bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultracentrifugal equilibrium measurement of high polymer solutions at elevated temperatures
Authors: Kotera Akira , Iso Naomichi , Senuma Akitaka , Hamada Takeshi
Published: April 2003

To investigate the solution properties of polyethylene, which has the simplest structure of the vinyl polymers, experiments were made with a magnetically suspended equilibrium ultracentrifuge. Preliminary studies were carried out with a polystyrene–chloroform system at 25°C. and a polystyrene–methylcyclohexane system at 68°C. (which is close to the theta temperature) in order to check the difficulties involved in the flotation equilibrium in the former case and the high temperature measurement in the latter. However, no trouble was encountered in either system, and the results were discussed and compared with earlier results for polystyrene solutions. It was found that chloroform is a good solvent for polystyrene, and the measured weight‐average molecular weight is somewhat smaller than the value obtained in a theta solvent. After overcoming some technical difficulties involved in studies at higher temperatures, we carried out experiments on polyethylene in α‐chloronaphthalene at 130°C. The results are considered reasonable by comparison with results obtained by other methods. The sample employed, Marlex 50 of melt index 0.7, has a wide molecular weight distribution: i.e., Mz/Mw = 5.2 and Mz+1/Mz = 2.4.
Diffusion coefficients in a halocarbon–polybutene system
Authors: Secor R. M.
Published: April 2003

The diffusion coefficient of 1,1,2‐trichlorotrifluoroethane (TTE) in a liquid polybutene was determined at 25°C. as a function of concentration over the range 1.0–19.5 g. TTE/100 cc. The diffusion coefficient increase with increasing TTE concentration, rising continuously from 3 × 10−8 cm.2/sec. at the lowest concentration to 15 × 10−8 cm.2/sec. at the highest. The magnitudes of the diffusion coefficients indicate that the diffusion mechanism for small molecules in polymeric media must afford vastly greater opportunities for diffusion than the Stokes‐Einstein relation allows. Similarly, self‐diffusion coefficients for the liquid polymer are much lower than the observed mutual diffusion coefficients. An explanation for this behavior is presented.
Structure and solution properties of radical‐initiated poly(vinyl chloride). II. Correlation of solution properties
Authors: Bohdanecký M. , Šolc K. , Kratochvíl P. , Kolínský M. , Ryska M. , Lím D.
Published: April 2003

The results of detailed measurements of osmotic pressure, light scattering, and viscosity of poly(vinyl chloride) solutions are used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl chloride) molecule, and to analyze critically the [η]–M correlations published hitherto.
Configuration and hydrodynamic properties of fully acetylated salep glucomannan
Authors: Juers David H. , Swenson Harold A. , Kurath Sheldon F.
Published: April 2003

The 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

The 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

Proceeding 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

A 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

The 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

Current 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

The 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

A 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

It 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

A 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

The 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

An 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

The 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

Free 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

The 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

Viscosities 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

Single‐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

The 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

This 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

Low‐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

Osmotic 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.
Time–temperature superposition of time‐dependent birefringence for low‐density polyethylene
Authors: Onogi Shigeharu , Asada Tadahiro , Fukui Yoshiharu , Fujisawa Takeo
Published: April 2003

The time‐dependent birefringence has been measured simultaneously with the stress relaxation on quenched and annealed low‐density polyethylene at various temperatures from 10 to 70°C. The strain‐optical coefficient increases generally with increasing time, and approaches the equilibrium value, which depends upon the temperature. When the strain‐optical coefficient at a fixed time is plotted against temperature, it first increases and then decreases after passing through a maximum at Tmax with increasing temperature. The higher the degree of crystallinity, the higher are the equilibrium values of the strain‐optical coefficient and Tmax. The curves for strain‐optical coefficient versus time and relaxation modulus versus time below Tmax can be superposed well by a horizontal shift along the abscissa. The optical shift factor obeys the original WLF equation, while the mechanical shift factor is much larger than the optical one. The molecular mechanisms corresponding to this dispersion of the strain‐optical coefficient and viscoelastic αc absorption peak near Tmax are discussed.
Time–temperature superposition of the dynamic birefringence of polyethylene
Authors: Takeuchi A. , Stein R. S.
Published: April 2003

The dynamic strain‐optical coefficient of low‐density polyethylene is found to decrease with increasing frequency and increase with increasing temperature (at temperatures up to 60°C.). It is found that a series of curves representing the real, K′, and imaginary, K″, parts of the frequency variation of the strain‐optical coefficient obtained at various temperatures up to 60°C. may be superposed by translation along the frequency axis. The temperature dependence of the shift factor corresponds to an Arrhenius type equation with an activation energy of the order of 25 kcal./mole. This may be compared with the similar value obtained by Takayanagi for the αc′ mechanical loss and with the dynamic x‐ray diffraction values reported by Kawaguchi et al., but is somewhat lower than the value of 34 kcal./mole reported by Onogi et al. from birefringence relaxation studies. Takayanagi has ascribed the αc′ peak to cooperative motion of crystalline and amorphous regions of the sort that might be involved in the suggested sliding of lamellae over each other. At temperatures higher than 80°C., horizontal superposition is not possible.
Déformation plastique des hauts polymères vitreux soumis á un système de contraintes quelconque
Authors: Bauwens Jean‐Claude
Published: April 2003

The theory of rate processes has been applied by Eyring to the plastic flow of solids, but he considers only the case of simple shear. Some assumptions concerning a generalization of this theory for an arbitrary strain tensor are here proposed and discussed. The components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated. According to these results, it can be proved that the yield condition of Huber, Hencky, and von Mises is valid when there is no hydrostatic stress. The discrepancy between the yield stresses corresponding to tensile and compressive tests is explained by the influence of the hydrostatic component and evaluated by taking account of the amount of free volume required for an elementary jump. The calculated value agrees with the experimental data. Measurements of the inclination of Lüder's bands and deformation components on poly(vinyl chloride) flat bars strained by tensile tests are in good agreement with the proposed theory.
Carbon black reinforcement in preswollen rubbers. Part II
Authors: Cotten G. R.
Published: April 2003

The mechanism of carbon black reinforcement was studied by examining stress–strain properties of preswollen (i.e., cured in the swollen state then deswollen) SBR‐1500 vulcanizates and the effect of heat treatment on such samples. It was found that the supercoiling of molecular chains leads to a purely viscous response at low elongations. On heating of preswollen samples, molecular rearrangement at the carbon black surface occurs, leading to a considerable increase in modulus. The activation energy of that process was determined by using the superposition principle.
Diffusion in glassy polymers. IV. Diffusion of methyl ethyl ketone in atactic polystyrene above the critical concentration
Authors: Odani Hisashi
Published: April 2003

Integral absorption and desorption of methyl ethyl ketone in atactic polystyrene were studied as functions of film thickness at 25 and 45°C. with concentrations above the critical concentration of the system. In all cases investigated, the reduced absorption and desorption curves for films of different thicknesses did not give a single curve, though the individual absorption and desorption curves appeared to have the shape expected from the Fickian diffusion mechanism. The initial slopes of the reduced curves increased with increasing film thickness for both absorption and desorption. The quantity R0, the value of the reciprocal of the half‐time for absorption or desorption extrapolated to zero concentration increment, provides a measure of absorption rate at a given initial concentration. The dependence of R0, on film thickness was almost unaltered in the concentration region concerned at both temperatures. The values of the mutual diffusion coefficient D of the system were calculated by assuming absorption and desorption processes for hypothetical film of infinite thickness to be controlled by the purely Fickian mechanism. The values of D evaluated by this method agreed quite well with those deduced by Kishimoto from steady‐state permeation measurements.
NMR studies of polymer solutions. II. Polyethylene
Authors: Liu Kang‐Jen
Published: April 2003

The intramolecular structure of polyethylene in solution was studied by a high‐resolution nuclear magnetic resonance technique. Highly purified n‐alkanes (99.5%) from C5H12 to C36H74 were used as its oligomers. The NMR spectra of the polyethylenes (oligomers) are very sensitive to the solvents used. The internal methylene protons of all polyethylenes of various chain length resonance at an identical frequency in carbon tetrachloride. A sharp transition in the NMR spectrum of polyethylene in α‐chloronaphthalene at 35°C. was observed at n‐C17H36, above which there exist two distinguishable NMR peaks for internal methylene protons, and below which (fewer carbons) only a single peak was seen. The NMR spectra of the internal methylene protons of the polyethylenes (oligomers) taken in benzene are very similar to those taken in pyridine. They are not as easily resolved as those NMR spectra taken in α‐chloronaphthalene solutions. The effect of the size of the aromatic solvent molecule on the NMR spectra of the internal methylene protons of the polyethylenes (oligomers) in solutions was demonstrated by using aromatic solvents of various sizes, such as chlorobenzene, α‐chloronaphthalene, and 9‐chloronathracene. The results indicate that the formation of polymeric structure of the internal methylene groups in the polyethylene chain is very sensitive to the size of the solvent used. The interaction of the solvent with the methylene groups of the polyethylenes varies as a function of chain length; it is stronger for those low member n‐alkanes and decreases gradually to an asymptotic value.
Mechanical structures in polymer melts. I. Measurements of melt strength and elasticity
Authors: Busse W. F.
Published: April 2003

The standard methods of measuring the elastic properties of polymer melts are briefly reviewed and a method of measuring another combination of viscoelastic properties, the melt strength, is described. Data are presented on the melt strength of various types of polyethylene resins and on ionomer resins. The effects on various viscoelastic properties of branching or of the addition of fine fibrils of Teflon perfluorocarbon resin are reported.
Molecular weight distribution and thermal characterization of polydimethylsilmethylene
Authors: Levin G. , Carmichael J. B.
Published: April 2003

1,1,3,3‐Tetramethyl‐1,3‐disilacyclobutane (I) was polymerized under the following conditions with H2PtCl6·6H2O as catalyst: (a) addition of I dropwise to a large excess of catalyst at room temperature, producing [(CH3)3SiCH2(CH3)2Si]2O in 90% yield; (b) polymerization at room temperature in the presence of 10% water with 23 ppm Pt, yielding 9% conversion to low molecular weight polymer after 4 weeks; (c) polymerization in an open vessel (25°C., 7 ppm Pt, M̄n = 1.2 × 105), a closed vessel (100°C., 28 ppm Pt, M̄n = 1.7 × 105), in a closed tube after twice freezing and evacuating (25°C., 23 ppm Pt, M̄n = 2.9 × 105); (d) polymerization in an oxygen atmosphere (25°C., 17 ppm Pt, M̄n = 2.7 × 105). The molecular weight distributions of the polymers with M̄n = 1.2 × 105 and 1.7 × 105 was studied by gel‐permeation chromatography. Ratios of M̄w/M̄n are 3.1 and 2.7, respectively. In both cases a long tail of high molecular weight polymer is evident. Interpretation of the molecular weight distributions is qualitatively discussed on the basis of a postulated seven‐step mechanism. Water is shown to be a source of chain termination. Evidence is presented for the existance of SiOSi and SiOH in the silmethylene polymers. Negligible cyclization occurs. Orders of thermal stability measured by DTA and TGA for polydimethylsilmethylene (A), polydimethylsiloxane (B), and polysiobutylene (C) are: in He, A > B > C; in air, in air, B > C ≅ A. A fractionally precipitated polydimethylsilmethylene had a weight loss of less than 5% by 600°C. by TGA analysis at 10°C./min. in He.
Effect of chlorosilanes on the radical polymerization of styrene and methyl methacrylate
Authors: Minoura Yuji , Enomoto Yasushi
Published: April 2003

Styrene (St) and methyl methacrylate (MMA) were polymerized by azobisisobutyronitrile at 50°C. in the presence of silanes such as tetramethylsilane, trimethylcholorosilane, dimethyldichlorosilane, methyltrichlorosilane, and tetrachlorosilane. The polymerization rates of both St and MMA in the presence of silanes were nearly equal to those in the absence of silanes. On the other hand, the molecular weights decreased gradually as the concentration of chlorosilane increased. The chain transfer constants of all the silanes in the polymerization of St and MMA at 50°C. were calculated by Mayo's equation. The chain transfer constants of Me4Si, Me3SiCl, Me2SiCl, MeSiCl3, and SiCl4 were 0.31 × 10−3, 1.25 × 10−3, 1.78 × 10−3, 1.92 × 10−3, and 2.0 × 10−3, for St and 0.13 × 10−3, 0.22 × 10−3, 0.245 × 10−3, 0.27 × 10−3, and 0.30 × 10−3, for MMA, respectively. From these results, it was found that the SiCl bond was radically cleaved. The Qtr values of the silanes, in the same order as above, were found to be 1.03 × 10−4, 2.33 × 10−4, 2.83 × 10−4, 3.10 × 10−4, and 3.35 × 10−4, respectively and the etr values were +0.58, +1.30, +1.50, +1.48, and +1.43, respectively.
Graft polymers from poly(vinyl chloride) and chlorinated rubber
Authors: Rao S. Prabhakara , Santappa M.
Published: April 2003

Graft polymers from poly(vinyl chloride) (PVC) and chlorinated rubber (CIR) with side chains of poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), or poly(ethyl methacrylate) (PEMA) were synthesized. For this purpose, a vinyl monomer was polymerized in the presence of small quantities of PVC or CIR with benzoyl peroxide as catalyst. The graft polymers were separated from both homopolymers by precipitation with methanol from methyl ethyl ketone solutions of the reaction products and the grafting efficiency was calculated. The graft polymers were characterized by infrared spectra, elemental analysis, NMR, and osmometric or light‐scattering determinations. From the results it is concluded that the PVC or CIR molecules contain side chains of PMMA, PMA, or PEMA. The graft polymers showed higher molecular weights, and the values of second virial coefficient for these polymers were much different from those of the starting polymers.
Ladder polyphenoxazines
Authors: Stille J. K. , Freeburger M. E.
Published: April 2003

Two ladder polyphenoxazines have been prepared by the polymerization of 4,6‐diaminoresorcinol dihydrochloride (I) with 2,5‐dihydroxy‐p‐benzoquinone (III), or 2,5‐diacetoxy‐p‐benzoquinone (II) and with 2,5‐dihydroxy‐3,6‐dichloro‐p‐benzoquinone (IV) in a hexamethylphosphoramide (HMP) solvent. When tetrahydrofuran (THF) was the polymerization solvent, the reaction of I with II or IV produced a linear poly‐Shiff's base which could be converted to the ladder polymer by heating in HMP. The thermal stability of the ladder polyphenoxazines was surprisingly poor; a slow decomposition started at ca. 275°C. under nitrogen.
Polymerization of styrene with ZrCl4 and ZrCl3 in combination with Al(C2H5)3
Authors: Malhotra S. L. , Deshpande A. B. , Kapur S. L.
Published: April 2003

The polymerization of styrene with two catalyst systems consisting of Al(C2H5)3 in combination with ZrCl4 or ZrCl3 has been studied. The rate of polymerization with catalyst concentration was first‐order with ZrCl4 system and second‐order with ZrCl3 system, but at higher catalyst concentrations in both cases, the rate progressively decreases and finally attains a low value. The rate of polymerization is, however, proportional to the square of the monomer concentration in both the cases. The overall energy of activation was 10.9 kcal./mole and 6.45 kcal./mole in these systems. The polymers obtained with ZrCl4 were of lower molecular weights as compared to those obtained with ZrCl3. The polymers in both the cases had amorphous character.
Benzimidazole‐ and oxadiazole‐modified aromatic polyimides
Authors: Frost L. W. , Bower G. M. , Freeman J. H. , Burgman H. A. , Traynor E. J. , Ruffing C. R.
Published: April 2003

Three series of aromatic primary diamines were synthesized. The first series of three contained one or two hydrazide groups. The second series of five contained one or two oxadiazole groups. The third series of four contained one or two benzimidazole groups. Reaction of each diamine with either pyromellitic dianhydride or 3,4,3′,4′‐benzophenonetetracarboxylic dianhydride gave a series of soluble polymeric amic acids, from which films of good thermal stability were cast. The heat‐cured films were either oxadiazoleimide or benzimidazole‐imide polymers, depending upon the diamine used. When hydrazide‐amic acid polymers were heated, the conversion of amic acid to imide was essentially complete before any substantial portion of the hydriazide linkages were converted to oxadiazole. The latter conversion was accompanied by degradation. A better method of preparation for these polymers is through the oxadiazole contaning diamines. One hydrazide‐imide polymer was prepared from trimellitic anhydride and was converted to an oxadiazole‐imide by heating. The reaction of equimolar quantities of a dianhydride with 3,5,2′‐triaminobenzanilde gave a soluble polymer which was converted to a benzimidazole‐imide by heating.
Lewis acid‐catalyzed reactions on polystyrene
Authors: Gaylord N. G. , Hoffenberg D. S. , Matyska B. , Mach K.
Published: April 2003

The action of aluminium halides upon polystyrene was studied as a function of the nature of the reaction medium and of the concentration of catalyst. It was demonstrated that polystyrene undergoes crosslinking, the extent of which is particularly important in chlorinated aliphatic solvents and at high catalyst concentrations. In additions, phenyl rings of the polymer are alkylated and halogenated by the solvent or catalyst. Infrared spectroscopic investigation of the structure of the products indicated that in most cases crosslinking was connected with the formation of 1,4‐disubstituted, and eventually 1,2,4‐trisubstituted benzenes. In carbon tetrachloride medium, meta substitution was also detected. In products obtained when polystyrene was treated with high amounts of the Lewis acid in CCl4 medium degrees of substitution even higher than three were probable.
Morphology of nascent polyolefins prepared by Ziegler‐Natta catalysis
Authors: Blais P. , Manley R. St. John
Published: April 2003

The morphology of nascent (i.e., as‐polymerized) Ziegler‐Natta polymers was studied by optical and electron microscopy and x‐ray and electron diffraction. Observations were made on six polyolefins: polyethylene, polybutene, polypropylene, polystyrene, poly‐4‐methylpentene‐1, and polyisoprene. These polymers were synthesized by using conventional techniques by polymerizing the undiluted monomer or monomer–diluent mixtures with a preformed heterogeneous catalyst obtained by reacting a titanium halide and aluminium alkyl. After the reactions were terminated the polymers were subjected to suitable purification treatments and stored in the wet state. Observations in the optical microscope revealed that, in most cases, the polymers is formed as discrete hollow particles with a fibrous texture, but in a few instances, depending upon experimental conditions, it could also form as fibrous sheets or webs. More detailed observations in the electron microscope showed that the polymer is composed of a profusion of fibrils 200–1000 A. in width and of indefinite length. The fibrils themselves have a fine structure as indicated by the presences of lamellae running prependicular to their length. Various interpretations of this appaerent structure are discussed. The x‐ray and electron diffraction studies show that the molecular chain axis is oriented prependicular, or nearly so, to the plane of fibril lamellae and suggest that the molecules are folded within the lamellae in a manner analogous to conventional polymer single crystals. As fibril formation is observed under most conditions of polymerization it is considered to be basic to the mechanism of Ziegler‐Natta catalysis. It is proposed that the fibrils are formed by the crystallization of polymer chains growing from the active sites on the catalyst surface. The process is likened to root growth in whiskers, new materials being added at the base or root. The detailed mechanism of fibril formation and of the organization of the fibrils into larger structural formations are obscure, but several possibilities are discussed.
Polymer reactions. II. Thermal decomposition of polyethylene hydroperoxide
Authors: Chien James C. W.
Published: April 2003

Polyethylene hydroperoxide (PEH) was prepared by low‐temperature autoxidation initiated by AIBN. Over 85% of the total hydroperoxyl groups decompose by a rapid process, the remainder dissociate at about one‐tenth of that rate. The results are the same whether PEH is decomposed in solution or in the solid state. Large amounts of scavenger have no effect on these decompositions; there is no radical‐induced processes. The results suggest mechanisms of decomposition involving neighboring group assistance.
Polymer reactions. IV. Thermal decomposition of polypropylene hydroperoxides
Authors: Chien James C. W. , Jabloner H.
Published: April 2003

The thermal decomposition of polypropylene hydroperoxide (PPH) consists of two consecutive reactions. The initial, faster reaction has rates up to 60 times that of the slower process. The former is largely suppressed by the addition of an excess of 2,6‐di‐tert‐butyl‐p‐cresol. The course of reaction is the same in either solid state or in solution. The results are consistent with an intramolecular radical‐induced mechanism for the initial reaction. This faster reaction consumes about 70–95% of the total hydroperoxides. The decomposition of PPH yields a maximum of about 1.8 radicals. Samples prepared from crystalline and amorphous polypropylenes have identical decomposition kinetics.
Polymerization of vinylcyclopropanes. II
Authors: Takahashi Takako
Published: April 2003

1,5‐Type polymerization of vinylcyclopropane proceeding by the opening of both the double bond and the cyclopropane ring was found. Some other vinylcyclopropane derivatives, 1,1‐dichloro‐2‐vinylcyclopropane, 1,1‐dibromo‐2‐vinylcyclopropane, isopropenylcyclopropane, 1‐methyl‐1‐vinylcyclopropane, 1,1‐dichloro‐2‐methyl‐2‐vinylcyclopropane, and cis‐ and trans‐1‐chloro‐2‐vinylcyclopropane, were investigated. The observation of infrared spectra, NMR spectra, and other data indicated that the radical polymerization of these compounds gave principally 1,5‐type polymer, while in cationic polymerization 1,2‐type was predominant. The behavior of the polymerization was discussed in terms of the stability of a cyclopropylcarbinyl ion or radical which is formed in the initiation and propagation steps.