bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of artificial nucleating agents on polymers structure and properties
Authors: Kargin V. A. , Sogolova T. I. , Rapoport N. Ya. , Kurbanova I. I.
Published: June 2010

The possibility of forming and stabilizing a supermolecular structure and properties of polymers by adding small amounts of dispersive solids to them is shown. Some problems concerning the mechanism of actions of artificial nucleating agents are discussed.
Eine Neue Rechnung zur Röntgenkleinwinkelstreuung an Fadenmolekulen. Die Ermittlung der Segmentgestalt
Authors: Kirste R. G.
Published: June 2010

The scattering function of chain molecules in the x‐ray small‐angle range depends on the shape of the segments. For instance, one obtains quite different scattering curves from solutions of isotactic and syndiotactic poly(methyl methacrylate) (PMMA) in the same solvent. From several models of statistically coiled polymer chains, the scattering functions were calculated with the aid of the Monte Carlo method. Again, a considerable difference between the functions obtained is observed. If the curvature of a thread varies statistically from one point to another, the mean curvature can be determined from the scattering function. A suitable measure for the mean curvature is the persistence length; i.e., the chain length of which the end points form an angle whose average cosine is equal to 1/e. If the curvature is nonrandom, one can detect this from the scattering function. From the position and amplitude of the waves that appear one can determine the degree of preferred curvature. The mean curvature of a thread need not be connected strictly with the radius of gyration or with the statistical chain element of the coil. In real molecules the x‐ray optical center line is essential for the scattering behavior. On syndiotactic PMMA in solution a preferred curvature has been found. It can be interpreted by assuming the presence of helix fragments in the coils.
Some aspects of the polymerization in the solid state
Authors: Berlin Al. Al. , Trofimova G. M. , Pakhomova L. K. , Prut E. V. , Barkalov J. M. , Kuzmina S. S. , Enikolopyan N. S. , Goldanskiǐ V. I.
Published: June 2010

The formal kinetics of the solid‐state polymerization allowing for the specificity of the solid state as such (the long times of diffusion, anisotropy, and inhomogeneity of the solid phase) was considered. All possible changes in inhomogeneity of the system in the course of polymerization were taken into consideration. The applicability of this kinetic scheme was shown for radiation‐induced post‐polymerization and cationic polymerization of trioxane in the solid state. The occurrence of chain transfer to polydioxalane in cationic solid‐state polymerization of trioxane was proven.
The crystallization of high molecular weight poly‐(tetramethylene oxide) and related polymers
Authors: Trick G. S. , Ryan J. M.
Published: June 2010

Using dilatometric techniques, detailed investigations have been made of the crystallization and melting behavior of high molecular weight poly(tetramethylene oxide), low molecular weight poly(tetramethylene oxide) glycol, and a high molecular weight copolymer prepared by the chain extension of the glycol. The degree of crys‐tallinity is expressed as a function of time and temperature. Using fast melting rates, the apparent melting point of the bulk polymers has been found to depend on both the temperature of crystallization and the level of crystallization allowed to develop before melting. Extrapolation gave an estimated equilibrium melting point for high molecular weight homopolymer of about 51°C. The highest experimentally observed melting point was 43°C. Visual observations have been made on crystallization of these materials from dilute solution (⪕3%) in toluene. Under some experimental conditions crystallization was accompanied by gel formation while under other conditions two distinct and separable phases were formed. Measurements were made on the dissolution temperatures of solutions crystallized under different experimental conditions.
Bonding in Macromolecular Crystals
Authors: Livingston H. K.
Published: June 2010

Crystallographic data show that many inorganic crystals are inorganic polymers in which chemical bonds extend across the boundaries of the crystallographic unit cell. Crystals with metallic bonds form space‐network (3‐dimensional) polymers, as do ionically bonded crystals unless there is a great disparity in ionic radii. Covalently bonded inorganic crystals may form space‐network, sheet (two‐dimensional), or linear polymers. Organic macromolecular crystals have only been fully characterized for those cases in which bonding is covalent and the structure is linear. Where ionic bonding is involved, organic macromolecules probably form “scrambled salt structures.” The relation between crystal structure and polymer structure for macromolecular crystals can be characterized by the ratio between c, the number of atoms per crystallographic unit cell, and p, the number of chain atoms per polymer repeat unit. The ratio c:p is 1:1 for many space‐network polymers, including most crystals of low symmetry. For linear polymers c:p is usually greater than 1:1. Factors contributing to the higher ratio are the number of chains passing through the unit cell and the number of substituent atoms that are attached to the polymer chain. In considering macromolecular crystals, the distinction between bond types (e.g., ionic versus covalent) is more significant than the distinction between chemical types (e.g., organic versus inorganic). Some of the most challenging problems exist in characterizing the crystals of macromolecules with intermediate bond type. Examples are gold iodide, where both covalent and metallic character must be recognized, and nylon, where hydrogen bonding is important.
Polymerization and spinning of PBI
Authors: Conciatori Anthony B. , Chenevey Edward C. , Bohrer Thomas C. , Prince Arthur E.
Published: June 2010

The polybenzimidazole polymer prepared by Vogel and Marvel from diaminobenzidine and diphenyl isophthalate has been scaled up and dry spun from DMAc for a full‐scale evaluation of the fiber for end uses requiring thermal stability. A process has been developed for the purification of diaminobenzidine suitable for making high molecular weight PBI. A nitrogen sweep process run at atmospheric pressure was substituted for the difficult vacuum cycle of the literature polymerization. Polymers prepared by this process had equivalent molecular weight, better solubility in DMAc, and less gel structure than those prepared in vacuum. Inherent viscosities of 0.75–0.85 and plugging values >1.0 in 97% sulfuric acid have been obtained consistently. An increase in the temperature of solutioning in DMAc was required to dissolve the higher molecular weight fractions of the polymer. Solutioning at 230°C. under pressure dissolved 95–100% of the polymer. 1–2% lithium chloride was required to prevent solution instability or “phasing‐out” of the polymer in DMAc. PBI fiber was dry spun from DMAc into a hot nitrogen atmosphere and steam stretched in tandem with spinning. Yarn was pressure washed on perforated bobbins with hot water, air dried, and oven dried prior to drawing. Drawing was performed at 520°C. and a 2:1 draw ratio. Final physical properties average 5.0 g./den. tenacity, 23% elongation, and 115 g./den. initial modulus. Small‐scale spinning of a high molecular weight fraction of polymer (ηinh = 1.2) gave fiber properties superior to those obtained from the same whole polymer (ηinh = 0.72). The bulk polymer and amorphous fiber were crystallized with phenol under pressure. An oriented and crystalline fiber was obtained by treatment of oriented fiber under pressure with phenol and water.
Continuous silicon carbide filaments
Authors: Hough Ralph L.
Published: June 2010

Cubic silicon carbide continuous filaments are prepared by vapor deposition from suitable gases upon tiny resistance‐heated tungsten wires. Homogenous deposits are prepared whenever the silicon is derived from silicon tetrachloride by utilizing hydrocarbons containing a carbonyl functional group such as acetone as the carbon source. If halogenated organosilanes are used, those with the higher halogen content produce superior deposits. The silicon carbide is near theoretical density, is highly resistant to air oxidation, and is of nominal 75–100 μ in diameter. The modulus of elasticity measures above 60,000,000 psi. Current tensile strength range above 100,000 psi with potential strengths over 400,000 psi. These filaments are intended for use as reinforcements in high strength, structural plastic composites with improved air oxidation resistance.
Preparation of graphite fibers from polymeric fibers
Authors: Ezekiel Herbert M. , Spain R. G.
Published: June 2010

The preparation of high tensile strength, high modulus of elasticity graphite fibers from polymeric fibers was investigated. Several polymeric yarns were subjected to TGA to 1000°C., the carbon yields of which indicated that polyacrylonitrile, an aromatic polyamide, and an aromatic polyimide were promising graphite precursors. Commercially available rayon‐derived carbon yarns from three sources were graphitized by a continuous process. Application of stress to the carbon yarns during graphitization was found to stretch the fibers and to induce high tensile strength and high moduli in the products. The increase in tensile strength and modulus were shown to be related to the degree of orientation along the fiber axis by x‐ray diffraction.
Molecular and supramolecular paracrystalline structure of linear synthetic high polymers
Authors: Hosemann Rolf
Published: June 2010

The paracrystalline state is a quite common state for all kinds of matter. Paracrystalline distortions arise, for instance, in solid‐solution crystals. From x‐ray scattering they are experimentally observed in polyethylene and polyethylene oxide. Values of g of about 2% for the mosaic blocks in single crystals and of 3% for the ultrafibrils in bulk material are found. The ultrafibrils of Lupolen 6001 have a very uniform thickness of n X 90.7 A., where n = 1, 2, 3, and build up manyfold superstructures. The (hh0) “netplanes” at the boundaries of all observed mosaic blocks both in single PE crystals and in hot‐stretched material fluctuate statistically by 0.6 A., hence are no longer planes. The structure in the grain boundaries is discussed. Measurements of the diamagnetic susceptibility give evidence of three types of conformation, α, β, and γ, which play an important role in the different superstructures.
Some problems in the X‐ray diffraction and electron microscopy of keratin fibers
Authors: Woods H. J.
Published: June 2010

X‐ray diffraction and electron microscopy studies of keratin “stained” with heavy metal have advanced our understanding of the supramolecular structure of keratin fibers. Problems arise in these investigations, the most serious of them being that thin‐section electron microscopy does not give much information about untreated material and that the intramicrofibrillar structure is sufficiently disordered to make it impossible to check with quantitative accuracy any theoretical evaluation of the x‐ray diffraction in terms of model structures. Nevertheless, a picture is emerging of the kind of structure necessary to satisfy the two kinds of experimental data. The major unresolved diffraction problem is associated with the long‐range periodicities which lead to meridional or near‐meridional reflections. These are known to be affected by a number of chemical treatments which, ideally, are specific for certain amino acid residues. Since individual protofibrils (groups of two or three polypeptide chains) can be examined by electron microscopy, it is possible that an integrated attack on the problem using the three disciplines (protein chemistry, electron microscopy, and x‐ray diffraction) may produce important advances.
The orientation of molecules in fibers
Authors: Statton W. O.
Published: June 2010

This paper reviews various methods for measuring molecular alignment and various interpretations of results. It is emphasized that exact knowledge of the molecular arrangement in fibers is non‐existent; many interpretations and models exist but none of them are accurate representations of the true state. Deformation causes reorganization at all of these dimensional levels: the segments of the basic molecule, the aggregate called a crystallite, the crystalline‐amorphous entity, the single crystal lamella, the larger aggregation called spherulite. Each of these levels may have its own deformation behavior and may be involved differently in the results from a particular experimental technique. No single technique describes the alignment of all molecules for their entire length. Most techniques represent an average orientation, whereas the distribution of orientation is ideally sought. These techniques were reviewed: x‐ray diffraction, birefringence, infrared dichroism, magnetic anisotropy, softening, shrinkage tension, dichroic dyestuffs, stress optical coefficient, sonic velocity, differential thermal analysis, and light scattering. The most useful data have been those for the relationship of orientation to physical properties. The seldom recognized increase of Tg by orientation is emphasized. Speculation is made of the morphology associated with stress‐crystallization and the role of dislocation motion in deformation.
The high‐sulfur proteins of α‐Keratins: Their relation to fiber structure and properties
Authors: Gillespie J. M.
Published: June 2010

Unrelated keratins, such as horn and fur, have markedly dissimilar physical properties, and these variations can exist, although to a lesser extent, between two non‐identical samples of the same keratin. Each keratin examined contains low‐sulfur proteins which bear resemblance to each other and this is in accord with the concept that all α‐keratins contain microfibrils of similar size and structure. However, these keratins can differ greatly in the type and amount of high‐sulfur protein which they contain. It is reasonable then to assume that variations in physical properties between keratins must be due, at least in part, to differences in the proportion or properties of the matrix (high‐sulfur protein) which surrounds each microfibril. High‐sulfur proteins have been found in every α‐keratin examined with horns containing as little as 7% by weight and furs as much as 45% by weight of these proteins. By the supplementary feeding to sheep of cysteine or methionine administered into the abomasum, the high‐sulfur protein content of wool can be increased by 50%. This opens the possibility of the control of fiber properties by the dietary manipulation of sheep.
Evaluation of analytical gel permeation chromatography columns packed with porous silica beads
Authors: Page Madeleine Le , Beau R. , De Vries A. J.
Published: June 2010

Spherical porous silica beads, a new material manufactured by Péchiney‐Saint‐Gobain, has been studied as a packing material for gel permeation chromatography columns. By choosing an appropriate pore size distribution, supports of good selectivity have been obtained. Universal calibration curves have been determined by plotting retention volumes for various polymer standards [polystyrene, poly(vinyl chloride), and dextran] against the logarithm of the product Mw[n]. The nature of the polymer and the solvent (tetrahydrofuran or water) does not appear to affect much the calibration curve for a given support. Column efficiency was evaluated by measuring zone spreading as a function of column length, flow rate, and average particle diameter. The experimental results show that reproducible, uniform, and inherently efficient columns of good selectivity can be prepared with silica beads of average diameter, larger than 100 μ. In view of the observed decrease of efficiency loss at higher flow rates and of the relatively low pressure drop, porous silica beads appear to be a promising packing material for high‐speed analytical gel permeation chromatography.
The mechanism of radiation‐induced ionic polymerization
Authors: Hayashi Koichiro , Okamura Seizo
Published: June 2010

The radiation‐induced ionic polymerization of bulk styrene has been studied under extremely dry conditions. It was found that the rate of propagation increases with more rigorous drying of the monomer, and this effect is accompanied by a change in the exponent n for the doserate dependence of rate of polymerization from n values near unity to 0.6. A mechanism involving bimolecular termination of free ions is thereby indicated. The kp value is estimated to be >3.5×106 1. mole−1 sec.−1 by the electrical conductivity method. The large kp value is explained as a characteristic ion dipole reaction for the free‐ion propagation process and by the considerable freedom of the growing end of a free ion in comparison with that of an ion pair end. Similar results were observed with isobutene, nitroethylene, and cyclic monomers such as trioxane and BCMO. The initiation mechanism induced by the ion radical formed by radiation was confirmed by direct observation with ESR, optical absorption, and mass spectrometry.
The reaction of chain transfer with rupture and modification of heterochain polymers
Authors: Davtjan S. P. , Irjak V. I. , Rosenberg B. A. , Enicolopjan N. S.
Published: June 2010

Processes of modifying polymers are compared, the modifications being made directly during polymer formation in the presence and in the absence of a chain‐transfer reaction with rupture (CTR reaction). The processes are those of copolymerization and give polymers with definite terminal groups. The CTR reaction during polymer formation independently of other elementary processes completely determines after all the distribution of macromolecules as to both size and composition (in the case of copolymers) and also as to terminal groups (if the polymer is formed in the presence of chain‐transfer agents). In the modifications considered the distribution of modifying additives in the polymer has an especially important role. It is shown that the CTR reaction leads to an increased yield of polymers with useful sequences of structural units. The CTR reaction in the modification of heterochain polymers completely determines the polymer properties that depend on distribution of modifying additives.
Optically active polyamides, polymers from α‐, β‐, γ‐, and ϵ‐Methyl‐ϵ‐Caprolactam
Authors: Overberger C. G. , Parker Gordon M.
Published: June 2010

Optically active polyamides were prepared from β‐, γ‐, and ϵ‐methyl‐ϵ‐caprolactam, and optically active α‐methyl‐ϵ‐caprolactam was racemized under polymerization conditions. The optically active polymers in solution and in the solid state were examined for the effect of an optically active carbon on the polymer structure and for changes occurring with the change in location of the optically active center on the polymer backbone. Significant differences were observed among these polyamides, in ease of formation, degree of crystallinity and melting points or softening ranges, infrared spectra, and optical activity in solution.
Synthesis of polymeric indigo
Authors: Liogońkii B. I. , Zelenetskii A. N. , Berlin A. A.
Published: June 2010

Polymeric indigo (PI), a representative of a new class of “vat polymers,” was prepared by oxidative polycondensation of diindoxyldicarb‐oxylic acid and a tetraacetic derivative of diindoxyl. Polyindigo can be transformed to soluble leuco forms, is essentially thermostable, and has semiconducting properties.
Relative Reactivities of Elements of Polymer Chains, Determined by Their Transformation in Solution, Initiated by Dicumyl Peroxide
Authors: Rado R. , Šimúnková D.
Published: June 2010

The kinetics of the degradation of polyisobutylene and polystyrene initiated by dicumyl peroxide in the undiluted state and in solvents of different composition has been studied. The degradation process was experimentally investigated by a viscosimetric method. The kinetic expression of the degradation carried out in such a way gives also the relative values of the rates of reaction of hydrogen atoms in polymers with radicals of the peroxide used, determined for polyisobutylene, polyethylene, polystyrene, and n‐heptane. The reactivities of CH3, CH2, and CH groups, calculated from the results, are in the ratio 1:6:17; the methine hydrogens of the polystyrene benzylidene groups are three times more reactive than hydrogens of the analogous ethylidene groups of polypropylene. The reactivity of the low molecular weight model substance, n‐heptane, is about 30% greater than would be expected from the sum of the reactivities of its elements determined from polymers. This fact suggests that the ability of macromolecules to enter into substitution reactions with free radicals is less than that of low molecular weight analogues.
Polymerization of vinyl chloride in the presence of chain transfer agents
Authors: Kolínský M. , Ryska M. , Lím D.
Published: June 2010

To elucidate the chemical factors influencing the structure of radical poly(vinyl chloride) the effect of chain transfer agents was studied. With decreasing degree of polymerization P the association capability of the polymer slowly decreases. From the region of about P = 250 down the aggregation abruptly increases independently of the chain transfer agent used. The influence of copolymerization with a small amount of vinyl acetate under the conditions given was followed. The stereoregularity of the products formed and the content of foreign groups were determined. The results were correlated with kinetic data. The conditions of formation of poly(vinyl chloride) with a regular structure and a strong ability to aggregate are discussed.
Synthesis and thermal stability of benzimidazole–aromatic imide copolymers
Authors: Kurosaki Toshikazu , Young Philip R.
Published: June 2010

Four kinds of aminophenylbenzimidazoles were synthesized by reacting 3,3′‐diaminobenzidine and 1,2,4,5‐tetraaminobenzene with p‐ and m‐aminobenzoic acid. These four diamines were polymerized with pyromellitic anhydride and 3,3′,4,4′‐benzophenone‐tetracarboxylic anhydride. Polymers of highest intrinsic viscosities were obtained by adding the powdered anhydrides to dimethylsulfoxide solutions of the amines. Permutation of the above monomers yielded eight different benzimidazole–aromatic imide copolymers which were cast from solutions and cured at 280°C. to 300°C. in air. The polymer films show excellent thermal stability.
High‐temperature degradation of polymers. Thermal gradients and diffusion‐controlled reactions
Authors: Jellinek H. H. G. , Kachi H.
Published: June 2010

Poly(methyl methacrylate) films of various thicknesses were degraded in stainless‐steel closed reaction vessels and in closed quartz vessels of different wall thicknesses over a range of temperatures from 350 to 500°C. Above certain temperatures monomer formation becomes diffusion‐controlled. The degree of this diffusion control depends on the type of reaction vessel, wall thickness of the vessel, and film thickness. The rates of monomer formation for a definite percentage of conversion depend on the thermal history of the polymer sample. Thus, for the same percentage of conversion and the same film temperature the rates can become quite different.
Rheological behavior of concentrated polystyrene solutions in good and in poor solvents
Authors: Tager A. A. , Dreval V. E. , Lutsky M. S. , Vinogradov G. V.
Published: June 2010

By means of capillary and rotational viscometers flow curves of concentrated polystyrene solutions were obtained. The measurements were carried out at concentrations of 0.184–0.573 volume fraction of polymer, shear stresses of 3 × 101−3 × 106 dyne/cm.2, shear rates of 1 × 10−6 to 1 × 106 sec.−1, and temperatures of 15–120°C. It was shown that both the deterioration of quality of solvent and the decrease of temperature increase the initial Newtonian viscosity and facilitates attainment of the upper Newtonian viscosity. The influence of the chemical nature of the solvent on the viscosity of the solution appeared stronger in the higher regions of shear stress and shear rate, that is, at the transition from the initial Newtonian viscosity to the upper Newtonian viscosity. This regularity was explained by the presence of two kinds of structural formation in concentrated polymer solutions: bundles of polymer chains and fluctuational networks composed of the bundles. The bundles can be dissociated in different degrees by good and poor solvents. The paper considers the application of some of the reduction methods to the experimental data.
Stress–strain relationships of unswollen and swollen elastomers
Authors: Yanai H. S.
Published: June 2010

The stress–strain relationships of crystallizable and noncrystallizable elastomers were determined in unswollen and swollen states. As expected, if a noncrystallizable elastomer is stretched and held at a fixed length, the subsequent swelling in a solvent decreases the stress as the elastomer is swollen. On the other hand, if a crystallizable elastomer is stretched to a medium extension at which some crystallization has occurred and held at that length, the subsequent swelling in a suitable solvent increases the stress as the elastomer is swollen and the crystallites are dissolved by the solvent. The phenomena are explained in terms of the network swelling and the crystallization and melting induced by the applied stress and the swelling solvent.
Anionic polymerization of unsaturated chlorine‐containing monomers
Authors: Erussalimsky B. , Mazurek V. , Krasnoselskaya I. , Ghassan‐zade V.
Published: June 2010

The polymerization of chloroprene (CP), vinyl chloride (VC), vinylidene chloride (VDC), and 2,3‐dichlorobutadiene, initiated by Li and Mg catalysts, has been studied. The kinetic schemes for the cases of CP–metal alkyl and VC–LiBu are given, and some of the reaction constants are calculated. New catalytic systems formed through the interaction of LiBu with Bu3Mg2I and with BuI are described. The main feature of the processes initiated by these systems is the decrease in the relative importance of the termination reaction as it was established for CP, VC, and VDC. A mechanism of the catalytic systems investigated is proposed.
The direction of propagation in carbohydrase‐catalyzed polymerizations
Authors: Hehre Edward J.
Published: June 2010

The schema of Ebert and Patat for enzymic polysaccharide synthesis from sucrose, by anhydroglycose insertion at the reducing end of the growing chain, cannot be supported. Basically it presents a propagation direction opposite to that expected from the process that can be considered the mode of all carbohydrase action, i.e., transglycosylation or glycosyl–hydrogen interchange. Direct examination by pulse labeling shows that the latest glucose units added during amylopolysaccharide formation from sucrose by amylosucrase are, in fact, located in the outer nonreducing chains. The insertion schema further assumes that segmer transfer is a capacity of the sucrose polymerizing enzymes. Evidence of this is lacking. Dimer transfer is not observed when the theoretically appropriate trisaccharides (maltosyl‐ or isomaltosyl‐β‐D‐fructofuranoside, levanbiosyl‐α‐D‐glucopyranoside) are incubated respectively with amylosucrase, dextransucrase, or levansucrase. Moreover, the dextranyl moiety of low molecular weight sucrose‐ended dextran (dextranyl‐β‐D‐fructofuranoside) is neither polymerized by dextransucrase nor transferred to the anomeric OH of fructose, in contrast to the glucosyl moiety linked similarly. The insertion schema, finally, restricts the number of propagation sites to one per polymer molecule. This also lacks an experimental basis. The transglycosylation model allows for the possible occurrence of multiple foci of propagative activity in individual molecules, which may account for their extremely rapid growth to a high degree of polymerization.
Propriétés de l'acétate de polyvinyle linéaire et branché en solution bi‐ et tridimensionnelle
Authors: Jaffé J. , Ruysschaert J. M.
Published: June 2010

The properties of branched and linear poly(vinyl acetate) are studied in the spreading of monomolecular films at the air–water interface. The two polymers are homodisperse and have the same molecular weight. It is confirmed that the spreading's support has the properties of a very poor solvent.

Measurements of superficial pressure and superficial viscosity, for very low concentrations when the interactions polymer‐support must only be considered, permit to obtain a quantitative definition.

The ratios of the superficial specific viscosities, of the second superficial virial coefficient and the temperatures are compared with the same ratios obtained in solutions for branched and linear polyvinyl acetate. According to these results, the superficial method may be considered as an interesting instrument in the study of branched polymers.
Cyclo‐ and cyclized diene polymers. XV. Cationic copolymerization of isoprene with styrene
Authors: Krauserová H. , Kössler I. , Matyska B. , Gaylord N. G.
Published: June 2010

Cationic copolymerization of isoprene with styrene in n‐heptane or benzene medium leads to copolymers in which isoprene units are linked to form cyclic segments. The kinetic course depends on the nature of the solvent. Relative monomer reactivity ratios determined in both solvents show that in n‐heptane styrene is the more reactive monomer, the reverse being true in benzene. It is concluded that the presence of benzene molecules favors the addition of isoprene to the active complex or to the cation. The extremely low value of the r1r2 product is not believed to indicate the tendency to alternation and is attributed to the special mechanism of cycloaddition. Polymerization of isoprene which leads to an equilibrium stage with low or zero reaction rate can be re‐established when styrene is added to the system in equilibrium. In this case formation of block copolymers results. The copolymerization is accompanied by an intensive chain transfer with polymer and the formation of highly crosslinked products. Grafted or crosslinked polymers can also be prepared by the polymerization of isoprene in the presence of polystyrene. Copolymers of isoprene with styrene prepared cationically in benzene are of low molecular weight. Higher amounts of isoprene units in copolymers result in an increase of the melting temperature.
The theory of the self‐sharpening effect of boundary gradient curves in sedimentation analysis of polymers
Authors: Poddubnyi I. Ja. , Grechanovskii V. A.
Published: June 2010

The effect of the hydrodynamic interaction between macromolecules in a Θ solvent on the experimental curves is discussed. This interaction is shown to result in a narrowing of the sedimentary boundary (self‐sharpening effect). Parameters determining the magnitude of the self‐sharpening effect have been established. A general equation, which takes account of diffusion, polydispersity, and the self‐sharpening effect on experimental sedimentation curves has been developed. It is shown that for polymer–solvent systems characterized by strong hydrodynamic interaction (determined by the value S0 – S) the experimental curves become narrow almost just after the formation of the sedimentary boundary. A rigorous method of polymer polydispersity determination has been developed, which is based on the compensating diffusion broadening due to self‐sharpening at a given time tc after the formation of the boundary: tc = (Dfrac12;/φω2x0ΔS)2. The time tc for cis‐1,4‐polybutadiene samples of different molecular weights in an ideal solvent mixture has been calculated.
Effect of temperature on piezoelectricity in wood
Authors: Fukada Eiichi , Date Munehiro , Hirai Nobuyuki
Published: June 2010

The piezoelectric modulus of Wood has been measured in the temperature range of −170°C. to +150°C. The kind of wood investigated is hinoki (Chamaecyparis obtusa Endl.). When a sinusoidal stress is longitudinally given to the thin plate specimen, the polarization is produced in the direction perpendicular to the surface of the plate. It has been found that the piezoelectric modulus generally increases with the rise of temperature. However, the modulus‐temperature curve shows discontinuous changes in slope at about −80, 30, and 130°C. These temperatures seem to be associated with transitions in amorphous regions of cellulose and other macromolecules in wood. Gamma‐ray irradiation up to 1.7 × 108 rad causes little variation in the magnitude and the temperature dependence of the piezoelectric modulus. Treatments with liquid ammonia, sodium hydroxide, and ethylenediamine result in a large increase in the magnitude and the temperature dependence of the piezoelectric modulus. The crystal lattices of cellulose II and III are more favorable than that of cellulose I for producing the piezoelectric effect.
Relationship between stereostructure of poly(vinyl alcohol) and its acetalization reaction
Authors: Shibatani Kyoichiro , Fujii Kiyoshi , Ōyanagi Yasuji , Ukida Junji , Matsumoto Masakazu
Published: June 2010

By measurement of peak areas in the dioxymethylene region of high‐resolution NMR spectra of partly formalized poly(vinyl alcohol), PVA, the relationship between tacticity of PVA, rate of formalization reaction, and stereochemical configuration of poly(vinyl formal) was studied. Formation of cis‐formal at an isotactic part of a PVA chain is faster than that of trans‐formal at a syndiotactic part. When the reaction is allowed to continue for a long period, the migration of formal rings from syndiotactic to isotactic portions is observed. Partition of formal rings in partly formalized PVA into cis and trans types is discussed in connection with the tacticity of original PVA and degree of formalization. The rate‐determining step of acetalization reaction is also discussed.
New polymers derived from dihydrazine derivatives
Authors: Takahashi Hiroshi , Hasegawa Masaki , Okada Akira
Published: June 2010

New types of N‐substituted polyureas and N‐substituted polysemicarbazides were prepared from the reaction of 1,6‐bis‐[α(or β)‐N‐substituted hydrazino]hexane or 4,4′‐bis‐[β‐N‐substituted hydrazino]diphenyl methane with diisocyanate. These hydrazine derivatives were derived from dihydrazine with diphenyl carbonate or phenyl benzoate. Successful results were obtained in solution polymerization. The polymers are soluble in N,N‐dimethyl formamide, m‐cresol, and hexamethyl phosphoramide, and show relatively high polymer melting temperature. The reactivity of the carbophenoxy group in the polymer side chain was also examined.
ESR studies of polypropylene with different stereospecificities
Authors: Kusumoto Naoshi
Published: June 2010

Isotactic (IPP), syndiotactic (SPP) and atactic (APP) polypropylene were irradiated by gamma‐rays of 60Co at −196°C., and ESR spectra were subsequently examined in conjunction with the stereospecificities and regularities of the polymers. All the polymers showed similar broad spectra at −196°C. APP gave a well‐resolved sextet spectrum above −40°C., which vanishes at about −10°C., owing mainly to its glass transition. IPP and SPP showed different spectra characteristic of their stereospecificities in the crystalline phase above room temperature. It was concluded that the radical species at room temperature are identical in IPP and SPP except for their steric conformations. The coupling constants of protons of the radical of SPP were determined in comparison with those reported for IPP, assuming the allyl‐type radical CH(CH3)CHCH(CH3)CHCH(CH3)2. The decay process of the radicals was found to be a second‐order reaction. The study shows that only the spectrum of IPP exhibits a singlet when the sample is kept at room temperature in vacuum. The spectrum of SPP is easily saturated compared with that of IPP when the power of the oscillating magnetic field is increased.
N‐substituted styrene–maleimide interpolymers
Authors: Pratt R. J. , Strand R. C.
Published: June 2010

The classic method of converting anhydrides to imides by reaction with ammonia or amines was applied to low molecular weight co(styrene–maleic anhydride) polymers. In preference to direct‐melt, solid–gas, and solid–liquid reactions, an in situ esterification step with amyl alcohol as solvent and reactant was employed for the imide synthesis. In this manner the reaction system was kept fluid, homogeneous, and selective even with difunctional reactants. This procedure was applied to ammonia, octadecylamine, dimethylaminopropylamine, and monoethanol‐amine. The maleimide copolymer resulting from ammonia was converted to hydroxmethyl, chloromethyl, pyridyl chloromethyl, aminoethyl, dimethylamino, and glycidyl derivatives.
Grafting of poly(vinyl acetate) to granular corn starch
Authors: Brockway C. E.
Published: June 2010

Vinyl acetate forms graft copolymer with granular corn starch when initiated by peroxide plus activator in an aqueous slurry of the starch. Grafting efficiencies are less than 50%, much lower than realized with either acrylonitrile or methyl methacrylate under comparable conditions. Grafting efficiency can be raised by including with the vinyl acetate a minor amount of comonomer. Among the comonomers used, methacrylic acid and methyl methacrylate were particularly effective for increasing the grafting of vinyl acetate.
Chemical modification of wheat gluten proteins and related model systems
Authors: Wall J. S. , Friedman M. , Krull L. H. , Cavins J. F. , Beckwith A. C.
Published: June 2010

Selected chemical modifications of wheat gluten protein were conducted to provide basic information on its chemistry and behavior and to improve it for various applications. Wheat gluten protein was subjected to acid‐catalyzed methanolysis of the numerous side‐chain amides of the glutamine residues. The formation of γ‐glutamyl methyl ester groups decreased the solubility of the protein in polar solvents and enhanced it in less polar solutions. Reduction and reoxidation of the disulfide bonds of cystine in gluten caused marked changes in the conformation and intermolecular crosslinking of the proteins. The rate and products of reoxidation were determined by concentration of the protein, nature of the solvent, and amino acid composition of the proteins. The rate of alkylation of polar functional groups of proteins by α,β‐unsaturated compounds such as acrylonitrile was shown to be determined by the pH, polarity, steric environment, and relative nucleophilicity of the specific group. According to these observations it may be possible to establish conditions in which sulfhydryl groups on proteins could be preferentially alkylated or extensive alkylation of other groups could occur. The polymerization grafting of methyl acrylate to gluten was accomplished by anionic mechanisms in a homogeneous system containing aprotic solvents. Grafting was found to occur on most functional groups.
Some properties of collagen modified by the Mannich reaction
Authors: Feairheller S. H. , Taylor Maryann M. , Gruber Helen A. , Mellon E. F. , Filachione E. M.
Published: June 2010

The Mannich reaction of several aliphatic active hydrogen compounds with formaldehyde and collagen, the principal protein of animal hides and skins, was investigated. These reactions were all carried out under extremely mild conditions: aqueous solutions buffered at about pH 4 and at or slightly above room temperature. The sites of the reaction in the protein were found to be the lysine, hydroxylysine, and histidine residues. The extent of the reaction and the effects of various factors on the reaction also were determined. Although polyfunctional active hydrogen compounds were used, there was little indication that cross‐linking had taken place. With acetylacetone and methyl acetoacetate the evidence indicated that dihydropyridines were formed. The extent of such a reaction was calculated from ultraviolet absorption data and from the amino acid analysis of the chemically modified proteins. The results of the two methods were in extremely good agreement with each other. With malonic acid a product was formed that offers potential for practical application. A number of new compounds were found in the hydrolyzate of the product. Two of these were identified as N ϵ‐(β‐carboxyethyl)‐L‐lysine and Nϵ, Nϵ‐bis(β‐carboxyethyl)‐L‐lysine.
Acryloylpolystyrene
Authors: Leavitt F. C. , Rubens L. C.
Published: June 2010

Reactive pendant acryloyl groups can be substituted for hydrogen in the para position on the phenyl groups in polystyrene. Acylation of the polymer with β‐chloropropionyl chloride in solution is followed by dehydrochlorination, yielding acryloylpolystyrene (AP resins). Both the molecular weight of the polymer and the number of acryloyl groups per polymer molecule can be varied over wide limits. AP resins dissolve readily in vinyl aromatic monomers and copolymerize readily with them to yield clear, colorless, infusible polymers with good strength properties. The rate of copolymerization of these mixtures increases with both the number of acryloyl groups and the amount of acryloylpolystyrene in solution. These resins are similar in polymerization behavior and strength properties to the unsaturated polyesters used for production of glass‐reinforced plastics. In addition, the acryloyl groups are available for other reactions in a manner comparable to that of monomeric analogues.
Chlorination of preformed polyethylene film
Authors: Luttinger Manfred , Cooper Charles W. , Hungerford Gordon P.
Published: June 2010

Substantial chlorination of polyethylene (PE) films has been accomplished, making available films having wide varieties of physical properties. The reaction of thin PE films of 0.918 to 0.935 g./cm.3 density was investigated in an atmosphere of Cl2 and in a liquid medium saturated with Cl2. Chlorine contents from 10 to 30% in low‐density films and up to 45% in medium‐density films were obtained by reaction in the gaseous phase. By the use of various light sources in conjunction with peroxydic catalysts chlorine contents of up to 70% were achieved in glacial acetic acid. In the gaseous atmosphere the tendency of the reaction rate to decrease after light chlorination suggests that diffusion may be the limiting factor here. In the liquid medium the barrier to substitution above 65 to 70% appears to have a thermodynamic basis. The tensile strength and stiffness of the films pass through a minimum below 40% chlorine content and are affected by the reaction temperature. Mildly chlorinated films that have reacted at 40°C. do not exhibit a marked change in tensile properties, suggesting possible chain scission or a decrease in crystallinity on chlorination at elevated temperatures. Significant increases in the fusion point of PE are realized even with low substitutions of chlorine.
Reactions at the terminal vinyl group in Phillips‐type polyethylene
Authors: Zeitlin R. J.
Published: June 2010

Polyethylene is commonly considered an inert aliphatic hydrocarbon similar to the lower alkanes. When produced by the Phillips process, it does contain one terminal vinyl group. The reaction in the melt with dibutyl maleate initiated by tert‐butyl hydroperoxide was studied in a Brabender Plastograph. Comparative reactions of alkanes, 1‐alkenes, and 2‐alkenes of low molecular weight with dibutyl maleate were also carried out. An appreciable addition of dibutyl maleate to vinyl groups occurred with Phillips polyethylene, 1‐decene, and 1‐octene, but not with 2‐octene or octane. Dibutyl succinate also is a principal product of the reaction. Polyethylene modified by chemical reaction with dibutyl maleate has greatly increased elongation and environmental stress‐crack resistance and lowered flexural modulus and brittle temperature.
Oxidation of butadiene polymers
Authors: Bevilacqua E. M.
Published: June 2010

Butadiene polymers and copolymers undergo both scission and cross‐linking during thermal oxidation, the scission exceeding the crosslinking by a small amount. As a result initially soluble polymer develops gel and insoluble polymer develops sol. A limiting solubility is reached rapidly. This affords a quantitative estimate of the scission‐to‐cross‐linking ratio. Vulcanization with sulfur and accelerators causes a much more complex change on oxidation, not easily described by solubility analyses. Reaction with sulfur causes an excess of crosslinking over amount of scission during oxidation. Formic acid is a major low molecular weight product of oxidation. Higher molecular weight fragments include acetone and acetaldehyde; others have not been identified. These products do not provide the helpful clues to the oxidation mechanism afforded, for example, by levulinaldehyde in the case of polyisoprene.
The hydrogenation of poly‐2‐alkylbutadienes
Authors: Gregg E. C.
Published: June 2010

Complete hydrogenation of cis‐polyisoprene has been effected at 240°C. and 3,600 psi of hydrogen pressure over Raney nickel for 48 hr. Only a moderate amount of polymer breakdown occurred. High molecular weight hydrogenated polyisoprene was obtained by fractionating the hydrogenated polymer. Under similar conditions trans‐polyisoprene, poly‐2‐ethylbutadiene, poly‐2‐n‐propylbutadiene, poly‐2‐n‐pentylbutadiene and poly‐2‐(2‐methyl‐2‐penten‐5‐yl) butadiene were completely hydrogenated. No rearrangement of the polybutadienes as a result of hydrogenation was observed.
Shell model calculations of translational and rotational frictional coefficients
Authors: Bloomfield Victor A. , Filson Don P.
Published: June 2010

Previous work has shown that it is possible to calculate the translational and rotational frictional coefficients of complex structures by modeling them by a surface shell of spherical elements. The basic equations of this shell model method and its application to spheres, prolate ellipsoids of revolution, proteins, and viruses, are reviewed here. Several new results are also presented. It is demonstrated analytically that the rotational frictional coefficient for a sphere, calculated according to the shell model, agrees with the Stokes‐Kirchoff law. The rotational frictional coefficients of right circular cylinders have been calculated by digital computation; end effects are less marked than they are according to a theory of Broersma. Finally, the sedimentation behavior of various geometrical arrays of oligomeric aggregates of spherical subunits has been tabulated, to facilitate application to multichain protein systems.
Computer solution of gel–crosslink relations
Authors: Kang H. Y. , Saito O. , Dole M.
Published: June 2010

Use of the Wesslau molecular weight distribution equation in the equations relating production of gel to total radiation dose leads to equations that can be solved only by means of computer techniques. This solution has been carried out for a number of initial values of the weight‐average to number‐average molecular weight ratios and for a number of ratios of chain degradation G values to crosslink G values. It is shown that the initial slope of the curve of s + s1/2 versus rg/r, where s is the soluble fraction after a dose r, and rg is the dose to the gel point, can be related to the type of initial molecular weight distribution in the polymer. For the first time definite evidence of an increase of the crosslinking rate with dose has been obtained.
The alteration of molecular weight distributions of polymers by ultrasonic energy
Authors: Heymach George J. , Jost Donald E.
Published: June 2010

Methods of producing selected monodispersed samples of addition polymers have gained importance in many phases of polymer research. The ability of cavitation resulting from intense ultrasonic energy selectively to degrade polymers by fracturing longer chains at a faster rate than shorter chains is investigated as a means of sharpening molecular weight distributions. Conflicting degradation theories and experimental findings are reviewed, and new degradation models based on reasonable degradation mechanisms are developed. An IBM 7040–1401 computer was used to simulate degradation for these models. The solutions show in detail how molecular weight distributions are shifted and altered, depending on the kinetic expression used. In all the cases investigated monodispersity is first seen to decrease and then increase as a function of time.