bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution properties of chlorinated stereoregular polybutadienes
Authors: Takeda Masatami , Endõ Ryūichi , Matsuura Yoshikatsu 
Published: June 2010

AbstractCommercial samples of cis‐1,4‐polybutadiene and trans‐1,4‐polybutadiene have been chlorinated with chlorine gas in a chloroform solution and precipitated with methanol. The precipitates were thoroughly washed with a large amount of methanol and dried in vacuum at 40°C. The samples were fractionated with the tetrahydrofuran‐water system at 40°C. The viscosity measurements were made at 30°C. in various solvents. The light‐scattering measurements were made with a modified Brice‐type light‐scattering photometer with unpolarized blue light and with a cylindrical cell, over the angular range from 35° to 145°, at room temperature. The relation between the intrinsic viscosity and the molecular weight was obtained for each sample. The unperturbed mean‐square end‐to‐end distance was estimated by the Stockmayer‐Fixman equation, and was used for calculating the conformational parameter \documentclass{article}\pagestyle{empty}\begin{document}$ \sigma = \;(\overline {r_0 ^2 } /\overline {r_{0f} ^2 })^{1/2} $\end{document} for each chlorinated sample. The relation between the chemical configuration and the chain conformation for each chlorinated sample was discussed in terms of the unperturbed molecular dimension and rotational isomers of model compounds for a rotation around the CC bonds in the main chain.
Osmotic pressures of moderately concentrated polydimethylsiloxane solutions
Authors: Kuwahara Nobuhiro , Okazawa Tadahiro , Kaneko Motozo 
Published: June 2010

AbstractOsmotic pressures of polydimethylsiloxane in chlorobenzene, toluene, and cyclohexane were measured over a wide range of concentration (0 < v2 < 0.25). A peculiar behavior of an apparent second virial coefficient, observed by others, was not observed in a transition region (c ≈︁ 0.05). The data were used for evaluating the excluded‐volume parameter z. The theories of the excluded‐volume effect were tested with the z values estimated. In the limit of z examined the modified Flory‐Fox relation seems to fit the observed dependence of the expansion factor α03 on z.
Critical factors affecting chemical reactions on polymers
Authors: Gaylord Norman G. 
Published: June 2010

AbstractChemical reactions on polymers are influenced not only by the reactivity of a funtional group but also by its accessibility. Although intrachain steric factors that result in neighboring‐group effects are well recognized, the interchain interactions that determine the availability of a potential reaction site have not been adequately considered. The factors that influence polymer reactions include amorphous or crystalline content, orientation, solubility, and compatibility. The interchain interactions involved are not only those between chains of the initial polymer but, more significantly, those between polymer chains that have reacted or partially reacted and polymer chains that have not. Chemical reaction may change solvent‐polymer interactions so that either chain extension or coiling occurs with resultant changes in the accessibility of reaction sites. Incompatibility between polymer that has partially reacted and polymer that has not may result in phase separation. Increased compatibility may result from the generation of block copolymers, due to localized or segmental reaction, which then act as compatibilizing agents and make the separation of reaction products, such as by extraction of unreacted material, extremely difficult.
Polymers with peroxidic functional groups. I. Copolymers of di(t‐butylperoxy) fumarate
Authors: Mageli O. L. , Light R. E. , Gallagher R. B. 
Published: June 2010

AbstractDi(t‐butylperoxy) fumarate was copolymerized with styrene, butadiene, acrylonitrile, methyl methacrylate, vinyl chloride and vinyl acetate to give copolymers containing pendant peroxyester functions. Another peroxide was generally used for initiating polymerization; however, experiments were carried out with di(t‐butylperoxy) fumarate as both initiating species and comonomer. The active oxygen contents and intrinsic viscosities were determined for these copolymers. A copolymer of styrene and di(t‐butylperoxy) fumarate synthesized from monomers in equal weight ratio had an active oxygen content of 5.3% and a peroxide half‐life of 7.7 hr. at 85°C. in benzene. This peroxide was used as a catalyst for the curing of polyester resins and as an initiator for styrene bulk polymerization. The monomer reactivity ratios for the monomer pair styrene–di(t‐butylperoxy) fumarate were determined. Graft copolymers were made by grafting methyl methacrylate on a styrene–di(t‐butylperoxy) fumarate copolymer and also by grafting styrene on a vinyl acetate–di(t‐butylperoxy) fumarate copolymer. These graft copolymers were used to enhance the stability of homopolymer–solvent mixtures. A novel ABS type of resin was synthesized by grafting styrene and acrylonitrile on the copolymer system butadiene–di(t‐butylperoxy) fumarate. Another novel resin was synthesized by grafting butadiene on the terpolymer system styrene–acrylonitrile–di(t‐butylperoxy) fumarate. A homopolymer of di(t‐butylperoxy) fumarate was also prepared and used as a catalyst for the curing of polyester resins.
Sulfur crosslinks in polybutadiene vulcanizates
Authors: Gregg Earl C. 
Published: June 2010

AbstractFor the first time the crosslink terminus structure of monosulfide crosslinks and the amount of that structure in an elastomer vulcanizate has been determined directly from a sample of the vulcanizate. By measuring the rate of swelling of vulcanizates, immersed in either methyl iodide or methyl bromide, the rate of crosslink cleavage was measured. Comparison of this cleavage rate with the cleavage rate of model monosulfide compounds permits a measure of the terminus structure of the monosulfide crosslinks. The fraction of each monosulfide structure was determined from the cleavage rate equation for the vulcanizate. The monosulfide crosslink terminus structure in a particular polybutadiene vulcanizate was saturated, having secondary carbon atoms on both sides of the sulfur atom, i.e., it was a saturated, tetrafunctional crosslink. Polysulfide crosslinks in 1,4‐polybutadiene vulcanizates are readily cleaved at room temperature by a solution of phenyl lithium in benzene. The number of polysulfide crosslinks was estimated from a measure of the volume swelling of the vulcanizate before and after treatment with phenyl lithium. This reagent does not cleave the monosulfide crosslinks in polybutadiene vulcanizates.
Computer calculations of binary and ternary copolymerization behavior
Authors: Chan Richard K. S. , Meyer Victor E. 
Published: June 2010

AbstractComputer programs in use in our laboratory for the calculation of binary and ternary copolymerization behavior are reviewed. In the case of binary copolymerization an analytical equation is available, allowing rapid and precise calculations of various parameters of interest. In the case of ternary and higher component systems numerical methods of integration are required. The application of the Runge‐Kutta method to ternary copolymerization systems is outlined. Examples and some of the difficulties encountered with both systems are presented.
Viscoelastic and ultimate tensile properties of styrene‐butadiene‐styrene block copolymers
Authors: Smith Thor L. , Dickie Ray A. 
Published: June 2010

AbstractA study was made of the stress–strain and ultimate properties in simple tension of an elastomeric styrene‐butadiene‐styrene block copolymer (Kraton 101) and also of a similar material (Thermolastic 226) that contains about 35% plasticizer as well as inorganic pigments. Stress–strain data were obtained at crosshead speeds from 0.02 to 20 in./min at temperatures from ‐40 to 60°C. The relaxation rate, derived from the data at constant extension rates, was about 8% per decade of time for both materials at temperatures from −40 to about 40°C and at extensions from about 20% up to 400%. Above −30°C, the shift factor log aT was found to vary linearly with temperature. These findings indicate that the time and temperature dependence of the mechanical properties results primarily from the plastic (or viscoelastic) characteristics of the styrene domains. The tensile strength for Kraton 101 below 40°C is somewhat greater than 4000 psi, sensibly independent of extension rate and temperature. For the highly plasticized Thermolastic 226, the tensile strength at an extension rate of 1.0 min−1 increases from 2200 psi at 0°C to 3600 psi at −40°C. Above 40°C for Kraton 101 and above 0°C for Thermolastic 226, the tensile strengths are quite dependent on extension rate and temperature owing to the increased ductility of the styrene domains. The high strength of these materials results from the uniformly dispersed styrene domains of colloidal dimensions. To obtain a crack of sufficient size to satisfy an energetic criterion for self‐sustained high‐speed propagation, domains must be disrupted. The plastic characteristics of the domains have a controlling effect on crack growth and thus on the ultimate properties of the materials. The strength and extensibility of other elastomers are considered in relation to those of the block copolymers.
Half‐life measurements in emulsion polymerization
Authors: Ley Gregor J. M. , Schneider Christel , Hummel Dieter O. 
Published: June 2010

AbstractIntermittent 60Co γ‐radiation was used in a study of emulsion polymerization of styrene, methyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, vinylidene chloride, vinyl acetate, and chloroprene. A sensitive recording dilatometer was used to follow the build‐up and decay of polymerization rate and radical concentration. Reaction rate versus time curves of these emulsion systems with intermittent irradiation are given and the values of the apparent half‐life times of the monomers are compared. Apparent half‐life of the propagating radicals in emulsion ranged from below 1 min in the case of vinyl acetate up to about 80 min in the case of styrene. Variation of half‐life of the styrene radical with conversion, temperature, monomer and emulsifier concentration, and transfer agents added was determined. Calculation of the apparent termination rate constant of styrene yielded values of about 1 × 103 1/mol‐sec in emulsion as compared to literature data of about 1 × 107 1/mol‐sec in homogeneous systems.
Synthesis of conjugated Schiff‐base polymers
Authors: Hodgkin J. H. , Heller J. 
Published: June 2010

AbstractAttempts to synthesize conjugated polymers with cyanine dyes attached to the conjugated backbone are described. The experimental approach is to prepare and characterize conjugated polymers with attached quinolinium ions and then to convert these to dyes by reaction with lepidinium methiodide. Aromatic Schiff‐base polymers were chosen as the conjugated backbone. Since unsubstituted Schiff bases show very little conjugation, a series of model compounds and model polymers were prepared and their electronic spectra were determined in order to correlate the effect of substituents on electron delocalization. Efforts are being made to prepare high molecular weight polymers by a Schiff‐base exchange reaction. The syntheses of various monomers for the Schiff‐base exchange reaction are described.
Applications of many body methods to large molecules
Authors: Gutfreund H. 
Published: June 2010

AbstractThe work which I am going to report on was performed about a year ago at Stanford in collaboration with Professor W. A. Little.1‐3 The motivation was the same as for this entire Symposium, but it differs from the other works reported here in the sense that it ignores the question of superconductivity and deals only with properties of the normal π‐electron system. We felt that a better understanding of the normal π‐electron system is an important factor in the theoretical investigation of organic superconductivity. To give an example, let me remind you that the most severe criticism of Little's original paper on organic superconductivity comes from Kuper.4 Kuper shows that in a narrow cylinder the screening of the Coulomb potential is much weaker than in an unrestricted geometry, so that the net potential remains always repulsive. It is thus of utmost importance to be able to calculate the screening of the interaction between two π‐electrons by the other π‐electrons in the medium.
The instabilities of the hartree‐fock solutions for cyclic polyenes with respect to the spin and charge density fluctuations
Authors: Paldus J. , Čížek J. 
Published: June 2010

AbstractThe stability conditions which ensure that the Hartree‐Fock (HF) determinant minimizes locally the energy expectation value are formulated. These conditions are then specified for the closed‐shell electronic systems with spin independent Hamiltonian, which enables classification of the instabilities into the so‐called “singlet” and “non‐singlet” ones. In the case that the HF solution is unstable, another single determinantal HF solution with lower energy expectation value must exist. Moreover, if the original HF solution is singlet unstable, the new HF solution is again a pure singlet function, but has a lower spatial symmetry than the original Hamiltonian. This leads to the electron density waves, while the non‐singlet instability leads to the spin‐density waves in the system considered. Generalization of these results to simple open‐shell systems is briefly mentioned. The numerical results for pi‐electronic models of cyclic polyenes using the three different semiempirical parameterization schemes, which are commonly used, are briefly reviewed. It is shown that for cyclic polyenes, both singlet and non‐singlet instabilities occur if a large enough polyene is considered. The equations determining new HF solutions may be expressed in a form resembling BCS‐Bogoliubov equations of superconductivity. Further, the singlet instability may lead, in this case, to either the atomic‐charge alternating solutions or the bond‐order alternating solutions. It is shown that in cases where both solutions are possible, the latter have the lowest energy while the former is again singlet unstable. The implications of the existence of singlet instabilities for the occurrence of an energy gap and for the occurence of bond‐length alternation as well as for the applicability of some many body techniques are briefly discussed.
Osmotic, viscometric and light scattering studies of polymers dissolved in a mixture of two non‐solvents (cosolvents)
Authors: Sarkar Dilip Kumar , Palit Santi R. 
Published: June 2010

AbstractPolystyrene has been found to be completely soluble in the following binary mixture of non‐solvents, viz. nitrobenzene and acetone, heptane and acetone, cyclohexane and acetone, nitrobenzene and diethyl oxalate, hexane and diethyl oxalate, cyclohexane and diethyl oxalate. Polymethyl methacrylate has similarly been found to be soluble in carbon tetrachloride and methanol, and in carbon tetrachloride and ethanol. These two polymers have been studied viscometrically, osmometrically and with respect to light scattering property. An optimum composition with a minimum in osmotic μvalue and viscometric Huggins constant, a maximum in [η]‐value and a maximum in dissymmetry coefficient has been found to exist. The above observations are considered to indicate that the composition showing maximum solvent power is a true optimum composition and the dissolved unit is laterally more extended in this optimum composition than at any other composition of the two non‐solvents. Five samples of polymers have been studied in a number of ø‐mixtures near room temperature with a view to obtain the Kø values of Flory‐Fox equation, [η] ø = K o M̄v0.5. It has been found that Kø values vary widely with the chemical nature of the theta mixture indicating solvent dependency of unperturbed polymer dimension.
Thermal degradation of polystyrene
Authors: Wegner J. , Patat F. 
Published: June 2010

AbstractLiving polystyrene samples, both solid and in dilute toluene solution, were thermal degraded under extremely clean conditions in a range of temperatures from 200 to 325°C. The degradation was found to be a first‐order reaction. Pyrolyzed samples were analyzed with regard to the change in molecular weight as well as in molecular weight distribution. For the latter, an extraction method is described, which permits, in addition, the activation energy of thermal degradation (48 kcal/mole for the overall reaction) to be obtained. The results are discussed with a view to earlier outlined degradation theories. The presence of weak links in polystyrene as well as the propagation of degradation by reverse polymerization could be excluded. A radical chain reaction is assumed to be the mechanism of degradation.
Upper and lower solubility gaps in the system butanone‐acetone‐polystyrene
Authors: Wolf B. A. , Breitenbach J. W. , Senftl H. 
Published: June 2010

AbstractDepending on the solvent‐nonsolvent ratio r of a quasibinary section through the binodial surface of the system butanone‐acetone‐polystyrene, two different cases for the resulting cloud‐point curve (CPC) can be distinguished: (1) separated solubility gaps at relatively high values of r with intermediate temperature region of complete miscibility; (2) overlapping solubility gaps at lower values of r with no temperature of complete miscibility observable. A thermodynamic interpretation is given on the basis of the free‐volume concept. The influence of preferential adsorption on the position of the critical points on the CPC is discussed.
Rotational isomerism, microstructure and molecular motion in polymers
Authors: Pechhold W. 
Published: June 2010

AbstractIn the first part the microstructure of polymer melts and semicrystalline bulk material is treated on the basis of the bundle model and with molecular parameters. The meander‐shaped arrangement of the bundles in the amorphous phase can be founded thermo‐dynamically and leads to a radius of the meander of 50 Å. Based on this model a molecular theory of the relaxation processes (α, β, γ) is given and experimentally proved for linear polyethylene. In the last part both limiting cases of the deformation behavior are quantitatively derived in a molecular picture: the ideal plasticity illustrated by the yield stress of linear polyethylene and the ideal para‐elasticity illustrated by the stress‐strain curve of the drawn polyamide fiber.
Rheological properties of dilute and concentrated solutions of polyvinylchloride branched by irradiation
Authors: Palma G. , Pezzin G. , Zaramella S. 
Published: June 2010

AbstractFollowing a previous study of two commercial poly(vinyl chloride) polymers, with Mw values of 130,000 and 70,000, the influence of γ radiation on the concentrated solutions of two other polymers in tetrahydrofuran was investigated. Their Mw values were 51,000 and 700,000, respectively; the second sample being crosslinked by copolymerization with a polyfunctional monomer.The irradiation‐induced changes were investigated by osmometry, light‐scattering, gel permeation chromatography and dilute and concentrated solution viscometry. From the experimental data obtained, it can be seen that the viscosity‐molecular weight relations are strongly affected by the molecular weight distribtuion and the presence of branching in the samples. By assuming the Stockmayer distribution, and using the equations developed by Kilb, the viscosities of the irradiated samples have been described satisfactorily.
Effects of internal stress on the yielding of oriented poly(vinyl chloride)
Authors: Rawson F. F. , Rider J. G. 
Published: June 2010

AbstractPoly(vinyl chloride) sheet was oriented by hot stretching at 80°C. Yield stresses in simple tension and compression were measured at 20°C and at a strain rate of 100% min−1 as a function of the angle between the test‐piece axis and the hot‐stretch direction. Simple tensile and compressive yield stresses were also measured in the temperature range −40°C to +80°C, in the hot‐stretch direction at strain rates of 100% min−1 and 1% min−1, and in the unstretched sheet at 100% min−1. The results are discussed in terms of a yield criterion based on that of von Mises but modified to allow for the effects of anisotropy, internal stress and mean normal stress, and are held to justify the inclusion of the internal stress term. By making specified assumptions, the magnitude of the internal stress term is separated from that of the normal stress term and shown to rise slightly with testing temperature and to be only two‐thirds as great at the lower strain rate. A reason is given for thinking that the strain‐rate effect may have been overestimated.
Study of the efficiency of plasticizers in poly(vinyl chloride) by dielectric spectroscopy
Authors: Kisbényi M. 
Published: June 2010

AbstractDielectric dispersion and absorption spectra of plasticized polyvinyl chloride systems were investigated in order to obtain information about the efficiency and compatibility of the plasticizer.Dielectric spectra were measured as a function of temperature at a constant frequency and a constant heating rate within the range of −170 to +150°C.The glass transition temperature [Tg] is found to be dependent on the quality (structure) and quantity of the plasticizer used. The dipole‐dipole interactions, and thus also the plasticizing effect, are characterized by the dielectric permittivity change [Δet] in the transitions range.Dielectric spectra of compounds prepared with either commercial or special‐type plasticizers were measured. The effect of the chemical structure on the dielectric spectra was studied on a series of compounds containing phthalate‐type plasticizers having alcoholic side chains of an increasing length. The results of dielectric measurements are compared with those obtained by standard mechanical tests.From this comparison of results it may be concluded that the investigation of dielectric spectra offers important information regarding the efficiency and compatibility of plasticizers.
Variations of the dielectric and mechanical characteristics of the poly (vinyl chloride) film: Electric discharges in air
Authors: Bagirov M. A. , Abasov S. A. , Malin V. P. , Abbasov T. F. 
Published: June 2010

AbstractOne of the principal reasons of the premature failure of the polyvinyl chloride electrical insulation is the action of the discharges in the air voids of the insulation. Therefore, investigation has been carried out of the changes of the dielectrical permittivity ε and the loss factor tan δ of a polyvinyl chloride (PVC) film, plastified by dibutyl phthalate, under the effect of the electrical discharges in the air. Since by the discharges in the presence of oxygen a vigorous formation of ozone takes place the changes of the above mentioned characteristics after the exposure of samples in the ozone have been investigated separately.It has been shown that under the effect of the electrical discharges in the air, the temperature dependences of ε and tan δ have changed essentially. ε is subjected to dispersion over the temperature range from 70 to 100°C; tan δ increases over the whole temperature range, the conductivity losses begin at lower temperatures, and the peak of dipole‐segment losses (DSL), which is strongly pronounced in the initial sample, is no more observed. This is due to the fact that under the effect of ozone and owing to the crosslinking of the polymer chains the peak of DSL is shifted to higher temperatures; as a result, both DSL and the conductivity losses are superimposed.The extension of the sample, leading to an additional orientation of macromolecules, weakens considerably the changes of the dielectrical characteristics due to the discharges.