bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possibility of a new method of polycondensation
Authors: Turska E. , Dems A. 
Published: June 2010

AbstractIt has been suggested, on the basis of theoretical considerations, that a polycondensation process in solution can be performed with a shifting of the equilibrium by precipitation of the highest fractions of polymer. A series of condensations of polycarbonates was carried out, starting with 2,2‐di(p‐hydroxyphenyl) propane (bisphenol A) and its dichloroformate in two different solvents, for preparation of polymers under equilibrium conditions and under conditions of equilibrium disturbance by an addition of nonsolvent. The molecular weights and distribution functions of both products were determined. It was found that the products obtained by this precipitation polycondensation, in agreement with the theoretical assumptions, have considerably higher molecular weights and molecular homogeneity.
Effect of conditions of glass formation on the density and energy of polystyrene
Authors: Allen Geoffrey , Ayerst R. C. , Cleveland J. R. , Gee Geoffrey , Price Colin 
Published: June 2010

AbstractSamples of fluid polystyrene are converted into the glassy state at 20°C. and 1 atm. pressure by two different routes: (a) by cooling at 1 atm. pressure and (b) by cooling at 1250 atm. and then decompressing. The heats of solution of the samples are determined in toluene at 30°C. The samples are found to have similar enthalpies, although their densities are different. An attempt is made to explain the results in terms of freezing of rotational isomerism at the glass transition temperature.
A study of the elastic deformation of butyl rubber at constant volume
Authors: Allen Geoffrey , Gee Geoffrey , Kirkham M. C. , Price Colin , Padget John 
Published: June 2010

AbstractStress–temperature measurements have been obtained for a butyl rubber strip, held in simple elongation at constant volume. The results have been used to evaluate the energetic component of the total elastic force. The results are compared with similar data, previously reported, for natural rubber, and with data based on indirect estimates of (∂ƒ/∂T)LV. The energetic contribution to the elastic retractive force was found to be of opposite sign to that reported for natural rubber, being small and negative. Dilation coefficients have also been estimated from a subsidiary experiment and the results compared with the predictions of current elasticity theory.
Influence of some friedel‐crafts halides on the polymerization of isobutylene catalyzed by aluminum bromide
Authors: Marek M. , Chmelíř M. 
Published: June 2010

AbstractThe rate of polymerization of isobutylene catalyzed by AlBr3 in the presence of some Friedel‐Crafts halogenides (TiCl4, TiBr4, and SnCl4) in nonpolar medium and in the absence of H2O is much higher than in polymerization catalyzed by AlBr3 alone. The catalytic activity increment decreases in the order TiCl4, SnCl4, and TiBr4. In the system AlBr3TiCl4 the conversion is dependent only on the concentration of AlBr3. A new mechanism of initiation by complex compounds is proposed.
Dependence of the steady‐state compliance on concentration and molecular weight in polymer solutions
Authors: Holmes Larry A. , Ferry John D. 
Published: June 2010

AbstractLow‐frequency dynamic viscoelastic measurements have been made on solutions of four polystyrenes with nearly uniform molecular weights (M) ranging from 19,800 to 860,000, in three chlorinated diphenyls covering a wide range of viscosities, at concentrations (c) up to 0.35 g./ml. The steady‐state compliances (Je), derived from these measurements, are proportional to M/c for M ≥ 82,000 and c ≥ 0.08 g./ml., and their magnitudes agree with the prediction of the Rouse theory. For M = 19,800, Je is abnormally small, and the frequency dependence of the viscoelastic properties also deviates from both Rouse and Zimm theories, suggesting that the molecular length is too small for applicability of the Rouse‐Zimm model. At decreasing concentrations deviations from M/c proportionality occur for two reasons: the magnitude of Je shifts from the Rouse prediction to the Zimm prediction, and the concentration dependence shifts from inversely proportional to directly proportional. Both changes are attributed to the disappearance of coil interpenetration with decreasing concentration, and in qualitative agreement with this interpretation they appear to be correlated with the product of concentration and intrinsic viscosity when data for different molecular weights are compared.
The conformational transformation in macromolecules of atactic poly‐β‐vinylnaphthalene
Authors: Eskin V. E. , Serdjuk I. N. 
Published: June 2010

AbstractLight scattering, viscosity, and dilatometric studies of poly‐β‐vinylnaphthalene solutions indicate the conformational transformation in the macromolecule near 50–60°C. This transformation separates two states of the macromolecule, characterized by the different temperature coefficients of the partial specific volume dv̄/dT. The transformation is accompanied by a decrease of the optical anisotropy of the macromolecules. These phenomena can reflect disordering of the regular short sequences in the macromolecule or overcoming the barrier to the rotation of their naphthalene groups. It is possible to admit the coexistence of these two mechanisms in some cases.
Mechanical dispersions of polar polymers sensitive to the presence of low molecular weight substances below the glass transition temperature: The influence of the side‐chain length and the end hydroxyl group of swollen poly(methacrylic acid) esters
Authors: Janáček Josef 
Published: June 2010

AbstractCharacteristic features of mechanical low‐temperature dispersions which arise in polymers with polar groups are studied. In poly(methacrylic acid) esters swollen to various extents by low molecular weight substances of different types the influences of side‐chain length and of OH and CH3interchange in the side‐chain endgroup are compared. In the case of poly(diethyleneglycol methacrylate) two types of dispersion were found: the temperature of one was dependent, the other independent, of the concentration and composition of the low molecular weight substances. An attempt at interpretation is given.
Glass transition and relaxation in the amorphous phase of isotactic polypropylene
Authors: Wada Yasaku , Hotta Yasuko , Suzuki Ryuji 
Published: June 2010

AbstractTwo breaks are observed in the temperature dependence of both specific volume and logarithmic retardation time in isotactic polypropylene, indicating two glass transitions. In correspondence with two transitions, two loss peaks are found in isochronal measurement of dynamic mechanical loss at 3 Mc./sec. The lower transition Tg1 is assigned to the amorphous phase, which is rich in atactic chains (A1 phase); the upper transition Tg2, to the amorphous phase, rich in isotactic chains (A2 phase). The lower transition shifts to high temperature with room temperature aging time owing to recrystallization in the A1 phase, accompanying the increase in flexural stiffness. The upper transition shifts to high temperature through annealing above 100°C. on account of recrystallization in the A2 phase. The situations of the two phases in the spherulite of polypropylene are suggested by variations of long period with annealing temperature and birefringence with aging time. The effects of molecular weight on Tg1 and Tg2 and on impact strength and brittle point are discussed.
Application of two‐phase mechanical model to viscoelastic properties of blends of high‐density and low‐density polyethylene
Authors: Okamoto T. , Takayanagi M. 
Published: June 2010

AbstractWith a two‐phase mechanical model the complex dynamic tensile modulus of blends of high‐density and low‐density polyethylene were calculated from viscoelastic properties of the components by a high‐speed computational technique. Agreement of the calculated values with the experimental values was satisfactory. For a given volume fraction of one component the mixing state of blends can be expressed by only one parameter, which is affected by crystallizing conditions. Differential thermal analysis of the blends was made to supplement information on the mixing state. Results of high‐speed tensile tests are discussed on the basis of the mixing state of the blends.
The role of crystallinity of polymer in the adhesion between chlorinated isotactic polypropylene and isotactic polypropylene
Authors: Aoki Yoshihide 
Published: June 2010

AbstractChlorinated isotactic polypropylene (CIP) has good ability to bond to isotactic polypropylene. The bonding strengths between the two polymers are affected by the preparation conditions of CIP, chlorine contents of CIP, isotacticity of raw polymer, and conditions of making joints. However, these factors are related to the crystallinity of CIP, and it is considered that the crystallinity of CIP is responsible for the bonding strengths between the two polymers. By using x‐ray diffraction and electron diffraction measurement the role of crystallinities of these polymers in bonding are discussed.
Patterns in terpolymerization
Authors: O'Driscoll Kenneth F. 
Published: June 2010

AbstractA program has been written and used to compute vinyl terpolymer compositions as a function of monomer feed. The results are presented as a set of triangular contour maps. Six hypothetical monomers of typical reactivity have been investigated in their 20 possible terpolymerizations. With respect to composition it is concluded that variation in electronegativity is less important than the variation in resonance stabilization commonly encountered in vinyl monomers. The approach of these terpolymer systems to azeotropic behavior is graphically derived from the contour maps. Loci of partial azeotropy are drawn for a number of systems. No true ternary azeotropes have been observed.
Calculation of relative reactivity ratios from composition–conversion data through use of a computer
Authors: Montgomery Donald R. , Fry Charles E. 
Published: June 2010

AbstractThe classical methods of determining relative reactivities of monomers to free‐radical polymerization, namely polymerization to low conversion of several initial monomer compositions, purification of the polymers formed, compositional analysis, and fitting of the data to the differential form of the copolymer equation by any of several techniques, suffer from several problems. In particular, the various methods of treating the data assume no change in monomer composition at low conversion. This is a reasonable approximation when the reactivities are similar, but when they are grossly different (e.g., r1/r2 > 100), even 2 to 3% conversion can cause highly significant shifts in the monomer composition, particularly for those points where the more reactive monomer is present in relatively small amounts. Illustrations of the potential magnitude of these errors are provided. A computer program has been written that utilizes one of the integrated forms of the copolymer equation and thereby includes the conversion corrections in the treatment of the data. This procedure should yield more precise r1 and r2 values than the classical techniques, with less direct computational effort on the part of the investigator.
Particle size analysis of polymer latexes by light scattering. II. Computer analysis
Authors: Wallace T. P. , Kratohvil J. P. 
Published: June 2010

AbstractAngular light scattering by polymer latex dispersions is used for determining the particle size distribution. The analysis consists of calculating the experimental Rayleigh ratios Vθ,v and Hθ,h for vertically and horizontally polarized components of scattered light. Corrections for solvent scattering and reflection effects are also applied. The polarization ratios are calculated for each concentration and extrapolated to infinite dilution, thereby correcting for multiple scattering at finite concentrations. The polarization ratios at infinite dilution are converted to polarizations and compared with theoretical values corresponding to anticipated possible size distributions. A topographical map of the root‐mean‐square deviations on a plot of the size parameter versus the distribution parameter is obtained. This map gives an indication of the uniqueness of the fit over the range of theoretical values searched. Data obtained on a Dow polystyrene latex are used for an example analysis. Details of the computer routine are discussed. Similar programs exist for the size distribution analysis and determination of number concentration of spherical particles utilizing the angular absolute specific intensities.
On semicontinuous emulsion polymerization
Authors: Gerrens Heinz 
Published: June 2010

AbstractSemicontinuous emulsion polymerization of styrene and methyl acrylate with a feed of either monomer or monomer emulsion has been investigated. Feeding rate Rz and initial charge were varied, reaction rate Rp, degree of polymerization Pζ, number of latex particles N, and particle size distribution were measured. With both monomers Rp and Pζ are independent of Rz as long as Rz is large enough to maintain the saturation value of monomer concentration [M] in the latex particles. If [M] falls below this value a steady state is reached with monomer feed as well as with emulsion feed, Rp equals Rz, and Pζ increases with increasing Rz. Taking the Smith‐Ewart theory as a basis for calculation, the propagation rate constant kp was determined for both monomers in the steady state. Emulsion feed produces less, i.e., larger particles than monomer feed or batch polymerization, the overall charge being kept constant. Emulsion feed gives a narrower particle size distribution, and the initial rate of polymerization and N are proportional to the initial charge, if formation of new latex particles during the emulsion feed can be avoided. If not, particle size distribution is broadened and can eventually become even broader than with the other two methods.
Electron microscope investigations on fibril formation
Authors: Bittiger H. , Husemann E. , Kuppel A. 
Published: June 2010

AbstractIn order to gain a better understanding of the formation and structure of natural fibrils as found in cellulose, chitin, etc., transitions from coils into fibrillar solid structures were investigated with some suitable polymers as model substances. Preliminary precipitation experiments of cellulose out of solution yielded no clear results. With cellulose tricarbanilate, rod‐like single molecules or single crystals with folded chains are formed at low concentrations and fibrils of different diameter with preferentially extended chains at higher concentrations. The results are discussed in terms of nucleation and chain stiffness. In the amylose iodine complex the transition from coils to fibrils with a uniform diameter of 40 Å could be shown. Alcohol complexes yielded only single crystals. With mannan and cellulose tribenzoate ribbon‐like fibrils are found. Trimethyl cellulose finally formed fibrils with a uniform diameter of 200 Å and a helical periodicity of 200 Å along the chain. On the basis of the above‐mentioned results a modification of Manley's model of the cellulose elementary fibrils is proposed and discussed in relation to properties and biosynthesis of cellulose.
On the biosynthesis of cellulose in higher and lower plants
Authors: Marx‐Figini M. 
Published: June 2010

AbstractKinetic experiments on cotton cellulose and cellulose from the alga Valonia show, that the degree of polymerization during the biosynthesis of the secondary wall is independent of conversion and reaction conditions. During the whole synthesis period it remains constant at a DPw ∼ 13,000 for cotton and 16,500 for Valonia, respectively. Fractionation experiments indicate complete uniformity of the degree of polymerization at every stage of the biosynthesis. This means that the biosynthesis of secondary wall cellulose for both higher and lower plants must be a structure‐controlled process and not a time‐controlled one. Contrary to this evidence the synthesis of primary wall cellulose takes place by another mechanism which results in a lower average degree of polymerization and a nonuniform distribution. Both, secondary wall and primary wall synthesis can occur simultaneously. Recent results of electron diffraction experiments on native cellulose and fibrils, precipitated from the original material, seem to indicate that crystalline and supermolecular structure of the cellulose fibrils are not determined by the biosynthetic process.
Interaction of cellulose with liquid water: Accessibility determined from thermal expansion
Authors: Neal J. L. , Goring D. A. I. 
Published: June 2010

AbstractThe apparent specific volumes in water of glucose and of three different types of cellulose were measured at 3° intervals between −5 and 25°C. The extent of the destructuring of the liquid water by the carbohydrate surface was determined from the thermal expansion near 0°C. If glucose in aqueous solution was taken to be 100% accessible, the accessibilities of cellophane, wood pulp and cotton linters ranked 50, 29 and 20 per cent respectively. These values are considerably lower than accessibilities measured by isotope exchange techniques. Possible reasons for this discrepancy are discussed.
Preparation and properties of grafted membranes for desalination. Part I
Authors: Hopfenberg H. B. , Kimura F. , Rigney P. T. , Stannett V. 
Published: June 2010

AbstractStyrene grafting to cellulose acetate has been studied in an attempt to synthesize a cellulose acetate reverse osmosis membrane with improved resistance to compaction. The studies reported here involved grafting to homogeneous cellulose acetateE‐398‐3 Eastman Chemical Company.
film and evaluation of the tensile creep and water sorption behavior of the resulting grafts. The grafting studies involving homogeneous cellulose acetate films indicated that the kinetics of grafting were rate controlled by monomer diffusion to the growth site. By controlling the ratio of styrene to pyridine (monomer/swelling agent) and controlling total dose, reproducible and predictable grafts were prepared. The tensile creep rate of wet cellulose acetate–styrene grafts decreases sharply with increasing styrene content up to 40% styrene and then decreases more slowly as styrene content is further increased. The creep rate of grafts containing 40% styrene is 7.5 times lower than that of ungrafted cellulose acetate. Unsteady‐state water vapor sorption experiments revealed that the equilibrium water content was decreased as a consequence of grafting although water diffusivities were increased or decreased as percent graft was increased according to the method and level of grafting. Water sorption deviated slightly from Henry's law behavior. The water diffusivity, as measured by the rate of sorption, was concentration dependent, decreasing with increasing water concentration. Membrane constants for water transport (defined as D 1C1 g‐cm/cm2‐sec) could be increased or decreased as a consequence of grafting.
High temperature superconductivity
Authors: Ginzburg V. L. 
Published: June 2010

AbstractThe critical temperature, Tc, for all presently known superconductors does not exceed 21'K. This fact obviously limits the range of applications of superconductivity in technology in a very fundamental way. On the whole, the reason why the value of Tc for “ordinary” superconductors would not exceed 20‐40oK is fairly well understood. At the same time, there apparently could exist high temperature superconductors for which Tc would reach liquid air temperature or even room temperatures. Possible means of producing high temperature superconductors are considered in this article which is based on the review published in Contemporary Physics, 9, 355 (1968), but includes also some new material. Special attention is paid to what can be called the exciton mechanism of superconductivity and its application to systems of the “sandwich” type and metallic conductors with layer structures.
Solid state possibilities of porphyrin structures
Authors: Adler Alan D. 
Published: June 2010

AbstractThe structures and chemical, physical, and biological properties of porphyrins are generally described. The problems inherent in their employment in physical studies are summarized. A semiconduction study of Langmuir films of ms‐tetraphenylporphin showing a cubic thickness dependence in resistance is detailed. Possibilities for employing these materials in organic superconduction research are presented.
The molecular weight dependence of lower and upper critical solution temperatures
Authors: Delmas G. , Patterson D. 
Published: June 2010

AbstractThe molecular weight dependence of the Lower Critical Solution Temperature in polymer solutions has been derived using the Prigogine smoothed potential cell model. Satisfactory agreement is obtained with experimental results for a number of systems. It is found that the new structural term (or equation of state term) in χ introduced by the Prigogine theory accounts for the LCST. Any difference in chemical nature between the polymer and solvent molecules may be largely ignored. The structural term also has an effect on the molecular weight dependence of the familiar Upper Critical Solution Temperature. It is predicted that fractionation of a polymer could be improved by choosing a solvent for which the UCST and LCST were separated by only a small temperature interval. Fractionation at the LCST should not be more efficient than at the UCST.
Simulation of the brownian motion of macromolecular chains in solution
Authors: Monnerie Lucien , Geny Francois 
Published: June 2010

AbstractThe first study by the Monte‐Carlo method of the dynamical comportment of macromolecular chains in solution was made by Verdier and Stockmayer. We have adapted the method proposed by these authors to the case of a chain built in a tetrahedral lattice with volume‐excluded‐condition, for analyzing the brownian motion of a macromolecular in solution. This is done by submitting the chain to a very great number of elementary motions of 1, 2, 3 or 4 bonds.
The lifetimes and intensities of positron states in several solid polymers as an indication of structure
Authors: Stevens J. R. , Edwards M. J. 
Published: June 2010

AbstractPositrons which penetrate and become trapped in polymeric solids form states which display complex annihilation time spectra. The average lifetimes and intensities of the posiltron states can be obtained from the exponentially decaying components of the time spectra. Usually three components can be resolved for solid polymers; with long, Intermediate and short average lifetimes. Experimental results of lifetimes and intensities for positrons annihilating in trans 1–4 polybutadiene, polyethylene, polyethyleneterephthalate are used to conclude that the intensity can be associated with regions of short range order and the intermediate lifetime and intensity with regions of long range order. It is also concluded that for both regions of long range and short range order there is a tightening of the microstructure in the polymer as the amount of long range order increases and/or molecular weight decreases.
On the general theory of polymer absorption at a surface
Authors: Hoeve C. A. J. 
Published: June 2010

AbstractPrevious theoretical work dealt with polymer adsorption in which the adsorbed segments (trains) interact in the surface layer only. In this work the treatment is extended to Include also interaction between the loops dangling in solution. Fortunately, the excluded volume effects for adsorbed polymer chains are found to be small. Therefore an approximate treatment is possible that leads to equations that govern polymer chains under a wide variety of conditions.