bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase separation in polymer solution
Authors: Dobry A. , Boyer‐Kawenoki F. 
Published: April 2003

AbstractThe phase separation in solutions of high polymers in the same solvent (technically known as incompatibility) has been studied for fourteen high polymers (cellulose, vinyl, and acrylic derivatives) dissolved in thirteen solvents. The influence of solvent, concentration, molecular weight and constitution of the macromolecules has been studied for 78 mixtures: the results are represented in triangular diagrams. Incompatibility appears to be the normal situation, compatibility the exception. Moreover, in cetain cases the exception may be only apparent. Phase separation is discussed in its relation to osmotic pressure, solubility, and the isomorphism of the molecules. Phase separation furnishes new means—useful at leat for technical research—of measuring the molecular weight of macromolecules. It is a simple and rapid procedure.
Use of perbenzoic acid in analysis of unsaturated compounds. III. Results of determinations of external double bonds in synthetic rubbers
Authors: Kolthoff I. M. , Lee Thomas S. , Mairs Mary Anne 
Published: April 2003

AbstractEmulsion polybutadiene and emulsion copolymers of butadiene and styrene (e.g., GR‐S) contain about 20% external double bonds. A systematic study has been made of the effects of temperature, type of “catalyst,” percentage conversion, microgel formation, and varying styrene content of emulsion copolymers of butadiene and styrene. None of these variables affects the amount of external double bonds. Copolymers of butadiene with styrene and a small amount of acrylonitrile, and of butadiene with various monochlorostyrenes and dichlorostyrene, all prepared by emulsion polymerization, were found to contain the same amount of external double bonds. Emulsion polyisoprene and the emulsion copolymers of isoprene and styrene (75:25) were found to contain only 13 and 5%, respectively, external double bonds. Polybutadiene, butadiene—styrene copolymer, and polyisoprene, all prepared by sodium—catalyzed, bulk polymerization at 50°C., contain 50–60% external double bonds. The amount of external double bonds in sodium polybutadiene is strongly dependent on temperature of polymerization. More external double bonds are formed at low temperatures than at high temperatures. The amount of external double bonds in sodium butadiene—styrene copolymer and in sodium polyisoprene is nearly independent of temperature in the range 30–50°C. A sample of sodium polyisoprene was found to contain 36% internal double bonds and 64°C external double bonds. From an analysis of the reaction—rate curve it was concluded that approximately 40% (absolute percentage) of the external double bonds were formed by 3,4 addition and 24% by 1,2 addition. The rates of reaction of the cis—and trans—forms of natural rubber are very nearly the same, the cis—form reacting slightly more rapidly.
Kinetic treatment of emulsion polymerization
Authors: Corrin M. L. 
Published: April 2003

AbstractThe kinetics of the emulsion polymerization of styrene are developed on the basis of the Harkins' theory of reaction loci. Only that portion of the reaction is considered in which essentially no polymer nuclei are formed. Agreement is obtained between experiment and theory when the reaction in the monomer‐polymer particle is considered three‐halves order with respect to monomer. This treatment is further substantiated by the fact that the concentration of monomer in the polymer, when a separate monomer phase exists, is correctly predicted by the kinetic theory. The activation energy for the polymerization of styrene in the monomer‐polymer particle is calculated as 22,600 calories per mole. A dilatometer for the precise determination of monomer conversion rates in emulsion polymerization is described.
Heat conduction and molecular structure in rubberlike polymers
Authors: Rehner John 
Published: April 2003

AbstractIn this paper experimentally determined values are reported for the thermal diffusivity (k) of various rubberlike polymers. Corresponding values of the thermal conductivity (W) can be computed from the well‐known relationship, W = kpcp, where p and cp denote the density and specific heat at constant pressure of the composition. Measurements were made on (a) pure gum stocks prepared with natural rubber, Butyl (GR‐I), Perbunan 18, Perbunan 26, Perbunan 35, Buna S (GR‐S), polybutadiene, neoprene GN, polyisoprene, Silastic 160, and Silastic 180; (b) pure gum stocks of the first five rubbers listed under (a) containing in addition 20 parts of a hydrocarbon softener (Bardol), based on 100 parts by weight of the polymer; and (c) the Bardol stocks containing in addition 54 parts of carbon black (Kosmobile 66). From measurements of the rate of change of temperature within a rubber sphere suddenly subjected to a change in its surface temperature, it was found possible to determine the dependence of k on temperature. A satisfactory definition of the “mean” temperature of a sphere under these conditions is described. In a discussion of the effect of chemical composition and structure on heat conduction, the bearing of hindered rotation, cross linking and branching and interatomic bond strength on the results is pointed out. Values are derived for certain other properties of some of the polymers, including their characteristic Debye temperatures, specific heats at constant volume, flexibility of the main valence chains, compressibilities, and sound velocities.
Polymeric amides from diamines and dibasic acids
Authors: Coffman D. D. , Berchet G. J. , Peterson W. R. , Spanagel E. W. 
Published: April 2003

AbstractMethods for the preparation of fiber‐forming polymeric amides from polymethylene diamines and polymethylene dicarboxylic acids, and the stabilization of these polymers against viscosity changes, have been described. The variation in physical properties, particularly melting points, of the polymeric amides with increasing chain length of the components has been discussed.
Recent ultracentrifugal investigations on cellulose and cellulose derivatives
Authors: Jullander Ingvar 
Published: April 2003

AbstractA review is given of physicochemical studies on cellulose and cellulose derivatives made during the years of World War II at the Institute of Physical Chemistry, Uppsala, Sweden. Emphasis has been laid on the principles of the subject and the review deals essentially with some investigations on nitrocellulose by the present author. An outline of the problems of the cellulose chemistry of today serves as an introduction. The principles of molecular weight determinations from Svedberg's equation are briefly mentioned, and the difficulties in the extrapolation of sedimentation constants to zero concentration are discussed. The problem of what sort of average molecular weight is obtained from Svedberg's equation is treated subsequently and methods for determination of distributions from combinations of osmotic and sedimentation experiments described. A table comparing five different sorts of average molecular weights for a numbe of nitrocelluloses is discussed.
Rapid method for sampling latices in bottle polymerizations in which positive gage pressure is maintained in bottle by a monomer
Authors: Williams D. E. , Johnson W. F. 
Published: April 2003

AbstractA procedure is described for the rapid sampling of latex during emulsion bottle polymerization. The equipment used consists of a hypodermic needle with holder, an adapter, a balance sensitive to one milligram, and dishes for determination of total solids. The equipment is used in connection with Paracon or Buna N self‐sealing caps. The procedure is very simple, rapid, and may be used in obtaining samples for total solids. mercaptan analysis, or gel and viscosity determinations.
Solubility, diffusion, and permeation of gases in gutta‐percha
Authors: Van Amerongen G. J. 
Published: April 2003

AbstractThe permeability of vulcanized gutta‐percha membranes to gases was determined in relation to the rate of diffusion and solubility. The measurements, as functions of temperature, with four gases were taken below and above the melting point of gutta‐percha. The evidence is that the rates of permeation and diffusion increase sharply at approximately 45°C., due to melting of the gutta‐percha. In the same way, although to a lesser degree, the solubility of the gas likewise increases at the melting point. The activation energies of permeation and diffusion with the heat of solution were computed from the temperature function of those quantities. It follows from the results that crystallization of the elastomer reduces the gas‐solubility, the diffusivity, and the permeability—and increases the activation energy of diffusion. The interpretation of this high activation energy of diffusion is that, because of the crystallization, the macromolecules of the membrane adhere so firmly that greater energy is required to admit the gas molecules.
Heats of polymerization of acrylic acid and derivatives
Authors: Evans Alwyn G. , Tyrrall E. 
Published: April 2003

AbstractThe heats of polymerization of acrylic acid, methyl acrylate, methacrylic acid, and methyl methacrylate have been measured. Values for the heat of polymerization of unstrained polymer molecules have been calculated, and the low heat of polymerization of methyl methacrylate has been attributed to the presence of steric hindrance in the polymer molecule.
Course of acetylation and deacetylation reactions of cellulose fibers. I. Optical and swelling properties
Authors: Vermaas D. , Hermans P. H. 
Published: April 2003

AbstractA description is given of the preparation, birefringence, and swelling capacity of a series of microscopically homogeneous, partially acetylated cellulose model filaments with an acetyl content varying from 0 to 2.3 acetyl groups per glucose residue, and obtained either by acetylation or by deacetylation. A higher degree of acetylation of these artificial fibers could not be attained without destruction of the fiber. The same holds true for native ramie fibers. The swelling was studied in water, acetone, and methanol. The degree of swelling of the filaments plotted against acetyl content yields entirely different curves for the acetylation and the deacetylation series. These curves can be readily explained by the hypothesis that the intercrystalline (so‐called amorphous) portion of the fiber substance is more accessible to the esterification and saponification reactions and is affected earlier than the crystalline portion. The birefringence of the acetylation series shows but a small—although apparently real—difference from that of the saponification series.
Products of initiation, retardation, and inhibition of peroxide‐induced polymerization of styrene
Authors: Cohen Saul G. 
Published: April 2003

AbstractThe inhibition by quinone and the retardation by hydroquinone derivatives of the peroxide‐induced polymerization of styrene have been studied. We have examined the end products of benzoyl peroxide at 74°C. in benzene, alone and in the presence of quinone and hydroquinone ethers, and in styrene in benzene, both with and without quinone. Absorption spectra have been obtained after several time intervals for some of these systems and for the benzoyl peroxide‐styrene‐benzene system, alone and in the presence of alkyl substituted hydroquinones. Consideration of the end products indicates that quinone interferes but little with the normal initiation process, particularly at low (0.0045 M) concentrations. Inhibition appears to result largely from reaction between the inhibitor and newly initiated chains. Quinone is converted to products—some of which are phenolic—which do not absorb in the visible. The phenolic products may react with the peroxide or radicals from it, interfering with the normal initiation reaction. The hydroquinone derivatives, which are retarders for the polymerization, appear to be converted initially to quinonoid products. The reactions in inhibition and retardation are discussed.
Preparation and properties of rubberlike high polymers. IV. Correlation between structure and properties of elastomers derived from dienes
Authors: Salomon G. , Koningsberger C. 
Published: April 2003

AbstractThe correlation between structure and properties of elastomers prepared from dienes, natural rubber, gutta‐percha, as well as those of some significant derivatives of natural rubber, are discussed. The similar influence exerted by methyl groups on the brittle point, elastic recovery, and permeability to gases is demonstrated and separated from the effect caused by insertion of —CH2—CHR— groups in straight‐chain polybutadiene, which takes place during copolymerization or 1,2 addition. The preponderant influence of an unbranched‐chain structure on tensile strength at elevated temperatures and in the swollen state is illustrated. Complex compounds with silver nitrate provide further evidence for the particular symmetry of the natural rubber chain: They are rein forcing agents for synthetic elastomers. The brittle points of hydrochlorides from natural rubber, gutta‐percha, and polyisoprene are compared with those of polyvinyl compounds. Correlation between the structure of molecular units in a polymeric paraffin derivative and its elasticity is pointed out.
Deformation mechanism of cellulose gels. III. Changes in orientation upon drying
Authors: Hermans P. H. , Hermans J. J. , Vermaas D. , Weidinger A. 
Published: April 2003

AbstractThe orientation of model filaments stretched to various extents in three different states of swelling was investigated by quantitative x‐ray analysis before and after drying. The change in orientation upon drying was found to be either very small or zero. This shows that the crystallites do not even approximately follow the rules of affined transformation which would require a very considerable increase in orientation on drying. There must be an entirely different mechanism which prevents the crystallites from being dragged along with the matrix in which they are embedded.
Deformation mechanism of cellulose gels. IV. General relationship between orientation of the crystalline and that of the amorphous portion
Authors: Hermans P. H. , Hermans J. J. , Vermaas D. , Weidinger A. 
Published: April 2003

AbstractTen series of model filaments with increasing orientation and swelling degrees ranging between 16 and 1.2 were prepared from three viscoses containing 4, 6, and 10.5% cellulose. Their birefringence was measured and their x‐ray diagrams taken and quantitatively evaluated in order to determine the over‐all orientation of the iiber substance and that of the crystalline portion. It is shown that a general relation exists between the orientation of the crystallites and that of the entire fiber substance which is the same in all fibers stretched in the swollen state. Once the birefringence of a filament is known, the orientation factor of its crystallitee can be computed without taking an x‐ray photograph. From the data further evidence can be derived to the effect that the orientation of the crystallitm cannot be accounted for by the theory of affined deformation.
Free energy, heat, and entropy changes accompanying the sorption of water vapor by proteins
Authors: Davis S. , McLaren A. D. 
Published: April 2003

AbstractRecently published measurements of moisture sorption vs. relative humidity for a series of proteins have previously been analyzed in a way which permits calculation of the integral free energy of sorption for any final pressure of water vapor. The present paper is an extension of these calculations to additional proteins from the list reported by Bull; integral and differential free energies and integral and differential heats and entropies of sorption have been calculated as functions of the amounts of water sorbed onsilk, wool, egg albumin (unlyophilized and heat coagulated), salmine, collagen, gelatin and lactoglobulin (crystalline and lyophilized). All calculations are referred to saturated water vapor as the standard state. Some of the proteins show positive net differential entropies of sorption at low vapor pressures. It is postulated that the partial molal entropy of sorption is made up of two terms, a negative entropy of sorption proper and a positive entropy of solution. Partial rearrangements of the protein chains at the beginning of the sorption process would effectively be an incipient solution which would give rise to a positive partial molal entropy of sorption if the second term is greater than the first. This speculation has support in the fact that the differential entropy of salmine, which dissolves at a relative vapor pressure of about 0.7, begins to show positive values at a relative vapor pressure of 0.35.
Polymerization of styrene in soap solutions
Authors: Frilette V. J. , Hohenstein W. P. 
Published: April 2003

AbstractA turbidimetric method has been developed for determining the styrene content in water and soap solution. The solubility of styrene in distilled water was 0.022% while in 2.0% potassium oleate solution it was 0.65 to 0.88%. The course of the polymerization of a saturated solution of styrene in 2% potassium oleate was followed by a colorimetric analysis based on reaction with dilute potassium permanganate. The rate of polymerization decreased rapidly after 50% conversion. The activation energy was estimated to be 17,000 kcal., somewhat less than in solution. The molecular weight of the polymer produced was 200,000. Occasional erratic results were ascribed to possible influence of various amounts of air sealed in the polymerization mixtures.
Aroyl disulfides as promoter‐modifiers for copolymerization of butadiene and styrene
Authors: Frank Robert L. , Blegen James R. , Deutschman Archie 
Published: April 2003

AbstractBenzoyl, anisoyl, veratroyl, p‐bromobenzoyl, p‐phenylbenzoyl, p‐benzoylbenzoyl, p‐methylsulfonylbenzoyl, p(N,N‐dimethylsulfonamido)‐benzoyl and ‐naphthoyl disulfides are promoters of the emulsion copolymerization of butadiene and styrene, but exhibit little effect on the polymer properties. Furoyl, phenyl, p‐chlorophenyl and p‐bromophenyl disulfides are neither promoters nor modifiers.
Reduction activation of emulsion copolymerization of butadiene and styrene: The benzoyl peroxide‐ferrous pyrophosphate system
Authors: Marvel C. S. , Deanin Rudolph , Overberger C. G. , Kuhn Beryl M. 
Published: April 2003

AbstractThe German redox system of emulsion polymerization of butadiene and styrene has been found to be very sensitive to exact details of experimental procedure. Soap may be substituted for the alkanesulfonate used by the Germans; it is then unnecessary to add ferric laurate to the system.Careful investigation of the soap‐emulsified mixture leads to the conclusion that 0.25 parts of benzoyl peroxide, 0.50 parts of ferrous sulfate heptahydrate, and 3.0 parts of sodium pyrophosphate decahydrate were the optimum concentrations of the essential ingredients for polymerization of an emulsion of 75 parts of butadiene and 25 parts of styrene in 200 parts of water and 5 parts of Procter and Gamble soap Flakes (S.F.) at 30°. At very low iron concentration the addition of a reducing agent as “booster” was beneficial; for this purpose sorbose can be replaced by fructose or, less satisfactorily, by a number of other reducing agents.
Photochemistry of proteins. III. Quantum yield for inactivation of soybean trypsin inhibitor by ultraviolet light
Authors: Katchman B. , McLaren A. D. 
Published: April 2003

AbstractCrystalline soybean trypsin inhibitor has been inactivated by ultraviolet light (λ2537 Å.) with a quantum yield of 0.0088 based upton loss of ability to inhibit the action of trypsin on casein. Inactivation involves a “one‐hit” process.
Initial rate of polymerization of styrene
Authors: Goldfinger G. , Lauterbach K. E. 
Published: April 2003

AbstractThe initial rate of polymerization of highly purified styrene in bulk has been measured dilatometrically at 38.4, 56.4 and 70.1°C. For conversions up to one per cent a well‐reproducible rate was observed for samples handled in complete absence of atmospheric gases. For samples saturated with air an equally reproducible, though higher rate, was observed initially. The duration of this higher rate decreases with increasing length of storage between saturation and measurement. After polymerization at higher rate, the sample continues to polymerize at the rate observed for the air‐free samples.
Use of cobalt complexes as activators in emulsion copolymerization of butadiene and styrene
Authors: Marvel C. S. , Inskeep G. E. , Dearborn Robert J. , Saunders J. H. , Johnston H. W. , Shepherd Douglas A. , Deutschman A. J. , Damman Joseph A. , Oppegard A. L. 
Published: April 2003

AbstractCobalt complex compounds exhibited varying degrees of activation and retardation in butadiene‐styrene‐soap emulsion polymerization systems at 20–50°C. An accompanying effect was the wasting of modifier, particularly by large concentrations of activator. The most active complexes for use with dodecyl mercaptan were those in which the cobalt was coordinated with two or more negative groups other than thiocyanate, and in which the neutral coordinated groups were not ethylenediamine.
Low‐angle scattering in polymers
Authors: Kratky O. 
Published: April 2003

AbstractThe diffraction of x‐rays at small angles occurs in the form of sharp interferences (discontinuous) or as diffuse scattering (continuous). The first effect is observed mostly in crystallized proteins and in protein fibers. New measurements on collagen were obtained by the author in collaboration with Sekora, and independently by Bear. Using these data, an attempt has been made to establish a connection between the orders of the intense reflections belonging to the giant period of 642 Å. along the fiber axis and the frequency of the amino acid residues (frequency is defined as the number of amino acid residues of a particular kind among the total 220 residues which constitute the basic period of 642 Å. along the fiber axis). With the exception of the most abundant amino acids, glycine and proline, it is possible to assign to each frequency a corresponding reflection, and vice versa. This indicates a high degree of regularity in the arrangement of these amino acid residues. But the relationships are apparently more complex than would be expected from the Bergmann‐Niemann rule. For example, the frequencies of 11 and 20 (corresponding to an identical residue at each 220/11 or 20th location or at each 220/20 or 11th location, respectively) appear to play a role. Fundamentally, however, we arrive at a picture in accordance with the comprehensive investigations and results of Astbury. It has not yet been possible to arrive at a detailed structure.In the theory of diffuse low‐angle scattering, it is necessary to distinguish between densely packed systems and dilute systems. For the latter case, molecular scattering is computed in accordance with Debye's theory of scattering. It is shown how size factor and form factor may be separated. Both of these properties can be approximated without making previous assumptions, though the accuracy of the form factor determination can be improved appreciably if the particle weight is known. Preliminary trial measurements on solutions of edestin, tobacco mosaic virus, and hemocyanin are in agreement for the first two substances mentioned. The measurements on insulin indicate associated particles that deviate strongly from spherical shape (however, these measurements were made at an earlier date and require checking). Those on hemocyanin indicate an association similar to a string of pearls, a result which probably explains the contradiction of the substance appearing as spherical particles under the electron microscope, while exhibiting flow birefringence when in solution. When this method is developed further it will undoubtedly become a valuable tool for the determination of form and size of polymer molecules and other colloidal particles.