bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some features of radical polymerization of acrylic and methacrylic acid salts in aqueous solutions
Authors: Kabanov V. A. , Topchiev D. A. , Karaputadze T. M. 
Published: June 2010

AbstractThe kinetics of radical polymerization of acrylic and methacrylic acids and their salts in aqueous solutions have been studied. A considerable increase in the polymerization rate at an increase in pH in the alkalinity area has been detected, the general trend of the rate‐enhancement being specifically dependent on the type of cation present in the solution. On the basis of the set of the experimental data an assumption was made on the kinetic role of ion pairs in the radical polymerization of ionizable monomers. Formation of ion pairs results in the increase of the elementary propagation rate constant Kp. Rotating sector measurements for individual kinetic constant confirmed the advanced hypothesis. The importance of the conformational state of polyelectrolyte growing chains in the kinetics of radical polymierzation of ionizable monomers has been shown. Participation of ion pairs in the propagation step leads to marked stereochemical effects and, in certain cases, to the formation of practically stereospecific polymers.
Unsaturated polymers from aliphatic nitriles
Authors: Wöhrle D. , Helling G. 
Published: June 2010

AbstractNitrile groups of fumaronitrile, succinonitrile, and polyacrylnitrile were polymerized with the anion of DMSO. Dark‐colored polymers with conjugated CN‐bonds were obtained with high yield. A reaction mechanism is discussed. The polymerization of succinonitrile with Ziegler catalysts such as Al(C2H5)2 Cl/TiCl4 also gave dark‐colored polymers with high yield.
Studies on the emulsion polymerization of vinyl chloride by seed polymerization
Authors: Ugelstad J. , Fløgstad H. , Hansen F. K. , Ellingsen T. 
Published: June 2010

AbstractKinetic experiments with homodisperse seeds of various particle size verified the previous results as to the effect of particle number, degree of conversion, and initiator concentration on the rate of polymerization. Also, experiments with mixed seeds consisting of two sets of homodisperse particles of different sizes were carried out and the relative growth of the particles was measured. A mathematical model involving desorption and reabsorption of radicals into particles was developed for such competitive growth experiments and applied to describe the experimental results. Experiments with mixed emulsifier systems consisting of an anionic emulsifier and different fatty alcohols in seed polymerization supported previous results regarding the effect of fatty alcohol on the rate of reaction. The application of certain systems of anionic emulsifier and fatty alcohol led to a much more effective emulsification of the monomer. It is suggested that in this case the monomer droplets may serve as loci for initiation and polymerization.
Morphology of segmented polyester thermoplastic elastomers
Authors: Cella Richard J. 
Published: June 2010

AbstractThe morphology of a new family of copolyester thermoplastic elastomers is described and the physical properties of these polymers are interpreted in terms of their unusual two‐phase domain structure. The elastomers were synthesized by the equilibrium melt transesterification of dimethyl terephthalate with 1, 4‐butanediol and poly (tetramethylene ether) glycol, resulting in a molecule in which crystallizable tetramethylene terephthalate (4GT) segments and amorphous poly (tetramethylene ether) glycol terephthalate segments are randomly distributed along the backbone. The 4GT sequences were found to crystallize as lamellar domains measuring approximately 100 Å in width and up to several thousand angströms in length. These crystalline regions are not discrete as are the polystyrene domains in the typical polystyrene‐polybutadiene‐polystyrene (SBS) triblock polymers, but rather are continuous and highly interconnected. Like the glassy regions in the SBS polymers, however, they serve as intermolecular tiepoints for the amorphous portions of the molecules and lead to the formation of a three‐dimensional network structure. At temperatures below the crystallite melting point, the material exhibits many properties characteristic of conventionally cured elastomers, but at elevated temperatures the melting of these thermally labile noncovalent junctures allows the material to flow and be processed as a thermoplastic. The stress‐strain behavior of these polymers is discussed in terms of their morphology, and thermal analysis, electron microscopy, and x‐ray diffraction results are presented.
TR: A new characteristic temperature for thermoplastic polymers
Authors: Aharoni Shaul M. 
Published: June 2010

AbstractTreatment of thermal data of fluids at their critical point Tc and of 31 polymers at their Tg according to a modified Goldhammer equation indicates that at these points they have a fractional free volume (FFV) averaging 0.113 magnified image and yields TR′S characteristic of each polymer. The FFV values obtained from magnified image showed small deviations from 0.113. These were in the direction and order of magnitude of chemically similar fluids at their Tc. When TR = 2Tg, eq. (2) reduces to FFV = (aL – aG) Tg. Plots of FFV versus TR – 2Tg show similarities in polymeric homologs behavior. A modified WLF equation with C1 = 3.85, C2 = 0.113/(aL – aG), and T – Tg = TR – Tg places all the data on a single curve. The stress concentration coefficient γ of long‐term polymeric strength is temperature dependent. magnified image
The influence of charged groups in gel permeation chromatography of polyelec‐trolytes
Authors: Forss K. G. , Stenlund B. G. 
Published: June 2010

AbstractWhen polyelectrolytes (lignosulfonates) with a broad molecular weight distribution are eluted from Sephadex gels with water, the fractionation is affected by steric exclusion, polyelectrolyte expansion, ion exclusion, and ion inclusion effects. The ion inclusion effect is due to interaction of charged sites in the macro‐ions which are more or less excluded from the gel with charged sites in more permeable macro‐ions. The ion inclusion effect depends on the cation of the lignosulfonates in such a way that the elution of lignosulfonates with a univalent cation is affected to a greater extent than the elution of lignosulfonates with a divalent cation. This is due to the existence of a higher density of free charges in the lignosulfonates with a univalent cation owing to a lesser tendency to form ion pairs. By choosing suitable eluents, it is possible to alter the retention volumes of lignosulfonates of different sizes and thus optimize the resolution.
Solution and bulk flow properties of linear and branched styrene–butadiene rubbers
Authors: Mieras H. J. M. A. 
Published: June 2010

AbstractThe solution and bulk flow properties of various styrene‐butadiene rubbers have been investigated. Bulk flow properties were measured with the Instron capillary rheometer, while the Weissenberg rheogoniometer was used to measure to steady‐state and oscillatory flow properties of 15% wt solutions in decalin.A comparison of the rheological information obtained from the solution and bulk behavior with GPC and intrinsic viscosity data makes it possible to distinguish between different forms of branching and between the effects of molecular weight distribution and branching.Branching decreases the hydrodynamic volume of a polymer coil relative to its molecular weight, so that branched polymers have lower solution viscosities at the same molecular weight than linear polymers. This effect is more pronounced for short‐chain and dendritic forms of branching than for star‐shaped long‐chain branching. At higher concentrations and especially for bulk polymers, however, star‐shaped long‐chain branching will give rise to much higher viscosities, which is hardly, if at all, found for short‐chain or dendritic forms of branching.Star‐shaped branching greatly affects the shear sensitivity of the bulk viscosity, whereas it has relatively little effect on polymer fluid elasticity either in bulk or in solution, this elasticity being mostly determined by the width of the molecular weight distribution Mz/Mw.
Investigation of anisotropic light scattering by solutions of polymers and copolymers
Authors: Ehrenburg E. G. , Piskareva E. P. , Poddubnyi I. Ya. 
Published: June 2010

AbstractThe intensity of depolarized components of light scatered by polymer solutions has been measured in solvents of different refractive indexes. It has been found that the dependence of the Rayleigh ratio (RHv/c) on the solvent refractive index (n0) for polymer solutions significantly differs from the corresponding dependence (RHv/c) = f (n0) for solutions of low molecular weight compounds. The interpretation of the observed relations (RHv/c) = f (n0) is given and the equation relating RHv/c with the polarizability tensor anisotropy 〈γ2〉 of dissolved macromolecules proposed. The equation differs from the corresponding equation applicable to low molecular weight compounds by the use of Λ in a medium. Values of 〈γ2〉 for atactic polystyrene determined by the equation given are compared with calculation reported by Flory and co‐workers.The difference between the statistical segment principal polarizabilities calculated from the anisotropic light scattering data has been also compared with that determined from birefringence data. All the results obtained are in agreement with the equation proposed. It is shown that the intensity of the anisotropic light scattering by block copolymer solutions is sensitive to disturbances in the regular block structure and, hence, the anisotropic scattering method can be used to characterize the alternating of monomer units in copolymer chains.
Investigation of chemical behavior of anthracene derivatives as monomers and reagents in synthesis of macromolecules containing anthracene groups
Authors: Skorokhodov S. S. , Krakovjak M. G. , Anufrieva E. V. , Shelekhov N. S. 
Published: June 2010

AbstractMethods for obtaining polymers with various content and position of anthracene groups in macromolecules (in the main chain, in the side radicals, or at the chain end) have been worked out. The methods are based on the copolymerization and on the reaction of synthetic and natural polymers with the participation of anthracene‐containing monomers or reagents. The pecularities of the anthracene group reactivity in these reactions were investigated. Investigation of free radical copolymerization of 9‐vinyl‐anthracenes has shown that the reaction center can shift from the α‐carbon of 9‐anthrylmethyl system to the 10th position. This permits the preparation of polymers with anthracene groups in the main chains. We established the structure and content of the anthracene groups in the polymers obtained (polyacrylic and polymethacrylic acids and their esters, polystyrene, polymethylene, polyvinylic ethers, some biopolymers) by UV‐spectroscopy and by measurements of their luminescent parameters (spectra, lifetime of excitation, and polarization of fluorescence). The polymers with very low amount of anthracene groups “luminescent marks” (one per more than thousand of monomeric units), differently placed in macromolecules, have been used for investigating intramolecular motion of macromolecules by the method of polarized luminescence.
Studies in heterocyclic polymers. III. A comparison of the thermal stability of some linear and related ladder polymers
Authors: Hodd K. A. , Holmes‐Walker W. A. 
Published: June 2010

AbstractStatic and dynamic thermogravimetry in an inert atmosphere and in air have been used to assess the thermal and oxidative stability of the ladder structured macrocyclic polymers and the related linear polymers the poly(benzobis (aminoiminopyrrolenes)) and their N‐substituted derivatives in the range 200–450°.The results of these weight loss studies have been analyzed using the methods discussed by Audebert and Aubineau,5 and by Zsako. The activation energies of polymer degradation derived by these analyses suggest that for this particular polymer system, contrary to the generally accepted theory, the ladder polymers are not significantly more thermally stable than the linear polymers. This deviation is explained in terms of macrocyclic strain and chain stiffness.
Determination of the crystalline fold period in poly(ethylene terephthalate)
Authors: Overton J. R. , Haynes S. K. 
Published: June 2010

AbstractThe morphological characteristics of poly(ethylene terephthalate) (PET) have been inferred from the selective chemical degradation of amorphous regions, including chain folds, and subsequent analysis of the molecular weight distribution of the reaction products. Bulk PET of known thermal and orientation history was reacted with 40% aqueous methylamine at 35°C and the reaction products examined by gel permeation chromatography. It was determined that the average crystalline fold period increased from six to nine monomer units over the crystallization temperature range of 126°C to 229°C. Evidence for the existence of a paracrystalline form at the lower crystallization temperatures was suggested by the presence of residual high molecular weight polymer in the reaction products. Samples crystallized at the lower temperatures exhibited multiple melting during DSC analysis. Results obtained by heating such samples in the DSC to a temperature between the two endotherms and quenching, followed by aminolysis and GPC, lead one to conclude that the first endotherm represents the initiation of melting and recrystallization. The second endotherm at ∼255°C, characteristic of PET, represents the melting of folded chain lamellae containing nine repeat units between folds. This material is formed during the DSC run as a result of melting and thermally compensatory recrystallization.
Structural data on crystalline polymers by thermal analysis
Authors: Wunderlich Bernhard 
Published: June 2010

AbstractLinear marcromolecules in the solid state may assume different macroconformations. While x‐ray diffraction and electron microscopy have been the prime instruments for the analysis of the highly ordered state, difficulties exist in the evaluation of less ordered portions. The enthalpy changes connected with changes in order can be determined by thermal analysis. Furthermore, modern instrumentation allows thermal measurements as a function of heating rate. Such mode of analysis can give kinetic information and data on metastable states. The macroconformations, thermal analyses, experimental techniques, and recent applications of thermal analysis to structural analysis giving information on folds, tie molecules, loops, and ciliae of poly(ethylene terephthalate), polyparaxylylene, selenium, and polyethylene are discussed.
Techniques used in applying regularization to the ill‐posed problem of determining a molecular weight distribution from sedimentation equilibrium.
Authors: Wiff D. R. , Gehatia Matatiahu 
Published: June 2010

AbstractInferring the Molecular Weight Distribution (MWD) of a polymer in solution from ultracentrifuge sedimentation equilibrium data has been a problem of major concern during the past decades. Recently, it has been shown that this problem is of itself mathematically ill‐posed, i.e., leads to unstable and unreliable results. To combat this difficulty, a technique of regularization applicable to the sedimentation equilibrium equation has been formulated which casts this into a well‐posed problem. This paper discusses the criteria for calling a problem mathematically ill‐posed; a regularization technique for circumventing this ill‐posedness; a regularization incorporated into linear programming technique; and a recent method for incorporating regularization into a quadratic programming algorithm. All examples are presented using arbitrarily assumed MWD. Good results were obtained by applying this technique to a unimodal through a pentamodal distribution.
Polyvinylimidazolium salts of varying hydrophilic‐hydrophobic character
Authors: Salamone J. C. , Israel S. C. , Taylor P. , Snider B. 
Published: June 2010

AbstractThe homopolymerizations of a series of 3‐n‐alkyl‐1‐vinylimidazolium iodides are described in which the length of the quaternizing alkyl group was varied from methyl to n‐propyl to n‐hexyl to n‐heptyl to n‐dodecyl to n‐hexadecyl. The preparations of these cationic monomers have previously been reported through reaction of 1‐vinylimidazole with the corresponding n‐alkyl iodide. All polymerizations were performed in aqueous solution at the same molar concentration of monomer using the free radical initiator 4,4′‐azobis‐4‐cyanopentanoic acid. It was found that the short side‐chain polyions (methyl and n‐propyl) were water soluble, whereas the more hydrophobic intermediate side‐chain polyions (n‐hexyl and n‐heptyl) were water insoluble. The long side‐chain polyions (n‐dodecyl and n‐hexadecyl), on the other hand, being highly hydrophobic, appeared to form polysoaps and remained in aqueous solution. The solution behavior of these polyions in water, in aqueous salt solution, and in chloroform is discussed as well as is the critical micelle concentration of a long side‐chain polyion and its corresponding monomer.
Applications of extracellular micro‐bial polysaccharide‐polyelectrolytes: Review of literature, including patents
Authors: Jeanes Allene 
Published: June 2010

AbstractHydrophilic macromolecular polysaccharides, selected for their distinctive constitution and unusual properties, are produced industrially from common sugars by nonpathogenic microorganisms. The α‐(1–6)‐linked D‐glucan dextran and fractions of defined lower molecular‐weight produced from it are derivatized chemically to a variety of ionogenic substances for uses such as: anticoagulant, antilipemic, and peptic‐ulcer alleviating agents; to enhance the sensitivity and covering power of x‐ray and photographic emulsions; and separations of sensitive biochemical products by two‐phase liquid distribution and ion‐exchange and affinity chromatography. The polyanionic heteropoly‐saccharide xanthan is used in many industries (such as agriculture, abrasives, ceramics, food, paint, petroleum production, and textile) for its thickening and suspending ability even in the presence of high salt concentrations, reversible shear thinning, synergistic interaction with galactomannans, and excellent stability to heat and to acidic and basic conditions. Other water‐soluble polysaccharide‐polyelectrolytes, produced in liquid cultures unattached to the microbial cells, have potentially useful properties.
Reactions of N‐methylolacrylamide in radiation‐chemical modification of cotton fabrics
Authors: Dziedziela W. M. , Rosiak J. 
Published: June 2010

AbstractThe reactions of N‐methylolacrylamide (NMA) occurring in the individual steps of the radiation‐chemical finishing of cotton fabric were investigated both qualitatively and quantitatively.Cotton fabric (poplin) was padded with an aqueous solution containing NMA, with zinc nitrate as an acid catalyst and a wetting agent. After being dried, the samples were gamma irradiated at ambient conditions and heat treated. In some experiments only irradiation or heating was used. Conclusions concerning the reactions of NMA were drawn on the basis of gravimetric measurements, nitrogen, double bonds, formaldehyde content, and from DTA and DTG of pure NMA and acrylamide.It has been noticed that during drying of padded fabric, NMA was decomposed with the evolution of free formaldehyde. The yield of decomposition depends mainly on the temperature of drying. Irradiation of a fabric containing NMA leads to the grafting of the latter onto cellulose and its homopolymerization, while the grafting is the predominant process. In the step of heat treatment, the fabric undergoes further decomposition of the methylol groups and condensation of the remaining ones with each other and with the OH groups of cellulose and thermal polymerization of NMA. The stability of the links between NMA and cellulose to acid hydrolysis has been examined.
Nonisothermal membrane phenomena through charged membranes
Authors: Tasaka Masayasu , Nagasawa Mitsuru 
Published: June 2010

AbstractApplying nonequilibrium thermodynamics, a theory of nonisothermal membrane phenomena through charged membranes is described. Agreement between theory and observed thermal membrane potential is satisfactory. In thermo‐osmosis, the effective temperature difference across the membrane is determined by measuring the thermal membrane potential. A qualitative explanation based on nonequilibrium thermodynamics is presented for the experimental results.
The significance of incompatible polymer systems
Authors: Battaerd H. A. J. 
Published: June 2010

AbstractA short review of multiphase polymer composites is given, biased towards some as yet unexplained observations. It is proposed that the interface between the two phases of such polymers has an important influence on the properties observed. It is also suggested that careful study of the interface may lead to improved polymer properties. Some methods that may be applied for such studies are listed and briefly discussed.
The chemical reactivities of macromolecules attached to an interface
Authors: Went Peter M. , Evans Robert , Napper Donald H. 
Published: June 2010

AbstractThe rates of alkaline hydrolysis of polyacrylamide chains attached to polystyrene latex particles have been measured and compared with the corresponding values in free solution. The attached chains exhibited a significant reduction in rate. The magnitude of this reduction increased with decreasing molecular weight. Consequently, the rates of hydrolysis of attached chains were a function of their molecular weight; this contrasted with the apparent second‐order rate constants for the chains in free solution, which were insensitive to the molecular weight. The reduction in rate was attributed to the decreased accessibility of the amide groups to the hydroxyl anions when the polymer chains were attached to an impenetrable interface.
Cyclopolymerization
Authors: Solomon D. H. 
Published: June 2010

AbstractDiallylamines readily undergo free‐radical polymerization to form polymers which contain cyclic structures. Five‐membered rings predominate, and this conclusion is supported by ESR spectroscopy of the radicals formed in a flow system, by chemical characterization of the compounds formed under nonpropagating conditions, and by NMR spectroscopy of the polymers. The presence of substituent groups in the diallylamine molecule has an important bearing on the cyclization reaction. For example, methyl groups in the β‐position, (dimethallylamines) form a mixture of 5‐ and 6‐membered rings, and the presence of bulkier groups, as in methyl bis‐2‐tert‐butyl allylamine, can prevent reaction with certain free‐radical initiators. Similarly, increasing temperature results in an increase in the amount of 6‐, relative to 5‐, membered ring structures with N‐methyldimethallylamine. These results are generally similar to those obtained with the carbon analogues.From a theoretical viewpoint, the formation of the 5‐membered ring structure indicates that the generally accepted less stable primary radical is formed in preference to the 6‐membered structure which would contain a secondary radical. This apparent conflict is explained by the kinetics of the reaction and particularly the stereo‐electronic effects which operate in the transition state. Thus, the reaction can be under kinetic control and lead predominantly to 5‐membered ring structures, but when thermodynamic control starts to operate, e.g., at higher temperatures, the more stable 6‐membered ring structures may become significant. Changing the polymer structure from a predominantly 5‐membered one to one containing 6‐membered rings can be expected to alter the properties of the polyelectrolyte. Thus, differences in the titration curves have been noted, and the possibility exists of relating these differences to the polymerization conditions and, hence, to polymer structure.