bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model for the degradation of cotton cellulose
Authors: Elema R. J. 
Published: June 2010

AbstractCertain correlations have been established experimentally on degraded cotton cellulose between degree of polymerization (DP) on the one hand and the polymolecularity (quotient of weight‐average DP and number‐average DP), tenacity, and rate of degradation, on the other hand. It was found that these correlations may be accounted for by the assumption of weak and reactive spots in the cellulose macromolecules at regular intervals of about 500 base units. The same characteristic length of 500 base units follows also from recent concepts of cotton fiber structure.According to our model all ends of the composing macromolecules in a newly matured yet undegraded cotton fiber cause areas of disorder in the crystalline elementary fibrils at intervals of 500 base units. These disorders bring about stresses that activate the chemical bonds in the rigid cellulose chains.This model is in agreement with current ideas and is supported by various other experimental results published in the literature.
Copolymerization of acrylil and methacrylil chlorides with vinyl compounds
Authors: Nazhmiddinov Sh. , Turayev A. S. , Usmanov Kh. U. , Bazarbayev A. 
Published: June 2010

AbstractRadical chain copolymerization of acrylil and methacrylil chlorides and vinyl acetate and vinyl pyrrolidone in presence of azobisisobutyronitrile allowed estimation of copolv‐merization constants. Besides, chloroanhydrides were shown to be reactive during this process. Later it was shown that in the case of vinylacetates the reaction is governed by the laws of a typical vinyl copolymerization, while the chloroanhydride‐vinyl pyrrolidone system can be characterized by certain stable relations. The formation and structural pecularities of such a compound as well as details of the process were explained by the fact of their participation in the reaction.
Multiphase structure and properties of crystalline polymers
Authors: Mandelkern L. 
Published: June 2010

AbstractAlthough lamella‐like crystallites are a well‐established characteristic of polymer systems crystallized either in bulk or from dilute solution, major misconceptions have been engendered with respect to interfacial structures and other morphological features. A detailed analysis of a wide range of properties has allowed for a molecular description of some salient features of the structure of semi‐crystalline polymers. Solution formed crystals possess a disordered amorphous overlayer. Associated with the crystalline regions of bulk systems is a diffuse interfacial layer as well as an interzonal region, wherein the chain units which connect crystallites are in nonordered conformations. These conclusions are in complete accord with electron microscope observations.
Investigation of the glass transition and melting of polymers by nuclear magnetic resonance
Authors: Zachmann H. G. 
Published: June 2010

AbstractInvestigations of the glass transition and melting of partially crystalline polymers by nuclear magnetic resonance provide valuable information on the nature of noncrystalline regions. The broad line NMR signal was separated into a narrow component and a broad component by using a new method which does not imply the ambiguity usually present. From the intensity of the narrow component the mobile fraction was determined. This fraction was extrapolated to “infinite” temperature. By subtracting the mobile fraction from the noncrystalline fraction, the noncrystalline rigid fraction was obtained. Comparison of the measured second moments of the two components of the NMR line with calculated second moments of chains with fixed ends shows the following: The mobile fraction is formed by chains with either one end fixed or both ends fixed in a comparatively small end‐to‐end distance (for example, loops with adjacent reentry); the noncrystalline rigid fraction is formed by chains whose ends are fixed in a comparatively large or medium end‐to‐end distances (for example, tie molecules connecting different crystals).More detailed information on the chains forming the mobile fraction as well as on the structure in the melt was obtained by high resolution NMR. It was shown that near range order in the melt, for example, the formation of bundles of parallel chains, causes deviations from the lorentzian shape of the NMR line. During primary crystallization the chains within the bundles of parallel chains crystallize. During secondary crystallization, extremely mobile chains outside these bundles are incorporated into the crystals.
Light scattering studies on the deformation of flexible macromolecules in flow
Authors: Heller W. 
Published: June 2010

AbstractThe theoretical background and a suitable apparatus have been developed for deriving from light scattering measurements in streaming polymer solutions information on the deformability, and therefore on the degree of flexibility of macromolecules. In order to differentiate between effects due to polymer deformation and those due to an extrusion, an argument based on the classical Langevin relation is used. Preliminary results on the flow deformation of polyacrylamide were encouraging as regards the potential of the method.
Monomer sequence distribution in ethylene‐propylene terpolymers measured by 13C nuclear magnetic resonance
Authors: Wilkes Charles E. , Carman Charles J. , Harrington Robert A. 
Published: June 2010

AbstractConsiderable progress has been made in the analysis of monomer sequence distribution in ethylene‐propylene copolymers and terpolymers. Fourier transform Carbon‐13 nuclear magnetic resonance spectra provide a significant increase in signal‐to‐noise over our previously published continuous wave (CW) spectra. Most of the methylene, methyl, and methine carbon resonances have been assigned and verified. A few uncertainties remain in the deconvolution of overlapping peaks or the prorating of coincident peaks for some of the minor constituent structures. For a series of four terpolymers containing approximately 1% ethylidenenorbornene as the third monomer, r1 r2 was determined to be 1.0. The precision is estimated to be better than ±0.2. The spectra contain enough data to ultimately provide several internal checks. When the methyl assignments are further refined, comparison may be made between the propylene sequence distributions calculated from methyl and from methine resonances. Devising a system for treating the effects of propylene inversion on the methylene resonances will allow description of the ethylene sequence distribution. The net result should be very reliable r1 r2 products for ethylene‐propylene copolymers and terpolymers of low third monomer content.
Gel permeation chromatography VII. Molecular weight detection of gpc effluents
Authors: Ouano A. C. 
Published: June 2010

AbstractA detector system for GPC has been built consisting of a pressure cell and capillary viscometer, a constant flow rate pumping system, a concentration detector, and a computer interfacing system. This detector system provides two chromatograms; pressure drop (ΔP) vs retention volume and concentration (C) vs retention volume. Since at constant flow rate ΔP is proportional to the effluent viscosity η, the intrinsic viscosity of any effluent fraction can be computed from the equation,
magnified image
where subscripts 1 and 0 refer to the solution and solvent, respectively.The precision and accuracy of the above technique were evaluated using well characterized broad and narrow molecular weight distribution polymers. Both the precision and accuracy were found to be comparable to light scattering and other classical molecular weight measurement techniques. In its present form, the molecular weight detector system was found to be very sensitive to polymers with very high molecular weights, as expected, and also useful for molecular weights less than 50,000.
Application of radiotracer techniques to polymer characterization
Authors: Screaton R. M. , Cullen P. F. , Seemann R. W. , Saunders M. D. 
Published: June 2010

AbstractA method for labeling the functional groups in polymers has been developed. This method converts the COOH (or OH) groups to a radioactive ester which is easier to characterize by GPC than the parent polymer. The method is more sensitive than classical analysis and gives functionality distribution in addition to total functionality. Applications of the method are given for polymers of acrylic acid and vinyl alcohol and liquid epoxy resin.Radiotracer techniques have been also used to confirm structure of bisphenol A epoxies by using 14C labeled bisphenol A.
Intramolecular and intermolecular aggregations in aqueous solutions of maleic anhydride copolymers
Authors: Barone G. , Di Virgilio N. , Elia V. , Rizzo E. 
Published: June 2010

AbstractA study on aqueous solutions of an alternating copolymer maleic anhydride‐2,4,4,‐trimethylpentene‐1 is reported. The main feature of the hydrolysis product (PTMLA) is the remarkable interaction between nearest neighbor carboxyl groups. The interaction between neighbor dipoles is favored by the presence of hydrophobic side chains, which cause the lowering of the “local” dielectric constant. As a result, the PTMLA behaves like a polydi‐basic acid. From viscosimetric trends and other properties, it is possible to deduce that this copolymer undergoes a transition to a highly coiled form at low pH's and then to an intermolecular aggregation. It maintains an expanded conformation in a wide range of alkaline pH's. It is possible to correlate this behavior with its capacity as dispersant as well as the structural characteristics of the side chain for this and other comonomers.
Ordering in solutions of poly (vinyl alcohol) in water as detected by light scattering
Authors: Gruber E. , Soehendra B. , Schurz J. 
Published: June 2010

AbstractThe tendency of poly (vinyl alcohol) in water to form aggregations was studied by light‐scattering measurements. On standing at 25°CC for several days an organized phase structure was formed. This could be seen in a change of the scattering functions (angular dependence of scattered light). At small scattering angles intensity increased and weak side maxima showed up in the scattering functions. This aging process is also characterized by negative A2‐values, by a decreasing limiting viscosity number, and by increasing Huggins‐k′‐values. Speed and character of this change was found to be dependent on the concentration of the solution and the molecular weight of the sample. Models are discussed, which can lead to the observed irregular scattering functions. The most probable explanation is, that during aging gel particles are formed, which have a negative surrounding function, which has an analogous effect as weak repulsion.
Polymer dynamics in solutions and gels from Rayleigh light‐scattered linewidths
Authors: King T. A. , Knox A. , McAdam J. D. G. 
Published: June 2010

AbstractLocal concentration fluctuations in polymer/solvent systems are probed by laser light‐scattered linewidth measurements. Dilute polystyrene solutions are studied over the molecular weight range 4 × 103 to 1.7 × 107 and as a function of concentration. The diffusion coefficient at zero concentration can be expressed as magnified image while the concentration dependence of the diffusion coefficient D is used as a measure of thermodynamic and hydrodynamic virial coefficients and compared with available theory. Results are also presented for light‐scattered linewidths from some polystyrene/tetralin gels of known concentration and crosslink density.
Conformational changes of heparin in concentrated urea solution
Authors: Yuan Leon 
Published: June 2010

AbstractConformational changes of heparin in concentrated urea solutions were examined by viscosity and kinetic measurements. The viscosity results are treated using the relation ζsp/C = [ζ]x (1 + k/√C) in an effort to separate out the factors controlling the overall conformational changes –they are, electrostatic interaction and backbone configuration. In 10 M urea, kinetic studies of heparin viscosity revealed the following: (1) after the solution has been shaken for 2.5 hr at 25°C, both [ζ]x and k agree well with the corresponding values previously obtained in the solvents of low dielectric constants; and (2) at higher temperatures, the viscosity decreases from this value. The kinetic data suggest that the reaction consists of two consecutive processes. The first process is too fast to be followed adequately by viscosity. The second process follows first‐order kinetics and the rate constants are proportional to temperature but inversely proportional to heparin concentration. The activation energy for the second process is 35 kcal/mole. For the first process, the parameter [ζ]x increases while k decreases. In the second process, both [ζ]x and k decrease. These kinetic viscosity results suggest that the relaxation of the electrostatic interaction at high dielectric constant will cause a rapid collapse of the ionic atmosphere with an expansion of back‐bone configuration. Then, thermal motion will cause the heparin molecule to become more compact. A molecular model for the polyelectrolyte is postulated, which is a modified version of the Strauss‐Ander model.
Structural interpretation of nonlinear viscoelasticity in polymeric solids
Authors: Matsuoka S. , Bair H. E. , Aloisio C. J. 
Published: June 2010

AbstractThe mechanical relaxation time in a glassy polymer depends on the magnitude of strain. The stress relaxation modulus of a styrene acrylonitrile and polybutadiene composite system (ABS) was measured at strains ranging from 0.005 to 0.10. The relaxation time was observed to shorten by up to four orders of magnitude. In addition, a decrease in the elastic contribution to the modulus was observed. These two aspects of nonlinear viscoelasticity are interpreted in terms of the excess entropy and enthalpy associated with dilatation under strain, a crucial factor for ductile behavior and the formation of crazes. Up to 0.9 cal/g of the excess enthalpy associated with the stress‐induced dilatation is obtained from the differential scanning calorimetry study. As a corollary, brittle behavior following annealing is explained by the fact that it would take a greater magnitude of strain to regain a critical amount of excess enthalpy by the stress induced dilatation.
Relaxation of damped debye lattices in the primary transition region
Authors: Aklonis J. J. , Rele V. B. 
Published: June 2010

AbstractA brief review of the literature concerning damped Debye lattices as models for viscoelastic relaxation in the primary transition region is presented.We have observed that polystyrene plasticized with dioctylsebacate behaves in a fashion which is inconsistent with previous predictions based on this model. We have suggested an expanded interpretation of the model which predicts that plasticizers with solubility parameters appreciably different from that of the polymer will behave differently from diluents with the same solubility parameter as the polymer. The results of further experimentation are in accord with this new prediction.Our work supports the contention that the damped Debye lattice is a viable model and clearly demonstrates that interchain interactions are important in determining physical properties in the primary transition region.
Properties of the polyurethane resin coating used in the control of area shrinkage of woolen fabrics
Authors: Beevers R. B. 
Published: June 2010

AbstractStress relaxation measurements are reported for the polyurethane resin Synthappret, which is used to prevent area shrinkage in woolen fabrics. The experimental data are in satisfactory agreement with computed stress decay assuming two independent first‐order rate equations with activation energies of 11 ± 6 and 29 ± 4 kcal/mole−1. It is considered that the decay process involving the lower activation energy arises from tearing of the resin, and this is supported by stereoscan electron microscope examination. The mechanism by which the resin controls fabric shrinkage is discussed.
Chemical transformation of polymers. XV. Poly(ethylene methacrylate arylsulfo‐nates) as alkylation agents
Authors: Peška J. , Štamberg J. , Schmidt P. , Beneš M. J. 
Published: June 2010

AbstractPolymers of ethylene methacrylate, toluene‐, and benzenesulfonate are shown to be strongalkylating agents. Their polymer‐analogous reaction with most nucleophiles proceeds smoothly under conditions comparable to those of low molecular analogs. The nucleophiles used successfully were of the nitrogen type: amines, pyridine, phthalimidate, azide; or oxygen: alkoxide, phenolate, carboxylate; sulfur: thioacetate, thiocyanate, thiourea; and other types: iodide. Further reaction of some of these derivatives, e.g., hydrolysis to thiol or amine, proceeds as expected.
Investigation of thermal polycyclocon‐densation of polyhydrazides
Authors: Korshak V. V. , Berestneva G. L. , Bragina I. P. , Astafiev S. A. 
Published: June 2010

AbstractThis paper presents the results of investigations on thermal polycyclocondensation of polyhydrazides to corresponding poly‐1,3,4‐oxadiazoles. A limiting character of conversion is associated with the mobility of polymeric chains due to the fact that they become rigid by conversion of linear hydrazide fragments into cyclic 1,3,4‐oxadiazole ones, as well as to an increasing content of the latter in the course of conversion. Hence, the kinetics of the solid‐phase polycyclization of polyhydrazides is determined not only by the reactivity of groups participating in cyclization, but also by some factors indicating the effect of the structure on the starting polymeric compound and that of the structure order.
L‐asparaginase from Escherichia coli II and Erwinia carotovora bound to poly‐(methyl methacrylate)
Authors: Hersh L. S. 
Published: June 2010

AbstractL‐asparaginase (ASNase) from Escherichia coli (EC) II and Erwinia carotovora (Erw. carot.) has been chemically coupled to poly(methyl methacrylate) (PMMA) via the bifunctional coupling agents γ‐aminopropyltriethoxysilane and glutaraldehyde.The level of bound activity was about 2 and 6 IU/100 cm2, respectively. The immobilized asparaginases were successfully used in previously reported in vivo experiments. Certain kinetic characteristics such as pH profile and temperature dependence were unafected by the immobilization process Both bound asparaginase's apparent Km were greater than the native enzyme's value by approximately an order of magnitude. The apparent Km for the EC ASNase was approximately the same in buffer solutions and in pooled canine blood.
Investigation of the formation of strongly acid cation exchange resins based on slightly cross‐linked copolymers
Authors: Schwachula G. , Hauptmann R. , Kain I. 
Published: June 2010

AbstractOur investigations of the cation exchange resins based on styrene‐divinylbenzene (DVB) have shown that because of its unfavorable reactivity towards styrene, the DVB causes great inhomogeneities in the copolymers formed with styrene. This affects, in a negative way, the mechanical stability of the strongly acid cation exchange resin produced. On the other hand, strongly acid cation exchange resins based on polystyrene may be produced by reacting polystyrene in two steps with chlorosulfonic acid in the presence of formaldehyde. Furthermore, it has been successfully tied to chloromethylate polystyrene in the presence of paraformaldehyde or methylal so that a cross‐linked chloromethylated product was formed.It has been the aim of our investigations to make sure if, on the one hand, on the basis of polystyrene, it was possible by chloromethylation to get a cross‐linked product that could be subsequently worked into a strongly acid cation exchange resin or, on the other hand, to verify if one could, based on polystyrene in the presence of a formaldehyde‐releasing substance, sulfonate in one step so that the product is cross‐linked at the same time. The quality criterion of all experiments is to guarantee that the characteristics of the final product, i.e., a strongly acid cation exchange resin, are comparable to those of the well‐known resin types based on styrene‐DVB.
Investigation of the surface structure of polymers by chromatographic methods. I. Hydrophilized polyethylene capillaries for medical applications
Authors: Hradil J. , Stamberg J. , Kaganov A. L. , Synek P. 
Published: June 2010

AbstractPolyethylene catheters being treated with chromosulphuric acid at room temperature became hydrophilic on the surface and readily accepted a hydrophilic polymer layer. Almost no differences in chemical composition between the original and the treated polymer samples were found by conventional methods. On the other hand, the method of inverse gas chromatography showed significant changes both in the physical and chemical surface structure. The Rohrschneider's polarity factors already attained the values for poly(2‐hydroxy‐ethyl methacrylate) after a short time of treatment. Hydrophilized polyethylene catheters coated with soluble poly(2‐hydroxyethyl methacrylate) were well tolerated by the patients and did not cause formation of thrombi or phlebitis.
Preparation and properties of heparin‐poly (methyl methacrylate) copolmers
Authors: Labarre D. , Boffa M. C. , Jozefowicz M. 
Published: June 2010

AbstractA new technique of covalent bonding of poly(methyl methacrylate) (PMMA) onto heparin (HEP) is described. The reaction involved implicates radical polymerization of methyl methacrylate (MMA) initiated by a heparin radical resulting from reaction between cerium (Ce) (IV) ion and heparin in aqueous solution.The characteristics of the grafting reaction and of the resulting polymers have been studied. The blood compatibility of powders or films of the polymers are actually studied. The preliminary results show that these copolymers might be interesting for medical applications.
Fixation de microchainons carbonyles sur des polyisoprenes et polybutadienes par hydroboration. reaction sur modeles macromoleculaires
Authors: Pinazzi C. P. , Guillaume P. , Reyx D. 
Published: June 2010

Abstract1,4 Addition of trialkylboranes on unsatured carbonyl compounds allows the fast synthesis of aldehydes and ketones. The application of this reaction to macromolecular trialkylborane microstructures derived from polyisoprenes and polybutadienes has been considered. The reaction involves the homolytic scission of one of the three C‐B bonds leading to the fixation of the oxoalkyl group on the considered carbon. In the macromolecular trialkylborane structures, fixation of the carbonyl microchain on the polymer is only realized by scission of the macromolecular carbon‐boron bond; the two other possible scissions lead to macromolecular borinic structures.Polydiene macromolecular models have been used to study the application of this hydroboration‐addition coupled reaction to the corresponding polymers. They have allowed the synthesis of modified microstructure models by use of diborane as hydroborating agent. Moreover, they have been used to measure the selectivity of the fixation γ‐oxoalkyl group on the modelized macromolecular carbon. Using bis‐boracyclanes as hydroborating agents, a quasi‐selective conversion of 1,4‐polydienes to carbonylated structures can be obtained; on the contrary, with 1,2 and 3,4 polydienes, the selectivity never exceeds 50%.
Chemical transformations of polymers. XIII. Effect of supermolecular structure on the transformation of polyethylene with chlorosulphonic acid
Authors: Baldrian J. , Hradil J. , Štamberg J. 
Published: June 2010

AbstractThe degree of transformation of polyethylene with chlorosulphonic acid depends on the number of branches. It is increased not only by using better swelling agents, but also—and prevailingly—by an increase in the amorphous portion of the starting polymer. Chlorosulphonation takes place in amorphous regions, because they are accessible to low‐molecular‐weight components and contain reactive parts of the polymer chains with tertiary carbon atoms. As the transformation proceeds, crystallinity falls down and dimensions of crystallites run low by oxidation splitting of chains.