bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractionnement du polyterephthalate d'ethylene par une methode en continu
Authors: Pailhes F. , Alliot‐Lugaz M. , Duveau N. , Kyritsos Et J. 
Published: June 2010

AbstractA method for the continuous fractionation of poly(ethylene terephthalate) is described. It is based on the distribution of the polymer between two liquid phases in a ternary system solvent‐nonsolvent‐polymer. Continuous fractionation is achieved in a cell where both phases coexist. A solvent‐nonsolvent mixture, with a time increasing solvent concentration, enters the lower layer, whereas the upper phase overflows continuously drop‐wise into the collector tubes. The polymer is thus progressively extracted in the order of increasing molecular weights, while the volume of the lower phase diminishes to zero. The choice of experimental conditions is indicated by establishing the ternary phase diagram solvent‐nonsolvent‐polymer in the demixing region. Among different solvent‐nonsolvent systems tested, the most convenient is the phenol‐n‐heptane mixture at 56°C. The molecular weight distribution of different samples obtained by this method is very close to Flory's theoretical distribution. Morever, a mathematical derivation is given which leads to a plot from which the discrepancy from this law may be estimated.
Polyimides
Authors: Sroog C. E. 
Published: June 2010

AbstractThe preparation and properties of aliphatic and aromatic polyimides are reviewed. The discussion includes a comparison of methods of synthesis of the aliphatic vs. aromatic polymers and a detailed consideration of chemical structure vs. properties. The discussion of properties includes, in addition to properties of films and similar articles, various aspects of polymer properties such as crystallinity and solution viscosity relationships.
Some peculiarities of the polymerization of propiolic acid and its salts
Authors: Davidov B. E. , Krentsel B. A. , Kchutareva G. V. 
Published: June 2010

AbstractThis paper treats some theoretical premises determining peculiarities of acetylene polymerization and properties of polyene systems containing carboxy groups. Some kinetic mechanisms of the radiation polymerization of propiolic acid in the liquid phase were experimentally studied. It is shown that solid‐state polymerization of propiolic acid leads to the formation of the polymer with a higher molecular mass and greater effective conjugate length. The solid‐state polymerization of propiolic acid salts illustrates the dependence of the inclination to polymerization of ion metal radius. Some properties of polypropiolic acid and its salts were investigated, in particular, their inclination to photochemical reactions. A certain influence of the polyconjugate system and of the type of polyene chain configuration on the polypropiolic acid property as polyelectrolyte was discovered.
On the cross‐fractionalion of copolymers
Authors: Litmanovich A. D. , Shtern V. Ya. 
Published: June 2010

AbstractA method of theoretical analysis of copolymers fraction is described. Using the method the cross‐fractionation of copolymers is considered. It is found for copolymers of a typical molecular and composition distribution that: the differential molecular distribution curves for almost all the fractions are symmetrical in shape; most of the fractions have sufficiently broad composition distribution, the composition heterogeneity of some light fractions being especially high; the molecular distribution curves of the original copolymer constructed from the cross‐fractionation data deviate, although insignificantly, from the true curves; the composition distribution curve of the original copolymer constructed from the cross‐fractionation data deviates essentially from the true curve, but does not distort the character of composition heterogeneity of the original sample in such degree, as in the case of successive precipitation procedure. The efficiency of the procedure of the cross‐fractionation of copolymers is discussed.
Precipitation of acidic polysaccharides by salts in ethanol–water mixtures
Authors: Smidsrød Olav , Haug Arne 
Published: June 2010

AbstractThe results of the present investigation show that precipitation with ethanol and inorganic salts may be a useful tool for the separation of the components of a polysac‐charide mixture. The solubility of neutal polysaccharides in ethanol–water mixtures is independent of the presence of salt except for high salt concentrations. The presence of anionic groups in the polysaccharide makes the solubility of the compound sensitive to the presence of ions, and the effect of the different cations depends on the type of anionic group on the polymer. Determination of cation activity by a cationic electrode revealed no correlation between the formation of ion pairs and the precipitating effect of the different cations. Viscosity determinations of dextran sulfate solutions showed that the viscosity at the salt concentration leading to precipitation was independent of the type of salt used. This result indicates that the different ion pairs formed on the polymer chain have a different effect on the interaction between the solvent molecules and the chain segments. Experiments with alginate showed that the divalent cations caused precipitation at higher viscosities than the monovalent ions, indicating that the divalent ions in this case have a different effect, probably by forming intermolecular bonds.
Formation of radicals in polymers
Authors: Sharpaty V. A. , Pravednikov A. N. 
Published: June 2010

AbstractThe results of the investigations of radiolysisof polyamides, polyacrylamide and its nitrogen derivatives, polymers of the triazine series and their low molecular analogs are reported. It was detected that the main radical formed during the radiolysis of polyamides is the radical with the formula –CONHĊHCH2—. Arcording to ESR and mass spectrometric investigations, some conclusions on mechanism of transformat ion of radicals are given. In the case of radiolysis of polyacrylamide and its nitrogen derivatives radicals arise as a result of breaking of CH bond of main polymer chain next to the amide group. The paramagnetic particles registered in irradiated polymers of triazine series are assumed to result from the transformation of the triazine cycle.
Critical opalescence of polymer solutions
Authors: Eskin V. E. , Nesterov A. E. 
Published: June 2010

AbstractThe critical opalescence of poly(butyl methacrylate) (PBMA) in isopropanol, poly(di‐methyl siloxane) (PDMS) in tetralin, poly(β‐vinyl naphthalene) (PVN) in three solvents, and poly (β‐naphthyl methacrylate) (PNMA) in four solvents has been studied. The general character of the phenomenon is in accord with the Debye theory. The critical concentrations V2c of the solutions are from 1.5 to 4 times greater than the theoretical values calculated according to the Flory‐Huggins theory. The relative dimensions (R̄c2/R̄o2)1/2 of the polymer coils near the critical temperature Tc decrease when the ratio of V2c to its theoretical value increases. The dependence of the square of the interaction distance for intermolecular forces l2 on the molecular weight M for PBMA and PNMA is nonlinear. For PVN in phenylethyl alcohol does not depend on M. A tendency is noted toward larger values of (1/R2)(dR2/dT) and of the range ΔT0 in which the dimensions (Rc2)1/2 remain constant for systems with small (R̄c2/R̄o2)1/2) values. The cohesive nergies of the polymers δ22V2 calculated from the critical opalescence data are as a rule in satisfactory agreement with the values obtained by other methods. The range l of the intermolecular forces and (R̄c2)1/2 are variable and depend on the difference between the cohesive energy densities of the polymer and the mixture δ22 –δ12 A correlation is noted between δ11 + δ22 – 2δ12 calculated from the critical opalescence data and the heat of dilution Rϕψ1.
Preparation of high molecular weight compounds on the basis of cyclic imides and diimides of dicarboxylic acids
Authors: Sheremeteva T. V. , Larina G. N. , Zhenevskaya M. G. , Gusinskaya V. A. 
Published: June 2010

AbstractInvestigation has been conducted in two directions: incorporation of the imide cycles into the macromolecule owing to the reactivity of double bonds, and preparation of polyamides involving the aminolysis of the imide cycles. Citraconimides are shown to polymerize by radical mechanism forming linear macromolecules consisting of the imide cycles. At the initial period the polymerization rate is proportional to the square root of the initiator concentration. The absolute values of the polymerization rates are low. Conversions attains 3% for 75 min. at 70°C. with 0.102 × 10−3 mole/liter of the initiator. The intrinsic viscosities are 0.07–0.1% Low polymerization rates and low molecular weights are due to the structure of this cyclic derivative of 1,2,2‐substituted ethylene with the methyl group at the double bond. An attempt to polymerize N‐methylcitraconimide by UV irradiation resulted in the formation of a mixture of crystalline oligomers; a tetramer was isolated and characterized. Migration copolymerization of diamines with diimides of unsaturated and saturated acids was also investigated. It was shown that the reaction depends on pH of the medium. In neutral medium in the absence of water diamines are added to the double bonds of maleindiimides forming poly‐alkylene‐polyimides of asparagic acid. In aqueous alcohol at pH 9–9.5 aminolysis of succinimides occurs and mixed polysueeinamides are formed with regular structure and molecular weight up to 20,000.
Poly[vinyl(oxyacetoxy)phosphinic acids]
Authors: Kafikov S. R. , Chelnokova G. N. , Artyemova Yu. V. 
Published: June 2010

AbstractOxidative chlorophosphination of poly(vinyl acetate) (PVA) results in poly[vinyl (acetoxy)phosphoryl chloride] formation and is not accompanied by significant destruction of the main chain. The maximum phosphorus contents in the product obtained have been as high as 12%, which corresponds to one phosphoryl chloride unit per two PVA units. Oxidative chlorophosphination is accompanied with side reaction of acetyl groupsphosphoryl oxychloride interaction. Depending on hydrolysis conditions of poly[vinyl‐(acetoxy)phosphoryl chloride], the mixture of poly [vinyl(oxyacetoxy)phosphinic acids] is formed with different ratio of acetyl and hydroxy groups, down to complete disappearance of acetyl groups. The derivatives of poly(vinylphosphinic acids) have been obtained which are soluble in DMFA, aqueous alkalis and (if phosphorus contents is high) in water. These compounds are very labile, easily undergo crosslinking, and when reacting with alkalis or metal acetates yield salts. The films obtained from acids and their salts are of amorphous structure and have certain complex of mechanical properties.
The nature of friction of polymers in high elastic and glasslike states
Authors: Bartenev G. M. , Elkin A. I. 
Published: June 2010

AbstractThe temperature dependence of the friction of polymers against hard surface is characterized by two maxima: main and low temperatures. The main maximum observed in the glass transition range, contrary to the widespread opinion, is not associated with the maximum of the mechanical losses observed in polymers. The temperature dependence of the friction force consists of three ranges. In the high elasticity range, with decreasing temperature, the friction force is observed to increase according to the molecular kinetic theory of the friction of rubberlike polymers. The nature of the friction for all polymers in this range is associated with the mechanical losses in the surface monomolecular layer of the polymer. The bulk‐mechanical losses in the polymer are not essential. The deviation from the theoretical dependence and the decrease of the friction force below a certain temperature in the transition range are associated mainly with the decrease in the actual contact area of suriaces of the friction pair at the glass transition of the polymer. In the glasslike state, for polymers the friction is essentially dependent on the bulk‐mechanical losses in the polymer at elastic and forced elasticity strain of the roughnesses in the polymer layer being in contact with a solid. Therefore, the low temperature maximum is associated with the maximum of the mechanical losses observed in the same range of temperature at dynamic tests. For polymers with no maximum of the mechanical losses at low temperatures, the maximum of the friction can be attributed to the increase in the adhesion forces and the drop in the actual contact area at temperatures at which the forced elasticity mechanism of compression of the polymer roughnesses is not realized.
Block polymers of controlled chain length
Authors: Yamazaki N. , Shirakawa H. , Kambara S. 
Published: June 2010

AbstractTo obtain block polymers of controlled chain length, the condensation reactions of poly‐α‐methylstyrene dianion polymerized with sodium naphthalene in tetrahydrofuran with α,ω‐dihalogenopolymethylene were investigated. The polymers obtained correspond to the formula + (α‐methylstyrene)m‐(methylene)n+x (m = 2, 4, and 10 and n = 4, 10, 20, and 34). Molecular weight of the polymers was 103‐104. Intensity of bands in the fingerprint region in infrared spectra of the polymers was found to change with increasing m. Melting point due to polymethylene microcrystallites was dilatometrically observed in the block polymers containing over 20 methylene groups.
The effect of extreme supercooling on the number of spherulitic centers in isotactic polystyrene
Authors: Boon J. 
Published: June 2010

AbstractThe bulk crystallization of isotactic polystyrene has been investigated by means of hot‐stage microscopy and dilatometry between 120 and 200°C. The linear growth rate of spherulites is independent of the thermal history. However, heating from the glassy state yields a ca. 102 times faster overall crystallization than cooling from the melt. So the number of spherulites in the former case is ca. 106 times as great as the number in the latter. This increase in density of spherulitic centers does not originate from nucleation during the thermal pretreatment, but from subcritical ordering near Tg. The density can be regulated between 1012 and 107/cc. by choosing pretreatment temperatures in the range from 75 to 110°C. and is independent of the later crystallization temperature (140–180°C.). It has been possible to determine the rate of nucleation out of the sub‐critical ordering over a wide temperature range. It shows a maximum at ca. 160°C., while the maximum of growth is at 175°C. The nucleation constants Kn and Kg were analyzed to obtain σ2σe = 174 ergs3/cm.6 and σσe, = 167 ergs2/cm.4, respectively. A work of chain folding q of 4.4 kcal./mole of folds was calculated.
Influence de l'Initiateur de Polymérisation et de la Masse Moléculaire du Produit Formé, sur l'Absorption des Ultrasons par les Solutions de Polyméthacrylate de Méthyle
Authors: Tondre C. , Cerf K. 
Published: June 2010

AbstractThe variation of the characteristic frequency N* (i.e., the frequency at which the rapid decrease of the ultrasonic absorption occurs) has been studied as a function of molecular weight Mw for different poly(methyl methacrylate) samples dissolved in benzene. Two categories of these products show up according to the initiator of polymerization. For the first one N* increases with Mw; for the second one N* does not depend on Mw. It appears that the variations of N*, either as a function of the initiator for the same molecular weight, or as a function of the molecular weight for a series of fractions, are not determined only by the global degree of NMR tacticity. The molecular weight does not seem to have a direct influence on the value of N*.
Über die Synthese und das Verhalten von Polyoxypropylenglykol‐Diglycidäthern
Authors: Jahn H. , Raubach H. , Goetzky P. 
Published: June 2010

AbstractPolyoxypropylene glycols with average molecular weights of 270, 425, 565, and 920 are converted by two different methods to the corresponding diglycidyl ethers. Polyoxypropylene glycol diglycidylethers (A) synthesized via chlorohydrin contain ClCH2 groups as a result of competition between the secondary hydroxyl groups of the poly‐oxypropylene glycol and those of the already formed chlorohydrin ethers in the presence of the epichlorohydrin. The formation of these ClCH2 groups consumes epichlorohydrin, thus causing a corresponding deficit of glycidyl groups. Treating the sodium alkoxides of the polyoxypropylene glycols with allyl bromide followed by epoxidizing the diallyl ethers with peracetic acid yields diglycidyl ethers (B), which contain acetyl groups Crosslinking mixtures from diglycidyl ether of bisphenol‐A and polyoxypropylene. glycol diglycidyl ethers A or B with diethylene triamine yields flexible epoxy resins. Properties of epoxy resin systems containing diglycidyl ethers A or B differ only slightly. By applying the theory of rubberlike elasticity the crosslinking density and thes hear modulus G of the flexible epoxy resins systems are calculated. The calculated shear moduli and those measured above the glass transition temperature are in relatively good agreement. Epoxy resin systems with none or a high content of flexibilizer show differences, which are caused by two effects.
Infrarot‐ und kernresonanzspektroskopische untersuchungen der umwandlungen des polytetrafluoräthylens bei 20 und 30°C
Authors: Kriegsmann H. , Seifert G. , Frigge K. , Dube G. 
Published: June 2010

AbstractThe well‐known transitions that occur in polytetrafluoraethylene at about 20 and 30°C. also appear in infrared and nuclear magnetic resonance spectra. In the infrared spectrum the band at 625 cm.−1 increases and the band at 638 cm.−1 decreases with an increasing temperature. At 20 and 30°C. two abrupt changes in intensity of these bands occur. In the nuclear magnetic resonance spectrum the linewidth and the second moment are reduced at the same temperatures. An attempt is made to explain these results on the basis of the known conception of the inversion of the helix. The motion producing this inversion is hindered very strongly by the existing crystal lattice below 20°C. At about 20°C. the thermal energy is high enough for motion to set in in spite of this hindering, accompanied by the transition into a new crystal lattice. The transition at about 30°C. is an analogous process.
Homo‐ and copolymerization of vinyl phosphates and phosphonates
Authors: Muray B. J. 
Published: June 2010

AbstractPhosphorus–containing monomers of general formulaemagnified imagehomopolymerized, copolymerized with methyl methacrylate, vinyl acetate, and styrene under a variety of conditions, and the products were characterized. The results of homopolymerization show that yields and the degree of polymerization depend on the purity of the monomers, method of polymerization, and the initiator used. With the exception of monomers containing β‐chloroethoxy group attached to the phosphorus atom, polymers obtained from the dialkyl vinyl phosphates had higher molecular weights than the corresponding dialkyl vinyl phosphonates. Dialkyl isopropenyl phosphates polymerized less readily than the dialkyl vinyl phosphates and diethyl styryl phosphate did not polymerize at all. An attempt is made to explain these results in terms of steric hindrance, charge distribution, and chain transfer. Examination of the copolymerization products, with a number of techniques used, indicates that these consist of polymers with a wide range of compositions and molecular weights. The copolymers with methyl methacrylate appear to consist of a large block of poly(methyl methacrylate) at one end and a smaller block of polymer formed from the vinyl phosphate or phosphonate at the other. Similar conclusions are drawn about copolymers involving styrene. It is likely that the monomer units in copolymers with vinyl acetate are randomly distributed.
Dynamic birefringence of poly(methyl methacrylate)
Authors: Read B. E. 
Published: June 2010

AbstractThe dynamic modulus, strain‐optical coefficient, and stress‐optical coefficient have been measured for conventional poly(methyl methacrylate) (PMMA) in the frequency range 16–10−2.5 cps and at temperatures between −130 and +140°C. Both the α (glass–rubber) relaxation and the β relaxation have been detected in plots of each of these observables, or the appropriate phase angles, against temperature or frequency. The extremely broad mechanical β relaxation suggests a wide distribution of relaxation frequencies. The high‐frequency modes lead to a relaxation of the strain‐optical coefficient while the stress‐optical coefficient remains essentially constant. Conversely, the low‐frequency modes result in a relaxation of the stress‐optical coefficient at constant strain‐optical coefficient. The results are discussed in relation to the polarizability anisotropy of the PMMA repeat unit, and comparisons are made with dielectric data and with earlier dynamic birefringence data obtained for poly(methyl acrylate) (PMA).
Die Kinetik der Biosynthese der Cellulose in den Höheren Pflanzen
Authors: Marx‐Figini M. 
Published: June 2010

AbstractKinetic investigations on the cellulose of cotton bolls with increasing maturity have shown that the degree of polymerization remains constant by P̄w = 13,000 during the entire course of secondary wall synthesis, from which arise more than 90% of the material. Therefore the conclusion had been drawn that the biosynthesis of the plant cellulose proceeds by a template mechanism. To confirm this result molecular weight distributions at conversions of 18 and 100% had been investigated. They show that the cellulose of the secondary wall has a nearly complete uniform degree of polymerization about Pw = 14,000 independent of the conversion. Both molecular weight distributions differ only in the percentage content of primary wall cellulose, which nearly disappears in the sample of 100% conversion, as was expected. The molecular weight distribution curve of a cellulose, which was harvested a short time before the beginning of the secondary wall synthesis, shows that the degrees of polymerization smaller than Pw = 6,000 belong to the primary wall cellulose. The template mechanism for the biosynthesis of the cellulose was confirmed further by the independence of the degree of polymerization from the rate of the synthesis and the variety of the cotton plants.
Zur Theorie der Glastemperatur von Vernetzten Polymeren
Authors: Kanig Gerhard 
Published: June 2010

AbstractIu a previous work the corresponding state at the glass temperature has been described: (1) by means of a material‐independent constant ratio between the holes volume and the vibrational expansion volume, and (2) by means of material‐dependent work parameters which are characteristic for the production of a hole and, at the same time, constitute a measure for the affinities between the local regions of the molecules. If a crosslinked polymer is considered as a copolymer of monomeric units and crosslinking units, a thermodynamic relationship corresponding to that for copolymers may be derived in the same way as before. By neglecting a square term, very simple relationships can be derived from this for more weakly crosslinked polymers. The relationships agree closely with experimental results.
Elastic and viscoelastic behavior of glass‐reinforced plastics
Authors: Zvonač Vladimír , Tamchyna Jiří 
Published: June 2010

AbstractThe measurements of short‐term creep in dry and wet states are interpreted in terms of relationships among the composition, adhesion, and properties of glass‐reinforced plastics. Elementary constants of a rheological model were determined and the factors controlling the behavior of glass‐reinforced plastics are discussed. The role of adhesion is emphasized and the influence of water is interpreted.