bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformation du Polystyrène en Solution
Authors: Reiss Claude , Benoit Henri 
Published: September 2014

AbstractThe thermal behavior of polystyrene in dilute solution has been studied by a number of methods of physical chemistry. By ultraviolet and infrared absorption measurements and other means, it has been shown that the helical conformation ascribed to the crystalline isotactic polystyrene is preserved in solution below 50°C. but vanishes beyond 80°C. Atactic polystyrene shows similar behavior, and thus probably contains stereoregular sequences. Detailed viscosity and light scattering studies in various theta solvents are presented.
Stress–birefringence properties of styrene–isoprene block copolymers
Authors: Henderson J. F. , Grundy K. H. , Fischer E. 
Published: September 2014

AbstractStress–birefringence measurements have been made on a number of styrene–isoprene block copolymers, and their mechanical properties have been interpreted in terms of their molecular structures. Essentially, the polymers consist of highly dispersed phases of polystyrene and polyisoprene and undergo elastic deformation with the polystyrene domains acting as crosslinks. Hysteresis measurements have been carried out to interpret the stress–strain behavior of the polymers in more detail and the conformational properties of films prepared with selective solvents have also been examined with similar birefringence techniques.
Cellulose ethers and esters with a low degree of substitution
Authors: Petropavlovskii G. A. 
Published: September 2014

AbstractCellulose ethers and esters with a low degree of substitution possess several new physico‐chemical properties as compared with the initial cellulose. Thus, ethers and esters with low degrees of substitution can dissolve in alkali solutions at low temperature and are more accessible to various reagents. These properties are explained by a distortion of supermolecular structure: its amorphization and the weakening of hydrogen bonding. This explanation is confirmed by x‐ray analysis and by infrared spectroscopy. X‐ray analysis of various cellulose ethers and esters with low degrees of substitution has shown that a considerable decrystallization of initial structure occurs even at the very first stages of etherification and esterification. The degree of this process depends both on the nature of the initial cellulose and on the type of the reaction (superficial, permutoid reaction). Infrared spectroscopy has shown that the substitution of a small part of hydroxyl groups in cellulose by various radicals evidently causes a new strength distribution of hydrogen bonds of the remaining hydroxyl groups. This distribution is distinguished by a greater percentage of weaker bonds.
Investigation of thermal and thermooxidative degradation of polyarylates
Authors: Rode V. V. , Rafikov S. R. , Zhuravleva I. V. 
Published: September 2014

AbstractA study of aging processes of polyarylates at low degrees of conversion revealed that crosslinking predominates during both thermal and thermooxidative processes. To evaluate the degree of crosslinking during the aging of polyarylates, calculation of the density of the polymer network has been carried out for the insoluble fraction of polymers according to Flory. An increase in temperature results in a regular increase of cross‐linkages. Polymer Ph‐2, however, loses the ability to swell at a greater rate than D‐9. The effect of oxygen on the amount of crosslinking is insignificant. The molecular weight has been found to increase in the temperature range of 250–275°C., this phenomenon is a result of branching as consequence of degradation processes. An increase of the temperature to 300–350°C. results in formation of insoluble structures. At 250–350°C. both crosslinking and cleavage of the macromolecule chain occur. Formation of three‐dimensional structures has also been proved by calculation of crosslinking and cleavage probabilities. Polyarylate Ph‐2 undergoes crosslinking to a higher degree. This is due to the peculiarity of its composition, in that its side substituent contains the easily broken lactone ring. The presence of this substituent increases the probability of crosslinking; this is well confirmed by other data obtained by us.
Radiation‐induced solid‐state polymerization of a homologous series of N‐tert‐alkylacrylamides
Authors: Zurakowska‐Orszagh Janina 
Published: September 2014

AbstractA study on the solid‐state polymerization of an homologous series of N‐tert‐alkylacrylamides under the action of γ‐radiation was carried out. More than twenty monomers of this series have been prepared starting from N‐sec‐isopropylacrylamide and N‐tert‐butylacrylamide to N‐tert‐tetradecylacrylamide. Some N‐arylacrylamides and N‐arylmethacrylamides were included also. For comparison the polymerization in solution of the same series of monomers induced by radiation as well as by chemical initiators was investigated. Results obtained for the series of N‐tert‐heptylacrylamides and N‐tert‐hexylacrylamides were discussed in more detail. An interesting coincidence between the reactivity of the particular isomers in the solid state and in solution was observed also for the radiation‐induced as well as chemically initiated polymerization. The comparison of melting points of both isomers series with their reactivity in the solid state shows that, in general, higher polymerization rates correspond to lower melting temperatures. The role of the symmetry and the structure of the homologous substituents on the polymerization rate was observed.
The theory of dielectric losses in amorphous polymers in the high‐temperature range (above glass‐transition point)
Authors: Gotlib Yu. Ya. 
Published: September 2014

AbstractSimple molecular models are proposed to explain the sharp decrease of the apparent activation energy Uα for the α relaxation process, observed in amorphous polymers in the high‐temperature region (50–100°C. above Tg). The intermolecular interaction in amorphous polymer is divided into collective and localized parts. The collective part is characterized by a large temperature coefficient. The α process includes the transition over the local potential barriers, which determines the rate of the β process. The sharp decrease of Uα occurs when the collective part of the interaction is weak; i.e., when the local potential barrier determines the net rate of the relaxation process. One of the models also explains the decrease in the magnitude of α absorption with increasing temperature observed in some polymers. The theory predicts a marked variation in dielectric relaxation properties as a consequence of kinetic factors alone, in the absence of any structural (phase) transitions.
Study of the movements of cycloalkyl side groups in polymethacrylates by dynamic mechanical measurements
Authors: Heijboer J. 
Published: September 2014

AbstractDamping and modulus have been measured in shear at about 1 Hz and in flexure at about 1000 Hz for polycyclopentyl methacrylate (PCPMA), polycycloheptyl methacrylate (PCHpMA), and polycyclooctyl methacrylate (PCOcMA), in the glassy region. The results are compared with those for polycyclohexyl methacrylate (PCHMA). All the cycloalkyl rings show a pronounced damping peak at low temperature. As a function of n the flexibility increases in the order 6 < 8 ≪ 7 ≪ 5. The corresponding apparent activation energies of the movements, in the same sequence, are 11.5, 10.5, ca. 6, and < 4 kcal./mole. The width of the relaxation spectrum increases in the order: 6 < 8 < 7.
The models of the denaturation of globular proteins. I. Theory of globula–coil transitions in macromolecules
Authors: Ptitsyn O. B. , Kron A. K. , Eizner Yu. Ye. 
Published: September 2014

AbstractThe theory of long‐range interactions in macromolecules is proposed for the region where the attraction forces predominate (that is below τ‐point). In an approximate analytical variant of the theory the free energy of segment–segment interactions is calculated without taking into account their bonding in the single chain, that is, by means of strict and approximate equation for the free energy of interaction of real gas molecules. The theory predicts that under some conditions the macromolecule undergoes below the τ‐point, during the change of temperature or solvent composition, the first‐order phase transition from the statistically coiled state to the compact (globular) state. The transition predicted by the theory is similar to the condensation of the real gas cloud to the liquid drop. This result is confirmed by the more strict Monte Carlo calculation which takes into account the bonding of the segments in a single chain. This calculation not only confirms the existence of a drastic compression of the macromolecule, when the attractive forces between its segments increase, but show also that, in the transition region, the macromolecules divide into poorly coiled chains (statistical coils) and highly coiled chains (globula), which directly prove the phase character of the transition. In common macromolecules the “intramolecular condensation” predicted by the theory must occur near to the point of intermolecular condensation so it is difficult to observe it experimentally. However, in macromolecules containing both lyophobic and lyophilic groups the intramolecular condensation may well occur due to the mutual attraction of lyophobic groups and lyophilic groups covering the surfaces of obtained globulas may prevent them from aggregation. In these macromolecules one can observe the intermolecular globula–coil phase transitions by changing the temperature or the solvent composition. It is most likely that the denaturation (and renaturation) of the globular proteins are the examples of such transitions.
The models of the denaturation of globular proteins. II. Hydrophobic interactions and conformational transition in polymethacrylic acid
Authors: Anufrieva E. V. , Birshtein T. M. , Nekrasova T. N. , Ptitsyn O. B. , Sheveleva T. V. 
Published: September 2014

AbstractTo model the compact structures of globular proteins and the processes of their breakdown, the local compact structures have been investigated in the nonionized (or weakly ionized) molecules of polymethacrylic acid (PMA) in aqueous solutions. The potentiometric titration curves differ markedly from the analogous curves for polyacrylic acid (PAA) and show the existence of the cooperative breakdown of the local compact structures in a definite region of the ionization degree. The presence of the local compact structures in the PMA molecules is also manifested in sharp differences between the luminescent characteristics of the dyes (auramine and acridine orange) in aqueous solutions with PMA and the same characteristics in aqueous solutions with PAA. In a certain range (which coincides with the interval of the breakdown of local compact structures) these differences disappear. This permits us to interpret them as the result of the dye molecules binding on the structurized parts of PMA. The assumption has been made that the local compact structures in the PMA molecules in aqueous solutions are stabilized by the hydrophobic interactions of methyl groups. This assumption explains the abnormal temperature dependencies of the properties of the aqueous solutions of PMA and the absence of the local compact structures in the PMA molecules in methanol as well as in the PAA molecules in any solvents. To check this assumption we have investigated the breakdown of the local compact structures in the PMA molecules when aliphatic alcohols are added to the aqueous PMA solution. It was shown that the transition of dye molecules from the bound state to the free one (which is the evidence of the breakdown of the local compact structures) takes place in the narrow range of alcohol concentrations decreasing in the series methanol–ethanol‐propanol–butanol. It means that alcohol destroys compact structures the better, the more hydrophobic groups it possesses. The investigations of intrinsic viscosity of PMA in the water–methanol mixtures have shown that the addition of alcohol leads not only to the breakdown of the local compact structures, but also the unfolding of the macromolecule as a whole. The analogy between the local compact structures in PMA molecules and the compact structures of globular proteins has been discussed.
Ion binding by polystyrenesulfonic acidX
Authors: Dolar D. , Špan J. , Pretnar A. 
Published: September 2014

AbstractTransference experiments and conductivity measurements carried out with solutions of polystyrenesulfonic acid are reported for the concentration range from 0.005 to 0.15 base molar. From these data the transport number and the ionic conductance of the polyion and the fraction of free hydrogen ions have been calculated. The transport, number and the ionic conductance of the polyion decrease with increasing concentration, whereas the fraction of free counterions increases from 0.38 to 0.58 in the range of concentration mentioned above. Furthermore, the fraction of free hydrogen ions obtained in this work is compared with the corresponding results of pH measurements and with osmotic coefficients. It was found that the fraction of free counterions calculated according to the theory of Katchalsky et al. is in good agreement with the experimental results.
Electron spin resonance studies on ziegler‐catalyst systems. Part IV. On the mechanism of the reduction of titanium (IV) halides with aluminum alkyl halides and the polymerization of ethylene
Authors: Adema E. H. 
Published: September 2014

AbstractElectron spin resonance measurements on the systems TiCl4(Al(C2H5)Cl2)2, TiCl3‐CH3(Al(C2H5)Cl2)2, and TiCl4(Al(C2H5)2Cl)2 have revealed the formation of a particle with an unpaired electron, S, the concentration of which could be continuously followed with time. The kinetics of the former two systems are estimated and a mechanism for the reduction of the Ti(IV) compounds is proposed. It is shown that the concentration of the unpaired electrons equals the concentration of trivalent titanium in solution. The rate of polymerization of ethylene with the catalyst TiCl4 (Al(C2H5)2Cl)2 proves to be proportional to the concentrations of unpaired electrons. The structure of the particle carrying the unpaired electron is probably a complex consisting of TiCl3 and the dimer aluminum alkyl chloride.
Photogeneration of charge carriers in acetylenic polymers and its sensitization by dyes
Authors: Mylnikov V. , Terenin A. 
Published: September 2014

AbstractA significant inner photoeffect in organic polymers with triple bonds R+CCR1CC+nR, and the metal polyacetylenides RCCM has been found and investigated by means of direct‐current photoconductivity and photoelectromotive force in intermittent light. The dependence of the photocurrent on the light intensity can be expressed by the equation iph ≐ αLn, where 0.5 < n < 1. The photocurrent relaxation in the range of 10−5 sec. to several minutes displays a second‐order process. Ohm's law is not obeyed. The absorption spectra have been compared with those of photoconductivity, photoelectromotive force, and luminescence. Preliminary short‐ultraviolet irradiation increases the photosensitivity; this is ascribed to bond rupture and electron‐trapping. The latter is confirmed by ESR measurements. Upon evacuation the dark conductivity and the photoconductivity are increased by 3 and 2 orders of magnitude, respectively, and the photoelectromotive force by 5. Oxygen and water vapor reversibly depress the dark and photoconductivity. A photodesorption of oxygen from the surface of metal polyacetalinide can be surmised. Electron acceptors (quinone, chloranil) and mercury vapor have a significant influence on the semiconduction. The photoeffect in the polymers can be spectrally sensitized by various adsorbed dyes. The proper sensitivity is equally changed on dye adsorption. The mechanism of the effects observed is discussed.
Conformations and molecular structure of the chains with (C—O)nbackbone
Authors: Oleinik E. F. , Enikolopyan N. S. 
Published: September 2014

AbstractConformations of linear chain molecules of X(CH2O)nX type were studied by infrared spectra of polyoxymethylenes (POM) and oligomers of CH3O(CH2O)nCH3type (n= 3–8). The study was performed at broad ranges of temperature (−80°C.– +200°C.). Infrared spectra of liquid oligomers point at preference of the helical conformation for these compounds.Bands of unstable isomers were found which disappeared under “freezing up” conditions. The results are the following: (a) the helical conformation of the isolated polyacetalic backbone molecules are the most advantages; and (b) rotational isomerism in these chains exists.
Synergistic stabilizer systems for the protection of polypropylene from thermal oxidation
Authors: Geleji F. , Holly Z. , Ocskay G. , Wein T. 
Published: September 2014

AbstractThe antioxidative behavior of 2,2′‐bis(4‐methyl‐6‐tert‐butylphenols) in polypropylene were investigated with and without dilauryl‐thio‐dipropionate. The experimental methods used in this study were thermogravimetric analysis for determining sample weight loss and differential thermoanalysis for obtaining information on oxidative processes and induction periods. The best antioxidant found was the dithio group bridged compound. The methylene‐, n‐butylidene‐, cyclohexylidene‐, and thio‐bridged systems were less active antioxidants. All compounds showed synergism with DLTP. The effectiveness of the synergistic mixtures decrease with decreasing activity of the bisphenol compounds. The pure dithio‐bridged compound was a better antioxidant in polypropylene than is its “synergistic” mixture with DLTP.
Bipolar electrolyte exchange resins. IV. Electric regeneration
Authors: Mikes J. A. , Haklits J. 
Published: September 2014

AbstractIt has been demonstrated that electric regeneration of so‐called bipolar electrolyte exchange resins into the H+OH− form may take place between permselective ion‐exchange membranes provided that the resin was placed in an aqueous medium. The level of regeneration of cation and anion capacities depends on the ratio of the amount of cationic and anionic active groups \documentclass{article}\pagestyle{empty}\begin{document}$ \[\underline{\underline + } \] $\end{document} index in the resin. In resins of ± > 1 type the cation exchange capacity in H+ form—expressed in percentage of total cation exchange capacity—is constantly higher than the anion exchange capacity in OH− form, /expressed in the same way/ while in the case of \documentclass{article}\pagestyle{empty}\begin{document}$ \[\underline{\underline + } &gt; 1\] $\end{document} < 1 type resins the situation is inversed. An explanation has been given for the mechanism of this phenomenon. A method has been elaborated for the determination of H+ and OH− capacities simultaneously.
Dynamic mechanical properties and impact strength
Authors: Heijboer J. 
Published: September 2014

AbstractImpact strength and damping as functions of temperature have been compared for eight polymers with typical differences in damping behavior, viz., four methacrylate polymers, a polyphenylene oxide, a polycarbonate, a polyoxymethylene, and a rigid polyethylene. If a damping maximum is caused by a movement within the main polymer chain, it is generally connected with an appreciable increase in impact strength. The temperature of the mechanical damping maximum and that of the transition in the impact strength may, however, differ considerably. If the damping maximum is caused by movements of sidechains only, it has at most a slight influence on the impact strength. Also a polymer with very low damping can have high impact strength and can even show a brittle‐tough transition. This occurs in the case of polyphenylene oxide.
Photoréticulation de Polyacroléines et de Copolymères Greffés d'Acroléine Préparés par Voie Anionique
Authors: Golé Jean , Calvayrac Henri 
Published: September 2014

AbstractThe polyacroleins were prepared anionically in the presence of a sensitizor containing carbonyl groups and irradiated in solution with a mercury vapor lamp. The polymers obtained after various polymerizing times were completely insoluble in organic solvents. Different factors affecting gelation speed were studied. New acrolein graft copolymers prepared from a polycarbanionic polymer are also described. These new copolymers are also crosslinked by light and their use as a photosensitive layer is described.
Hydrogen iodide cocatalysis in iodine‐initiated polymerization of styrene
Authors: Giusti P. , Andruzzi F. 
Published: September 2014

AbstractThe cocatalytic effect of hydrogen iodide on the polymerization of styrene by iodine has been studied. The kinetics of this system have been followed by a dilatometric technique at 30°C. in (CH2Cl)2 solutions. The initial hydrogen iodide concentration has been varied for each iodine concentration from 1/10 up to twice the iodine concentration. The polymerization shows no acceleration period and the rate increases with increasing hydrogen iodide concentration for each given iodine concentration. The molecular weight of the polymers obtained decreases as the acid concentration increases. A reaction mechanism has been proposed.
Preparation and three‐dimensional polymerization of polyester methacrylates
Authors: Mihailov M. , Budevska H. , Nenkov G. , Gerdjikova S. 
Published: September 2014

AbstractTwo methods for the preparation of polyester methacrylates are described: (1) Methacrylation of hydroxy containing oligoesters obtained by the reesterification of the esters of alcohols and polyhydric acids with polyhydric alcohols. Terephthalic, furan 2,5‐dicarboxylic, and benzylphosphonic polyester methacrylates, which cannot be obtained by means of condensation telomerization, are synthesized by this method. (2) Addition telomerization of mixtures of epoxy compounds with anhydrides of methacrylic and polyhydric acids. A closer study of this reaction revealed that it permits the preparation of a wider range of polyester methacrylates than does condensation telomerization. The three‐dimensional polymerization of some of the synthesized polyester methacrylates was investigated.
Internal plasticization of bisphenol‐a polycarbonate
Authors: Conix A. , Jeurissen L. 
Published: September 2014

AbstractIt is well known that crystallization of poly[2,2‐bis(4‐hydroxyphenyl) propane carbonate] by thermal treatment is a slow process. In order to achieve equilibrium crystallization extent, heating for very long periods of time (8 days) at high temperatures (180°C.) is required.1 The rate of crystallization of polycarbonate can be increased by swelling the polymer in suitable solvents such as xylene and acetone.2 In a previous article,3 an extensive study was made of the crystallization behavior of polycarbonate plasticized with tricresyl phosphate. It was shown that the addition of small amounts of plasticizer markedly increases the crystallizability of the polycarbonate. It is the purpose of this study to investigate the possibility of increasing the crystallizability of polycarbonate by internal plasticization achieved by incorporating small amounts of flexible repeat units into the polymer chain through copolycondensation. At the same time, the thermal properties of the copolymers will be discussed.