bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alternative procedures for equilibrium determinations in the ultracentrifuge
Authors: Charlwood P. A. 
Published: June 2010

AbstractProcedures have been described which enable solute concentrations in ultracentrifugal equilibrium to be evaluated more directly than hitherto. The first two variations, quite general in application, involve allowing a layer of solvent to flow on to solution and then following the subsequent rise in concentration of solute in the region just below the meniscus. The observations are made with Rayleigh interference optics. These methods have been tested with substances ranging in size from sucrose to γ‐globulin, and good agreement obtained with accepted molecular weights. Alternative procedures, which depend on increasing the rotor speed after equilibrium is reached, and observing the fall in concentration at the meniscus, are more critically dependent on base‐line reproducibility, but a satisfactory method has been found which is applicable to proteins of molecular weight down to 10,000 or even lower. The validity of this method has been confirmed by means of albumin and γ‐globulin. Not only have procedures for obtaining molecular weights been simplified, but the new techniques can be operated so as to reduce the time taken to reach equilibrium.
Effect of solvent and metal on the formation equilibria of naphthalene and diphenyl anion radical
Authors: Shatenshtein A. I. , Petrov E. S. , Yakovleva E. A. 
Published: June 2010

AbstractThe anion polymerization process is affected by the solvent and the counterion. A study has been made of the quantitative aspects of this effect using as a model reaction the formation of aromatic anion radicals in various ethers. The solvating capacity of the ethers with respect to alkali metal cations has been compared. The stability of the solvate complexes is due more to steric factors than to the electron donor and dielectric properties of the solvent or the polarity of its molecules. The heat of solvation of the cation contributes considerably to the energetics of anion‐radical formation. Therefore the structure of the solvent molecules strongly affects the thermodynamic parameters of the reaction. The solvation mechanism and its role in the ion association are discussed.
Entmischungseffekte in Hochmolekularen Lösungen
Authors: Rehage G. , Möller D. 
Published: June 2010

AbstractCurves of phase equilibria of binary liquid systems at constant pressure are usually obtained from measurements of the cloud points. For high polymer solutions of a poly‐disperse polymer the cloud‐point curve alone is insufficient to describe the phase separation. This could be demonstrated by means of diffusion measurements in the polys‐tyrene‐cyclohexane system that show, below 28°C., a miscibility gap. Therefore, phenomena of phase separation have been examined more closely for this system. Besides cloud‐point curves, phase equilibria have also been measured as a function of the overall concentration, and it was found that the phase equilibrium curves shift with the overall concentration. Generally these curves are not closed. One branch of the equilibrium curve ends at the cloud point of the primary solution; the other one terminates freely. Only when the overall concentration corresponds to the critical concentration is a closed curve of phase separation obtained. The critical point is shifted with respect to the maximum of the cloud point curve to higher concentrations of polymer and is located at lower temperature. The location of the critical point can be derived from the determinations of phase equilibria by osmotic and diffusion measurements, from the volume ratio of the coexisting phases, and from the shape of the cloud‐point curves. The results can be interpreted on the basis of a model of a three‐component system, the solvent, and two polymer species of the same homologous series.
Polymerization by transition metal derivatives. IV. Investigations on the mechanism of butadiene polymerization by rhodium salts
Authors: Dauby R. , Dawans F. , Teyssié Ph. 
Published: June 2010

AbstractData are presented which detail the influence of several kinetical and structural factors on the polymerization of butadiene by rhodium chloride: the influence of catalyst concentration, the different activation energies, the requirements in emulsifier structure and concentration, and the striking influence of some diolefins were successively investigated; polymerization of butadiene and piperylene mixtures was also achieved. Indications concerning the type of this polymerization reaction are inferred from these results, and compared to the usually proposed coordination polymerization mechanisms.
A study of the polymerization of vinylic and diene compounds in the presence of amines
Authors: Margaritova M. F. , Stavrova S. D. , Trubitsyna S. N. , Medvedev S. S. 
Published: June 2010

AbstractInvestigation of the diene and vinylic compounds polymerization initiated by the four systems containing an amine have been carried out: I. benzoyl peroxide–dimethyl‐aniline: II. benzoic acid–dimethylaniline; III. ester–dimethylaniline; and IV. benzoyl peroxide–N‐cetylpyridinium chloride in alkaline condition. Systems II, III, and IV were not known before. Acrylonitrile and methyl acrylate are not polymerized in emulsion when systems II and IV are used. The scheme of interaction between benzoyl peroxide and dimethylaniline (system I) was proved by the spectral investigation. After the analogy of system I the mechanism of reaction for systems II and III was studied. It is proved experimentally that the initiating action of system IV is caused by the transformation of N‐cetylpyridinium chloride (in alkaline condition) into heterocyclic oxacompounds. These products have amine properties that interact with benzoyl peroxide according to the scheme mentioned for system I. On the basis of the proposed mechanism of polymerization initiation, the most probable explanation of the fact that acrylonitrile and methacrylate do not polymerize in emulsion with systems II and IV is given. The activation energy (E) and the predexponent (B) of the Arrhenius equation for methyl methacrylate polymerization are determined. The value of E for all the systems does not change in transition from mass to emulsion. B is by 2–4 orders more in emulsion than that in mass. The explanation of this fact may be given regarding the specific features of initiation with amines. The investigation of the poly(methyl methacrylate) microstructure showed that syndiotactic polymer is formed in the presence of system IV.
Studies in network formation
Authors: Bamford C. H. , Dyson R. W. , Eastmond G. C. 
Published: June 2010

AbstractNetworks are formed when free‐radical polymerization is initiated (thermally or photochemically) by a system consisting of a metal carbonyl or other zero‐valent metal derivative and a polyfunctional halide [e.g., poly(vinyl trichloracetate)] in a monomer for which termination is at least partly by combination. These reactions are suitable for investigations of the formation and also the preparation of networks. In ideal cases the ratio of combination to disproportionation in the termination reaction may be estimated. Some factors which may cause deviation from ideal behavior will also be discussed.
Energy gap and pre‐exponential factor in dark conduction by organic semiconductors
Authors: Eley D. D. 
Published: June 2010

AbstractThe values of Δε and σ0 in the expression σ = σ0 exp {−Δε/2kT} for the dark conductivity σ, tend to increase together over the whole range of organic semiconductors. They fall into a broad band of values confined roughly between two lines given by log σ0 = αΔε + β, the compensation rule, with log σ0 varying from 5 ± 4 for Δε equal to 1.0 e.v., to 14 ± 2 for Δε = 4.0 e.v. The parameter σ0 is related to the mobility of charge carriers μ, and the present paper attempts a broad qualitative discussion of the factors determining μ. The following mechanisms are considered to apply for the origin and motion of the charge carriers in order of increasing Δε and log σ0: (a) intrinsic bulk thermal generation, transport by hopping over intermolecular barriers, (b) bulk generation, with tunnelling through intermolecular barriers going over to, (c) narrow‐band theory, (d) electron or hole injection from the electrodes into the conductivity band for high energy gap substances. It is shown that process (b) can only account for a restricted range of log σ0, from 4 to 1.0, except perhaps for proteins where log σ0 = 4, may reflect a high mobility along the C0 … HN network. Electron injection may give rise to log σ0 = 1.6 and it seems possible that very much higher apparent values may arise from a temperature‐variable adsorbed film, on the semiconductor or the metal. Somewhat scanty evidence suggests that while atactic polymers may have low Δε values they may also have low values of log σ0. Going over to isotactic polymers may lower Δε somewhat, and increase σ0 by a factor of 10. It is suggested that to achieve high mobility values, e.g., μ = 104 cm.2 v.−1 sec.−1, it will be necessary to develop intermolecular bridging by metal atoms or hydrogen bonds, to assist charge‐carrier transport through the crystal.
Electrical properties of some solutions with charge‐transfer interaction
Authors: Wisdom N. E. , Forster E. O. 
Published: June 2010

AbstractLiquid binary mixtures of pyridine‐benzonitrile, pyridine‐trinitrotoluene, and mesitylene‐benzonitrile are expected to exhibit charge‐transfer interaction between the two components. These pairs of compounds have also been found to exhibit maxima in electrical conductance in mixtures as compared with either pure component. Conductance enhancement of as much as 100‐fold has been observed. A very great conductance enhancement was observed in the mixture pyridine‐iodine which has its maximum at the saturation limit of iodine in the solution. The conductance of these solutions has previously been ascribed to ionization. Conductance properties now measured under direct current make this description appear inadequate. Iodine solutions in pyridine have been found to conduct current at low d.c. voltages with no apparent polarization and to sustain the passage of high d.c. currents for long times without change after an initial decline. These results, coupled with those of other earlier workers, indicate that both electronic and ionic conductivity at comparable levels can occur in these solutions. Application of polarizing direct current was found to produce peculiar changes in the capacitative properties of the electrode interface in pyridine‐iodine solutions. The capacity in a parallel‐plate conductance cell was increased by application of a sufficiently great d.c. voltage. The amount of increase depends upon the duration of the voltage application and could be reversed by a reverse voltage.
Low resistivity polyacenequinones
Authors: Mason J. W. , Pohl H. A. , Hartman R. D. 
Published: June 2010

AbstractA group of polyacenequinone radical polymers prepared from a homologous series of heterocyclic acenes and two aromatic anhydrides including mellitic trianhydride were studied in an attempt to produce materials with enhanced conduction. The specific resistivities, thermal activation energies, and energy intervals of these materials are reported. It has been shown that the conductivity of these polymers can be enhanced by about three orders of magnitude by the substitution of heterocyclic acenes.
The meaning of crystallinity when judged by x‐rays
Authors: Statton W. O. 
Published: June 2010

AbstractThis discussion of the variability of polymer x‐ray diffraction patterns tries to show that there is no simple definition of crystallinity when judged by x‐ray diffraction, and that x‐ray crystallinity may differ sharply from judgments of order by other techniques. It is recommended that a clear distinction be made between a measurement obtained from a diffraction pattern and the model which is used to interpret that measurement. Many precise and valuable measurements can be made of the varying aspects of the pattern. These measurements are perfectly valid and, if done in a consistent and verifiable manner, allow one to compare and relate samples having different treatment histories or different physical properties. These relationships are useful and meaningful as such. Difficulties arise from the interpretation of these measurements. The interpretation involves an unfortunate combination of semantics, morphology, and mental models. It is shown that there is no unequivocable interpretation that completely satisfies everyone in this fast‐changing area of study. The cause of this dissatisfaction stems from the simple fact that we do not really know the exact arrangement of the polymer chain from one of its ends to the other. Thus, all models and all interpretations have no meaning beyond being useful concepts. Difficulty comes when we make the mistake of assuming that our models are true pictures of the solid state of polymers. It is hoped that, in time, enough detailed measurements will be obtained so that generalities can be drawn and so that some of the dilemmas of interpretation can be resolved.
Aromatic Poly‐1,3,4‐Oxadiazole Fibers
Authors: Frazer A. H. , Reed T. A. 
Published: June 2010

AbstractThis work has demonstrated the preparation of aromatic poly‐1,3,4‐oxadiazole fibers with a high level of physical properties by the cyclodehydration of undrawn high molecular weight copolyhydrazide fibers and subsequent drawing of the converted fiber to high orientation. The fibers have a high level of thermal stability, good property retention at high temperature testing, and excellent resistance to hydrolytic degradation.
Anisotropic inorganic glass fibers
Authors: Kroenke William J. 
Published: June 2010

AbstractThe synthesis of inorganic glass fibers with oriented structures analogous to those obtained in orientable organic fibers is discussed. Emphasis is placed on the orientation of molecular structure in vitreous silicate fibers. A comprehensive review of the pertinent literature is given. A new research study to prepare anisotropic glass fibers is described. Anisotropic glass fibers of spodumene, LiAlSi2O6, were prepared. However, the anisotropy did not result from the orientation of molecular structure. It is concluded that orientation of molecular structure in vitreous inorganic fibers has not been demonstrated. Anisotropic inorganic glass fibers apparently result from the orientation of crystalline material or some other phase in an amorphous matrix. Several possibilities are given to explain the failure of many investigators to orient molecular structure. Property‐composition relationships of glasses and glass fibers from a simple binary join of a quaternary silicate system are reported. The results of this physicochemical study further supports the importance of phase equilibrium relationships in understanding the structure and properties of glasses and glass fibers. For example, the molar volume‐composition curves exhibited breaks at compositions corresponding to the phase boundary. This suggests a possible dependence of the glass structure on the structure of the primary crystalline phase.
Uniaxial stretching and anisotropy
Authors: Müller F. H. 
Published: June 2010

AbstractAccording to a classic process of Sénarmont, the values of heat conductivity in the parallel and the horizontal stretch directions may be determined if the absolute value for the isotropic condition is known. Changes of stretch speed and stretch temperature in the range above the freezing temperature determine essentially the anisotropy attained. By careful deductions a deformation mechanism of the network is deduced. The relationships which were found here and in connection with other anisotropic properties permit a statement concerning the anisotropy of segments.
Gel permeation chromatography: A study of several factors affecting chromatogram interpretation
Authors: Hazell J. E. , Prince L. A. , Stapelfeldt H. E. 
Published: June 2010

AbstractVarious gel permeation chromatography (GPC) factors affecting chromatogram interpretation have been studied. These include the variation of refractive index with polymer concentration and molecule size, the concentration effect, calibration curve selection, and column deterioration. Several assumptions inherent in GPC interpretation were found to be valid with reasonable limitations. The area under the GPC trace was found to be directly proportional to the weight of dissolved polymer, and the advantages of a method of calculating molecular weight averages by means of area rather than the conventional count height technique have been demonstrated. A synthetic broad distribution standard, composed of a wide molecular‐size range of narrow‐distribution standards, has been proposed for the diagnosis of the condition of GPC column systems.
Gel permeation chromatographic studies of polynuclear aromatic hydrocarbon materials
Authors: Edstrom T. , Petro B. A. 
Published: June 2010

AbstractInformation on the molecular size or weight distribution of pyrogenous raw materials that are complex mixtures of aromatic hydrocarbons has been difficult to obtain. The relatively new technique of gel permeation chromatography (GPC), augmented by the excellent apparatus made available by Waters Associates, offers the opportunity to measure routinely such distribution curves. For years we studied the composition, properties, and thermal reaction mechanisms of complex polynuclear aromatic mixtures such as coal tars, pitches, and heavy petroleum residues. A great deal of work has also been done on pure compounds, with the result that we have accumulated a large number of high‐purity reference aromatic and heterocyclic compounds. We recently determined the elution behavior of more than a hundred polycyclic compounds and also fractionated a variety of thermally produced aromatic residues, using a Model 200 Waters Gel Permeation Chromatograph. Our results with model compounds in tetrahydrofuran solutions indicate that GPC separations occur, not as a function of a single parameter, but as a complex function of molecular size, shape, and polarity. The simplicity of operation and reproducibility of the GPC method will make it extremely useful both as a means of studying the composition of thermal residual products and as a routine screening technique.
Characterization of the chain length distribution of wood celluloses by gel permeation chromatography
Authors: Muller Thomas E. , Alexander W. J. 
Published: June 2010

AbstractCellulosics are similar to synthetic polymers in that they are composed of molecules with a given size distribution. Analysis of the chain length distribution of wood celluloses by gel permeation chromatography (GPC) is a new approach to the characterization of cellulose purity and uniformity. Cellulosics are either nitrated or acetylated prior to analysis in a tetrahydrofuran solution under ambient conditions; a column combination consisting of one each of 107, 106, 105, and 104 A. columns was found to be applicable for a wide range of degree of polymerization (DP). Narrow‐distribution cellulose standards were prepared for calibration studies. Cellulosics analyzed included a 650 and 2000 DP sulfite and a 1075 DP sulfate pulp, cotton linters representing several DP levels, cellulose sponge and fibrous casing, regular and high wet modulus rayon, and microcrystalline cellulose. The extraction of a 650 and 2000 DP pulp with 10 and 18% NaOH at 20°C. was monitored by GPC. Alpha, beta, and gamma portions of cellulose were clearly distinguished; the low‐DP carbohydrate fractions reflect a predictable pattern of chain length distribution. GPC offers advantages in speed, ease of operation, and potential versatility over precipitation or solution fractionation. The method is reproducible.
Polymerization of Styrene with ZrCl4 and ZrCl3 in combination with Al(I‐C4H9)3
Authors: Malhotra S. L. , Deshpande A. B. , Kapur S. L. 
Published: June 2010

AbstractThe polymerization of styrene with two catalyst systems, consisting of Al(i‐C4H9)3 in combination with ZrCl4 and ZrCl3 respectively, has been examined in toluene at 40°C. The catalyst complexes formed in both the systems exhibited the dual effect of accelerating and retarding the polymerization reaction. The rate of polymerization with respect to monomer and the total catalyst concentration was found to be first‐order for ZrCl4‐Al(IC4H9)3 and second‐order for ZrCl3‐Al(i‐C4H9)3. The second‐order dependence on total catalyst concentration in the latter system has been explained on the assumption that the solid catalyst species interact bimolecularly to produce an active center, which takes part in the polymerization reaction. Thus the order with respect to active‐center catalyst concentration remains 1. The overall activation energy of polymerization was 14.74 kcal./mole for ZrCl4‐Al(i‐C4H9)3 and 10.3 kcal./mole for ZrCl3‐Al(i‐C4H9)3. These catalysts exhibited very high rates of polymerization and gave low molecular weight, amorphous polymers.
Participation of imidazole in vinyl polymerization in the absence of radical initiator
Authors: Imoto Minoru , Takemoto Kiichi , Sutoh Hiroyuki , Azuma Heiichi 
Published: June 2010

AbstractA study of radical polymerization in the absence of radical initiator, in which imidazole or imidazyl groups may participate, was made. Polymerization of 1‐vinyl‐2‐methylimidazole was found to proceed easily at low temperatures in the presence of macromolecule, carbon tetrachloride, and water. Kinetic results showed that the polymerization concerned was of radical character, the overall activation energy being estimated to 13.7 kcal./mole. Vinyl polymerization could be also initiated in the presence of imidazole and carbon tetrachloride, and it was found that the polymerization was accelerated by the addition of some macromolecules in the system. The initiation mechanism is discussed.
The synthesis of organic polymers containing hypervalent Iodine
Authors: Livingston H. K. , Sullivan J. W. , Musher Jeremy I. 
Published: June 2010

AbstractPolyesters of the formula have been made from iodosobenzenes + acid anhydrides and from iodobenzene diacetates + dicarboxylic acids. The products do not resemble in solubility behavior the iodosobenzene esters of monocarboxylic acids, the polyesters of convential diols, or the ionic salts of dicarboxylic acids. Under the best conditions they are more stable thermally than iodobenzene diacetate or dipropionate, but none is stable above 200°C. There are indications that polymers containing hypervalent atoms represent a new class of polymers by virtue of their unusual solubility behavior and physical properties.
The addition of carbalkoxycarbenes to stereoregular unsaturated polymers
Authors: Lishanski I. S. , Tsitokhtsev V. A. 
Published: June 2010

AbstractThe reactions of electrophylic addition of carbalkoxycarbenes to cis‐1,4‐polybutadiene and cis‐1,4‐polyisoprene, resulting in the formation of ester‐substituted cyclopropane groups in the polymer chains, were investigated. The conversion of double bonds into the cyclopropane groups is accompanied by a gradual increase in the glass‐transition temperature, tensile strength, and relative elongation at break. Infrared spectroscopic study with the aid of model substances demonstrated that the addition of even unsymmetric carbene does not destroy the stereo‐regularity of the macromolecule. Only a certain transformation of stereoregularity takes place: the cis configuration of the substituents at the carbon‐carbon double bond is replaced with a new type of stereoregularity, characterized by the steric positions of the substituents (including a new one due to the carbene) with respect to the cyclopropane ring. The ozonolysis of modified polybutadiene (30% conversion of double bonds) indicates that the addition of the carbene does not lead to a block distribution of cyclopropane units. The study of competitive reactions of carbene addition showed that the relative rate constant of carbene addition to polymer does not depend on the degree of conversion, and at low degree of conversion is independent of temperature and of the nature of the solvent and is slightly affected by the nature of the catalyst.