bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large scale preparative gel permeation chromatography
Authors: Montague P. G. , Peaker F. W. 
Published: June 2010

AbstractThe design and construction of a large‐scale gel permeation chromatographic unit is described, and it is a tenfold scale‐up of the usual analytical instrument. Important aspects of the column packing procedure are given. Fractions prepared using this apparatus were isolated and reinjected into an analytical instrument. In this way the efficiency of preparative fractionation was investigated using several polystyrene samples covering a wide range of molecular weights and distributions. Generally the highest molecular weight fraction isolated from a sample had the narrowest molecular weight distribution.
Structurization in the poly (m‐phenylene isophthalamide)–dimethylacetamide system
Authors: Klenin V. J. , Prozorov L. V. , Prozorova M. Yu. , Zhizdyuk B. I. 
Published: June 2010

AbstractThe methods of turbidity spectrum and viscometry have been used to investigate structurization in the concentrated solutions of poly (m‐phenylene isophthalamide) (Pm‐PIPA) in dimethylacetamide (DMA). The kinetics of formation of the supermolecular order (SMO) were studied under isothermal conditions within the temperature and concentration range of 30 to 150°CC and 5 to 25 g/dl, respectively. Two stages of formation of SMO were observed, viz., a comparatively slow stage and after that a very fast increase in the SMO level. In the first stage, the average particle radius, rλ, decreases, which probably is related to the continuous formation of nuclei. In the second stage, rλ and the turbidity, τ, of solution increase steeply. In the same stage, an increase in the viscosity of solution was also observed. A diagram of the properties of the system was constructed, which is analogous to the phase diagram. The temperature limit of the stability, Tbi, fulfills the requirement of Vτ = 0, where Vτ (the rate of increasing turbidity), was determined. Tbi determines the binodal curve depending on the polymer concentration. The temperature limit of absolute instability, Tsp, fulfilling the requirement of Vτ→∞, was determined. Depending on the concentration of solution, Tsp was identified with a spinodal curve. The property diagrams obtained are characteristic of the curves of amorphous separation with the lower critical solution temperature. With increasing molecular weight, Mζ, Tc decreases. Additions of a third component cause a deformation of the binodal curve and shift it to higher (lithium and calcium chlorides) or lower (water) temperatures. The time, ts, of reaching a certain level of SMO during thermostabilization at T = 80°CC was taken as a measure of stability of technological solutions.
Viscoelastic relaxation times of a homogeneous block copolymer
Authors: Shen Mitchel , Hansen David R. 
Published: June 2010

AbstractThe molecular theory of viscoelasticity has been modified in a previous publication for homogeneous block copolymers; the theory predicts that the maximum relaxation time of the block copolymer can be computed with the knowledge of submolecular sizes and monomeric friction coefficients. Stress‐relaxation experiments were carried out for two samples of styrene‐(α‐methyl styrene)‐styrene triblock copolymers. Maximum relaxation times were determined from the viscoelastic master curve through the use of procedure X developed by Tobolksy and Murakami. Experimental results were found to be in reasonable agreement with theoretical predictions. The theory also predicts the existence of a singularity in the distribution of relaxation times at very short relaxation times, but as is discussed, this prediction cannot be verified by existing experimental techniques.
Correlation between molecular structure and some bulk properties of highly crosslinked polysiloxanes
Authors: Katz D. , Zewi I. G. 
Published: June 2010

AbstractLittle consideration has until now been given to the effect of microphase separation in crosslinked polymers. This work deals with the correlation between the network chain length and some bulk properties of a series of seven highly crosslinked polymers prepared from dimethylsiloxane diacrylate oligomers with different lengths between their acrylic terminal groups. The occurrence of multiple transitions in the shear modulus versus temperature behavior, probably due to microphase separation, and the dependence of the transition regions and shear moduli on the siloxane network chain length were studied. The findings are compared with those of a similar work reported by us earlier, in which carboxyl‐terminated poly(dimethylsiloxanes) of similar chain lengths of the prepolymers were condensed with a trifunctional imine and yielded polymers exhibiting multiple transitions.Multiple transitions were observed in some of the crosslinked polymers, but this phenomenon disappeared with an increase in the amount of siloxane groups in the prepolymers. It seems that the reason for this suppression of microphase separation, as compared with the crosslinked carboxyl‐terminated oligosiloxanes, derives from the absence of sufficiently long organic sequences, from their limited number in the network chains, and from internal plasticization by the side chains formed as a result of inefficient crosslinking. The nature of the crosslinking site and the mechanism of crosslinking have a decisive influence on the structure and properties of the polymers including the occurrence of multiple transitions, even when the prepolymers are almost identical between their functional end groups.
Production of high‐molecular amphoteric compounds by means of polymer‐analogous conversions
Authors: Pashkov A. B. , Vakulenko V. A. , Samborsky I. V. , Makarov M. K. 
Published: June 2010

AbstractPolymer‐analogous transformations of styrene and divinylbenzene (DVB) copolymers permit us to obtain sulfonic cation‐ and anion‐exchange resins of a different basicity. In the last few years, new methods for the production of complex‐forming resins for nonferrous metals have been intensively developed. This paper is also devoted to this problem. Among the series of complexing resins, those derived from the ion‐exchange resins are the best known; they contain aminocarboxylic groups obtained by thermal treatment of an ion‐exchange resin with monohaloacetic acid in a low‐alkaline medium:
magnified imageFor the improvement of the complexing ability, the presence of iminodiacetic acid groups is desirable. In our opinion, the simplest among many possible variants is oxidation of the ion‐exchange resin with diethanol amine groups. An acid solution of sodium dichromate may be applied as the oxidant. Other oxidizing agents tested do not give the desired results. The oxidation process requires great skill; otherwise, the resulting product could not be completely or excessively oxidized. An amphoteric ion exchanger of this type has been successfully used for the copper pulp process:
magnified imageThe 2,5 methyl vinyl pyridine (MVP) and DVB copolymer can be transformed by two‐stage synthesis into an amphoteric ion exchanger containing an α‐picolinic acid group:
magnified imageThe degree of transformation in the oxymethylation stage amounts to 85%; that in the oxidation stage ranges from 92 to 100%. To obtain a better complexing ability of the result‐ ing amphoteric ion‐exchange resin, it is necessary to use a macroporous modilkation.Anion‐exchange resins containing secondary amino groups can be converted into ion exchangers with dithiocarbamate groups if processed by carbon disulfide:
magnified imageIn this case, the capactiy of the exchanger with respect to silver, mercury, and molybdenum greatly increases.Interaction of the high‐molecular hydrocarbon compound with chlorosulfonic acid and subsequent treatment of the resulting polysulfochloride with aliphatic diamines or poly‐ amines yielded compounds with cation‐ and anion‐exchange amino groups:
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Uber den einflub der chemischen struktur von phosphorsauren kationenaustauschern auf deren thermischen stabilitat in wasser
Authors: Polyanskii N. G. , Nikitina A. I. , Polyanskaja N. L. , Isaeva G. Ja. , Slabkaja L. D. 
Published: June 2010

AbstractThermal stability of different phosphorus‐containing cation exchangers in water has been studied. It has been shown that at heating to temperatures of 80–180°C the phosphorus content decreases on account of (1) thermal hydrolysis leading to phosphoric acid formation and (2) matrix splitting leading to phosphorus‐containing soluble organic compounds. Therefore for precise percentage loss determination [so‐called dephosphorilation degree (DD)] it is necessary to mineralize the organic compounds. A comparative study of the following cation exchangers has been carried out: KF‐I—nonporous styrene‐divinyl‐benzene phosphorylated copolymer (A); KF‐II—the same, but macroporous (B); KFP—macroporous exchanger with styrene‐divinylbenzene matrix containing methylene‐phosphoric acid groups (C); KF‐7—nonporous exchanger prepared by copolymerization of β‐β‐dichlorethyl‐phosphoric acid ester, vinylacetate, and divinylbenzene (D). The most stable are the macroporous exchangers with styrene‐divinylbenzene matrix B and C. The nonporous exchanger A having the same chemical structure as B is less stable. With increasing temperature the phosphorus splitting increases, though the Arrhenius equation is not fulfilled. The DD values at 80°C and a heating duration of 1 to 20 days are not more than 5%. At 180°C DD is as high as 6 to 50%, depending on resin structure and heating duration.
Chemical transformation of polymers. XVII. Amination of poly(oxy(2,2‐bis‐chloromethyl‐trimethylene)) (penton)
Authors: Kahovec J. , Štamberg J. 
Published: June 2010

AbstractPoly(oxy(2,2‐bis‐chloromethyl‐trimethylene)) reacts with methylamine, dimethylamine, and ethylenediamine in N‐methylpyrrolidone at 115–190°C forming corresponding amino derivatives; trimethylamine does not react under these conditions. The aminations are accompanied by a decrease in molecular weight. The dimethylamino derivative was quaternized with methyl iodide in dimethylformamide, and from the iodide the corresponding quaternary ammonium polybase was prepared using a strongly basic anion exchanger. This base, in an approximately 10% aqueous solution, was thermally degraded at 120°C for 70 hr. Under these conditions, the quaternary ammonium base was completely degraded, viz., about 63 %, to the polymeric dimethylamino derivative and methanol and about 37 % to the polymeric alcohol and trimethylamine. The unexpected splitting off of trimethylamine during the degradation is explained by the proximity of the ammonium groups in geminal CH2N+(CH3)3OK−.
Chemical transformations of polymers. XVI. Preparation and splitting of poly (methacryloyloxyethyltrimethyl‐ammonium hydroxide)
Authors: Holata J. , Ševčík S. , Štamberg J. 
Published: June 2010

AbstractPoly (methacryloyloxyethyltrimethylammonium hydroxide) was obtained by polymer analogous transformations or polymerization and transformations from poly (2‐hydroxyethyl methacrylate), chloroethyl methacrylate, or methacryloyloxyethyltrimethylammonium salts. The preparation from these latter compounds by polymerization and anion exchange was the most advantageous.At elevated temperature (60‐120°C) in aqueous solutions, the poly (methacryloyloxyethyltrimethylammonium hydroxide) split only hydrolytically; no Hofmann's degradation of quaternary ammonium hydroxides appeared. Kinetic measurements performed both on the polymer and on the low‐molecular weight model compounds (2‐hydroxyethyl pivalate and pivaloyloxyethyltrimethylammonium hydroxide) showed that the introduction of a quaternary ammonium group into the structure of an aliphatic ester considerably accelerates its alkaline hydrolysis.
Methods for forensic comparison and characterization of commercial polymer‐based materials
Authors: West J. C. 
Published: June 2010

AbstractThe methods used to examine forensic samples of commercial materials containing polymeric substances are summarized. The materials most commonly encountered are paint, textile fibers, fabrics, plastics, wire insulation, adhesives, adhesive tapes, and buttons. These materials are basically organic polymers which are filled to various extents with inorganic stabilizers, pigments, and/or extenders. The materials are therefore examined for both organic and inorganic constituents.Techniques used to examine organic constituents include infra‐red, pyrolysis and infra‐red, pyrolysis gas chromatography, and chemical modification such as hydrolysis, followed by derivatization and gas chromatographic analysis of the derivatives.Techniques used to examine inorganic constituents include spectrography, x‐ray fluorescence spectrometry, infra‐red, and scanning electron microscopy when coupled to an x‐ray analyzer.
Analogies and discrepancies between cationic and anionic polymerizations
Authors: Pepper D. C. 
Published: June 2010

AbstractResults are reviewed on cationic polymerizations initiated by γ‐rays, by carbocation salts, and by strong acids, especially HClO4, with the conclusion that in no case are all criteria for true living polymerization satisfied.Detailed information is presented on bimodal molecular weight distributions found in polystyrenes initiated by HClO4 in CH2Cl2 between 0 and −97°C, showing that at all temperatures, polymerization can take place via both pseudo‐cationic and true ionic species, with the former in numerical preponderance. Transfer reactions prevent these species from being in simple ionization/recombination equilibria with each other, hence precluding a true living polymerization situation.The chief reason for these kinetic complexities is concluded to be a strong monomer‐complexation of the HClO4 initiator and of propagating species. Indications of similar complexation in styrene/H2SO4 and Ph3CClO4, and between HClO4 and five other monomers suggests it may be a fairly widespread feature in cationic polymerizations.
Copolymerization and the hot radical theory
Authors: Tüdöds F. , Kelen T. , Berezhnikh T. Földes 
Published: June 2010

AbstractA new improved linear graphic method allowing simple and reliable determination of the reactivity ratios and estimation of the adequacy of the composition equation (i.e., of the mechanism of copolymerization) is presented.After a brief description of the basic principles of the hot radical theory, a complete treatment of the binary copolymerization, with the aid of this theory, is given. A kinetic analysis shows that for the complete characterization of the copolymerization, 13 parameters are required. According to this theory, four parameters of the classical theory depend on concentration and dilution, and only one value is a real constant. The requirements of experimentation and computation for the real estimation of all 13 parameters are elaborated.
Chemical transformations of cyclo and related polymers
Authors: Butler George B. 
Published: June 2010

AbstractThe 1:2 regularly alternating copolymer of divinyl ether and maleic anhydride produced via the cyclocopolymerization mechanism has been converted to a number of derivatives, and certain of these derivatives have been found useful as antitumor agents. Citraconic anhydride was substituted for maleic anhydride in the above cyclocopolymerization and its derivatives also exhibited antitumor properties, as did the derivatives of the copolymers of furan with maleic anhydride and with itaconic anhydride, respectively. The divinyl ether‐maleic anhydride copolymer reacts with dimethylformamide to yield a copolymer possessing polyelectrolyte character. The completely methylated copolymer was found to be useful in determining the molecular weight distribution of the original copolymer by gel permeation chromatography.A second series of reactive polymers were prepared by cationic initiation of o‐, m‐, and p‐(2‐vinyloxy)ethoxy‐β‐nitrostyrenes, propagation occurring only through the vinyloxy group. The polymer of the p‐isomer was crosslinked through anionic initiation on the nitrovinyl group. The m‐ and p‐isomers were converted to linear polymers through the nitrovinyl group via anionic initiation which underwent crosslinking through the vinyloxy group upon standing in air. The o‐isomer was not converted to polymer via anionic initiation. This unusual “ortho effect” appears to be a steric effect, as the only ortho derivative of β‐nitrostyrene which has been polymerized by anionic initiation is o‐fluoro‐β‐nitrostyrene. Poly‐m‐β‐dinitrostyrene was converted to the polyanion by sodium methoxide.A third series of reactive polymers were synthesized via anionic initiation on the o‐, m‐, and p‐(2‐vinyloxy)ethoxystyrenes. Propagation occurred through the styrene double bond leaving the vinyloxy group pendant. Hydrolysis of this vinyl ether was accomplished in all cases to yield the poly‐2‐hydroxyethylstyrenes. Further reactions of these polymers with acrylonitrile, phenyl isocyanate, and diisocyanates led to new polymeric systems. Hydrolysis of the vinyloxy group of the original styrenes followed by esterification with acrylyl chlorides led to monomers that were cyclopolymerized by a radical mechanism to polymers containing ten‐membered rings.
The paracrystalline state of synthetic polymers
Authors: Hosemann R. 
Published: June 2010

AbstractThe combined analysis of x‐ray small‐ and wide‐angle scattering (SAXS and WAXS) or oriented synthetic polymers provides much information about their molecular and supermolecular structures. Special liquid‐like distortions exist as a consequence of chain conformations, typical to polymers. They can be described quantitatively by paracrystalline distorted microdomains. Their size is determined by the concentration of these distortions. The microparacrystallites are interconnected by segments of chains, both in lateral and chain directions. This three‐dimensional network is the reason for a rubber‐like elasticity of all polymers, whatever their degree of crystallinity. The microparacrystallites are the knots of the network, which can also be described by a paracrystalline superlattice with nematic‐ and smectic‐like properties dependent on the mechanical and heat prehistory. On the basis of this very general concept, stretching and annealing phenomena can be described quantitatively, as well as structural changes by graft copolymerization of polyethylene with styrene under 60Co‐irradiation. The insufficiency of the two phase model is pointed out.
Organization of macromolecules in the solid state: A personal approach
Authors: Keller A. 
Published: June 2010

AbstractThe purpose of the article is to highlight the existence of large‐scale regular organizations in high polymers in order to provide a contrast with the more traditional conceptions based on randomness in the solid polymeric state. The selection adopted in this article is highly personal. Not unnaturally the author's own material forms the backbone of the survey; other material featured is quoted selectively to fit into the spirit of the narrative. It is hoped nevertheless that the overall impression given will be a balanced view, particularly in the more controversial aspects of the subject, emphasizing the complementary part played by order and disorder in a solid polymer. The material selected ranges from “historical” items to most recent developments, some still unpublished, which perhaps in retrospect are not as far apart as it may appear at first sight.Most of the material quoted is concerned with crystallization. The main items featured are macroscopic single crystals obtained by solid‐state polymerization, spherulites, chain‐folded lamellae with current issues relating to the nature of the fold surface, fibrous crystals, and the range of validity of the fringed micelle concept. In the course of this the nature of disorder in all these systems is also outlined and an appreciation is given of the usual technological material. The final section is devoted to some examples of remarkably regular organizations in twophase amorphous block copolymers.
Some photochemical reactions in solid polymer systems
Authors: Smets G. J. , Thoen J. , Aerts A. 
Published: June 2010

AbstractThe influence of the polymeric matrix on photochemical reactions proceeding in solid polymers has been examined in the case of a free radical photosensitive svstem and in the case photochromic polymers. The free radical photosensitive system is composed of polyvinylcarbazol matrix (PNVC) containing carbon tetra‐bromide as activator and di‐β‐naphthospiropyran as dye‐precursor in an average ratio 5/0.1.1. The latent image formation results from the photolysis of the charge‐transfer complex between PNVC and CBr4 (γ = 405 nm); hydrobromic acid is produced and reacts with the dye‐precursor with formation of a pyrylium salt. This pyrylium salt (latent image) and its CBr4 complex act as photosensitizers (Λ = 600–700 nm) for further HBr formation; the optical development results thus from the dve accumulation at the sites of primary irradiation. Quantum yields of photolysis of CBr4 and coloration efficiencies have been measured under different experimental conditions. With respect to photochromic polymers, the influence of the molecular size of indoleninobenzopirans on the thermal decoloration reaction has been examined. It was found that bisphotochromes oligomers dissolved in a poly(ethylene terephthalate). poly(ethylene isophthalate) (50/50) or in polystyrene and irradiated above 60°C show only a very limited fading in a first phase. and then are stabilized. On the contrary, low molecular photochromes or photochromic dimers present a rapid initial fading followed by a slow first‐order decoloration reaction.
Telomerization of styrene initiated by the system magnesium‐isopropanol‐carbon tetrachloride
Authors: Bormann Patrick , Franta Emile , Rempp Paul 
Published: June 2010

AbstractTelomerization of styrene and of some other vinyl monomers is achieved by means of an initiating mixture made of a metal with a single positive degree of oxidation, a transfer agent, a solvent, and a monomer. The four constituents have to be present at the beginning of the reaction.The yield and the molecular weights of the polymers produced have been studied as a function of temperature and concentration of reactants.Propagation and termination steps proceed via a radical mechanism. The initiation reaction shows a surprisingly low activation energy.
Relative reactivities in cationic polymerization of styrene, acenaphthylene, 4‐vinyl biphenyl and 2‐vinyl fluorene influence of experimental parameters
Authors: Cohen Sylvain , Marechal Ernest 
Published: June 2010

AbstractThe relative reactivities of the following monomers: acenaphthylene, 4‐vinyl biphenyl, and 2‐vinyl fluorene are determined both experimentally and through quantum chemistry methods. Styrene is the reference monomer. The influence of experimental conditions: solvent, temperature, nature of the initiator are studied and the activation enthalpy and entropy differences determined. The comparison of these values with the 1/r2 (index 2 is relative to styrene) shows that, in a general way, the activation entropy is the determining reactivity factor. The stabilization energies are calculated both by Hückel's and Pople's methods and the values so obtained are in close agreement with experimental results. The discrepancy observed for acenaphthylene, between Hückel on the one hand, and Pople and experimental determinations on the other hand, is due to the strain of the pentagonal ring.