonuclease, and insulin. The application of the centrifuge to the determination of molecular weight distributions is discussed.
Configurational effects on binding of magnesium to polyacrylic acid
Authors: Jacobson Ada L.
Published: April 2003

The effect of added Mg++ on the acid ionization of oxalic, citric, and polyacrylic acids is reported. The extent of ionization of the acids was varied by pretitration to various degrees with the strong base tetra‐n‐propylammonium hydroxide. The effect of subsequent addition of MgCl2 to these pretitrated acids was determined by pH measurements. The pH changes indicated that the strong counterion binding Mg++ caused release of H+, the amount of H+ released being markedly dependent on both the nature of acid and the extent to which it had been pretitrated. While the simple oxalic and citric acids behaved in a “normal” manner, H+ release by Mg++ from polyacrylic acid passed through maxima and minima as a function of degree of ionization of the acid. The maxima and minima observed can be explained by the combined effects of coulombic binding and chelation of magnesium ions, or by the effect of variation in polymer configuration on ion binding. The former explanation involves several questionable assumptions. The latter explanation can be coupled with the concept of “available” and “buried” carboxyl groups in the various possible polymer configurations. The configurational explanation appears to be the more plausible and suggests a possible new technique for the study of the effect of charge distribution in a polyelectrolyte on its configuration and on the mechanism of counterion binding.
Crystallization of CH2‐chain molecules condensed from vapor phase
Authors: Lampe G. R. , Hellwege K.‐H.
Published: April 2003

In a high vacuum vessel thin films of n‐paraffins and of decomposition products of polyethylene were condensed on cooled plates of rock salt. The films are amorphous at a condensation temperature of −170°C. Owing to the splitting of the infrared absorption band at 725 cm.−1 one can observe the partial crystallization of the film with increasing temperature. Evidently a complete interpretation of the observed absorption bands is not possible by assuming only a doublet due to the crystalline part and a singlet due to the amorphous part. There are intermediate states, the absorption spectrum of which is neither that of the completely amorphous nor that of the completely crystalline material. The amount of material which is in the intermediate phase is about 30% at −170°C.; at room temperature it becomes zero for n‐paraffins and goes down to only a few per cent for technical polyethylenes. By the same method epitaxy and texture at higher temperature can be proved.
The effect of pressure on glass temperature and dielectric relaxation time of polyvinyl acetate
Authors: O'reilly James M.
Published: April 2003

In an attempt to clarify the criteria satisfied at the glass transition (Tg) the effect of pressure on Tg of polyvinyl acetate has been measured by dielectric and volumetric techniques. Dielectric constant and loss has been measured as a function of temperature (25–120°C.), pressure (0–3300 atm.) and frequency (0.06–10 kcycles/sec.). At fixed frequency the temperature at which ε″max occurs increases with pressure by 0.022°C. atm. and this value is identified with (∂Tg/∂P). The In τD (where τD is dielectric relaxation time) is linear in the pressure. This dependence of In τD on pressure is different from the dependence of In τD on (T − Tg), which can be described by the WLF equation. By assuming f = (f0 + αfΔT)/(a + bP) and using the free volume model, we find In ap = bP/(f0 + αfΔT). If a = 1, f0 = 0.025; then the calculated value of b is 3.1 × 10−4 atm., and 1/b = 3.2 × 103 atm. is the same order of magnitude as an internal pressure. Volume measurements were made by the piston displacement method and by use of an Instron tester for recording force and length. The change in compressibility at Tg was used to follow ∂Tg/∂, and ∂Tg/∂P = 0.021°C./atm. in good agreement with the dielectric measurements. It was found that the volume of the sample at the same final pressure is smaller when compressed at high temperature than at low temperatures. In other words, vitrification at high temperatures and pressures produces a more dense sample than can be achieved by compression at low temperatures and seems to be a property of many glass forming systems. These results and other examples were used to show that the application of thermodynamic equations, namely ∂Tg/∂P = TgVΔα/ΔCp, to the glass transition is justified.
Thermodiffusion fractionation of polymethyl methacrylate and determination of molecular weight distribution
Authors: Kössler Ivo , Krejsa Jan
Published: April 2003

The time dependence of concentration separation and fractionation of polymer according to molecular weights was estimated with polymethyl methacrylate in benzene during thermal diffusion in a two‐reservoir apparatus. Values of the reduced separation coefficient γ as a function of time were determined for the fractions obtained by fractional precipitation and for their mixtures. The Soret coefficients were calculated from the values of γ for t → 0 and the values of s0 for c → 0 was determined; it was found that for single fractions the relation s0 = a[η] + b (where a and b are constants holds), and that for a mixture of fractions the relation is s0 = Σ (where gi is the weight of fraction i). An inversion effect was found in following the changes of limiting viscosity number both of nonfractionated polymer and of the fraction mixtures. The use of a five‐reservoir apparatus slightly improves the fractionation according to molecular weight. A considerable improvement, however, which allows the construction of a distribution curve identical with the curve obtained by fractional precipitation, was achieved by stepwise addition of the solvent into the lower part of the working space of the apparatus without reservoirs.
Proton magnetic resonance studies on synthetic rubber. I. Polybutadienes and polyisoprenes
Authors: Takeda Masatami , Tanaka Koji , Nagao Rumika
Published: April 2003

The behavior of the molecular motions of nine synthetic polybutadienes, two synthetic polyisoprenes, and an ethylene—propylene copolymer were studied by proton magnetic resonance absorption. The values of the line widths and the second moments were estimated as a function of temperature from −190°C. to room temperature for all samples except for the trans‐polybutadienes, for which measurements were made from −190 to 120°C. The transition temperatures determined from the inflection points of the line width versus temperature curves were compared with the transition temperatures detected from the volume versus temperature curves of dilatometric experiments for each sample. The difference between the value of the transition point obtained from the δH—T curve and that obtained from the V—T curve for each sample was not very large. The average transition temperature of cis‐polybutadienes was about −100°C., while that for cis‐polyisoprene was about −50°C. The great difference between the transition temperatures of two polymers is explained by the fact that the potential barrier for internal rotation around the carbon‐carbon single bond of cis‐polybutadiene is expected to be lower than that of cis‐polyisoprene. The second moment at liquid nitrogen temperature is found to be about 20 gauss2 for polybutadiene and about 18 gauss2 for the polyisoprenes; the value for polyisoprenes increases with descending temperature. From this fact the existance of another transition resulting from methyl group rotation is suggested.
Adiabatic crystallization of amorphous polycaprolactam
Authors: Wichterle O. , Šebenda J. , Tomka J.
Published: April 2003

The course of adiabatic crystallization of caprolactam followed by the change of temperature reversed in contraction of the samples. It was found that the contraction came to an abrupt stop in a very early stage of crystallization. The dimensional fixation set in when only about 30% of the amorphous polymer was transformed into spherulites. It is assumed that the fixation of the bulk is caused by the growing together of spherulites from which a three‐dimensional framework results.
Effect of polymethylhydrosiloxane on propylene polymerization catalyzed by Ziegler catalyst
Authors: Shiihara Isao , Kawai Wasaburo , Ichihashi Taichi
Published: April 2003

Polymethylhydrosiloxane was added to the Ziegler catalyst in propylene polymerization, and a kinetic study carried out for this system was in good agreement with the results obtained in the polymerization carried out in an autoclave under pressure. The experimental equations for polymerization rate are

for constant siloxane and AlEt3 concentrations and

for constant siloxane and TiCl4 concentrations, where α, A, and β are constants. From experimental results of studies of the chemical properties of polymethylhydrosiloxane, a reasonable reaction mechanism was proposed which can explain the experimental results in the polymerization process. The polymers were separated by use of several solvents, and both the residue and extracted parts showed the presence of silicon. On the basis of chemical analysis and infrared absorption spectra, it was concluded that the polymers obtained were copolymers of polypropylene and polymethylsiloxane.
Polymerization of styrene with n‐butyllithium–titanium tetrachloride catalysts
Authors: Tsou K. C. , Megee J. F. , Malatesta Alberto
Published: April 2003

The polymerization of styrene by n‐butyllithium and titanium tetrachloride has been examined. Isotactic polystyrene is obtained only when 3.00 > n‐BuLi/TiCl4 > 1.75. At ratios less than 1.75 and greater than 3.00 only amorphous polystyrene (soluble in MEK) was formed. The molecular weights of the amorphous fraction were determined, and it was interesting to note that the amorphous polymer shows strong fluorescence under ultraviolet light. Concomitantly with the formation of isotactic polystyrene, trans‐stilbene was also formed.
The effects of inadequate mixing in anionic polymerization: Laminar mixing hypothesis
Authors: Litt Morton
Published: April 2003

The basic ideas of Figini and Schulz on inadequate mixing have been further developed using a laminar mixing model. It was found that the derived equations explained semiquantitatively the initiation phenomena as well as the molecular weight distributions found in anionic polymerization, while the “expanding drop” hypothesis of Figini and Schulz failed. When the theory of slow initiation was examined, no agreement with experimental data was observed; in fact, inadequate mixing was able to explain all the phenomena previously attributed to slow initiation. The rate of initiation is probably greater than the rate of polymerization with an initiator such as sodium naphthalene. Ways to obtain monodisperse polymer were discussed; polymerization in a solvent such as dioxane seemed to be the best solution.
High molecular weight poly(vinylene carbonate) and derivatives
Authors: Field N. D. , Schaefgen J. R.
Published: April 2003

The preparation, structure and physical properties of poly(vinylene carbonate), polyhydroxymethylene, and polyacetoxymethylene are discussed. Vinylene carbonate was prepared by chlorinating ethylene carbonate in carbon tetrachloride solution, dehydrohalogenating the product, and refluxing the bulk monomer with small weight percentages of sodium borohydride. Monomer prepared and purified in this way gave very high molecular weight polymer by free‐radical initiation. Poly(vinylene carbonate) films were converted to polyhydroxymethylene films by hydrolysis with sodium methylate in methanol. Drawn polyhydroxymethylene films were crystalline and oriented and had good tensile properties. Polyacetoxymethylene was prepared by treatment of polyhydroxymethylene with acetic anhydride in molten urea.
Poly(ethylene oxide) in solution
Authors: Rossi C. , Magnasco V.
Published: April 2003

Measurements of the limiting viscosity number and dipole moments in benzene at 25°C. have been performed on carefully fractionated low molecular weight poly(ethyleneoxide) (M.W. ranging from 194 to 7770). The results of these measurements have been related to some hypotheses on the structure of molecules in the dissolved state. We have realized that internal rotations of the bonds are hindered by asymmetric potentials with a minimum near the gauche position. Although the exact shape of these potentials has not yet been defined, the so deduced conformation of the molecule in solution agrees very well not only with our measurements, but also with the most probable hypotheses obtained from x‐ray studies on crystalline structure and infrared spectra of POEG in various physical states.
Interaction of polysaccharides in the calcium oxalate system
Authors: Zinsser Hans H. , Light Igo
Published: April 2003

The stabilizing effect of various synthetic polymers as well as naturally occurring urinary mucoproteins and mucopolysaccharides upon the kinetics of the calcium oxalate system has been tested and evaluated by calculating slopes (rates) and lags (nucleation time) of calcium oxalate formation. This was accomplished by means of a Fisher Nefluorophorometer. The experimental part was carried out in aqueous as well as urinary media. This problem has been also approached by testing the calcium‐bonding properties of the polymers and urinary fractions. The results of the conducted experiments show that nondialyzable urinary fractions and polymers of glucose and its sulfonated derivatives, and to a lesser extent polymers of mannuronic acid exhibit some diminishing effect upon the rate of calcium oxalate formation, while prolonging their nucleation times.