bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymers containing anthraquinone units: Polyimidazoles and polypyrrolones from 1,2,5,6‐tetraaminoanthraquinone
Authors: Pense Rolf , Marvel C. S. 
Published: April 2003

Abstract1,2,5,6‐Tetraaminoanthraquinone has been condensed with isophthalaldehyde and terephthalaldehyde and their bisulfite addition compounds to yield new heat‐stable polymers. It has also been condensed with pyromellitic anhydride to give the pyrrolone. The highest viscosities were obtained in polymers prepared with acid catalysts. The polymers were nearly all soluble in concentrated sulfuric acid but not in organic solvents. Those soluble in sulfuric acid could also be solubilized by reduction with sodium dithionite and potassium hydroxide in aqueous organic solutions. A few polymers were apparently crosslinked, since they would not dissolve in either sulfuric acid or in base on reduction. Weak fibers were obtained by spinning the reduced alkaline solutions of the polymers into aqueous acid.
Polymers containing anthraquinone and quinoxaline units: Polypyrrolones
Authors: Dutt Prabir K. , Marvel C. S. 
Published: April 2003

AbstractFour ladder or partial ladder polypyrrolones containing anthraquinone recurring units have been synthesized by condensing the dianhydride of 1,2,5,6‐bis(α,β‐dicarboxyl‐pyrazino)anthraquinone with four different tetraamines, 1,2,4,5‐tetraaminobenzene tetrahydrochloride, 3,3′,4,4′‐tetraaminodiphenyl, 3,3′,4,4′‐tetraaminodiphenyl ether, and 1,2,5,6‐tetraaminoanthraquinone in dimethylacetamide and tetramethylene sulfone as reaction media. A prepolymer with an open structure was first formed which on further heating gave a closed‐ring structure. These polymers which were highly colored, powdery materials, were insoluble in common organic solvents and slightly soluble only in concentrated H2SO4. They could, however, be solubilized in alkali by reduction with sodium dithionite. These polymers with an inherent viscosity in the range of 0.2–0.5, showed good thermal stability.
Viscous flow and structure of linear polymers
Authors: Bartenev G. M. 
Published: April 2003

AbstractThe viscosity of linear polymers obeys the logarithmic additivity rule. This is associated with the fact that the activation energy of the viscous flow within certain limits of parameters changes does not depend on temperature, stress, molecular weight, and content of active filler. The mechanism of viscous flow of linear polymers is associated with the reversible destruction of an unstable supramolecular structure typical of the polymers in the state of viscous flow. The effect of shear stress on the viscosity of linear polymers does not obey the Eyring equation. It is supposed that the effect of shear stress on viscosity is associated with the peculiar mechanism of the destruction of the supramolecular structure. At higher rates of viscous flow of the polymer, the activation energy can decrease as a result of the deep destruction of the supramolecular structure. This is a reversible process, as after removal of stress the supramolecular structure slowly reverts to its original state.
Photosensitization of vinyl polymerization by uranyl ions
Authors: Venkatarao K. , Santappa M. 
Published: April 2003

AbstractMonomer acrylamide was used as quencher of uranyl ion fluorescence and Stern‐Volmer plots were constructed at three monochromatic wavelengths of exciting radiation. The results indicated that the reaction between excited uranyl ion and monomer is one of energy transfer. The rate parameters kp/kp½ and kd′/ki were calculated from the polymerization kinetics at high monomer concentrations. A general mechanism for the photopolymerization of vinyl monomers sensitized by uranyl ions is proposed and discussed.
Copolymerization of styrene and butadiene in emulsion. III. Crosslinking studies by partial conversion properties
Authors: Burnett G. M. , Cameron G. G. , Thorat P. L. 
Published: April 2003

AbstractCrosslinking in the styrene–butadiene emulsion copolymerization (21 parts styrene:79 parts butadiene) prior to gelation has been studied by means of partial conversion number‐average molecular weights at 5, 15, and 25°C. It is shown that the macromolecular population begins to diminish at progressively lower conversions as the reaction temperature is increased. This is attributed to the relative increase in crosslinking over propagation as the reaction temperature is increased and also to the decrease in mercaptan regulating index with increasing temperature.
Direct rotating‐sector studies of the systems: Styrene–methyl methacrylate and styrene–methyl acrylate
Authors: Marano J. P. , Shendalman L. H. , Walker C. A. 
Published: April 2003

AbstractThe rotating‐sector technique was applied directly in a study of two copolymerization systems: styrene–methyl methacrylate and styrene–methyl acrylate. The two coupled rate expressions which describe the change in radical concentrations for two‐component polymerizations degenerate into a single expression identical in form to the radical expression for a homopolymerization when the ratio of the radical concentrations under intermittent illumination is assumed constant and equal to the ratio under steady illumination. Numerical solutions of the complete rate expression by use of constants from the literature confirm that this assumption is valid for a rotating‐sector experiment. The overall lifetimes of these two‐component systems were defined and measured experimentally as a function of monomer composition and then compared with lifetimes calculated by using literature rate constants. The agreement was satisfactory. The direct application of the technique to the two‐component system provides an independent experiment which for some systems seems to be more sensitive to the value of the cross‐termination constant than the usual steady‐state method.
Dependence of the catalytic activity of organoaluminum compounds and some of their complexes on their composition
Authors: Mateva R. , Konstantinov Ch. , Kabaivanov V. 
Published: April 2003

AbstractThe influence of the acidity of organoaluminum compounds and their complexes on the catalytic activity in polymerization of trioxane has been studied. It is found that the catalytic activity of organoaluminum compounds of the type RnALX3−n depends on n as well as the nature of R or X. Catalytic activity of the complexes also depends on the type of cocatalyst used. The change of electroconductivity in the course of formation of some initiator complexes has been studied and an attempt has been made to determine the relation between conductivity and polymerization activity.
Temperature variation of piezoelectric moduli in oriented poly(γ‐methyl L‐glutamate)
Authors: Date Munehiro , Takashita Saburo , Fukada Eiichi 
Published: April 2003

AbstractThe real and imaginary components of the complex piezoelectric strain constant, which relates the polarization to the applied stress, have been determined for elongated films of poly(γ‐methyl L‐glutamate) over the temperature range −170°C to +170°C at a frequency of 20 Hz. The variation of the piezoelectric constant with temperature is similar for both α‐helical and β‐form molecular conformations. The sign of piezoelectric polarization is opposite for L and D polymers. A simple model, representing the piezoelectric crystallites as embedded in nonpiezoelectric amorphous regions, is proposed to account for the piezoelectric temperature dispersion curves.
Effect of molecular structure on polyethylene melt rheology. I. Low‐shear behavior
Authors: Mendelson R. A. , Bowles W. A. , Finger F. L. 
Published: April 2003

AbstractThe melt rheological properties of both linear and branched polyethylene were investigated by use of narrow molecular weight distribution fractions and experimentally polymerized samples. Studies carried out in steady shear and in oscillatory shear yielded information concerning both the melt viscosity and the melt elasticity as a function of molecular structure, where the latter was characterized by various solution property techniques. The 3.4–3.5 power dependence of the low shear limiting viscosity on molecular weight was confirmed for linear polyethylene. The effect of long‐chain branching on rheological properties was defined both at constant molecular weight and at constant molecular weight distribution and coupled with variation of molecular weight.
Dynamic and steady‐shear melt rheology of and ethylene‐methacrylic acid copolymer and its salts
Authors: Sakamoto Kunisuke , MacKnight William J. , Porter Roger S. 
Published: April 2003

AbstractStudies have been made on the dynamic and steady‐shear melt rheology of an ethylene–methacrylic acid copolymer and two of its salts obtained by partial neutralization with sodium and with calcium bases. Measurements were made with a Weissenberg rheogoniometer over a broad range of shear rates and frequency in the temperature interval mainly from 100 to 160°C. The temperature coefficients of dynamic and steady shear viscosity are evaluated at both constant shear rate and constant stress. Likewise, complex dynamic viscosities and apparent high steady‐flow viscosities and intercompared at equivalent frequencies and shear rates. The un‐ionized acid copolymer shows good correlation between the frequency dependence of the complex viscosity and the shear rate dependence of the apparent viscosity. This is not true for either the sodium salt or the calcium salt. These results are consistent with the two‐phase structural model for these materials, i.e., a matrix of hydrocarbon in which are embedded ionic domains.
Transitions of the hydrogen bond in epoxy–diamine networks
Authors: Williams J. G. , Delatycki O. 
Published: April 2003

AbstractThe variation of the fundamental hydroxyl stretching frequency in the infrared spectrum of a number of epoxy–diamine networks has been determined as a function of temperature. Short‐range hydrogen bonds appear to be formed in all the epoxy networks examined. For polymers formed by using short‐chain α,ω‐diamines, it appears that a hydroxyl–hydroxyl bond is dominant. For longer chain lenghts, a hydroxylamine bond becomes important. The hydroxyl–hydroxyl bond breaks at the glass transition temperature, whereas the hydroxyl–amine bond breaks at a higher temperature. At the highest temperatures studied, all hydroxyl groups form weak short‐range bonds to the alkyl‐aryl ether function. The absorption frequency for the hydroxyl group in all types of hydrogen bonds formed shows a strong dependence on temperature and absorption moves to a higher wavenumber with increase in temperature.
Normal stress and shear stress in a viscoelastic liquid under oscillatory shear flow
Authors: Endo Hiroshi , Nagasawa Mitsuru 
Published: April 2003

AbstractNormal stress and shear stress of concentrated polystyrene solutions in a chlorinated diphenyl were measured under steady flow and oscillatory shear flow in a Weissenberg rheogoniometer. The normal stress difference was observed to oscillate at double the frequency of the applied shear strain with amplitude proportional to the square of the applied amplitude, while the shear stress was found to oscillate at the same frequency with amplitude proportional to the applied amplitude. A theoretical relation between the displacement of the oscillatory normal stress difference from zero level and the dynamic modulus derived by Lodge and other investigators was confirmed experimentally, and the theoretical predictions of Coleman and Markovitz concerning the relation among steady‐flow normal stress difference and dynamic modulus were also confirmed. However, the theoretical predictions of Lodge, of Spriggs, Huppler and Bird, and of Williams on the relation between the amplitude and phase of oscillatory normal stress and those of oscillatory shear stress did not agree with experimental results.
ESR study of the initial reaction of the photodegradation of nylon 6
Authors: Heuvel H. M. , Lind K. C. J. B. 
Published: April 2003

AbstractThe free radicals formed on irradiation of nylon 6 have been studied by means of electron spin resonance (ESR). The irradiation was performed at liquid nitrogen temperature with wavelengths in the region of solar radiation. The spectrum so obtained could best be fitted by assuming CH2ĊHCH2 and CH2ĊO to be the trapped radicals. The assignment of the spectrum supports the idea that the first step in photodegradation is the breaking of the amide bond. The splitting constant of the α proton of the alkyl radical has been found to be nearly the same for drawn and undrawn yarn. This strongly suggests that the low‐energy radiation is capable of breaking bonds only in the unoriented amorphous regions.
Structure of a typical amine‐cured epoxy resin
Authors: Bell James P. 
Published: April 2003

AbstractA technique for estimating Mc, the molecular weight between crosslinks, of amine‐cured epoxy resins is described. The technique is based upon the stoichiometry of the curing reaction and the amount of primary amino and epoxy groups remaining in the polymer at a given time. The Mc values so calculated are shown to be consistent with Mc results obtained from separate measurements of swelling and the polymer–solvent interaction parameter χ1 for the range of polymer concentration in which both measurements could be obtained. A means of estimating the relative reaction rates of the primary and secondary amino groups with the epoxy groups is given. Under proper curing conditions the amine–epoxy reaction goes very nearly to completion. The presence or absence of an exotherm has no noticeable effect on the course of the reaction between bisphenol A‐epichlorohydrin (Epon 828) and methylene dianiline.
ESR studies on gamma‐irradiated (KPO3)n crystals
Authors: Hukuda Kenzi , Nakahara Motohiro , Kusumoto Naoshi 
Published: April 2003

AbstractTwo types of (KPO3)n crystals have been obtained: transparent crystals and semitransparent crystals that grew in the neighborhood of the wall of the crucible. In the latter type of crystals, four kinds of radicals, denoted B, C, D, and E, are observed by ESR measurements at 77°K on crystals irradiated with γ‐rays at the same temperature. The probable structure of B, C, and D radicals is concluded to be OPO̊2O from their g values and hyperfine constants (the superscript circle indicates a hole trapped in the radical). When these crystals are heated to room temperature, the ESR spectra of B, C, and D radicals disappear and the spectrum of another radical appears. This radical, designated A, has the possible structure OṖO2. The assumption that B radicals thermally decompose into A radicals is confirmed by experiment. With the transparent crystals, C, D, and E radicals are observed at low temperature, but only E radicals are stable at room temperature. The structure of the E radical is thought to be\documentclass{article}\pagestyle{empty}\begin{document}${\rm \hbox{---}O \hbox{---}PO}_2{{_\circ} \atop ^{\hbox{---}}} {\rm PO}_2 {\rm \hbox{---}O\hbox{---}} $\end{document}, but more detailed studies are required.
Viscoelastic properties of branched polyethylene melts
Authors: Chartoff Richard P. , Maxwell Bryce 
Published: April 2003

AbstractThe dynamic mechanical properties of branched polyethylenes in the molten state were determined in the frequency range 10−3–10 radians/sec. The materials tested have remarkably similar rheological properties even though they vary greatly in molecular weight and molecular weight distribution. The similarity in properties is attributed to the influence of long chain branching on the relaxation spectra. A mechanistic argument is proposed to relate the observed behavior to molecular entanglement coupling. The concept of entanglement coupling involving long‐chain branching leads to the expectation that the quasi‐Newtonian and non‐Newtonian viscosities of branched polymers may be either greater or less than those of linear polymers of the same species, which have comparable molecular weights. This is borne out by experiment.
Effect of birefringence on light scattering from deformed spherulitic polymer films
Authors: Motegi Masahiko , Moritani Masahiko , Kawai Hiromichi 
Published: April 2003

AbstractLight scattering from oriented samples of crystalline polymers is affected by the birefringence of the sample. An extension of the theory for scattering from uniaxially deformed two‐dimensional and three‐dimensional spherulites is made so as to include the retardation of the incident and scattered beams in passing through the birefringent sample. Strain influences scattering, in that it changes the birefringence of the sample and it also changes the anisotropy and shape of the spherulites. Scattering intensities are calculated for both crossed and parallel polarizers as a function of Ω, χ, and Φ, where Ω is the angle between the stretching direction of the sample and the horizontal direction, and χ and Φ are the angles between the stretching direction and the polarization directions of the polarizer and analyzer, respectively. It is shown that for crossed polarizers with Φ = 45° and χ = 45° birefringence changes largely influence the results but that for the polarizers parallel at Φ = 0° and χ = 0° or crossed at Φ = 90° and χ = 0° the birefringence effect is minimized. The intensity distributions for crossed polarizers at Φ = 45° and χ = 45° from polyethylene films stretched to give retardations up to several wavelengths, are found to be in good agreement with the calculated results.
Photocurrents in simple polymer systems
Authors: Binks A. E. , Campbell A. G. , Sharples A. 
Published: April 2003

AbstractPhotocurrents have been detected in a wide range of simple polymer systems at irradiation wavelengths as high as 365 mμ. These photocurrents are shown to be due to phtoemission from the electrode system. Pulsed photoconductivity experiments show that at least two stages of charge transport are involved. In the first stage photoemitted electrons travel a short distance into the polymer before being trapped. This is followed by a slower process of trap‐dominated charge transport.
Thermal expansion, free volume, and molecular mobility in a carbon black‐filled elastomer
Authors: Kraus Gerard , Gruver J. T. 
Published: April 2003

AbstractThe thermal expansion of a butadiene–styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated. The glass transition was unaffected by MT and was raised only 0.2°C for every 10 parts per hundred by weight of polymer of HAF black added. The coefficient of expansion of the polymer component of the composite in the rubbery region was substantially unaffected by either carbon black, but decreased markedly with increasing black loading in the glassy state. These results suggest that free volume is not altered appreciably by the presence of the filler in the rubbery state, but expands with decreasing temperature below Tg. The latter effect is explained by dilatation due to stresses set up around filler particles, arising from differences in the expansion coefficients of filler and polymer, which are not relieved in the glassy state. The near invariability of Tg and of the rubbery fected by adsorption of polymer segments on the carbon black surface. A conservative rough estimate indicates that restriction of segmental motion is confined to a 30 Å layer around the particles in which Tg is elevated by only 10°C.
Fracture surface of polystyrene: Mackerel pattern
Authors: Murray J. , Hull D. 
Published: April 2003

AbstractCharacteristic markings of concentric bands are formed on the fracture surface of tensile specimens under certain loading conditions. The marking form in the fast crack growth region of the mirror area of fracture. Optical and electron optical microscope techniques have been used to study the morphology of the markings. It is shown that in this region the crack propagates along the interface between the craze, in which the crack nucleated, and the bulk material. The mackerel pattern is caused by the crack jumping from one craze–matrix interface to the other.
Effect of bending and stretching of polyethylene strips on the adsorption of surface‐active substances
Authors: Seimiya T. , Yamamoto H. , Sasaki T. 
Published: April 2003

AbstractThe adsorption of tritium‐labeled sodium stearate and 35S‐labeled sodium dodecylsulfate from aqueous solution on bent and on stretched polyethylene strips was directly measured. The amount of adsorption increased from 2.5 to 4.5 times on surfaces of various polyethylene samples stretched from 5.2 to 5.3 times the original length. For one sample, adsorption increased 8 and 2.5 times, respectively, on the convex and concave surfaces of a bent strip. Autoradiographs of the strips taken after adsorption revealed the appearance of both homogeneous and heterogeneous adsorption on the stretched surface of the polyethylene. The electron micrographs of the strips showed that many small fissures, about 1–5μ in length, formed on their surfaces after the strips were bent or stretched. Enhanced adsorption of the surface‐active substance along these fissures was suggested. On the basis of these observations, it is proposed that in stretching or bending, fissures increase adsorption of the detergent, and the adsorption in turn promotes further development of fissures. Thus, bending and adsorption mutually promote the growth of fissures which finally result in failure of the polyethylene.
A molecular approach to chain entanglement in linear polymers
Authors: Tonelli A. E. 
Published: April 2003

AbstractThe phenomenon of chain entanglement in undiluted linear amorphous polymers is treated by calculating the probability of forming closed intramolecular loops. Adoption of the rotational isomeric state model of polymer chains permits an appropriate accounting of the detailed molecular structure to be made through the configurational characteristics of the polymer. The second (〈r〉0) and fourth (〈r〉0) moments of the vector rhk connecting groups h and k in the isolated polymer chain and averaged over all chain conformations are calculated and used to evaluate the probability Wx(0) that rhk is 0, or that an intramolecular loop of x = k − h bonds is formed. Several linear polymers with widely differing molecular structures are treated. An attempt is made to correlate the degree of chain entanglement they manifest in the bulk with their ability to fold back upon themselves to form closed intramolecular loops.
Crystallization kinetics of dilute polyethylene solutions
Authors: Devoy C. , Mandelkern L. , Bourland L. 
Published: April 2003

AbstractThe crystallization kinetics of a high molecular weight fraction of linear polyethylene was studied in dilute solutions of p‐xylene, n‐hexadecane, and decalin by dilatometric methods. For all solvents and temperatures, the experimental isotherms could be quantitatively described by the Avrami formulation for the complete transformation. This result is unique in the realm of polymer crystallization, since marked deviations from this theory are usually observed in more concentrated systems. The Avrami exponent is found to be n = 4 in all cases. The temperature coefficients of the rate constants are indicative of a nucleation controlled process. The data fit either a two‐dimensional or three‐dimensional nucleation mode, and a discrimination can not be made between these two cases. The interfacial free energies are found to be independent of the solvent medium. It is also shown that, irrespective of the type of nucleation control governing the kinetics, the same type governs the crystallite thickness of the lamella‐like crystals that are formed.