bluuebunny/crossref_metadata_2025_split huggingface dataset:
Configurational effects on binding of magnesium to polyacrylic acid
Authors: Jacobson Ada L. 
Published: April 2003

AbstractThe 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

AbstractIn 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

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractPolymethylhydrosiloxane 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractMeasurements 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

AbstractThe 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.
Effects of high speed electrons on the structure of polyethylene terephthalate
Authors: Slovokhotova N. A. , Sadovskaya G. K. , Kargin V. A. 
Published: April 2003

AbstractPolyethylene terephthalate (PET) films were irradiated with high speed electrons in vacuo. Their infrared spectra, solubility, and degree of swelling in o‐chlorophenol were measured as a function of the irradiation dose. The investigation has shown that irradiation causes both crosslinking and degradation. In the absence of air, crosslinking predominates over chain scission. The irradiation dose required for crosslinking of PET by far exceeds that required for crosslinking of polystyrene. Irradiation of PET is accompanied by the formation of polyphenyl systems. The initial partly crystalline PET becomes completely amorphous on irradiation. Irradiation causes isomerization of O(CH2)2O groups in the polymer chain from the trans to the gauche form. Isomerization of O(CH2)2O groups under irradiation may be interpreted as indicating that a part of the ionizing radiation energy is dissipated and transformed into thermal energy.
Infrared dichroism and molecular conformation of α‐form poly‐γ‐benzyl‐L‐glutamate
Authors: Tsubio Masamichi 
Published: April 2003

AbstractPrecise measurements were made of the dichroic ratios of several absorption bands of α‐form poly‐γ‐benzyl‐L‐glutamate. From the results obtained, directions were determined for the transition moments of these bands, and possible orientations are given for the peptide, ester, and phenyl groups in the polymer with respect to its fiber axis. On the basis of these orientations a model is proposed for the molecular conformation of this polypeptide.
Equation of state for monolayers of chain molecules
Authors: Llopis J. , Subirana J. A. 
Published: April 2003

AbstractAn equation of state for high linear polymer monolayers is discussed. It is shown that different theoretical approaches should be considered according to the range of surface concentration of the monolayer. For high dilution the theory here proposed is similar to that used in bulk solutions of polymers. An ideal temperature T = θ for which the second virial coefficient vanishes is defined. The behavior of these monolayers for higher concentrations can be explained by considering energetic interactions. In these conditions the chain configuration entropy becomes negligible. The difficulties involved in developing a theory for temperatures lower than θ have also been considered.
Tacticity as a problem in copolymerization: Influence of neighboring units on reactivity of growing chains
Authors: Ham George E. 
Published: April 2003

AbstractMost copolymerizations and stereoregular homopolymerizations have been interpreted in the past solely in terms of the contributions of the terminal units in growing chains to reactivity with adding monomers. Equations are presented which offer the opportunity of weighing the specific contributions of all significant terminal sequences of several units on monomer reactivity. Rigorous proof of the validity of the “penultimate” equation is offered for the first time.
Block copolymers of α‐olefins prepared from macromolecules with long chain lifetimes
Authors: Kontos E. G. , Easterbrook E. K. , Gilbert R. D. 
Published: April 2003

AbstractIt has been shown that certain Ziegler‐type catalysts, i.e., mixtures of TiCl4 with lithiumaluminium alkyls or VOCl3 with aluminum chloroalkyls, produce “living” macromolecules having lifetimes of the order of several days or more in the homo‐ and copolymerization of α‐olefins. The long‐lived macromolecules made it possible to prepare stereoblock copolymers of α‐olefins consisting of blocks of random copolymers alternating with blocks of homopolymers with a certain steric isometry and with a wide range of physical properties. Some of the relationships existing between the molecular structure and the physical properties of these model block copolymers have been studied and compared with random copolymers and homopolymers of α‐olefins. Crystallizable elastomers composed of amorphous random copolymer blocks of ethylene and propylene or ethylene and butene‐1, alternating with homopolymer blocks of ethylene, propylene, or butene‐1 are discussed. In particular, the homogeneity of the products, the stress–elongation behavior, the x‐ray diffraction patterns in the unstretched and stretched states, and the physical properties of the reinforced and vulcanized products of the crystallizable stereoblock rubbery copolymers are presented.
Interaction of carboxyl‐containing butadiene–styrene rubbers with polyamides and ε‐caprolactam
Authors: Tutorskiǐ; I. A. , Smelyǐ; Z. I. , Bystrov V. M. 
Published: April 2003

AbstractMixtures of carboxylated butadiene–styrene rubbers containing 30% styrene, and 1, 3, 4, 5, 10, and 15% methacrylic acid (MAC) were investigated with ε‐caprolactam in a melt or in masticated mixtures for 10 hr. at 220°C. The lactam was found to add to the rubber both in the presence and in the absence of water, as was shown by extraction of the resultant specimens with acetone, followed by formic acid and determination of nitrogen in the extracts. The compression heating of carboxylated butadiene–styrene rubber containing 30% styrene and 1% methacrylic acid with ε‐caprolactam at 200–220°C. leads to addition of the lactam to the rubber. BF3 served as reaction catalyst. Methods have been developed for the synthesis of graft and modified carboxylated butadiene–styrene rubbers and polyamides through the stage of rubber acid chlorides and sodium (potassium) derivatives of the polyamides. The rubber acid chlorides are obtained according to the reaction:
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The polyamides derivatives, according to the reaction:
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and
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Modification of the carboxylated butadiene–styrene rubber with ε‐caprolactam was carried out according to the reaction:
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or
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Rubbers with a MAC content of 0.3% to 10% were employed. The modified rubbers possess greater strength characteristics than the original carboxylated polymers. They are less soluble in pure benzene and soluble in benzene–ethyl acetate mixtures. Insoluble, crosslinked polymers are obtained on reaction of the rubber acid chlorides with sodium substituted polyamides. Under particular conditions soluble products are formed. The products possess enhanced adhesion to polyamide films and ensure a strong bonding between rubber and fabric in rubber textile goods.
Polyethers. XIII. The effects of catalyst concentration and oxygen on the polymerization of 4‐halo‐2,6‐dimethylphenol
Authors: Price Charles C. , Chu Nan Shieh 
Published: April 2003

AbstractThe oxidative polymerization of haloxylenol has been found to be markedly faster than earlier reports. With 10 mole‐% of ferricyanide initiator it was complete in less than 1 min. at 5°C. Oxygen can act as initiator but also results in a decreased molecular weight. Increase in ferricyanide initiator concentration from 1 to 10 mole‐% resulted in a remarkable increase in conversion and a small increase in molecular weight. Polymer prepared with ferricyanide initiator under nitrogen had a large excess of halogen over phenolic endgroups, rather than the one‐to‐one ratio, found earlier for polymer prepared under air.
Evaluation of the molecular weight distribution and crosslink density of the sol and gel components by intrinsic viscosity measurements
Authors: Kotliar A. M. 
Published: April 2003

AbstractA theory is developed utilizing the partitioning of a partially crosslinked polymer into sol and gel fractions when the initial molecular weight may be expressed as a Schulz‐Zimm or sum of Schulz‐Zimm distributions. The results show that the initial molecular weight distribution may determined from the ratio of the initial and sol fraction intrinsic viscosities. The treatment is also extended to the case where chain degradation accompanies the cure. The theory also permits the evaluation of the gel, sol, and overall crosslink index and coefficient of each component distribution of the polymer as a function of the weight soluble fraction. The components may be the same kind or different kinds of polymers or copolymers. The computed results for a two‐component system clearly show how the differences between the molecular weights or the distributions of the two components influence the difference between the crosslink indices of the two components in the vulcanized gel.
Electron microscope studies on polyethylene and polypropylene
Authors: Bailey G. W. 
Published: April 2003

AbstractReplication techniques for electron microscopy have been used to relate the microstructural characteristics and physical properties of polyethylene and polypropylene. This study included polymer particles and molded pads. The low penetrating power and damage from heating prevents the direct examination of polymer particles in the microscope. Replication, however, has given details of the surface structure of these particles. The spherulitie structure of these polymers in molded form has been determined by replicating etched surfaces. Marked differences in the spherulitic structure of polyethylene and polypropylene have been observed The effect of molecular weight on spherulitic structure of both polymers has also been established.