bluuebunny/crossref_metadata_2025_split huggingface dataset:
The thermodynamics of solutions of some normal and branched alkanes in polyisobutylene: an investigation by gas‐liquid chromatography
Authors: Hammers W. E. , de Ligny C. L. 
Published: June 2010

AbstractGas‐liquid chromatography is a separation method for volatile compounds which is widely used in analytical chemistry. It is based on the partition of the components of a sample between a moving gas phase and a stationary liquid phase of low volatility, the latter in the form of a thin coating on inert support particles filling a long, narrow column. Under proper conditions, values of the standard partial molar free enthalpy of vaporization from infinitely dilute solution in the stationary phase can be obtained from retention times, as a function of temperature. Combination with the standard molar free enthalpy of vaporization of the pure compounds yields the standard partial molar free enthalpy of mixing with the stationary phase. As a method for the investigation of the thermodynamics of interactions in polymer solutions, gas‐liquid chromatography is unique in the sense that it easily yields accurate data at a mole fraction of the polymer near unity and at high temperature. Here the method is applied to solutions of some normal and branched alkanes in polyisobutylene. The results are discussed in terms of a simplified version of the Prigogine solution theory, used by Patterson et al., and in terms of the solution theory of Flory, Orwoll, and Vrij.
On the adsorption of a polymer chain at a boundary
Authors: Bellemans A. 
Published: June 2010

AbstractOn the basis of a simple lattice model, the adsorption of a polymer chain on a surface is discussed, taking excluded volume effects (intrachain interactions) into account. Configurations of finite chains of n elements (self‐avoiding walks) are enumerated exactly for n ≤ 13 on the simple cubic lattice. Some predictions concerning the asymptotic behavior of long chains are derived from these data by using extrapolation methods previously devised by Domb and Sykes for bulk properties.
The reactivity of antioxidants with peroxy and alkoxy radicals in the presence of transition metals. I. Relation between the structure of free antioxidant radicals and inhibition of oxidation in polymers
Authors: Tkáč A. , Omelka L. , Holčík J. 
Published: June 2010

AbstractThe efficiency of homolytic splitting of the OH bond of different phenols, bisphenols, thiophenols, naphthols, and benzophenones and the transfer of the hydrogen atom to an alkoxy or alkyl‐peroxy radical is a function of the electro‐affinity of the substituent in the ortho position. The stability of the formed phenoxy radical is in relation to the delocalization of free electron in the para position, especially if the substituent has aromatic character. The inhibition effect of thermal oxidation is found to be the highest in that case where the substituent does not hinder the recombination of RO2 radicals with those of antioxidant.According to the electron paramagnetic resonance spectra of the generated phenoxy radicals the differently substituted phenols can be divided into five main groups: 1) phenols which form primary stable free radicals; 2) phenols which form secondary stable free radicals, 3) phenols which give stable phenoxy radicals only after coordination into the ligand field of the transition metal; 4) phenols whose radicals undergo disproportionation; 5) phenols substituted with NO2 groups which do not form free radicals in nonpolar solvent.Cobalt traces induce the decomposition of hydroperoxides generated in thermal initiation of polymer oxidation by quite a similar redox mechanism as the one observed in the fixation of RO2 radicals on transition metal. But the cobalt compounds are not active in polymers if those are free from oxidation products (hydroperoxy groups).
Oxidative stabilization of dimethyl silicone fluids with iron between 70 and 370°C
Authors: Nielsen J. M. 
Published: June 2010

AbstractLong term oxidation tests below 150°C on dimethyl silicone (DMS) fluids with controlled iron content, in conjunction with previous work, have provided a broad concept of the processes of oxidation in DMS fluids between 70 and 370°C. A nonfree radical, iron‐catalyzed oxidation of DMS fluid occurs both below and above 150°C. A diverging, free radical chain reaction which is inhibited by iron is initiated by direct attack of oxygen on the methyl groups of DMS above 150°C. It is believed that a ferric iron complex is the key mechanistic species both in the catalyzed oxidation and in the free radical reaction inhibition.When temperature, iron dispersion, and aeration are held constant, the oxidation rate of a DMS fluid below 150°C varies directly with its iron level. Above 150°C the oxidation rate is still dependent on iron level, but an ‘optimum iron level’ for a minimum oxidation rate exists for each temperature of oxidation. This optimum iron level increases with the temperature.A conceptual diagram has been developed to unify and summarize these effects over the temperature range 70–370°C, providing a basis for the most effective use of iron to stabilize DMS fluids.
Antioxidants and stabilizers. XXXVII. A contribution to the elucidation of differences between the antioxidative activities of isomeric dihydric phenols
Authors: Lisá E. , Pospíšil J. 
Published: June 2010

AbstractDifferences in the antioxidative properties of isomeric dihydric phenols, observed in the stabilization of polypropylene, were thoroughly followed in initiated oxidations of tetralin, cumene, styrene, and 9,10‐dihydroanthracene. 2‐tert‐Butylhydroquinone and 4‐tert‐butylpyrocatechol were used as stabilizers. Values of the induction periods and of the stoichiometric factor, n, were used to rate the activities. In all cases, 2‐tert‐butylhydroquinone caused lower n values than 4‐tert‐butylpyrocatechol. The value n of the latter was not significantly influenced either by the temperature or by the concentration of the reaction components. Under similar conditions, the value n of 2‐tert‐butylhydroquinone was increased with increased rate of initiation. It is possible to state, on the basis of the obtained results, that a side initiation of chains is the cause of the low activity of 2‐tert‐butylhydroquinone in the inhibited oxidation of tetralin. Such a side initiation can be precipitated by an interaction between an aryloxy radical derived from 2‐tert‐butylhydroquinone and tetralyl hydroperoxide.
Antioxidants and stabilizers. XLIII. Structure of phenolic antioxidants and infrared spectra of the hydroxyl groups
Authors: Pivcová H. , Jiráčková L. , Pospíšil J. 
Published: June 2010

AbstractInfrared spectra of 2,2′‐alkylidene, 2,2′‐thiobisphenols, and 2,2′‐biphenyldiols have been measured in the range of the OH stretching vibrations. From these measurements the possible conformers present in dilute CCl4 solutions are proposed. A correlation between the amount of the free and the intramolecularly bound hydroxyl groups in 2,2′‐bisphenols and their antioxidative activity is discussed.
Ionically crosslinked hydrophilic polymer membranes: Synthesis and measurement of transport properties
Authors: Huang Robert Y. M. , Jarvis Neil R. 
Published: June 2010

AbstractWater soluble polymer and copolymer systems containing a poly(carboxylic acid) as one component have been ionically crosslinked in the form of membranes using multivalent metal salts. The permeability coefficients for a homologous series of poly(ethylene glycols) permeating through the ionically crosslinked membranes and a commercial cellophane membrane were determined using a continuous flow dialysis apparatus. Solute concentration changes occurring during dialysis were determined by using an in‐line continuous flow differential refractometer. For the ionically crosslinked membranes the permeability coefficients were found to decrease exponentially with increasing permeant molecular weight. For the cellophane membrane the permeability coefficients were observed to be inversely proportional to the square root of the permeant molecular weight. This square root correlation appears to be consistent with a porous flow model for transport through cellophane membranes.
Anionic polymerization of α‐pyrrolidone and α‐piperidone using their quaternary ammonium salts as catalysts
Authors: Sekiguchi Hikaru , Tsourkas Panayota Rapacoulia , Coutin Bernard 
Published: June 2010

AbstractQuaternary ammonium salts of α‐pyrrolidone, α‐piperidone and ε‐caprolactam, prepared extra situ, were used as catalysts in anionic polymerization of these lactams. Pyrrolidone and piperidone salts gave the corresponding lactam polymers of increased molecular weight, with an improved yield, as compared to those obtained using classical alkaline catalysts (a true high polymer of piperidone with a reduced viscosity of 4.58 was obtained for the first time). The caprolactam polymerization succeeded only at comparatively low temperatures (∼ 100°C).The high activity of these catalysts permitted us to prepare high polymers, using slow initiators or initiators of inferior activity. The influences of coexisting functional groups extraneous to the polymerization, namely water, are demonstrated.The polymerization data indicate that the dimension of catalyst cation plays an important part in molecular growth in the heterogeneous reaction phase and provide some arguments in favor of our mechanism.
The kinetics of anionic polymerization of styrene in 1,2‐dimethoxiethane
Authors: Alvarino J. M. , Chmeliř M. , Schmitt B. J. , Schulz G. V. 
Published: June 2010

AbstractKinetic measurements in a flow apparatus in combination with conductance measurements, permit the determination of the two equilibrium constantsKesandKdiss* and the three propagation rate constantsk(±)c, k(±)sandk(−) as a function of temperature. The great differences in the polymerization rate in various solvents are mainly caused by their influence on the equilibrium constants. The influence of the solvent on the rate constants is not greater than in other chemical reactions.
Radical copolymerization of 2‐vinyl‐1,3‐dioxane with vinyl compounds and maleic anhydride
Authors: Acosta J. L. , Enriquez M. , Mateo J. L. 
Published: June 2010

AbstractA exploratory study on the copolymerizability of 2‐vinyl‐1,3‐dioxane (VD) has been carried out.VD was polymerized with styrene, vinyl acetate, methyl methacrylate, and acrylonitrile. Acrylonitrile was the only one which provided copolymerization products. For the acrylonitrile (M1)‐VD (M2) pair, r1 = 3.64 ± 0.1 and r2 = 0.057 ± 0.01 at 70°C. The transfer reactions of a series of 1, 3‐dioxane compounds in the styrene polymerization were investigated, with the result that the acetalic hydrogen is responsible for the transfer values found. VD was also copolymerized with maleic anhydride yielding alternating copolymers.
Kinetic studies on the preparation of polycarbonates in solution
Authors: Turska Eligia , Dems Andrzej , Bortnowska‐Barela Barbara 
Published: June 2010

AbstractThe results of previous works have shown that the coil expansion factor of the reacting macromolecules is a parameter directly affecting the values of the kinetic constants measured. Since this factor is also dependent on the molecular weight, the present study was carried out using a homogeneous polymer fraction as one of the substrates and mono‐functional model compound as the other. The results show that the rate constant is dependent on the density of segments in the coil of the reacting macromolecules. The changes in the density of segments in the coil will characterize here the variation of diffusion coefficient inside the macromolecule coil.
Studies on poly(vinyl chloride) compatibility with other polymers. IV. Poly(vinyl chloride) with butadiene‐α‐methyl‐styrene copolymer blends
Authors: Feldman Dorel , Rusu Mihai 
Published: June 2010

AbstractOne studies the compatibility of poly (vinyl chloride) with butadiene‐α‐methylstyrene copolymer (BAMS) using the dielectric and dynamic properties and also the physico‐mechanical indexes; these values were determined at various temperatures and compositions.The results showed that the compatibility of these two polymers depends on their blending ratio. Systems which have less than 60% BAMS copolymer are incompatible, while the blends with more than this amount of elastomer are compatible. The compatibility of the blends in which the elastomer is predominant is due to the polarization action of high polar groups of poly (vinyl chloride) on the benzene rings from the copolymer macromolecules.
Thermal conductivities of amorphous polymers
Authors: Hands D. , Lane K. , Sheldon R. P. 
Published: June 2010

AbstractAlthough at the present time no precise agreement between theory and experiment exists for amorphous polymers, as might be expected on the limited understanding of the liquid state, nevertheless certain trends in the thermal conductivity of these materials may be predicted with some confidence. This paper considers the influence of two factors, temperature and polymer density, with a view to providing guidance to engineers concerned with the manipulation and use of amorphous polymers.
Dilute and semidilute solutions: Light and neutron scattering and osmotic pressure
Authors: Cotton J. P. , Farnoux B. , Jannink G. , Strazielle C. 
Published: June 2010

AbstractLight and neutron scattering data and osmotic pressure measurement are analyzed in polystyrene solutions up to concentration of 0.1 g cm−3. The results show two different ranges of concentration. These two ranges are consistent with the dilute and semidilute ranges proposed by S. F. Edwards. The transition occurs at the concentration for which the average distance between chain is of order of magnitude of the radius of gyration.
A light scattering study of the optical anisotropy of polystyrene and polyvinylacetate latices
Authors: Petres J. J. , Deželić G. J. 
Published: June 2010

AbstractBy the method of light scattering, measurements were made on particles of polystyrene and polyvinylacetate latices. The angular distribution of the scattered light was measured and the partial Rayleigh ratios as well as the polarization ratios were determined. These values were measured as a function of the concentration and the measurements were extrapolated to the zero concentration. Values of the specific partial Rayleigh ratios (Hv:/c)0 and (Vh/c)0 proved to be significantly different from zero indicating the existence of the optical anisotropy of particles. The polarization ratio Dv was also found to be significantly different from zero. The optical anisotropy of polystyrene latices was found to be significantly higher than that of polyvinylacetate latices. This was ascribed to a structural anisotropy of the polymeric material within the particles. The hard polystyrene spheres show a small but existing degree of crystallinity, whereas the soft polyvinylacetate spheres, although having a finite anisotropy, show a vanishing degree of crystallinity.
The influence of cellulose structure on the swelling of cellulose in organic liquids
Authors: Philipp Burkart , Schleicher Harry , Wagenknecht Wolfgang 
Published: June 2010

AbstractUsing the method of a modified water‐retention value (LRV), the time dependence and final value of swelling of cellulose in various liquids are found to be determined by the cellulose structure as well as by molar volume and the solubility parameter δH of the liquid, especially its hydrogen bonding part δH and the polar part δP. The different kinetics of swelling of native and regenerated cellulose samples in some liquids of high swelling power like DMSO, as well as the strong influence of the state of drying on the final LRV with native samples, and on swelling kinetics with regenerated cellulose are interpreted by means of the concept of a “pore and void” model of cellulose structure.
Synthesis of polymers of 1,2‐disubstituted ethylenes (polymeric alcohols and their derivatives) and investigation of the influence of the nature of side groups on the properties of macromolecules
Authors: Skorokhodov S. S. , Anufrieva E. V. , Koltsov A. I. , Lushchik V. B. , Pautov V. D. , Stepanov V. V. 
Published: June 2010

AbstractMethods for synthesis of polymeric alcohols and their ethers of type poly‐1,2‐disubstituted ethylenes have been considered. Cationic polymerization of cis‐1,2‐dimethoxy‐ethylene was carried out in a solvent‐nonsolvent mixture, and a polymer was obtained with a molecular weight of about 200,000 which is unusually high for this type of polymers. On the basis of PMR spectra of model compounds, poly‐1,2‐dimethoxyethylene (PDME) is assumed to be threo‐diisotactic. Intramolecular mobility and its relationship with microstructure of the polymer chain were investigated by the polarization fluorescence method. A strong influence of side group interactions on the properties of macromolecules in solution was observed. It was probably caused by the peculiarity of the chemical structure of poly‐1,2‐disubstituted ethylenes.
The rheo‐optical and mechanical behavior of a systematic series of hard‐soft segmented urethanes
Authors: Samuels S. L. , Wilkes G. L. 
Published: June 2010

AbstractA battery of characterizational tests have been performed on a systematically varying series of segmented polyurethanes. These tests include small angle light scattering (SALS), small angle and wide angle x‐ray diffraction, optical and electron microscopy, and mechanical testing (both tensile and dynamic).Observable macroscopic properties are directly correlated with and interpreted by a model based on the observed anisotropic spherulitic macrostructure which is dependent on the chemical microstructure and the sample history.
On the nature of polymeric liquid crystals
Authors: Frenkel S. 
Published: June 2010

AbstractStarting from the theory of formation of liquid crystalline mesophases in solutions of rod‐like rigid chain macromolecules, developed by Flory and DiMarzio, the situation is analyzed where the flexibility parameter, f, which is essential in this theory, is variable and concentration dependent. It is shown that energetic factors of physical‐chemical origin expressed by the polymer‐solvent interaction parameter, χ1, and connected with the selectivity of these interactions may influence substantially f, changing its value from the supercritical ( > 0.63), when self‐organization in an ordered mesophase is impossible, to the subcritical, i.e., values down to f→ 0, when a spontaneous formation of a liquid crystalline phase occurs. In quite a similar manner (the analogy encompassing even the corresponding formulae) f is affected by external fields, as a result, in a stationary orienting field a system of flexible chain macromolecules may become equivalent to a unperturbed system of rigid chain macromolecules. The external field can also decrease the critical concentration of the formation of the liquid crystalline phase in rigid chain systems and liquidate the domain structure, thus transforming such a system into a unique “liquid single crystal”. This is shown to be true for the behavior of a rigid chain polymer polyparabenzamide in strong magnetic fields.The analysis leads to the conclusion that a purely entropic formalism for the description of the formation of extended chain liquid crystals is neither necessary nor sufficient, and purely energetic factors most certainly must be taken into account. However, following incorporation of these data, it becomes possible to reduce the formation of the ordered phase to the “entropic” mechanism of Flory‐DiMarzio.
Thermodynamic nature of supermolecular order in the aqueous solutions of poly (vinyl alcohol)
Authors: Klenin V. J. , Klenina O. V. , Shvartsburd B. I. , Frenkel S. Ya. 
Published: June 2010

AbstractThe temperature dependence of the second virial coefficient, A2, in an aqueous solution of poly (vinyl alcohol) (PVA) has been studied by the light‐scattering method within the temperature range from 20 to 130°CC.The experiment was carried out under conditions which rule out the aggregation of macromolecules. The temperature dependence of A2 has the form of an extremum with an unpronounced minimum between 80–90°CC. In the temperature region studied here, A2 > 0, this condition is regarded as a proof of the stability of the system with respect to amorphous separation. Consequently, the supermolecular order which forms in the PVA‐water system over this range of temperatures (see Chem. Abst, (1967), 66: 11295u; (1971) 73, 56516x; (1971) 74, 23183d) has a crystalline nature.The literature noting an increase in the degree of sweiling with increasing temperature in the PVA‐water system in the interval 20–80°CC, which seems contradictory to a decrease in the solvent power (decrease in A2), may be explained by a decrease in the degree of crystallinity (degree of physical crosslinking) of the polymer.
Thermodynamic properties of polystyrene gels of different crosslinking density in cyclohexane
Authors: Borchard W. 
Published: June 2010

AbstractAn optical‐mechanical device is described with which the length of a gel and the transmitted light can be registered. The swelling curves of gels of the crosslinked polystyrene in cyclohexane have been measured in the temperature range from 10 to 70°CC. Glycol dimeth‐acrylate was used as the crosslinking agent varying from 0.05 to 3% by weight of the polymer. The swelling curves are in good agreement with those determined gravimetrically. From the slightly crosslinked gels nearly 50% soluble polymer could be extracted.The results are compared with those of other authors and are discussed on the basis of statistical theories of swollen networks.
The effect of ion‐site interactions on the apparent molal volume of polystyrenesulfonic acid and its salts in aqueous solutions
Authors: Caillé A. , Daoust H. 
Published: June 2010

AbstractApparent molal volumes of two samples of polystyrenesulfonic acid and p‐toluenesulfonic acid and their alkaline salts in water have been determined at 25°C using the magnetic float technique. The results show that the monomeric acid and salts behave like ordinary strong electrolytes. In the case of the polystyrenesulfonates, the variation of the apparent molal volume with molar concentration does not follow the simple Masson's equation, i.e., φv decreases rapidly at concentration below 0.005 mole/liter. Furthermore, the additivity rule (applied to the ionic partial molal volumes at infinite dilution) does not hold too well for the strong polyelectrolytes investigated in this work. This anomalous behavior is discussed in terms of persisting ion‐binding at infinite dilution. Theoretical calculations on the variation of degree of ion‐binding with concentration indicate that the number of bound cations at infinite dilution is a function of their size.
Solution rheological properties of a copoly(ethyl acrylate‐acrylic acid)
Authors: Rauscher Raymond J. , Garfield Lawrence J. , Connelly Richard W. 
Published: June 2010

AbstractThis study was carried out to determine the effects of various solution and molecular parameters on the characteristic entanglement molecular weight of a copoly(ethyl acrylate‐acrylic acid) of 55:45 molar ratio. Fractions obtained by bulk precipitation, varying in molecular weight from 5,000 to 500,000, were characterized by intrinsic viscosity, light scattering, aqueous exclusion chromatography, and titration. Polydispersities of the fractions were about two; their chemical compositions were independent of molecular weight. Dilute solution properties of both the ionized and unionized polymer in several media suggest that, depending upon polymer‐solvent and polymer‐polymer interactions, the polymer may exist in a compact or a highly extended conformation. However, on the basis of the entanglement properties in concentrated solutions in the same media, it appears that the ionized and unionized polymers in concentrated solutions assume their unperturbed dimensions. Thus it follows that for this polyelectrolyte the factors contributing to chain contraction present in concentrated solutions are large enough to overcome the substantial chain expansion factors.