bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular and supramolecular paracrystalline structure of linear synthetic high polymers
Authors: Hosemann Rolf 
Published: June 2010

AbstractThe 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

AbstractX‐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

AbstractThis 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

AbstractUnrelated 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

AbstractSpherical 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

AbstractThe 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

AbstractProcesses 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

AbstractOptically 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

AbstractPolymeric 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

AbstractThe 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

AbstractTo 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

AbstractFour 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

AbstractPoly(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

AbstractBy 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractCationic 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

AbstractThe 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

AbstractThe 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.