bluuebunny/crossref_metadata_2025_split huggingface dataset:
Configuration and hydrodynamic properties of fully acetylated salep glucomannan
Authors: Juers David H. , Swenson Harold A. , Kurath Sheldon F. 
Published: April 2003

AbstractThe polysaccharide of salep orchid tuber was shown to be a glucomannan with a glucose/mannose ratio of 2.6 and an acetyl content of 2.1%. After extraction from the powdered root with water, the triacetate derivative was prepared and its configurational and hydrodynamic properties examined. The polymer yielded a series of fractions from 615 to 4170 in weight‐average degree of polymerization. Light‐scattering, viscosity, and osmometry experiments were conducted. Intrinsic viscosity results were interpreted according to the hydrodynamic theory of Eizner and Ptitsyn resulting in a value of ζ/η0 = 20 ± 6 A. for the ratio of monomeric friction coefficient to solvent viscosity and a corresponding value of a = 55 ± 4 A. for the persistence length, closely similar to those reported for other β‐1,4‐linked polysaccharides. The theoretical Flory coefficient increased with increasing molecular weight but was less than the limiting value of Φ0 = 2.86 × 1023 mole−1. The dependence of the light‐scattering radius of gyration of the glucomannan polymer on the contour length showed that the configuration of the heteropolymer was similar to that of other β‐1,4‐linked polysaccharides which have only glucose or mannose in the main chain. Calculated radii of gyration based on the Porod‐Kratky persistence length were found to be smaller than radii found by light scattering on the fractions.
Configurational statistics of poly(ethylene terephthalate) chains
Authors: Williams A. D. , Flory P. J. 
Published: April 2003

AbstractThe length of the span of the terephthaloyl residue in poly(ethylene terephthalate) guarantees independence of the conformations of successive repeating units of the chain. Interactions within units of the chain are amenable to interpretation by comparisons with related polymers; cis and trans conformations of the terephthaloyl residue are given equal weighting. The mean‐square dimension ratio (〈r2〉0/M)∞ estimated on this basis is in substantial accord with the value deduced from experiments.
Unperturbed dimensions of copolymer molecules
Authors: Scholte Th. G. 
Published: April 2003

AbstractProceeding from the work of Zimm and Stockmayer and of Benoit, a general formula is derived for the calculation of the radius of gyration of block and graft copolymers. It appears that with linear block copolymers the ratio of the mean‐square radius of gyration and the mean‐square end‐to‐end distance is usually not far from 1/6. With a great number of blocks the difference from 1/6 can entirely be neglected. Also the influence of the composition of the molecules on the scattered light intensity has been considered.
Calibration of gel permeation chromatographic columns for measuring the molecular size of poly(vinyl chloride) in tetrahydrofuran
Authors: Rohn C. L. 
Published: April 2003

AbstractA calibration plot of the intrinsic viscosities of poly(vinyl chloride) fractions against elution volumes gives a good correlation between the first moments, i.e., mean elution volumes, and intrinsic viscosities of poly(vinyl chloride) whole polymers. This is evidence that column permeation of chain macromolecules is governed by some sort of hydrodynamic size in a manner akin to that in which hydrodynamic size affects capillary viscosity measurements.
Morphology of polypropylene crystals. I. Dilute solution‐grown lamellar crystals
Authors: Kojima Morio 
Published: April 2003

AbstractThe dependence of crystalline morphology of isotactic polypropylene crystallized from dilute solutions on its molecular weight and growing conditions and the mechanism of crystal growth were studied by electron microscopy and electron diffraction. Lathshaped lamellar crystals 150–300 A. in thickness are obtained from fractionated polypropylene powders of Mw (average molecular weight) = 600,000 and 240,000, but not from the samples of Mw = 82,000 and 44,000, by means of isothermal crystallization at 130°C. for 20 hr. in dilute α‐chloronaphthalene solution (0.005 wt.‐%). Precipitation of the fractionated polypropylene sample of Mw = 82,000 from a dilute solution of carbitol gives typical dendritic crystals under the same isothermal crystallizing conditions as mentioned above. The mode of chain folding in these crystals based on the orientation and the crystal structure of the lamellar crystals agrees with that proposed by Sauer, Morrow, and Richardson. From the morphological observations, the mechanism of growth pertinent to polypropylene lamellar crystals is presumed to be as follows: fibrils at first aggregate, then the molecular chains are folded to form small lamellae, and then these small lamellae accumulate compactly to grow to large, lath‐shaped, lamellar crystals.
Elastic properties of crosslinked poly(vinyl alcohol) gels: Network topology
Authors: Jackson J. F. , Gill S. J. 
Published: April 2003

AbstractCurrent network theory exhibits inconsistencies which show up particularly clearly in deformation of networks prepared by crosslinking a polymer in solution. A check of theory can be obtained if one knows precisely the number of crosslinks in the network and if a range of deformations is applied to the network. In an effort to explore this problem we have examined the relation of shear modulus to crosslink density, primary molecular weight, and polymer concentration for a series of poly(vinyl alcohol) gels at low to intermediate concentrations. Aqueous poly(vinyl alcohol) solutions were crosslinked to form infinite networks using terephthalaldehyde. We find a large discrepancy with these poly(vinyl alcohol) gels between measured shear modulus and that calculated from classical elasticity theory assuming quantitative reaction of crosslinking. The ratio of measured to calculated modulus is independent of crosslink density for a given primary molecular weight and concentration. It shows linear dependence on polymer concentration prior to crosslinking and extrapolates to a critical concentration which is consistent with the effective sizes of the polymer molecules.
Streaming birefringence. VII. Influence of the intermolecular hydrodynamic interaction on the viscosity and streaming birefringence of polymer solutions
Authors: Munk P. 
Published: April 2003

AbstractThe cavity model used in the theory of dielectrics was applied to hydrodynamics to calculate the force exerted by a system of soft dumbbells on a reference dumbbell in a hydrodynamic field. The influence of this force on the viscosity and flow birefringence and its dependence on both the concentration and velocity gradient were calculated. The system of equations has a real solution only for values of β = M[η]η0γ/RT which are smaller than a critical value rapidly decreasing with increasing concentration. At zero concentration the results obtained agree with the theory of a single isolated dumbbell model. The calculated Huggins constant is k′ = 0.4. The extinction angle is connected with the relative viscosity very nearly as derived from experiments. However, the theory fails at higher concentrations and gradients yielding an increase in viscosity with the gradient and infinite zero‐shear viscosity for the concentration c = 2.5/[η].
Models of spherulite deformation taking into account changes in volume
Authors: Moore Robert S. 
Published: April 2003

AbstractA general method is presented for taking into account changes in volume in several types of calculations concerned with spherulite deformation in semicrystalline polymers. The method is applicable at large strains for which the low‐strain limiting form of the equation defining Poisson's ratio is no longer valid. Applications are made to calculations of the three crystal orientation functions for models of spherulite deformation based on those proposed by Wilchinsky, Stein et al., and Oda et al. The effects of changes in volume are considered in detail and are compared with previous results in which the volume change was neglected. Calculations of spherulite birefringence are considered in a similar manner, as are the equations for determining spherulite deformation by means of low‐angle light‐scattering measurements. Results indicate that in several cases details of deformation mechanisms previously proposed should be revised in light of the effect of the change in volume on the calculated orientation functions. The equations in each case are presented in terms of a parameter β, the square root of the third strain invariant of the deformation tensor. Results are presented in numerical form for many of the basic parameters. Equations for all such results are expressed in explicit form and, in most cases, are displayed graphically together with available experimental data.
Adhesion of high polymers. I. Influence of diffusion, adsorption, and physical state on polymer adhesion
Authors: Lee Lieng‐Huang 
Published: April 2003

AbstractIt is possible to identify three distinct types of polymer adhesion on the basis of the physical state of adhesive and adherend: (1) rubbery polymer–rubbery polymer (R–R adhesion); (2) rubbery polymer–glassy polymer (R–G adhesion); (3) rubbery polymer–nonpolymer (R–S adhesion). Limitations of the diffusion and adsorption theories and their conflicting results are discussed within the framework of the proposed classification. By defining the physical state of the polymer as an adhesive or as an adherend, it is possible to eliminate many of the discrepancies commonly noted in attempted application of the diffusion and adsorption theories. As predicted by the Bueche‐Cashin‐Debye equation, the diffusion of a polymer into another should be greatly reduced as it changes from the rubbery to the glassy state. For this reason, diffusion, which depends to a great extent on the physical state of the polymer, is actually a limited, selective process. Assuming a 1013 poise bulk viscosity at glass temperature, self‐diffusion constants of forty polymers were calculated to be 10−21cm.2/sec. or 10−5A.2/sec. This slow rate of diffusion is unmeasurable and insignificant. Adsorption, which is less dependent on the physical state of the polymer, is more frequently encountered.
Apparatus for the measurement of the flow birefringence of polymer melts
Authors: Wales J. L. S. , Janeschitz‐Kriegl H. 
Published: April 2003

AbstractA description is given of a modified cone‐and‐plate apparatus suitable for the measurement of the streaming birefringence of molten polymers. Some results are given of measurements on a polystyrene and a poly(dimethyl siloxane). Those on polystyrene are compared with solution measurements of the same material by use of the well‐known Bueche‐Harding parameter. Measurements on the silicone oil have been compared with measurements of the dynamic moduli on the same material, after ascertaining the validity of the stress‐optical law for this system as well.
Birefringence dispersion in oriented polystyrene
Authors: Gurnee Edward F. 
Published: April 2003

AbstractThe dispersion of birefringence in oriented amorphous polymers is discussed. It is shown that for polystyrene, the birefringence can be considered as the product of an orientation function and a function of the wavelength of the light. This leads to a method for expressing the birefringence dispersion as a function that is characteristic of the polymer. This function is determined for polystyrene, and from it the birefringence at infinite wavelength is found to be 11% lower than that measured with the mercury green line (5461 A.).
Viscoelastic properties of polystyrene
Authors: Akovali Güneri 
Published: April 2003

AbstractAn extension of the results of a previous to higher molecular weights is made. The viscoelastic parameters ηt, Je, τm, and Em are found experimentally through stress relaxation tests. The predictions of the Rouse‐Bueche (RB) theory and its modified Ferry, Landel, Williams (FLW) form concerning the molecular weight dependencies of these perameters are compared with the data. It is found that the RB and FLW predictions are not rigorously obeyed.
Synthetic thermally reversible gel systems. II
Authors: Haas Howard C. , Moreau Robert D. , Schuler Norman W. 
Published: April 2003

AbstractThe homopolymer and many of the copolymers of N‐acrylylglycinamide yield thermally reversible gels in water. These systems are uniquely suitable for studying synthetic photographic gelatin substitutes and for understanding the mechanism of the gelation process. Polymerization of N‐acrylylglycinamide has been studied under a variety of conditions. The homopolymer is aggregated in dilute aqueous solution and probably molecularly dispersed in 2M thiocyanate solution. At concentrations of several per cent, in water, thermally reversible gels are formed whose melting points rise with increasing concentration and increasing molecular weight. The heat of gelation crosslinking has been calculated to be −8.8 kcal./mole of crosslinks. Introduction of small amounts of carboxyl groups into the polymer raises the melting points of the aqueous gels. The effect of various organic and inorganic reagents on gelation is presented. The ability to prepare copolymers which can be flocculated has been demonstrated as well as the usefulness of the monomer in certain types of photoresist systems. Copolymerization with acrylic acid and β‐aminoethyl vinyl ether has been studied, and the r1 and r2 values for these systems have been calculated as well as Q and e values for N‐acrylylglycinamide.
Configurations of the free radicals in irradiated polypropylene and the relation of their decay reactions to the molecular motion
Authors: Nara S. , Kashiwabara H. , Sohma J. 
Published: April 2003

AbstractFree radicals produced in irradiated polypropylene were studied by the electron spin resonance method. Two temperature regions in which the free radicals decay rapidly were found at around 170°K. and 260°K. The first temperature region corresponds to the γ‐dispersion of polypropylene and the second to the β‐dispersion. Steric configurations of the free radicals were investigated, and it was concluded that the free radicals trapped in polymer, conformation of which is appreciably twisted from the stable 31‐helical structure, decay with small‐scale motion of the matrix polymer. The decay of free radicals trapped in polymer of less twisted conformation is associated with the large‐scale motion of the matrix polymer. Activation energies of decay were found to be 11 kcal./mole at the lower temperature and 48 kcal./mole at the higher temperature. Time constants of the decay reactions were compared with those for molecular motion of the matrix, with results reflecting the relations of the decay of the polymer radicals to molecular motion in the matrix.
Deformation of polybutene‐1 spherulites
Authors: Yang Rena , Stein R. S. 
Published: April 2003

AbstractThe deformation of fresh and aged polybutene‐1 spherulitic samples has been investigated by microscopic observation, interferometry, studying macroscopic and spherulitic birefringence changes, and study of light‐scattering patterns. The spherulite deformation is not affine, the microscopic deformation ratio being less than the macroscopic deformation ratio of the sample and greater in the equatorial regions of the spherulite than in the polar regions. The deviation from affine deformation is less for fresh spherulites than for the aged, where void formation occurs in the equatorial part of the spherulite. This gives rise to large scattering by this part of the spherulite and to form birefringence. The spherulite birefringence and its change with elongation is dependent upon the degree of aging of the sample. The spherulite birefringence is more negative for the aged sample. In the polar regions of the spherulite, this negative birefringence decreases and turns positive at higher elongations, characteristic of a reorientation of the crystals with their optic axes turning from being perpendicular to parallel to the spherulite radius. The spherulite birefringence in the equatorial direction becomes somewhat more negative on stretching a fresh sample but less negative on stretching an aged one. Spherulite distortion and orientation changes are apparent from the light‐scattering patterns of films possessing small spherulites. The changes in Vv and Hv scattering patterns upon stretch are different for the fresh and aged samples. The Vv patterns of the fresh samples decrease in intensity with time after stretching a fresh sample with the Hv patterns do not.
Viscosity of polydimethylsiloxane–pentamer systems
Authors: Kataoka Tadao , Ueda Shigeyuki 
Published: April 2003

AbstractViscosities of polydimethylsiloxane–pentamer systems were measured over the whole range of concentration. Twelve samples having molecular weights from about 1000 to 5 × 105 were studied. The empirical reduction scheme, plots of log η versus log cM0.68, suggested by Ferry and co‐workers is applicable to samples of M̄v ≥ 22,000 over the entire concentration. Such satisfying superposition of data may be attributed to the systems being the homologous mixtures in which glass temperatures of polymers are very low. On the basis of the treatment of Fox and Allen, the effects of the number and weight‐average molecular weight on viscosity were examined, and the friction coefficient ζ per chain atom at constant M̄n was calculated over a wide range of M̄n. The value ζ is almost constant (ζ = 7.4 × 10−9 dyne‐sec./cm.) in the region of M̄n ≥ Mc, and where otherwise it decreases rapidly with decreasing M̄n. The length of the chainend segment was tentatively calculated.
Investigation of the fold‐surface problem in polyethylene single crystals with the nitric acid oxidation technique
Authors: Blundell D. J. , Keller A. , Connor T. M. 
Published: April 2003

AbstractSingle‐crystal preparations of polyethylene were treated with the selective oxidizing agent, fuming nitric acid. The degraded products were examined as regards layer thickness (by low‐angle x‐ray studies), chemical and weight changes, recrystallization and annealing treatments, and by broadline NMR, as part of a systematic investigation aimed at clarifying the nature of disordered material in single crystals. It emerges that there is a disordered‐mobile region along the fold surface of the crystals in agreement with other parallel works along similar lines. In a more detailed analysis we can now decompose the nitric acid attack into components affecting the basal and side surfaces, respectively. Taking into account the recrystallization–annealing observations, we infer that the fold surface is heterogeneous with folds of more than one kind. These results were combined with a preliminary molecular weight distribution study by gel permeation chromatography. Taking into account all the available evidence, we are led to suggest a composite structure where surface looseness, coresponding to long loops and hairs, is superimposed on the more regular folded surface. This model is in the process of being tested. The problems concerning the assignment of a value to the amount of surface looseness are being discussed. In addition, a discontinuity in the thermal behavior of the crystals between 75 and 80°C. has been detected.
Polyelectrolyte behavior and conformation of poly‐L‐methionine S‐methylsulfonium salts in aqueous solution
Authors: Makino Shio , Sugai Shintaro 
Published: April 2003

AbstractThe influence of the species of counterion on the polyelectrolyte behavior and the conformation of poly‐L‐methionine S‐methylsulfonium salts in aqueous solution was studied by viscometric, electrochemical, and optical measurements. The degree of binding of small counterions to charged polyions increases in the sequence: chloride ≲ bromide < iodide < thiocyanate. The conformations of chloride and bromide salts are independent of polymer concentration. On the contrary, iodide and thiocyanate salts indicate a conformational transition, probably from a random‐coil conformation to an intermolecularly stabilized β‐form, with the increase of polymer concentration. The results suggest the existence of a strong specific interaction between counterion and macroion in iodide and thiocyanate salt solutions at high polymer concentration.
Caractérisation des polymègres réaticuléas sous tension
Authors: Evrard G. , Job C. 
Published: April 2003

AbstractThis paper is devoted to the determination of the number of intermolecular bonds in a polymer crosslinked according to the following process: (1) crosslinking in the usual isotropic state, (2) additional crosslinking of the strained primary network. The Flory equation for swelling in solvents has been modified in order to take into account the oriented state of the initial network at the time of secondary crosslinking. The combination of this equation with those relating the modulus of elasticity and the dimensions of the relaxed sample to the deformation of the primary network at the time of secondary crosslinking leads to different possible evaluations of the number of intermolecular bonds. Their significance is discussed. The equations thus established are tested with natural rubber samples vulcanized according to the above‐mentioned process. The validity of the number of crosslinks thus calculated is discussed; a partial degradation of the primary network occurs during the second crosslinking. Its influence is taken into account by using the approximated equations proposed by Flory. The efficiency of the vulcanizing agent (TMTD) is consequently shown to be practically independent of the deformation of the primary network at the time of secondary crosslinking.
Low‐angle light scattering of ionotropic gels
Authors: Bettelheim Frederick A. 
Published: April 2003

AbstractLow‐angle light‐scattering patterns were obtained on ionotropic gels formed by the diffusion of Ca++ into a polygalacturonate sol. Near the sol–gel boundary, diffraction patterns were obtained which indicated organized structures with repeating units of 1100, 250, and 12.5 μ. Microscopic investigations confirmed that at this gel boundary capillaries run parallel to each other and perpendicular to the direction of diffusion. The diameter of capillaries was 12 μ while their length was in the 1000 μ range. Short interconnecting capillaries were about 200–300 μ in length. Inside the gel, in the more highly crosslinked parts, a disorientation occurs during the aging process with the partial disappearance of capillaries. However, at the gel–sol and gel–semipermeable membrane boundaries, the highly organized structures remain even during prolonged aging. The kinetics of the gel formation was also investigated.
Comparison of osmotic pressures from EMF measurements, obtained according to cell‐model considerations and exact Gibbs‐Duhem integrations
Authors: Shatkay Adam , Michaeli Isaac 
Published: April 2003

AbstractOsmotic pressures of aqueous solutions of poly(diethylaminoethyl methacrylate) hydrochloride, in equilibrium with a precipitate of the un‐ionized polybase, at various concentrations of polymer and NaCl in solution and at different values of pH are derived from emf measurements and the “cell” theory for polyelectrolytes. Single‐ion activities are evaluated according to two procedures. The first is based on measurements with ion‐specific electrodes versus a calomel electrode. The second makes use of a salt bridge, but assumes that the co‐ions have activity coefficients equal to the mean activity coefficient of the salt in a polyelectrolyte‐free solution of the same concentration. The results show that the calculated values of the osmotic pressures are consistent with those obtained by the exact integration of the Gibbs‐Duhem relationship, when the first procedure is employed. If, however, the single‐ion activities are evaluated by the second procedure, the osmotic pressures obtained are consistently lower by about 10%. These differences arise because the two methods yield different values of the activity coefficients of the single ions.