bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of microstructure on the hydrodynamic behavior of poly‐α‐methylstyrene
Authors: Cowie J. M. G. , Bywater S. 
Published: April 2003

AbstractThe theta temperature of poly‐α‐methylstyrene in cyclohexane has been found to vary with the stereostructure of the polymer. The observed values range from 305.5°K. for highly syndiotactic material (0.95 syndiotactic diads) to 310.0°K. for anio ically polymerized samples (0.67 syndiotactic diads). Results indicate that the unperturbed dimensions of the polymer increase with increasing isotacticity of the chain, whereas the entropy parameter ψ1, measured in cyclohexane, decreased as the structure became more isotactic. Measurements of the second virial coefficient in toluene showed an increasing interaction with the solvent as the polymer became more syndiotactic.
Identification of a stereoblock poly(methyl methacrylate) sample with a stereocomplex
Authors: Liquori Alfonso M. , Anzuino Giuseppe , D'Alagni Maria , Vitagliano Vincenzo , Costantino Lucia 
Published: April 2003

AbstractAcid hydrolysis of a stereoblock poly(methyl methacrylate) sample leads to a mixture of isotactic and syndiotactic poly(methacrylic acid) which can be separated by electrophoresis. The experiment confirms the stereochemical identity between the so‐called “stereoblock” poly(methyl methacrylate) and the stereocomplex which syndiotactic and isotactic poly(methyl methacrylate) form in the ratio 2:1. A possible mechanism of replica polymerization is suggested to account for this effect.
Conformation and normal frequency distribution of polymer chains
Authors: Jannink G. 
Published: April 2003

AbstractIt is argued on the basis of a simple model for a polymer chain that characteristics of conformation can be determined from the analysis of the frequency distribution of backbone vibrations. In a chain with one degree of freedom per repeat unit, a fold tends to uncouple the motions on each side of the fold. This transfers highest and lowest modes towards the mean value. Conversely, a local unfolding of a random chain enhances the coupling and produces out‐of‐band modes. From the ordering of these modes, statistical aftereffects can be detected. The Green's function method allows a calculation of the single localized mode as a function of angular parameters. The dynamical matrix elements of the Kirkwood‐Pitzer model are calculated for a folded polyethylene backbone chain. The eigenvalue distribution is determined with the Givens‐Sturm procedure. It indicates a one‐to‐one correspondence between modes in the vicinity of 670 cm.−1 in the stretch‐bend gap and chain folds, for low concentration of folds. We conclude that conformations should have two characteristic parameters distinctively reflected in the frequency distribution, namely the range of allowed dihedral angles and the ordering of configurations along the chain. The frequency distribution for a given conformation depends however on the force constant ratios when the degree of freedom is greater than one. Interpretation of the frequency spectrum is then made by adjustment of dynamical and geometrical parameters. These are seen to be dependent variables with respect to the spectrum.
Load drop at the upper yield point of a polymer
Authors: Brown N. , Ward I. M. 
Published: April 2003

AbstractThe stress‐system curves have been measured for isotropic and oriented specimens of poly(ethylene terephthalate) in extension, shear, and compression. It was found that for all these types of deformations there was an intrinsic yield drop, i.e., a fall in true stress. It is concluded therefore that the stress for initiation is greater than the stress for propagation of yielding.
Distribution of tensile data of vulcanized rubbers. I. Tensile data of SBR vulcanizates loaded with light calcium carbonate
Authors: Yabuta Shiro , Kase Shigeo 
Published: April 2003

AbstractWhen the first asymptotic probability function of smallest values was applied to analyze the distribution of tensile strength data for rubbers, good agreement between observed values and theory did not always result. In order to improve the agreement, use of another distribution function, the third asymptotic probability function, was proposed. Experiments verified that this function yielded good agreement with theory for the distribution of tensile strengths of rubbers, especially for SBR vulcanizates loaded with light calcium carbonate. The third asymptotic probability function contains three parameters: the characteristic value V, the lower limit ε, and the shape parameter k which is dimensionless. Analysis is made by use of a logarithmic extremal probability paper on which the probability function plots as a straight line if ε = 0. There appears to be a lower limit for the distribution of tensile strengths but not for the distribution of elongations. This suggests that the tensile properties follow the third asymptotic distribution function, with the breaking elongations following the simplified form of the Weibull distribution.
Studies of solution properties of copolymers. II. Copolymer of maleic anhydride and styrene
Authors: Endō Ryūichi , Hinokuma Teruo , Takeda Masatami 
Published: April 2003

AbstractStyrene and maleic anhydride were copolymerized in benzene. The whole polymer thus obtained was fractionated with acetone and petroleum ether as the solvent and precipitant, respectively. The viscosities and osmotic pressures of the fractions were determined in tetrahydrofuran. The relation between the intrinsic viscosity and the molecular weight, [η] = 5.07 × 10−5 M̄n0.81, was obtained in tetrahydrofuran. The unperturbed mean square end‐to‐end distance was estimated by the Stockmayer‐Fixman equation. A theoretical equation for the mean square end‐to‐end distance for a chain of repeating units of different bond lengths a and b with a fixed valence angle θ and without restriction of internal rotation was presented and applied to this copolymer. In addition, the equation of the mean‐square end‐to‐end distance derived by Wall for trans‐polyisoprene without rotational restriction was modified for application to this copolymer. The result evaluated with our equation was about 26% smaller than that from the modified Wall equation. A steric parameter for the present copolymer is defined and discussed in comparison with those of polystyrenesulfone and polystyrene.
Solution properties of poly(methyl acrylate) and (1:1) poly(styrene‐co‐methyl acrylate)
Authors: Karunakaran K. , Santappa M. 
Published: April 2003

AbstractPoly(methyl acrylate) (PMA) and 1:1 poly(styrene‐co‐methyl acrylate) (PSMA) were prepared by solution and bulk polymerization, respectively. The copolymer was analyzed with NMR to ascertain its composition and microstructure. The solution properties of unfractionated PMA and fractionated PSMA in ethyl acetate were investigated by light‐scattering and viscosity techniques at 35°C. Narrow composition heterogeneity as revealed from the light‐scattering measurements in different solvents justified the use of a single solvent for the copolymer characterization. The equations relating the limiting viscosity number to molecular weight, the molecular dimension to molecular weight, etc., were found for homopolymer and copolymers in ethyl acetate at 35°C. In the evaluation of the Flory constant K for the unperturbed state by methods based on Flory‐Fox‐Schaefgen, Kurata‐Stockmayer, and Stockmayer‐Fixman expressions, only the first method gave a value for PMA in ethyl acetate, consistent with that obtained in other solvents, whereas similar values of K were obtained by the three methods for PSMA in ethyl acetate. The studies indicate reduced thermodynamic interaction for PSMA–ethyl acetate compared to PMA–ethyl acetate, but increased steric effect in the copolymer compared with the homopolymer.
Unperturbed chain dimensions of isotactic polypropylene in theta solvents
Authors: Nakajima Akio , Saijyo Akira 
Published: April 2003

AbstractThe unperturbed mean‐square end‐to‐end distance 〈R02〉 and its temperature variation d In 〈R02〉/dT for isotactic polypropylene have been estimated from intrinsic viscosity data in three theta solvents, i.e., diphenyl, diphenyl ether, and dibenzyl ether, measured at their θ temperatures as determined by precipitation temperature measurements. The characteristic ratios, 〈R02〉/nl2, where n is the number of bonds of length l in the main chain, evaluated by assuming Φ = 2.87 × 1021, are 5.80 in diphenyl (at θ = 125.1°C.), 5.41 in diphenyl ether (at θ = 142.8°C.), and 4.56 in dibenzyl ether (at θ = 183.2°C.). These values lead to the temperature coefficient d In 〈R02〉/dT = −4.09 × 10−3 deg.−1 Results are compared with the data previously reported on polyethylene.
Nucleation of crystallization in molten isotactic polybutene‐1
Authors: Burns Joanne R. , Turnbull D. 
Published: April 2003

AbstractDroplet experiments have been performed on polybutene‐1. It was found that this polymer can be cooled to room temperature without homogeneous nucleation of crystallization. It was also found that when the polymer was heterogeneously nucleated, form I (as well as form II) could be crystallized directly from the melt. The melting point of droplets crystallized in form I near room temperature decreased with increasing crystallization temperature, while the melting point of the droplets crystallized in form I at the highest temperatures increased with increasing crystallization temperature. There was a broad minimum at about 60°C. in the melting point versus crystallization temperature curve.
Crosslinked oligoethylene glycols: Correlation between their structure and some rheological properties
Authors: Katz Dov , Salee Gideon 
Published: April 2003

AbstractSix oligoethylene glycols were crosslinked with triphenylmethane triisocyanate, and polymers with systematically changing network chain lengths were obtained and investigated. The 10‐sec. torsion moduli versus temperature, glass transition temperatures, and cohesive energy densities of the polymers were determined and studied. The 10‐sec. torsion modulus versus temperature plots show that all six polymers have a glassy transition and rubbery region of rheological behavior. The front factor calculated from the equation for the torsion modulus in the rubbery region when measured values of the modulus were used was compared with the front factor computed from equations that take into consideration molecular structures of the rubbery networks. With the exception of the case of crosslinked diethylene glycol the agreement in all the other cases between the values obtained for the front factor in both ways was good. In the investigated range of temperatures the polymers have below the glass transition temperature another transition point. The solubility parameters of the polymers, calculated from swelling experiments, were with the exception of the first member in the series almost identical.
Effect of x‐rays on extended chain crystals of polyoxymethylene
Authors: Jaffe M. , Wunderlich B. 
Published: April 2003

AbstractExtended chain crystals of polyoxymethylene were irradiated with x‐rays of about 105 r./min. An immediate decrease in superheating on melting was noted. After 90 min. of irradiation the melting point level, refractive indices, and density also decreased. After 480 min. the DTA melting peak at a heating rate of 20°C./min. had decreased 25°C., the melting point decreased about 18°C., and the density calculated from refractive indices decreased 0.031 g./cm.−3. These effects are interpreted as indication of chain scission and formation of amorphous defects.
Heat capacities for atactic polystyrene of narrow molecular weight distribution to 360°K.
Authors: Chang S. S. , Bestul A. B. 
Published: April 2003

AbstractPrecise heat capacity values are reported over the temperature range from 10 to 360°K. for a sample of atactic polystyrene having a narrow molecular weight distribution. This sample was taken from the stock from which National Bureau of Standards Standard Sample 705, Narrow Molecular Weight Distribution Polystyrene, was established. Data are reported for the sample as received, and after an annealing procedure. At temperatures below about 60°K. a systematic difference comparable with the limits of experimental precision appears between the values obtained for the present sample as received and after the annealing, although at higher temperatures the values for the two conditions showed no systematic difference beyond the limits of precision of the measurements. At temperatures above 100°K., previously published values for atactic polystyrene samples of various molecular weight distributions and for isotactic polystyrene agree within about 0.5% of the values from this investigation. At temperatures below 100°K. significant heat capacity differences appear, especially between values for the atactic and the isotactic isomers, and even between atactic samples of different molecular weight distribution.
Crystallization kinetics of polymer–diluent mixtures. Influence of benzophenone on the spherulitic growth rate of isotactic polystyrene
Authors: Boon J. , Azcue J. M. 
Published: April 2003

AbstractAs an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.
Hydrogen bonding in butadiene copolymers. II. Network relaxation
Authors: Otocka E. P. , Eirich F. R. 
Published: April 2003

AbstractThe mechanical lability of intermolecular hydrogen bonds in stoichiometric mixtures of acidic and basic butadiene copolymers has been studied by both infrared and mechanical methods. Comparison is made between the weight‐averaged E(t) and H(τ) spectra of the parent copolymers and those of the mixed copolymers. The results indicate that the maximum contributions of bond‐interchange relaxation migrate to shorter times as the concentration of bonding groups increases.
Ionic bonding in butadiene copolymers. II. Stress relaxation
Authors: Otocka E. P. , Eirich F. R. 
Published: April 2003

AbstractThe mechanical lability of quadrupolar links in cationic and anionic polyelectrolytes and of ion‐pair links in mixed polyelectrolytes is investigated in terms of deviations from the WLF viscoelastic theory. The behavior of E(t), log AT, and Evisc indicate that the quadrupolar links do not interchange below the second transition Tt* found in these materials. The blended polyelectrolytes exhibit low yields of the desired ion pair linking and have transitions characteristic of quadrupolar migration of the unreacted polyelectrolytes.
Anisotropy of viscoelastic transitions in oriented polyethylenes
Authors: Stachurski Z. H. , Ward I. M. 
Published: April 2003

AbstractMeasurements have been made of the anisotropy of viscoelastic behavior in cold‐drawn low‐density and high‐density polyethylene sheets. In the low‐density polymer the β transition was shown to be highly anisotropic, maximum losses corresponding to shear on planes containing the axis of drawing and on planes perpendicular to this axis. In high‐density polyethylene the α transition shows anisotropy.
Interactions between Co(III) and Ni(II) complex ions and polyelectrolytes
Authors: Crescenzi V. , Pispisa B. 
Published: April 2003

AbstractAn investigation has been carried out of the interaction of optically active tris(ethylenediamine)–Co(III) and of tris(o‐phenanthroline)–Ni(II) complex ions with different polyelectrolytes in dilute aqueous solution. Optical rotatory dispersion measurements reveal that binding of the Co(III) complex ions occurs with a noticeable degree of specificity which in addition to depending on the nature of the fixed charges is also affected by the chemical constitution of the polyelectrolytes chain backbones. The dependence of tris(ethylenediamine)–Co(III) optical activity on polyelectrolyte concentration also exhibits interesting features. Polarimetric measurements of the rate of racemization of tris(o‐phenanthroline)–Ni(II) ions in the presence of different polyelectrolytes lead to similar conclusions. Sodium dextran sulfate is shown to interact selectively with one of the antipodes of tris(phenanthroline)–Ni(II) complex.
Relation of the decay of free radicals in irradiated polyethylene to the molecular motion of the polymer and the configurations of the free radicals
Authors: Nara S. , Shimada S. , Kashiwabara H. , Sohma J. 
Published: April 2003

AbstractDecay reactions of the free radicals produced in irradiated polyethylene (high‐density and low‐density materials) were examined in connection with the molecular motion of the matrix polymer. Three temperature regions, in which the free radicals decay very rapidly, at around 120, 200, and 250°K, were designated TA, TL, and TB, respectively. The decay of the free radicals at these temperatures had activation energies in high‐density polyethylene of 0.4 kcal/mole for TA, 9.4 kcal/mole for TL, and 18.4 kcal/mole for TB. In low‐density polyethylene these quantities were 0.7 kcal/mole for TA, 23.1 kcal/mole for TL, and 24.8 kcal/mole for TB. Comparison of time constants for the decay reactions and for molecular motion of the matrix polymer indicate that the decay in TA and TB is closely related to molecular motion in the amorphous regions of the polymer. The decay of the free radicals at TL in high‐density polyethylene is due to molecular motion associated with local mode relaxation at lamellar surfaces, while that of low‐density polyethylene is due to local mode relaxation in the completely amorphous region. Steric configurations of the free radicals which decay in the respective temperature regions were also investigated.
Infrared spectra of polymer solutions. I. Conformational stability of isotactic polymer chains in solution
Authors: Kobayashi Masamichi , Tsumura Katsusuke , Tadokoro Hiroyuki 
Published: April 2003

AbstractThe infrared spectra of isotactic polystyrene, polypropylene, and poly‐p‐chlorostyrene were measured in dilute solutions or gels at various temperatures ranging from room temperature to −100°C. For isotactic polystyrene and polypropylene, all the absorption bands characteristic of the helical conformation of the molecules increase in intensity with decreasing temperature, and show intensities at low temperature as strong as in the highly crystallized samples. This suggests that the molecules can assume very regular conformations even in solution. Similar temperature dependence of the spectra was observed for a homogeneous gel of isotactic poly‐p‐chlorostyrene, which is believed to be noncrystalline. These experimental facts lead to the conclusion that the stability of the TG type helical conformation of these isotactic polymers may be ascribed to the intramolecular forces within a molecule. The fact that these spectral changes are reversible has permitted a thermodynamic treatment of the conformational regularity in solution on the basis of the infrared data. The temperature dependence of the absorption intensities has been interpreted quantitatively by a simple statistical mechanical model, and the enthaply and the entropy differences between the helical and the random states of the monomeric residue in the molecular chain have been estimated.
Huggins constant k′ for flexible chain polymers
Authors: Sakai Tsukasa 
Published: April 2003

AbstractThe Huggins constant k′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k′[η]2c2 + …), is calculated. For polymers in the theta condition, k′ is estimated to be 0.5 < kθ′ ≤ 0.7. For good solvent systems, the Peterson‐Fixman theory of k′ has been modified; the equilibrium radial distribution function in the original theory is replaced with a parametric distribution for interpenetrating macromolecules in the shear force field. Comparison of the modified theory with experimental k′ for polystyrenes and poly(methyl methacrylates) of different molecular weights in various solvents shows good agreement. An empirical equation which correlates the Huggins constant k′ and the viscosity expansion factor αη for polymers has been found to coincide well with the modified theory.
Structure of gum arabic and its configuration in solution
Authors: Swenson Harold A. , Kaustinen Hilkka M. , Kaustinen Ola A. , Thompson Norman S. 
Published: April 2003

AbstractGum arabic was found to have an osmotic molecular weight of 250,000, in agreement with earlier determinations. A molecular weight of 365,000 was found by light scattering, somewhat higher than obtained earlier by sedimentation equilibrium analysis but lower than light‐scattering values reported by other investigators. The M̄w/Mn ratio, 1.46, is quite low in gum arabic. The angular dependence of light scattering exhibited the upward curvature to be expected of a spherical molecule and a radius of gyration of about 100 A. or less, as estimated from a Zimm plot. Fractionation of the original gum arabic was done by precipitation of a 0.5% solution in aqueous 0.5% NaCl with acetone. Comparison of the curves of viscosity versus molecular weight and the estimated radius of gyration shows that the hydrodynamic volume is less than that of branched dextran of similar molecular weight. The electroviscous effects for gum arabic in aqueous solution were shown by reduced viscosity curves at various acidities and in salt. The degree of dissociation was calculated for each pH level. The minimum intrinsic viscosity was found in 0.04N HCl where the degree of dissociation at pH 1.5 was found to be 0.049. When the acidity was increased, further reduction in viscosity was found to be negligible. Routine determination of the viscosity and molecular weight of the fractions was done in 0.35M NaCl at pH 10 to which 0.25% of the sodium salt of ethylenediaminetetraacetic acid was added as a sequestrant. The intrinsic viscosity in this solvent was nearly as low as in 0.04N HCl. Light‐scattering dissymmetries in water and in 0.35M NaCl plus EDTA at pH 10 were similar, 1.13 and 1.09, respectively, which showed that actual expansion of the macroion is not the cause of the large increase in viscosity of gum arabic when the ionic strength of the solvent is reduced. Periodate oxidation of the polymer confirmed the existence of a 1–3‐linked backbone of galactose. Subsequent treatment of the oxidized polymer with alkali reduced the osmotic molecular weight to 45,000 but failed to remove oxidized side branches. The oxidized polymer was fractionated by gel permeation chromatography and the intrinsie viscosity–molecular weight relation compared with relations for fractions of the unoxidized polymer and for other branched and crosslinked polymers.