bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of swelling on radiation‐induced grafting of styrene to polyethylene
Authors: Machi Sueo , Kamel Ihab , Silverman Joseph 
Published: April 2003

AbstractThe radiation‐induced grafting of low‐density polyethylene in contact with styrene solution was studied. The effect of the degree of swelling of the polymer on the rate of grafting was investigated by diluting the styrene with methanol and with n‐octane. For styrene‐methanol solution, the rate of grafting was found to increase with degree of swelling, passing through a maximum when the sorbed solvent reaches 6.2 wt‐% (70 vol‐% methanol in the outside solution) and decreasing therafter. The methanol fraction of the sorbed liquid is far too small to cause precipitation of the grafted chains and inhibition of their termination rate. The dilution of styrene by octane has no effect on the swelling of polyethylene, but it decreases the grafting rate over the entire concentration range. The results are explained in terms of the concentration of sorbed monomer and the viscosity of the amorphous region of the polyethylene swollen by nonpolar liquids. Supporting evidence for the mechanism is presented in the form of grafting kinetic data as a function of dose rate (2.8 × 102−9.5 × 104 rad/hr), and post‐irradiation grafting measurements for polyethylene in methanol‐styrene (70/30, v/v). The data indicate that at the maximum grafting rate an optimum is achieved between a high concentration of sorbed monomer and a low viscosity for the poorly swelled polymer matrix.
Synthetic thermally reversible gel systems. VI
Authors: Haas Howard C. , MacDonald Ruby L. , Schuler Alan N. 
Published: April 2003

AbstractForming and conditioning thermally reversible aqueous gels of polyacrylyglycinamide (PAG) at various temperatures has little effect on either the melting point (Tm) of the gels or the heat of crosslinking (ΔHc) except at temperatures where partial hydrolysis can occur. This is added evidence that unlike with gelatin, crystallite formation does not play a role in gel formation. For unfractioned PAG, the linear relationship between the logarithm of molecular weight and 1/Tm predicted and observed for gelatin gels, does not hold. With mixed gelatin‐PAG gels, a gelatin/PAG ratio of ≥4 completely inhibits the formation of a PAG gel network. At lower gelatin/PAG ratios, the PAG network forms, and if gelatin is considered as an inert diluent, normal values for the melting points and ΔHc for PAG gels are observed. At a gelatin/PAG ratio of 4, the presence of PAG reduces the ΔHc for the gelatin gel by inhibiting the formation of as large or as ordered crystallite crosslinks. To reconcile the problem of aggregation preceding gelation one can assume that M̄w of an aggregate is a linear function of C2. If this is done, the same relationship which normally relates C with Tm is obtained. The equilibrium swelling of PAG films in water at 25°C is markedly molecular weight‐de‐pendent and can vary from below 5 to about 40 wt‐% polymer at equilibrium. It has been found that long‐term dark storage of dry samples of PAG under ambient temperature conditions results in pronounced decreases in the intrinsic viscosities of their aqueous solutions. It is speculated that this results from weak links, perhaps peroxy, in the polymer backbone. The possible relationship of this phenomenon to the slow stage of the viscosity deterioration of aqueous polyacrylamide solutions is pointed out. The higher viscosity of low DP PAG in 2M NaCNS compared to H2O and the larger percentage increse of [η] with increasing temperature in the latter, verify the greater solvent power of 2M aqueous thiocyanate for PAG. At a concentration level of 3%, aqueous PAG solutions are almost Newtonian whereas at higher concentrations (5%), the viscosity decreases appreciably with increasing rates of shear. The copolymerization of AG with isopropylacrylamide has been studied and the somewhat unusual results discussed. Copolymers containing an AG mole fraction greater than 0.40 do not exhibit a cloud point up to 100°C. If the isopropylacrylamide mole fraction approaches 0.60, the solutions do not gel down to 0°C. This ability to prepare copolymers over a narrow composition range that neither gel or undergo phase separation in the temperature range 0–100°C is probably related to the random distribution of monomer units in the copolymer backbone.
Radiation‐induced polymerization of 3,3,4,4,5,5,5‐heptafluoropentene‐1 at high pressure
Authors: Brown Daniel W. , Lowry Robert E. , Wall Leo A. 
Published: April 2003

AbstractA study was made of the radiation‐induced polymerization under pressure of 3,3,4,4,5,5,5‐heptafluoropentene‐1. Polymerization rates increase with pressure (activation volume equals − 11 cc/mole) and temperature (activation enthalpy equals 6.5 kcal/mole) in liquid phase. At 13800 atm and 25°C, freezing occurs; the polymerization rate in the solid is very small. In liquid phase polymerization can continue for many hours after the irradiation is terminated. An active species is formed by radiation which initiates polymerization in the dark period.
Quaternary ammonium polymers from 1,4‐diaza[2.2.2]bicyclooctane
Authors: Salamone J. C. , Snider B. 
Published: April 2003

AbstractMenschutkin reactions of 1,4‐diaza[2.2.2]bicyclooctane with various α,α‐dibromoalkanes and α,α′‐dibromoxylenes have been studied in two solvent systems and at different temperatures. It was found that quaternary ammonium polymers could easily be prepared from this rigid, bicyclic, ditertiary amine.
Catalysis of olefin isomerizations by boron trifluoride
Authors: Roberts J. M. , Katovic Z. , Eastham A. M. 
Published: April 2003

AbstractThe kinetics of isomerization of butenes by boron trifluoride with acetic acid or methanol as cocatalysts have been re‐examined. The results, over a wide concentration range, and at temperatures from −20 to +20°C, are consistent with previous data, but it is shown that the previously suggested mechanism cannot apply. By using deuterated acetic acid as cocatalyst it has been found that isomerization exactly parallels protonation, which is consistent with a mechanism involving a classical carbonium ion.
Mechanical properties of radiation‐induced graft copolymers of styrene to polyethylene
Authors: Machi Sueo , Silverman Joseph 
Published: April 2003

AbstractMeasurements were made of the tensile properties polyethylene‐styrene grafts prepared by irradiating polyethylene films in liquid styrene. The films contained true graft and occluded styrene homopolymer. It was shown that yield strength, tensile strength, and initial modulus of elasticity increase while elongation decreases with increasing polystyrene content. The tensile strength and elongation were reduced when the grafted film was soaked in benzene more than 15 hr. The film prepared by a post‐irradiation graft gave higher tensile strength and elongation than those of grafts formed by simultaneous irradiation of the film and the monomer. These results indicate that radiation‐induced grafting makes the system of polyethylene and polystyrene compatible and potentially useful, provided the samples are not subjected to drastic solvent extraction procedures for the removal of homopolymer.
Copolymerization of 2‐sulfoethyl methacrylate
Authors: Kangas Donald A. , Pelletier Ronald R. 
Published: April 2003

AbstractCopolymers of 2‐sulfoethyl methacrylate, (SEM) were prepared with ethyl methacrylate, ethyl acrylate, vinylidene chloride, and styrene in 1,2‐dimethoxyethane solution with N,N′‐azobisisobutyronitrile as initiator. The monomer reactivity ratios with SEM (M1) were: vinylidene chloride, r1 = 3.6 ± 0.5, r2 = 0.22 ± 0.03; ethyl acrylate, r1 = 3.2 ± 0.6, r2 = 0.30 ± 0.05; ethyl methacrylate, r1 = 2.0 ± 0.4, r2 = 1.0 ± 0.1; styrene, r1 = 0.6 ± 0.2, r2 = 0.37 ± 0.03. The values of the copolymerization parameters calculated from the monomer reactivity ratios were e = +0.6 and Q = 1.4. Comparison of the monomer reactivities indicates that SEM is similar to ethyl methacrylate with regard to copolymerization reactivity in 1,2‐dimethoxyethane solution. The sodium salt of 2‐sulfoethyl methacrylate, SEM⊖Na⊕, was copolymerized with 2‐hydroxyethyl methacrylate (M2) in water solution. Reactivity ratios of r1 = 0.7 ± 0.1 and r2 = 1.6 ± 0.1 were obtained, indicating a lower reactivity of SEM⊖Na⊕ in water as compared to SEM in 1,2‐dimethoxyethane. This decreased reactivity was attributed to greater ionic repulsion between reacting species in the aqueous medium.
Studies in ring‐opening polymerization. I. 5,5‐diethyl‐1,3,2‐dioxathiolan‐4‐one‐2‐oxide
Authors: Blackbourn G. P. , Tighe B. J. 
Published: April 2003

AbstractThe polymerization of 5,5‐diethyl‐1,3,2‐dioxathiolan‐4‐one‐2‐oxide has been examined in various solvents at 60–100°C. Kinetic studies have shown that steric hindrance by the C5 ethyl substituents prevents the occurrence of a bimolecular propagation reaction involving direct attack by a terminal hydroxyl group on the ring. In dry, nonhydroxylic solvents, the first‐order rate‐determining step in the sequence of reactions leading to polymer formation is a primary ring scission reaction in which a reactive intermediate is formed and sulfur dioxide eliminated. This intermediate, which is formally depicted as an α‐lactone, then takes part in a very rapid chain‐propagation process, the individual steps of which govern the molecular weight distribution of the polymer. The values of the activation energy (25–30 kcal/mole) and frequency factor (1011−1013 sec−1) for this polymerization reaction are, therefore, those associated with monomer decomposition and not the chain growth process. The molecular weight of the resultant polymer, poly‐(3‐pentylidene carboxylate) is controlled by adventitious traces of water which produce one carboxyl and one hydroxyl group per chain. Polymers having M̄n ∼ 20,000 are readily obtained; these are materials of moderately high melting point (Tm ≃ 200°C) which crystallize from the melt into a banded spherulitic structure.
Preparation of long‐chain paraffins from nitric acid degradation products of polyethylene; some consequences for polymer crystal structure studies
Authors: Keller A. , Udagawa Y. 
Published: April 2003

AbstractIt is demonstrated that dicarboxylic acids of uniform lengths, obtained by degrading chain‐folded polyethylene single crystals, can be converted to paraffins via the intermediate diiodide by means of the procedure of Barton et al. Thus we are now in the position of obtaining uniform paraffins of chain lengths longer than hitherto available for the study of the crystallization of oligomeric chains. Measurements of melting points and heats of fusion revealed major differences between the paraffins and the corresponding parent dicarboxylic acids. It follows that such measurements on the unmodified products of the nitric acid degradation cannot be used directly for the assessment of the chain traverse length and the degree of crystallinity. It was found further, that the intermediate diiodide is a sufficiently close approximation to the paraffin for the purposes just quoted.
Conformational characteristics of polymorphous optically active macromolecules: A statistical zigzag model
Authors: Birshtein T. M. , Zubkov V. A. , Volkenstein M. V. 
Published: April 2003

AbstractThe conformational properties of optically active macromolecules are considered. A statistical zigzag model is used for the calculation of averaged physical properties. The macromolecule is considered to consist of segments of two different types with a statistical distribution of lengths. The expressions for the mean square of the end‐to‐end vector h2 and the dipole moment μ2 and also of the mean optical anisotropy ΔA and the anisotropy of the optical rotation tensor ΔG were obtained in the cases of freely jointed and freely rotating segments. The equations obtained were applied to the problem of the helix–coil transition. In the case of poly‐α‐olefins the values of h2, μ2, and ΔA, are larger than corresponding values for typical optically inactive macromolecules. The anisotropies ΔA and ΔG of two poly‐α‐olefins of similar structures were calculated. The polarizability theory of optical activity was used for the calculations of ΔG. The values obtained for ΔA are similar, but the values of ΔG differ markedly. The possibility of obtaining valuable information about the structure of optically active macromolecules in solution by a study of anisotropy of the optical rotation tensor is considered.
Nuclear relaxation in atactic polystyrenes: T1 and T1ρ measurements
Authors: Connor T. M. 
Published: April 2003

AbstractMeasurements have been made on a series of linear atactic polystyrenes whose molecular weights range from 900 to 1.8 × 106, where Mw/Mn ≪ 1.2. Spin lattice relaxation times have been measured in the laboratory frame (T1) and in the rotating frame (T1ρ) in the temperature range 90–500°K. Two major relaxation minima were observed in both sets of measurements. The high temperature process corresponds to the glass transition (α process), the position of the minimum depending on the chain length. The low temperature process appears to originate from the n‐butyl endgroups in the polymer, its position being independent of chain length while its intensity is inversely proportional to molecular weight. No other minima were observed, in contrast to some other observations made by broadline and pulsed NMR techniques. Relaxation was exponential in all cases except in the region of the high temperature T1ρ minimum and above. This nonexponential behavior is possibly connected with the transition at T > Tg observed by a number of other techniques and which is thought to correspond to a transition between two types of liquid state. A correlation frequency diagram has been drawn for all the processes observed in polystyrene by other techniques, (α, β, αβ, γ, and δ) which shows that the T1 and T1ρ minimum positions correlate well with the α process and that there is a possible contribution to the relaxation due to the γ process on the low temperature side of the α process. At these measurement frequencies the α and β processes are merged into an αβ process. There is no evidence for a contribution from the mechanical δ process. The effect of the endgroups is observed to very high molecular weights (4.98 × 105), and it seems that a three‐dimensional diffusion model would be more adequate than the one‐dimensional model used to interpret similar behavior of paraffins and polyethylenes. Measurements of T1 in the low‐temperature region would constitute a method for a rough measurement of the molecular weight of these polymers.
Precipitation chromatography theory
Authors: Smith W. V. 
Published: April 2003

AbstractA discussion is given of the behavior of a mathematical model chosen to approximate conditions during precipitation chromatographic fractionation of polymer (Baker Williams fractionation). With only one molecular weight species of polymer a complete solution of the mathematical model was obtained. With more than one species it was necessary to use a computer solution. Curves showing the movement of polymer containing one and two species of polymer are given for a variety of conditions of operation. It was found that the degree of fractionation of polymer approaches a limiting value with increasing length of column. Under some conditions the degree of fractionation may go through a maximum with length of column. The equilibrating distance (distance of travel of the liquid phase required to establish equilibrium of polymer between the liquid and the bed) was found to be very important in determining the fractionation.
Intrinsic viscosity and axial extension ratio of random‐coiling macromolecules in a hydrodynamic shear field
Authors: Cottrell F. R. , Merrill E. W. , Smith K. A. 
Published: April 2003

AbstractThe shear dependence of the intrinsic viscosity and the conformation of high molecular weight polyisobutylene in dilute solutions of decahydronaphthalene under shear were determined simultaneously. Experimental variables investigated were the shear rate (0 to 2 × 103 sec−1), the molecular weight (1.0 × 107 to 1.7 × 107) and the polymer concentration (1.8 × 10−4 to 8.4 × 10−4 g/cc). Correlations allowing concentration and shear rate normalization for any one sample are described. Conformational extention ratios along the orientation direction of the deformed molecule to 1.42 and intrinsic viscosity ratios (sheared to zero shear) to 0.5 were observed.
Effect of diluents on the melt viscosity of branched polybutadienes
Authors: Kraus Gerard , Gruver J. T. 
Published: April 2003

AbstractThe enchanced low‐shear melt viscosity of branched polybutadienes is shown to be sensitive to dilution with low molecular compounds. The viscosity of branched polymers falls more rapidly with dilution than that of linear polymers, i.e., branched polymers show increased response to plasticization. At least one instance is demonstrated in which the viscosity ratio ηbr/ηlin reverses from a value greater than unity to less than one in passing from dry polymer to rubber extended with relatively large quantities of oil.
Microstructure and rheological properties of polybutadienes
Authors: Vinogradov G. V. , Malkin A. Ya. , Kulichikhin V. G. 
Published: April 2003

AbstractThe viscosities, rubbery deformations, densities, and their dependence on temperature have been measured for several series of polybutadienes with molecular weights ranging from 5,000 to 400,000 and differing in proportions of cis and trans structures (cis content from 40 to 95%). On the basis of the viscosity measurements the critical molecular weight Mc has been determined, corresponding to a sharp change in the nature of the viscosity versus molecular weight dependence. Rubbery deformations are displayed pronouncedly in specimens with M > Mc and are closely related to the appearance of non‐Newtonian flow. The value of Mc depends on the relative content of cis and trans forms. When M > Mc, the initial viscosity is a parameter sensitive to the microstructure of polybutadienes, so that with at a single molecular weight, depending on the ratio of cis and trans units, the viscosity may vary over a more than tenfold range. The glass transition temperature and activation energy of viscous flow rise regularly with increasing trans content in the polymer chain, these parameters becoming independent of the molecular weight for specimens with M > Mc within a series of polybutadienes of equal microtacticity. Thermomechanical investigations of polybutadienes also made it possible to define more accurately the boundaries of the crystallization region and the dependence of the melting point on the microtacticity. The results obtained are discussed on the basis of modern ideas of polymer structure.
Properties and structures of films drawn from polyethylene single‐crystal mats
Authors: Maeda Masahiko , Miyasaka Keizo , Ishikawa Kinzo 
Published: April 2003

AbstractThe properties and structures of polyethylene films drawn from mats of single crystals were investigated in comparison with films drawn from bulk polymer. The most important result obtained is that the structural reorganization stimulated by mechanical stress and annealing occurs with much greater difficulty in the mat‐drawn film. The chief mechanical characteristics of the film are a very low extensibility and a very high modulus. Structural characteristics, such as the double‐orientation of the crystalline region and the morphology of the crystals, do suffer no substantial changes during annealing at high temperatures. This stability of the structure can be related to the characteristic fine structure of the mat‐drawn film in which there are a much larger number of tie chains, connecting neighboring crystals, than in the bulk‐drawn specimen. Relaxation of the amorphous region and a notable increase in long spacing take place in the mat‐drawn sample as in ordinary bulk‐drawn samples. However, the morphological changes of the crystals accompanied by the folding back of chains seem to take place with great difficulty during annealing even in the vicinity of the melting point.
Relation between the network structure and dynamic mechanical properties of a typical amine‐cured epoxy polymer
Authors: Murayama T. , Bell J. P. 
Published: April 2003

AbstractThe dynamic mechanical properties of a series of epoxy polymers of known network structure have been investigated. It was shown that the distance between crosslinks could be predicted from either the shift in the glass transition temperature Tg or by use of the dynamic modulus above Tg. The front factor in the equation of state for rubber elasticity was near unity for stoichiometric equivalence of epoxy and amine and increased slowly with excess of either component.
Effect of birefringence on low‐angle light‐scattering patterns from oriented polymer films. II
Authors: Chu W. , Stein R. S. 
Published: April 2003

AbstractA quantitative theoretical calculation is made of the effect of birefringence of the surrounding medium on the light‐scattering pattern from a two‐dimensional anisotropic spherulite. The calculated modification of the light‐scattering pattern is in accord with the prediction previously made on the basis of qualitative considerations and model experiments.
Thermodynamic properties of some monomeric compounds in the standard ideal gas state
Authors: Joshi R. M. 
Published: April 2003

AbstractThermodynamic functions of ten monomeric compounds have been calculated for three temperatures by the statistical method using molecular structural data and vibrational assignments. The ideal gas state entropies at 298.15°K are: maleic anhydride, 71.9; β‐propiolactone, 69.1; vinylene carbonate, 70.1; cyclopentadiene, 65.3; diketene, 72.3; cyclopropene, 58.7, vinyl fluoride, 60.4; ethyleneimine, 62.8; butatriene, 71.7; and carbon suboxide, 66.0 cal./deg‐mole. The standard free energies and equilibrium constants of formation are also derived by using mostly the published data on the heats of formation of these monomers.
Nature of DC conductivity in polyamides
Authors: Baird M. E. 
Published: April 2003

AbstractThe dc conductivity of poly(sebacyl piperazine), a polyamide prepared from the secondary diamine piperazine, in which no NH groups are present and no hydrogen bonding can occur, has been examined and compared with that of a normal 610 polyamide. The results obtained point clearly to the conduction in the 610 polyamide being electronic below about 100°C but probably involving protons as well as electrons above this temperature. This is largely consistent with the findings of earlier work and clarifies the nature of conduction below about 80°C as being almost certainly electronic where previously it was in doubt. A definite and sometimes marked hysteresis in the conductivity was observed with regard to raising and lowering the temperature of the polyamides. This is explained in terms of the space‐charge polarization developed in the materials at higher temperatures and which becomes clearly evident in their dielectric behavior. This shows the importance of discharging specimens at a sufficiently high temperature before making conductivity measurements. The polarization is a bulk and not an electrode effect, and it will probably depend to a marked extent on the morphology of the polyamides.