bluuebunny/crossref_metadata_2025_split huggingface dataset:
The theory of branching processes and kinetically controlled ring—chain competition processes
Authors: Gordon M. , Scantlebury G. R. 
Published: September 2014

AbstractThe statistical theory of branching processes provides unified and powerful methods for calculating statistical parameters, especially for branched polymer systems. A review of some recent calculations provides examples such as the sol fraction, molecular weight and configurational size averages, and the concentration and mean length of active network chains in f functional random or nonrandom polycondensations. The theory furnishes a useful approximation to the calculation of thermodynamically or kinetically controlled ring–chain competition processes in branched systems.
Étude de la Distribution des Compositions au Sein de Copolymères Préparés Par Voie Radicalaire
Authors: Herz Jean , Decker‐Freyss Danielle , Rempp Paul 
Published: September 2014

AbstractThe instantaneous composition of a radically prepared copolymer is a function of the composition of the monomer mixture. Thus, if a copolymerization is carried out to give a high yield, the obtained copolymer is not homogeneous in composition. In the present paper, it has been tried to relate the fluctuations in composition within a copolymer sample with the copolymerization yield, knowing the reactivity ratios of the two corresponding monomers. Integration of the Skeist equation, which expresses in a differential form the copolymer composition as a function of copolymer yield, has been performed by means of an electronic computer, for three different monomer systems: styrene—methyl‐methacrylate, styrene—p‐bromostyrene, and styrene—α‐vinyl‐naphthalene. Copolymerization experiments were carried out to various yields, and followed by careful characterization of the obtained products, by analysis, fractionation and UV spectroscopy. The obtained results concerning composition distribution within the samples and the average composition of the copolymers as well are in satisfactory agreement with the corresponding data theoretically established in the first part of the work.
Structure and reversible deformability of oriented crystallizing polymers
Authors: Slutsker A. I. , Sanphirova T. P. , Yastrebinskii A. A. , Kuksenko V. S. 
Published: September 2014

AbstractThe effect of reversible (elastic) extensions of oriented crystallizing polymers on long periods within them, recorded by small‐angle x‐ray diffraction, has been investigated. The reversible shift of the meridian maximum of diffraction intensity toward small angles (which means the increase of long periods) as well as the maximum diffraction intensity increase with polymer loading have been established. The agreement of relative increments of long periods and polymer‐specimen dimensions is rather common, although some instances when the period deformation exceeded the specimen deformation have been observed (for highly annealed oriented polymers). The invariability of crystallites with polymer extension (according to large‐angle x‐ray diffraction) indicates that the deformation of long periods, which are formed by the alternation of crystalline and amorphous regions along the orientation axis, is caused by crystallites transference due to stretching the amorphous interlayers between them. The increase of small‐angle diffraction intensity with the extension of oriented polymers is supposed to be due to two factors: (1) the reduction of crystallite share in long periods; and (2) the decrease of the density of extended amorphous interlayers which results in increasing the density difference of alternate crystallites and amorphous regions. The problem of more precise definition and checking of these conclusions is raised and attention is drawn to the great interest in investigating the amorphous‐region properties in oriented crystallizing polymers, which determine the mechanical properties of polymers.
Untersuchungen über die Eigenschaften hochvernetzter Polymerer mit Hilfe der mechanischen Relaxation
Authors: Pohl G. , Kästner S. 
Published: September 2014

AbstractIn this paper we report on the mechanical behavior of maleic acid hexandiol polyester cured with styrene. The measurements show a broad relaxation region which is composed of two components. To explain this result we must consider the structure of the polyester resin. Besides polyester chains we also have polystyrene maleic acid copolymer chains. Both components give a specific contribution to the mechanical relaxation behavior, but simultaneously a strong interaction to each other.
Spectrophotometric titration of polymethacrylic acid
Authors: Michaeli Isaac 
Published: September 2014

AbstractOptical density measurements were performed on aqueous solutions of polymethacrylic acid (PMA) at different degrees of neutralization with NaOH, both in the presence and absence of added Na2SO4; the wavelength region studied was 188–250 mμ. The data could be consistently interpreted in terms of an equilibrium between two conformational states of the macromolecules. The distribution of the total monomeric units and of the charged groups between the two states could be spectrophotometrically determined; this provided the necessary information for the evaluation of the titration curves of each conformational state separately. Free energies of transition from the “low pH” form to the “high pH” form, at zero ionization, were derived from the above data, and found to be of the order of one kT unit per monomer.
Small molecule—Protein interactions and the conformation of serum albumin
Authors: Arvidsson E. O. 
Published: September 2014

AbstractPrevious studies on small molecule—protein interactions by the present author and studies on the denaturation of serum albumin by Gorbacheva et al. and by Janatová indicate that the tertiary structure of the native serum albumin molecule does not represent the thermodynamically most probable conformation. It is suggested that the amino and carboxyl groups of the albumin molecule are locked into positions which are metastable with respect to solvent, probably by means of the S—S bonds. The resulting intramolecular interactions (“salt bonding”) in serum albumin then affect intermolecular interactions as manifested by its “abnormal” binding properties. These interactions should also be considered when discussing “abnormal” titration and denaturation properties as an alternative to masking of groups and/or heterogeneity.
Magnetic susceptibility as an application to the study of order—disorder phenomena in polymers
Authors: Calleja F. J. Baltá 
Published: September 2014

AbstractThe diamagnetic susceptibility of differently prepared polyethylene samples was measured. The application of an expression for the molecular susceptibility based on Pascal's additivity law permits the calculation of intermolecular constants associated with different physical states. Treatments such as hot and cold drawing or crystallization from the melt or solution give rise to susceptibility values χ corresponding to intermediate degrees of order between those of the pure “gaseous” and the pure “crystalline” state. Chain folding does not affect the χ values. Chain branching provokes an increase of χ, indicative of a decrease of order.
Untersuchungen über die Beziehung zwischen Langperiode und Kettenlänge in Poly(äthylenoxyd)‐Kristallen
Authors: Calleja F. J. Baltá , Hosemann R. , Wilke W. 
Published: September 2014

AbstractThe study of annealed polyethylene oxide crystals grown from solution has been carried out in the molecular weight range where the transition from the extended chain conformation to the folded chain conformation was expected to occur. Both the variation of the long period with chain length and the chain orientation with respect to the vertical direction to the crystal lamellae plane have been investigated. The value of the long period for crystals grown in p‐xylene closely corresponds to that calculated for a 72 helix. During annealing no change of the long period takes place due to the effect of hydrogen bonds of the endgroups.
Influence de la Stereorégularite des Chaînes sur les Transitions du Polyméthacrylate de Méthyle
Authors: Wittmann J. C. , Kovacs A. J. 
Published: September 2014

AbstractDilatométric studies on five PMM samples of different tacticities show generally three transition ranges between −35 and 150°C. The main glass transition temperature depends on the relative proportion of the iso‐ or syndiotactic segments. The secondary transition, located around 60°C., seems to be related to the presence of heterotactic segments. The third transition range, common to all the five samples, located around 0°C., may be attributed tentatively to the freezing in of the ester side groups.
Organic semiconductors: Donor—acceptor complexes of conjugated bases with a repeating structural unit
Authors: Honzl J. , Ulbert K. , Hádek V. , Tlusťáková M. , Metalová M. 
Published: September 2014

AbstractIodine complexes of some mono‐ and diamino derivatives of diphenylamine, N,N′‐diphenyl‐p‐phenylenediamine and 4,4′‐bis(phenylamino)‐diphenylamine and their N‐methyl derivatives were prepared and their conductivity, thermoelectric power, activation energy of conductivity, and the spin concentration in the solid state were investigated. For complexes prepared from the bases with a repeating unit in the chain, the conductivity increased in most cases with the length of the chain. Complexes of bases with methylated nitrogens were more stable and had a smaller conductivity than analogous complexes prepared from nonmethylated bases. Conductivity and spin concentration in most of the substances investigated were reproducible in different batches of the same compound, and were only slightly influenced by aging and the presence of oxygen. The activation energy of conductivity and thermoelectric power exhibit larger variations. The most conductive compound had a specific conductivity of 2 × 10−1 Ω−1 cm.−1.
The effect of applied pressure in some solid state polymerizations
Authors: Fydelor P. J. , Charlesby A. 
Published: September 2014

AbstractWe report some preliminary observations on the influence of applied pressures up to 90,000 psi on some gamma‐initiated, solid state polymerizations. Four monomers have been studied: acrylamide and methacrylamide, both of which are believed to yield atactic polymer but show markedly different rates of reaction in the solid state, and some crystalline modifications of calcium acrylate and barium methacrylate, which can give rise to stereoregular polymer. The rate of polymerization of the former monomers is reduced by the application of pressure but this rate is substantially increased for the metal salts. These results are discussed with reference to the possible polymerization mechanisms.
Mechanisms of reinforcement of silicone rubbers crosslinked by radiation
Authors: Charlesby A. , Morris J. , Montague P. 
Published: September 2014

AbstractThe tensile strengths and elastic moduli of elastomers can be greatly influenced by the presence of fine particles such as carbon black or silica. This reinforcement can be due to either physical or chemical processes. The use of radiation to provide crosslinks in such systems permits the mechanism of this reinforcement to be studied. The results of some experiments on physical properties, gelation, and swelling behavior for a series of mixtures in dimethylsiloxane polymer are given. An extension to model compounds of low molecular weight allows the chemical bonding effects to be measured in the absence of geometrical inhibition arising from a network structure.
Structure of copolymers of polyacrylic acid grafted on ethylene propylene elastomers as determined by chemical/physical methods
Authors: Crugnola A. , Pegoraro M. , Severini F. 
Published: September 2014

AbstractThe raw product obtained from the emulsion polymerization of acrylic acid and ethylene–propylene copolymer is subjected to extraction to remove the polyacrylic acid homo‐polymer and the unreacted ethylene‐propylene copolymer. The residue is essentially the grafted copolymer. A determination of the force/temperature coefficient (∂f/∂T)I revealed that this material has the apparent properties of a vulcanized elastomer. We sought to single out the nature of the physical and chemical ties that are the cause of this behavior. We found that the material is heterophasic and that the intermolecular bonds are found in the phase constituted of polyacrylic acid; these bonds are of a physical nature (hydrogen bonding) and of a chemical nature. The latter are only present if the molding is carried out at sufficiently high temperatures. Intermolecular bonds have been recognized as resulting from a dehydration of the carboxyls with consequent formation of anhydride, and also from a complicated reaction involving a partial degradation of the polyacrylic acid.
Polyaddition and polycondensation. Substitution effects in polycondensation systems
Authors: Aldersley J. W. , Gordon M. 
Published: September 2014

AbstractDeviations occur from the classical postulate that all pairs of functionalities in a condensation reaction have equal rates of engaging in bond formation or bond breakage. In so‐called first‐shell substitution effects, which can be treated most readily, the rates involving functionalities X and Y are influenced at most by the existence or absence of other links borne by the two units to which X and Y are directly attached. Quantitative analyses are made of data on melamine and urea‐formaldehyde systems in terms of first‐shell substitution effects.
The molecular conformation of isotactic poly (methyl methacrylate)
Authors: Coiro V. M. , De Santis P. , Liquori A. M. , Mazzarella L. 
Published: September 2014

AbstractThe molecular conformation of isotactic poly(methyl methacrylate) (PMMA) has been investigated without considering the mode of molecular packing in the crystal lattice. The analysis has been carried out on the basis of the interpretation of the x‐ray fiber diagram with the aid of the Fourier transform method. The molecular conformation is helical, with a monomer repeat on the fiber axis equal to 2.11 A. The best agreement between the experimental x‐ray diffraction pattern and the cylindrically averaged optical Fourier transform was obtained for a helix with five monomeric units per turn.
Carhorane polymers
Authors: Gregor V. , Plešek J. , Heřmánek S. 
Published: September 2014

AbstractMonomers were prepared of substituted methacryloyloxymethyl earboranes and submitted to radical polymerization. From derivatives bearing other substituents than hydrogen on the carbon atoms in the carborane skeleton, linear polymers were obtained. Crosslinked polymers always result from carboranes, substituted on one carbon atom only. Obviously, crosslinking is the result of an interaction of the CH bond in the carborane skeleton with the growing chain of methacrylate groups.
Infrared spectra of polycarbohydrates and their model systems
Authors: Zhbankov R. G. 
Published: September 2014

AbstractThe relationship of the infrared spectra of polycarbohydrates with their specific structural properties investigated with various model systems, for example, mono‐, di‐saccharides, etc., is discussed.Obtaining the carbohydrate spectra at the temperature of liquid nitrogen has allowed to split the OR group band into distinct components and to find out peculiarities of their low‐temperature shift, and to study the relationship of OR group hydrogen bond with the configuration of certain hydroxyls more thoroughly. Due to the considerable difference in the low‐temperature shift of OR group bands in the probable frequency ranges of intra‐ and intermolecular R bonds have been established as 3350‐3560 cm.−1 and 3100‐3450 cm.−1, respectively. The frequencies and intensities of OR group bands inserted in the H bond are observed to depend strongly upon the configuration of separate hydroxyl groups, suggesting a considerable interaction between the hydroxyls of the pyranose unit. The obtained results furnish ample grounds to conclude that the frequency of OR groups inserted in the hydrogen bond is detennined not only by the energy of the R bond but by the interaction ring, depending on the configuration of separate OR groups.The establishment of a relationship between the mutual spatial arrangement of CR groups and the spectrum in the 800–950 cm.−1 region allowed us to determine the frequency intervals specific for the combinations of axial (A) and equatorial (E) CR groups EA for 810–855 cm.−1; AE for 860–855 cm,−1; AA for 885–920 cm.−1. This allows us to predict the appearance of possible frequencies in the considered region in the process of conformation transitions of the pyranose ring.The investigation of mono‐, di‐, and polysaccharide spectra in the region of CH2 group deformation vibrations and calculation of the potential function of CR2OH group inner rotations permitted us to base the essential possibility of the existence of CR2OH group rotation isomers in carbohydrates and their polymers. The investigation of the spectral feature of crystalline cellulose triesters and triethers has been carried out. It is shown that their spectra are characterized by: an intensity increase of all or the majority of the absorption bands; the selective intensity increase of separate bands; and the appearance of new absorption bands. The intensity increase for many absorption bands is explained by the prevalence of certain types of rotation isomers and the appearance of new bands by the intermolecular interaction in crystals.
Fractionation of polypropylene glycols in the molecular weight range of 1200–2400 using a novel apparatus
Authors: Frank W. A. , Kutsche H. D. 
Published: September 2014

AbstractCompounds of polypropylene glycols are used for testing the distillability of thermally very unstable substances. By means of these compounds it is demonstrated that it is possible to design molecular distilling apparatus which allows the distillation of substances that are by far more sensitive than hitherto. This was made possible by a rotation principle, which not only fulfills the other requirements of high‐vacuum distillation but also avoids catalytic effects during the distilling process.
Polymerization of ethylene glycol monomethacrylate in the presence of solvents
Authors: Wichterle O. , Chromeček R. 
Published: September 2014

AbstractHydrophilic gels have been prepared by polymerization of glycol methacrylate monoesters in the range of very low diester concentrations. The monomer mixture has been diluted with various solvents and the range has been investigated, in which swelling is independent of the dilution of the monomer mixture on polymerization. The quality of the gel is independent of the concentration and character of the solvent used in polymerization in a very broad range.
Simple approach to derivatization of alcohols and phenols for the analysis by matrix(surface)‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Borisov Roman S. , Zhilyaev Dmitrii I. , Polovkov Nikolai Yu. , Zaikin Vladimir G. 
Published: September 2014

RATIONALEDirect analysis of hydroxyl‐containing compounds by matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry (MS) methods is not always possible due to the neutral character of analytes. The suggested fixed‐charge derivatization may increase the ionization efficiency for various alcohols and phenols in specific matrix‐ and surface‐activated LDI conditions.METHODSAliphatic and steroid alcohols, as well as chlorophenols, were converted into various ammonioacetyl derivatives, containing a covalently bonded charged group, by reaction with bromoacetyl chloride and amine‐type compounds such as triethylamine, pyridine or quinoline. The derivatives are suitable for MALDI‐time‐of‐flight (TOF)MS analysis.RESULTSTriethylammoniumacetyl, pyridyliumacetyl and quinoliniumacetyl derivatives were prepared from aliphatic alcohols, some sterols and chlorinated phenols in one stage with quantitative yields. The derivatives produced characteristic MALDI and SALDI mass spectra.CONCLUSIONSThe suggested derivatization approach for the modification of alcohols is simple and does not require any expensive reagents. The derivatives include a fixed charge and produce intense signals in MALDI (preferentially non‐acidic matrices) and matrix‐free SALDI (nanostructured target) conditions. Corresponding mass spectra are suitable for the determination of molecular mass and profiling of alcohols. Copyright © 2014 John Wiley & Sons, Ltd.
Ambient analysis of leachable compounds from single‐use bioreactors with desorption electrospray ionization time‐of‐flight mass spectrometry
Authors: Liu Jian , Kennedy Joseph H. , Ronk Michael , Marghitoiu Liliana , Lee Hans , Nashed‐Samuel Yasser 
Published: September 2014

RATIONALETrace levels of bis(2,4‐di‐tert‐butylphenyl)phosphate (BdtbPP) leaching from single‐use bioreactors (SUBs) were recently found to be highly detrimental to mammalian cell growth. The traditional approach to detect the leachable requires time‐consuming solvent extraction of SUBs. To assist the qualification of SUBs and/or their manufacturing raw materials in biopharmaceutical development and manufacturing, it is essential to develop a rapid and sensitive analytical approach for detecting this leachable and related compounds, which is described in this study.METHODSNative films from several commercially available SUBs were directly examined by desorption electrospray ionization (DESI) time‐of‐flight mass spectrometry (TOFMS) without sample preparation. As a comparison, the same SUBs were also analyzed by high‐performance liquid chromatography (HPLC)/ultraviolet (UV) following the solvent extraction.RESULTSWith a suitable spray solvent selected in this study, DESI‐TOFMS enabled rapid and sensitive detection of leachable compounds directly from SUBs. Accurate mass measurement from TOFMS allowed ready identification of BdtbPP, its parent analog compound, and other polymer components in the SUBs from their protonated surrogates. The relative abundances of BdtbPP in different SUBs measured by DESI‐TOFMS exhibited good correlation with those from the traditional extraction‐based approach with HPLC/UV.CONCLUSIONSA rapid and sensitive approach was developed for direct detection of BdtbPP and other leachables from SUBs using DESI‐TOFMS. The results are in high accordance with those from conventional approaches, which indicates the usefulness of the proposed method as a qualification tool for SUBs in biopharmaceutical development and also its great potential in the analysis of extractables/leachables in a wide variety of materials, process components, devices and containers used in the pharmaceutical industry. Copyright © 2014 John Wiley & Sons, Ltd.