bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of cellulose gels by small angle light scattering
Authors: Beebe E. V. , Coalson R. L. , Marchessault R. H. 
Published: June 2010

AbstractAn experimental evaluation of the light scattering from two water‐swollen cellulose gels and the corresponding solvent‐exchanged cellulose gels has been made. The two gels were prepared from a commercial viscose by methods which gave different degrees of swelling. The solvent exchanged gels were finally imbibed with silicone fluids whose refractive indices (n) covered the range 1.40–1.59. The Debye‐Bueche theory for scattering from a heterogeneous solid was applied to the data. The observed scattering could be interpreted in terms of refractive index or density fluctuations which were less for the sample with lover degree of swelling. The average periodicity of the density fluctuations increased as n of the imbibition fluid in the solvent‐exchanged samples approached the value, na, for the amorphous regions and maximized in this region. Comparative lateral order distribution information could be derived from the data. From the results it could be shown that the water‐swollen gel is more homogeneous then after solvent exchange but the difference was less for the less swollen system. The evidence collected supports the idea that cellulose gels are, to a first approximation, three‐phased systems involving high order and low order regions as well as micropores. Electron micrographs of thin sections of the solvent‐exchanged gels served to confirm this hypothesis.
Small angle x‐ray scattering from bulk crystalline polymers
Authors: Geil P. H. 
Published: June 2010

AbstractIt is tempting to correlate the discrete small angle x‐ray diffraction (SA) spacings obtained using polymers crystallized from the melt with the thickness of the lamellae present in the sample. There is a good correlation of SA spacing and the electron microscope (EM) observed thickness for polymers crystallized from solution. However, a review of available data in which SA and EM observations have been made on the same sample (for polyethylene, polyoxymethylene, polychlorotrifluoroethylene, and polyethylene oxide) show that the largest HA spacing is not in agreement with the EM observed thickness. In several of the polymers the second largest spacing, which is often not an order of the largest, is in reasonable agreement with the EM value. Possible causes of these discrepancies are discussed.
Introductory remarks for symposium on transitions and relaxations in polymers
Authors: Royer R. F. 
Published: June 2010

AbstractMost organic polymers show a complex array of transition and/or multiple relaxation phenomena in addition to the classical glass transition and the melting point. An amorphous hydrocarbon backbone polymer such as an equimolar, random copolymer of ethylene and propylene, can exhibit, four types of relaxation regions: (1) motion of the entire chain as a unit; (2) motion of a chain segment of perhaps 50–100 carbon atoms, i.e., the glass transition; (3) motion of a 2, 3, or 4 carbon atom moiety about the chain axis, i.e., the γ transition: (4) motion of a side group, such as CH3 in a propylene unit. A moderately crystalline hydrocarbon backbone polymer, i.e., polypropylene, can show all of the loss peaks noted above but in addition may exhibit peaks as follows: (1) melting point; (2) a first‐order transition from one crystal type to another; (3) motion of side groups such as CH3 within the crystallites; (4) interactions between crystallites and amorphous regions; (5) frictional losses within crystallites. Single crystals of linear polyethylene show several loss peaks related to loss peaks in partially crystalline polyethylene. Additional types of loss mechanisms arise in polymers such as polyethylene glycol terephthalate, polycarbonates, cellulose derivatives, and nylon, in which different types of moieties alternate along the chain. Different teat methods varying in specificity toward molecular groups in frequency and in sensitivity are needed to elucidate the full spectrum of loss mechanisms. Brief comment is made on the dielectric data of Kheir showing two clearly resolved loss peaks for 5% cellulose acetate in dioxane.
Ellipsoid model for polyelectrolytes
Authors: Kurata Michio 
Published: June 2010

AbstractThe expansion factor of polyelectrolytes is calculated by using an equivalent ellipsoid model which is essentially the same as that used by Kurata, Stockmayer, and Roig in the theory of excluded volume effect of non‐ionic polymers. The Donnan‐Kimball approximate solution of the Poisson‐Boltzmann equation is used for evaluating the electric free energy of a chain. The result h applied to the calculation of the intrinsic viscosity [η] as a function of the molecular weight M and salt concentration ρs, As a consequence, [η] is predicted to be expressible in the form

over a wide range of the variables. Here K, Bn and Φ0 are constant independent of M and Ps. In a limited range of large ps values, for example 0.1 ∼ 1 mole 1.−1 for a 1:1 added salt, the parameter Be(Ps) is proportional to Ps−1; but in the range of lower value, of Ps, for example 0.005 ∼ 0.1 mole 1.−1, Be(ps) becomes proportional to a lower inverse power of ps. For still lower values of ps, the above equation is no longer valid, because Be(Ps) becomes a function of M rather than of ps, In this range, the polyelectro‐lyte chain is in an extended rodlike form.
Temperature dependence of polymer viscosity. The influence of shear rate and stress
Authors: Porter Roger S. , Johnson Julian F. 
Published: June 2010

AbstractApparent flow activation energies evaluated from viscosity changes with temperature can be calculated in the non‐Newtonian region at either constant shear rate, E, or at constant shear stress, E. For many linear, amorphous polymere, it can be shown that E is independent of stress over the full range for which shear stress data tire reported. This conclusion also holds for solutions of several polymer types. Anomalous results are documented only for branched polyethylene. E decreases with shear in the non‐Newtonian region approaching a lower limit corresponding to the “power law” region. The relative changes in E with shear rate can be expressed in terms of reduced variables. The absolute change in E with shear rate can he used as a measure of polymer molecular weight distribution.
Normal stresses, non‐Newtonian flow, and dynamic mechanical behavior of polymer solutions
Authors: Kotaka Tadao , Osaki Kunihiro 
Published: June 2010

AbstractComplex dynamic shear moduli, shear and normal stresses in steady shearing flow, and complex moduli with superposed steady shear are investigated in both theoretical and experimental aspects. Firs) it summary of phenomenological and molecular theories is given. Experimental tests of phenomenological theory are made by comparing dynamic (linear viscoelastic) data and steady shearing flow (nonlinear viscoelastic) data. It is found that the recent theory of memory fluids is quite satisfactory and also the results show that the action of normal stress in steady shearing flow is mainly pull in the direction of the flow line. The behavior of dilute polymer solutions (near A condition are best approximated by the molecular theory of Zimm, particularly at very low shear rates. At higher shear rates, the Zimm theory fails in predicting the appearance of non‐Newtonian viscosities and nonquadratic normal stresses. Various proposed modifications of the theory are examined experimentally. The behavior of concentrated polymer solution does not seem to fit any of the existing molecular theories; therefore, some typical features of the experimentally observed behavior of concentrated solutions are simply summarized. The results of the measurements of complex moduli with superposed steady shear show that in the low‐frequency region the effect of superposed shear rate results in a much larger decrease in the real part of the complex modulus that in the imaginary part, while in the higher‐frequency region the real part is again decreased but the imaginary part is increased with the increase of superposed shear rate.
On the Structure and Properties of Polyamides. XXVIII. Crystallization of Polycaprolactam Without a Thermal History
Authors: Tomka J. , Šebenda J. , Wichterle O. 
Published: June 2010

AbstractThe time lags for crystallization of polycaprolactam without a thermal history have been measured by nephelometry. The effects of crystallization temperature, degree of polymerization, diluent, and crosslinking have been investigated. Polymer without a thermal history was prepared by activated alkaline polymerization at the desired crystallization temperature, so that the polymer had never previously been crystalline. The dependence of the time lag τ on temperature T and the degree of polymerization P obeys the theoretical relation τ = const. (Tm — T)‐−bPc If we substituted for Tm the melting temperatures corrected for the content of noncrystallizable material we obtained b = 5.85. This value is close to the theoretical value 6, derived under the assumption that the diffusion of segments into the nucleus is proportional to the number of chains forming the surface of the cylindrical nucleus. Measurement of time lags for polycaprolactam crosslinked by means of methylenebiscaprolactam has corroborated the assumption that the viscosity near the surface of the crystal is not identical with the macroscopic viscosity of the melt, in agreement with the fact that the determined value of c = 1.58 is lower than 3.4. The effect of the diluent, N‐methyl‐caprolactam on the depression of Tm outweighs that of the viscosity decrease. The dilatometric measurements of the kinetics of crystallization of polycaprolactam without a thermal history have confirmed that both the time lag and the secondary crystallization can appreciably affect the value of the exponent n in Avrami's equation. If we evaluate the kinetics of the primary crystallization in terms of Avrami's equation using experimental values of time lags, the value of the exponent n is close to 4, which corresponds to a sporadic nucleation and three‐dimensional growth. If, however, the secondary crystallization is not separated and the start of the crystallization is considered to be the moment when the volume change is perceivable experimentally, then we obtain n ≈ 2. This indicates that conclusions on the mechanism of crystallization drawn from the value of the exponent n may be questionable.
Endgroups in Poly (methyl Methacrylate) Initiated by Photosensitized Ferric Salts in Aqueous Media
Authors: Saha Mihir Kumar , Mukherjee Asish R. , Ghosh P. , Palit Santi R. 
Published: June 2010

AbstractPhotosensitized ferric salts (ferric chloride, as well as bromide and perchlorate) have been used as initiators of aqueous polymerization of methyl methacrylate under varied conditions. Analysis of endgroups in the resulting polymers have been made by the application of dye techniques. Both hydroxyl and halogen endgroups have been traced in the polymers in varying proportions except in case of perchlorate where only hydroxyl endgroups have been detected. Some of the results are in sharp contrast with those reported by Evans et al. While increasing concentration of both ferric chloride and bromide was associated with a sharp fall in the total endgroup content of the polymers, ferric perchlorate did not show such effect. Specific action of some anions derived from additives such as salts and acids on the total endgroup content of the polymer was also investigated. Total endgroup content of the polymer decreased appreciably when a halide or a halogen acid was used in the polymerization medium, the effect of bromide being more predominant than the chloride. No such effect was observed in the case of potassium perchlorate, perchloric acid, and potassium sulfate as the additive. An explanation has been suggested for such specific action of anions.
Analysis of NMR and Vibrational Spectra and Conformational Structure of Stereoisomers of 2,4,6‐Trichloroheptane
Authors: Doskočilová D. , Štokr J. , Schneider B. , Pivcová H. , Kolinsky M. , Petránek J. , Lím D. 
Published: June 2010

AbstractThe infrared and NMR spectra of syndiotactic, isotactic, and heterotactic 2,4,6‐trichloroheptane, model compounds of poly(vinyl chloride), have been measured over a wide temperature range. Conformational structures of these stereoisomers have been determined from C—Cl stretching vibrations in infrared spectra and from the temperature dependence of vicinal coupling constants obtained by a four‐spin analysis of the methylene proton bands in NMR spectra.
Fries Rearrangement of Polyphenyl Esters to Polyhydroxyphenones
Authors: Belluš D. , Maňásek Z. , Hrdlovič P. , Sláma P. 
Published: June 2010

AbstractSix different polyphenyl esters were rearranged in a nitrobenzene solution under the action of AlCl3, in melt under the action of AlCl3, TiCl4, and SnCl4 and under the action of UV light. In the rearranged polymers a characteristic absorption band at v = 1636–1656 cm.−1 attributed to vibrations of o‐hydroxycarbonyl groups in IR spectra and a new one with λmax = 322–337 mμ in UV spectra were found. For model compounds, p‐cresyl benzoate and resorcinol monobenzoate, quantum yields of the formation of the corresponding o‐hydroxyphenones Φphi = 0.55 and 0.36 mole‐einstein−1 at λirr = 254 mμ were found. In a rearrangement initiated by UV light, as well as in that catalyzed by Lewis' acids, a decrease in molecular weight occurs and in the latter occurs crosslinking also. A reaction mechanism is suggested. The AlCl3‐catalyzed rearrangement in nitrobenzene solution is governed in the initial phases by the first‐order reaction with an activation energy for the disappearance of ester groups E = 20 kcalμ.‐mole−1 for poly‐2,2‐bis(4‐hydroxyphenyl)propane isophthalate and E = 19 kcalμ‐mole−1 for p‐cresyl benzoate.
Effect of Diluent Content during Polymerization on Equilibrium Deformational Behavior and Structural Parameters of Polymer Network
Authors: Hasa J. , Janáček J. 
Published: June 2010

AbstractThe deformational behavior of poly(ethylene glycol monomethacrylate) which was crosslinked by ethylene glycol dimethacrylate in a concentration range c = 0.05–1.0 × 10−4 mole/cm.3 and polymerized in the presence of 0.05–0.75 volume parts of water was studied. The deformational behavior of these systems may be described by a two‐parameter equation. We found that the value of the constant C2 and the content of permanent entanglements increased linearly with increasing content of polymer in the polymerizing mixture v0. The efficiency of crosslinking also increased and approached the theoretical value at v0 = 1. The measured data can be expressed by the relation v = Kv + Q, where v is the number of effective network chains, and K and Q are the constants depending on the crosslinking agent content, the crosslinking efficiency, and the entanglement content. On the basis of experimental data obtained it is assumed that the entanglements show partly a permanent effect and partly a labile one, the latter influencing the value of the constant C2.
Alkaline Polymerization of Caprolactam. XX. Changes in Catalytic Activity in Activated Alkaline Polymerization of Caprolactam
Authors: Šebenda J. , Masař B. , Bukač Z. 
Published: June 2010

AbstractThe degradation of imide groups (I) in the presence of strongly basic sodium salts (Na) of alkylamides or caprolactam was followed at temperatures of 80‐210°C. in order to elucidate the decay of the catalytic activity during anionic polymerization of caprolactam. It was found that the degradation of I is accompanied by the formation of substances with a strong absorption at 280 mμ, the absorption being proportional to the decrease of the imide group concentration. At temperatures up to 100°C. the rapid degradation of I stops after one I per molecule of Na has disappeared. This may be explained by the formation of acidic derivatives of β‐keto acids through condensations of I. These acidic groups decrease the basieity to such an extent that the further condensation of I is markedly slowed down. At higher temperatures, e.g. 210°C., the equilibrium between the mesomeric enolate anions of the β‐keto acid derivatives and amide groups favors the formation of strongly basic amide anions (—CON—)° which in turn give rise to further condensations of I. At temperatures around 200°C. as much as 3I disappear per Na within a few minutes. The degradation of I is accompanied by a corresponding decrease of the concentration of amide or lactam anions and therefore polymers prepared at 200°C. with I/Na = 3 reveal practically no catalytical effect. On the other hand, polymers prepared with I/Na > 3 or <3 contain either I or strong bases. This could be proved by the use of such polymers as components of the catalytical system instead of I or sodium caprolactam. If more than 3I per molecule of sodium caprolactam are used as catalyst at 200°C. then the decay of the catalytic activity is so rapid that the polymerization stops before the monomer–polymer equilibrium has been attained. Although there is a simple ratio at which I and Na are destroyed, the scheme of the decay of the catalytic effect is not so simple because the extent of the individual side reactions will depend on the temperature and on the initial I/Na ratio.
A Comparison of the Viscoelastic and Dielectric Properties of Natural Rubber—Sulfur Systems
Authors: Havranek A. , Bakule R. 
Published: June 2010

AbstractThis paper presents a comparison of viscoelastic and dielectric retardation time spectra of a rubber‐sulfur system with a sulfur concentration ranging from 1.75 to 16.4%. The viscoelastic spectra were obtained from creep measurements which were carried out in the time interval 3 × 10−2 to 5 × 10+1 sec. and a temperature range from −40°C. to + 70°C. The dielectric spectra were derived from measurements of the frequency dependence of the real and imaginary part of the complex dielectric constant in the frequency range 3 × 101 to 3 × 104 cps or temperatures between −50° and +35°C. The temperature‐time superposition principle was used in the derivation of the spectra. The following conclusions may be deduced from the comparison: (1) The retardation times corresponding to the spectral maximas for mechanical measurements are displaced by several orders toward longer times with respect to those for dielectric measurements. (2) The reference temperatures T determined from the WLF equation are higher for viscoelastic measurements than for dielectric measurements, especially for samples with a higher sulfur content. (3) The viscoelastic spectra become narrower, while the dielectric spectra broaden with increasing sulfur content. Further, it was ascertained that the results of dielectric measurements correspond to the presumption that the logarithmie retardation time spectrum has the Gaussian form in logarithmic time scale.
Preparation of Alternating Copolymers of the N‐Substituted Maleimides
Authors: Cubbon R. C. P. 
Published: June 2010

AbstractAlternating copolymers of the N‐substituted maleimides with styrene, propylene, and ethylene have been prepared by reacting the appropriate maleic anhydride copolymer with primary amines in glacial acetic acid. The x‐ray spectra of these alternating copolymers indicate that the N‐substituted maleimide units form the same 31 helix found in the N‐substituted polymaleimides.
Copolymers of Butene with α‐Olefins. Cocrystallizing Behavior and Polybutene Type II Type I Crystal Phase Transition
Authors: Jones A. Turner 
Published: June 2010

AbstractThe cocrystallizing behavior shown by copolymers of butene with a number of linear and branched α‐olefins has been investigated by x‐rays over a range of copolymer compositions; degrees of crystallinity, crystal phase changes from those of the relevant homo‐polymers including lattice expansion and contraction and helix modification, and melting points have been observed. Lack of randomness in the copolymers is discussed. Pentene forms a highly cocrystallizing system based on type I polybutene (PB‐I); propylene shows limited, and ethylene no isomerism of monomer units. These three comonomers markedly accelerate the well‐known spontaneous transition from PB‐II to PB‐I, and in sufficient amount cause direct crystallization from the melt to PB‐I. Hexene and octene units can enter the PB‐II lattice, but α‐olefins with C > 8 do not. Butene‐3‐methylbutene is a highly cocrystallizing system; 4‐methylpentene and 4,4‐dimethyl‐pentene copolymers show limited cocrystallization and no cocrystallization, respectively. Linear α‐olefins with C > 5 and the branched comonomers retard the PB‐II PB‐I transition and in sufficient amount stabilize the PB‐II form completely. For comonomers which enter the PB‐II lattice, stabilization is attributed to steric inhibition of the change from an 113 (PB‐II) to a more tightly coiled 31 (PB‐I) helix, but for those that do not, it is believed that the large units act as “stops” at the fold boundaries, which prevent the helical chains being drawn through the crystallites and thus inhibit the transition.
Cyclo‐ and Cyclized Diene Polymers. X. Formation of Cyclopolyisoprenes on Ziegler‐type Catalysts
Authors: Krauserová H. , Mach K. , Matyska B. , Kössler I. 
Published: June 2010

AbstractPolymerizations of isoprene in n‐heptane medium catalyzed by the systems Et2AlX + TiCl4 (X = F, Cl, Br) are characterized by a strong dependence of the reaction rate on the Al/Ti ratio. Changes in the polymerization rate are accompanied by the changes of the microstructure of polymers. Polymers obtained at Al/Ti ratios lower than 1.5 contain very low amounts of common linear forms and can be thus considered as practically cyclic. The highest polymerization rate in formation of cyclic polymers lies for all three diethylaluminum halide catalysts at the ratio Al/Ti = 0.75. The systems EtAlX2 + TiCl4 are considered as actual catalysts. When diethylaluminum iodide is used as the organoaluminum compound formation of cyclopolymers takes place at all Al/Ti ratios.
ESR Study on the Mechanism of UV‐Initiated Polymerization of Methyl Methacrylate
Authors: Komatsu T. , Seguchi T. , Kashiwabara H. , Sohma J. 
Published: June 2010

AbstractThe ESR spectrum of methyl methacrylate, which had been mixed with 0.1 wt.‐% benzoyl peroxide as the initiator and irradiated by UV at 77°K., was observed. The observed spectrum was found to be the superposition of the singlet, triplet, quintet, and septet spectra. In addition to this superposed spectrum, the spectrum due to hydrogen atom was also observed. The four kinds of radical which give these four components of the superposed spectrum could be identified. On warming up the sample to 115°K., 195°K., both the pattern and the intensities of ESR spectra were found to be changed. Based on this change of spectra induced by the heat treatment and on the identification of the radical species, the initiation mechanism of this UV‐induced polymerization is discussed.
Preparation and Polymerization of Tetrolonitrile
Authors: Beneš M. J. , Peška J. , Wichterle O. 
Published: June 2010

AbstractA polyconjugated polymer obtained by polymerization of tetrolonitrile with anionic catalysts is described. The monomer was synthetized from methyltetrolate via tetrol‐amide with better yields and purity than obtained with other methods. Polymerization was initiated by butyllithium and lithium naphthalene in tetrahydrofuran at 0° and −80°C., yielding a dark‐brown product, soluble in polar solvents. Molecular weight, electrical conductivity in solid state and in solution, as well as infrared and ESR spectra were determined. The properties of the substance are discussed in connection with the proposed polyenic structure.