bluuebunny/crossref_metadata_2025_split huggingface dataset:
The infrared spectra and structures of polybutadienes
Authors: Binder John L. 
Published: April 2003

AbstractAssignments are suggested for many bands in the spectra of various kinds of polybutadienes which either confirm those deduced from olefin spectra or are new. In particular the band at 1355 cm.−1 (7.38 μ) is probably due to trans‐CHCH, that at 1311 cm.−1 (7.63 μ) is due to cis‐CHCH as is a band at 740 cm.−1 (13.5 μ). These assignments are based on the study of polarization spectra, of the spectra of hydrogenated polybutadienes and maleic anhydride adducts of polybutadienes and on isomerization experiments of cis‐1,4‐polybutadienes. Evidence is offered which indicates that presently known high cis‐1,4‐polybutadienes are not simply butadiene polymerized by cis‐1,4 addition and that probably other structures are present in the polymer. It is shown that the 1355‐ and 1311‐cm.−1 bands appear in the spectra of polypiperylenes and polyisoprenes (shifted somewhat in the latter spectra) and consequently are due to a CH vibration of the trans‐ or cis‐CHCH group. Thus they are group frequencies.
Cocatalysts for the linear polymerization of epoxides by dibutylzinc
Authors: Garty K. T. , Gibb T. B. , Clendinning R. A. 
Published: April 2003

AbstractA study of the nature and quantity of materials that will react with dibutylzinc to act as cocatalysts for the polymerization of phenyl glycidyl ether has led to the finding of several very effective catalyst systems. These cocatalysts may be grouped in the following classifications: (1) highly effective: water and acetone; (2) effective: methanol, ethanol, n‐butanol, and oxygen; (3) slightly effective: isopropancl, tert‐butanol, diethylamine, n‐butyraldehyde, and phenol; and (4) inhibitors: acetic acid, ethyl acetate, and carbon dioxide. The poly(phenyl glycidyl ether) produced by these catalysts is a high melting (204°C.), high molecular weight crystalline polymer which is insoluble in most common organic solvents. Ethylene oxide and propylene oxide have also been polymerized by the dibutylzinc–water system to high molecular weight polymers in high yield. Epichlorohydrin, on the other hand, gave only low molecular weight oils in low yields, probably due to reaction of the catalyst species with the reactive chlorine of the monomer.
Melting transitions in diene polymers
Authors: Cooper W. , Smith R. K. 
Published: April 2003

AbstractThe melting transitions of natural rubber, cis‐polyisoprene, gutta‐percha, balata and synthetic trans‐polyisoprene, and cis‐polybutadiene have been examined by means of differential thermal analysis. Natural rubber melts over a wide range of temperature giving several transitions, the magniture and temperature of which depend on the experimental conditions. At heating rates feasible for differential temperature measurements the values observed are markedly below the equilibrium melting points. Natural and synthetic trans‐polyisoprenes possess similar melting points and extents of crystallinity. The ratio of the peaks associated with the α and the β forms is not only dependent on the rate of cooling and temperature of crystallization, but also on the temperature to which the sample was heated before crystallization. This is thought to be due to the persistance of crystalline nuclei in the polymer melt. Under certain conditions a small melting transition occurs at a lower temperature. Synthetic cis‐polyisoprenes show melting characteristics similar to those of natural rubber, but the upper transition is lower than that of the natural product and correlates with the cis content of the polymer. cis‐Polybutadienes melt slowly over a wide range of temperature below the characteristic melting transition which is dependent on the cis content. The highest melting point observed for a polymer of 98% cis content was +1°C.
A thermodynamic method for the comparison of the order distribution in cellulose and in other polymers
Authors: Ticknor L. B. 
Published: April 2003

AbstractPrevious definitions of order (i.e., lateral order) in cellulose materials have been essentially in terms of the experimental method and order has been interpreted as the extent of hydrogen bonding. These definitions are inadequate. Order is defined herein as the difference in free energy of the element of polymer in its present state and in a completely amorphous state. The free energy of swelling is equated to the conceptual process of fusion of the element of polymer plus mixing the amorphous and crosslinked (by crystallites) polymer with swelling agent as would be given by the Flory‐Huggins theory of mixing and the Flory‐Rehner or Hermans theories for the swelling of networks. For those elements of polymer for which the free energy of swelling is zero the free energy of fusion (i.e., “order”) may be determined. This limiting order of the polymer elements that are swollen may be reduced by lowering the pressure of the swelling agent if it is in the gaseous state or if the swelling agent is a liquid by mixing it with a nonswelling liquid. Such a variation in the swelling agent gives a variation in the quantity of polymer swollen. The summative mass order (quantity accessible vs. limiting order) and order distribution (slope of summative curve vs. limiting order) plots are made as usual. This method should give realistic qualitative comparisons of the order distribution among various samples of the same polymer, and it should be applicable to other crystalline polymers as well as to cellulose.
Radiolysis of the isomeric poly(butyl methacrylates)
Authors: Ungar Israel S. , Kircher John F. , Gager William B. , Sliemers Francis A. , Leininger Robert I. 
Published: April 2003

AbstractA study has been made of the effect of gamma irradiation on the production of free radicals in poly(butyl methacrylates). A mechanism of radiation attack on the polymers is proposed. Free‐radical measurements and the determination of the products of irradiation have been used in establishing this mechanism. The effects of configuration of the ester chain on radiation susceptibility are discussed.
Probability matrices, chain dimensions and statistical thermodynamics for semicrystalline macromolecules
Authors: Tobolsky Arthur V. 
Published: April 2003

AbstractIn a previous paper the end‐to‐end dimensions of semicrystalline macromolecules were computed by the Markoff chain method, by use of a normalized probability matrix with two probability parameters α and p. The values of these parameters that actually obtain may result from kinetic conditions (as in rapidly quenched specimens) or the values may in some cases be equilibrium values that can be determined by statistical mechanical considerations. In this paper we calculate the overall partition function Q of a semicrystalline macromolecule by a method similar to that employed by Zimm and Bragg for polypeptide chains. Q is computed in terms of segment partition functions fr, fh, and fk. By working out the consequences of this Ising‐type model, we are able to relate α and p to fr, fh, and fk. In an appendix we show that the phenomenon of ceiling and floor temperatures in equilibrium polymerization can be regarded from the same mathematical point of view as the helix–coil transition. Moreover, the mathematical results from this approach can be correlated with the results previously obtained by Tobolsky and Eisenberg by direct application of the law of mass action.
Solution properties of polysaccharides. IV. Molecular weight and aggregate formation in methylcellulose solutions
Authors: Neely W. Brock 
Published: April 2003

AbstractLight scattering has been employed to investigate the aqueous solution properties of partially methylated cellulose. The data indicate a random coil for the polymer with a stiffness characterized by a value of 21.8 A. for the effective bond length b. An increase in ionic strength in the methylcellulose solution causes aggregation which is temperature‐dependent. Once the aggregates are formed in the salt solution, they may be dispersed by lowering the temperature of the solution. Within probable error the intrinsic viscosity–molecular weight relation is given by [η] = 3.16 × 10−3 M̄w0.55 throughout the region investigated.
Effect of crystallization on the thermal stability of polyvinylphthalic acid and its methyl ester
Authors: Winslow Eugene C. , Marriott Jean A. 
Published: April 2003

AbstractThe synthesis of dimethyl 4‐vinylphthalate was accomplished by direct esterification of 4‐vinylphthalic acid with diazomethane. This monomer was polymerized stereospecifically by the use of boron trifluoride etherate. The polymer was crystallized by refluxing in n‐octane. The preparation of crystalline poly(4‐vinylphthalic acid) was realized by hydrolyzing crystalline poly(dimethyl 4‐vinylphthalate) with concentrated sulfuric acid. The thermal behaviour of the prepared polymers was studied by the techniques of differential thermal analysis and thermogravimetry. Crystallization apparently retards thermal breakdown somewhat but the temperature of major weight loss by volatilization is essentially the same for the crystalline and the noncrystalline polymer. Differential thermal analysis indicates that anhydride formation occurs in the noncrystalline polymeric acid at 200°C. This transition is less pronounced in the case of the crystalline polymer.
Fundamental studies on cationic polymerization. II. Mechanism and theory of inversion temperature
Authors: Kennedy J. P. , Kirshenbaum I. , Thomas R. M. , Murray D. C. 
Published: April 2003

AbstractFurther studies with the isobutene‐aluminum chloride‐methyl chloride system has led to a better understanding of the dependence of degree of polymerization on monomer concentration and on temperature. Polymerizations were also carried out in C14‐labeled methyl chloride to determine solvent incorporation in the polymer. A quantitative kinetic theory has been developed which explains the behaviour of the isobutene–aluminum chloride system in polar solvents such as methyl chloride, vinyl chloride, and ethyl chloride. The rate‐determining step in propagation is polymer activation, presumably by ion separation. The DP of the polymer is determined principally by two competing chain‐breaking processes; namely, chain transfer to monomer and/or chain breaking involving the solvent. The latter reaction becomes important in polar solvents at higher temperatures. The influence of phase separation has also been studied. The results indicate that the polymer molecule precipitates after it has under gone either a chain breaking or a chain termination reaction.
Separated aluminum alkyl–titanium tetrachloride catalysts for isoprene polymerization
Authors: Saltman William M. 
Published: April 2003

AbstractThe liquid portions of triisobutyl–aluminum TiCl4 catalysts were partially or completely removed from catalysts formed at Al/Ti ratios of 0.5, 0.6, 1.0, 1.2, 2.0, 3.0, and higher. The partially separated catalysts (0.5–1.2 Al/Ti) are still highly active for the polymerization of isoprene to a high cis polymer. The completely separated solid is inactive, but regains polymerization activity if triisobutyl aluminum or diisobutyl‐aluminum chloride is added back. Polymer yield quickly reaches a maximum and then falls off sharply on addback of more trialkyl; the drop in yield is much slower on addback of excess dialkyl halide. The results indicate that trialkyl or dialkyl halide plus β‐TiCl3 make active catalyst systems for cis‐polyisoprene; the alkyl dihalide is not satisfactory. Excess trialkyl changes the solid surface or mechanism and results in lowered solid polymer yield and increased oily oligomer formation. Completely separated high ratio (2.0 and 3.0 Al/Ti) catalysts are more active than those only partially separated but still much less active than catalysts formed at lower ratios. Addbacks of either aluminum trialkyl or dialkyl halide depress the solid cis polymer yield. Without any separation no solid polymer at all forms. The results suggest that the catalyst at these high ratios is a solid complex of β‐TiCl3 with an organometallic. A simple coordination mechanism is sufficient to correlate all the experimental results.
Hydrogen bonding in amine–epoxide adducts
Authors: Harrod J. F. 
Published: April 2003

AbstractThe infrared spectra of several alcohols and aminoalcohols were measured in bulk and in dilute solution in the 2800–4000 cm.−1 region to determine the nature of hydrogen bonding in these compounds. An epoxy resin was cured with both an aliphatic monoamine and a diamine, and the OH‐stretching bands of the polymers were studied in the temperature range 30–200°C. It is concluded that the hydroxyl groups in the polymers are extensively involved in long‐range hydrogen bonding, particularly of the OHN type, at room temperature. The shift in the bonded OH band to lower frequency with increasing temperature is attributed to a shift from long range to short range bonds. Even at 200°C. there are relatively few free hydroxyl groups in these polymers.
The molecular weight distribution in polypropylene
Authors: Westerman Lowell 
Published: April 2003

AbstractLight scattering, osmotic pressure, and dilute solution viscosity measurements were utilized to determine the weight‐average, number‐average, and viscosity‐average molecular weights of 10 unfractionated commercial and pilot unit polypropylene samples. Weight‐average molecular weights evaluated from angular scattering data by the method of Zimm were found to agree with those determined by means of the “dissymmetry” method when proper solution clarification procedures were employed. As would be predicted, the z‐average dimension, \documentclass{article}\pagestyle{empty}\begin{document}$\overline{{R_Z ^2 }}$\end{document}, for these polydisperse samples was found to be larger than those reported by Chiang for fractionated samples of comparable weight‐average molecular weight. A general trend toward increased breadth of molecular weight distribution with increasing average molecular weight was detected from the variation of M̄w/M̄n values with average molecular weight, and is supported by the [η]‐M̄w relationship found for these unfractionated samples as compared with the relationship established by Chiang for fractionated samples. The log‐normal distribution function of Wesslau was applied to data on M̄w, M̄n, and M̄v, demonstrating that commercial Ziegler‐type polypropylene displays this type of molecular weight distribution within the molecular weight range studied.
Kinetics of propylene polymerization catalyzed by α‐titanium trichloride–diethylaluminum chloride
Authors: Chien James C. W. 
Published: April 2003

AbstractThe kinetics of propylene polymerization catalyzed by α‐titanium trichloride–diethyl‐aluminum chloride in heptane diluent were studied. Initiation and transfer processes were followed by using C14‐labeled (C2H5)2AlCl. There was no important termination process in this system. The initial C14 activity found in the polymers gave the concentration of active ethyl groups on the surface, [C]. The propagation step was first order in [monomer] and [C], with an activation energy of 13.0 kcal. mole−1; kp at 50°C. was 0.426 ± 0.018 l. mole−1 sec.−1. There were two transfer processes: (1) Rtr1 = ktr1[C] − [(C2H5)2AlCl]1/2, with an activation energy of 18.6 kcal. mole−1, and a value of ktr1 at 50°C. of 6.54 × 10−5 mole−1/2 sec.−1; and (2) Rtr2 = ktr2 [C] [α‐TiCl3], with an activation energy of 7.6 kcal. mole−1, and a value of ktr2 at 50°C. of 9.45 × 10−4 l. mole−1 sec.−1. These kinetic data were used to calculate number‐average molecular weights M̄n, which agreed well with the ones obtained directly from the C14 specific activity in the polymer. Furthermore, fractionation of four polypropylene samples gave values of M̄n in agreement with those obtained above. At low temperatures, [C] is sensitive to the Al/Ti ratios. This dependence was interpreted as the result of an equilibrium between an active complex containing (C2H5)2AlCl and a much less active complex containing (C2H5)AlCl2. At higher temperatures, [C] is insensitive to the Al/Ti ratios, and polymerization to give amorphous polymers becomes important. Qualitative information was obtained about the processes which give amorphous polymers.
Behavior of polymer solutions in a velocity field with parallel gradient. I. Orientation of rigid ellipsoids in a dilute solution
Authors: Takserman‐Krozer Rachela , Ziabicki Andrzej 
Published: April 2003

AbstractThe spatial orientation of rigid ellipsoidal particles was analyzed as proceeding in a dilute solution flowing in a velocity field with parallel gradient, i.e., in a field characterized by the deformation rate tensor:

On the basis of general relations given by Jeffery, the hydrodynamic equations of motion of a single ellipsoid were obtained as Ψ = 0, φ = 0, θ = −¾qR sin 2θ, where q = ∂Vκ/∂κ is the parallel velocity gradient and R = (a2 − b2)/(a2 + b2) is the shape coefficient of ellipsoids. Considering the action of velocity field and that of Brownian motion (rotational diffusion), a distribution density function ρ(t, θ) was derived, which describes the spatial orientation of the axes of symmetry of the ellipsoids:

where

is the steady‐state distribution. In a similar way, the axial orientation factor f0 = 1 − 3/2 sin2θ was obtained:
Behavior of polymer solutions in a velocity field with parallel gradient. II. Viscosity of dilute solutions containing rigid ellipsoids
Authors: Takserman‐Krozer Rachela , Ziabicki Andrzej 
Published: April 2003

AbstractOn the basis of Jeffery's general relations, formulas for the rate of dissipation of energy due to the motion of a rigid rotational ellipsoid in a liquid, uniaxially drawn, were derived. By use of the previously found distribution function, intrinsic viscosity v, was calculated and effects of ellipsoid shape, velocity gradient, diffusion rate constant and time were discussed. The intrinsic viscosity monotonically increases with velocity gradient and with time t. This behavior is quite different from that observed in shear flow. It was stated that phenomena connected with a velocity field with parallel gradient (i.e., flow with uniaxial deformation):

such as liquid jets, fiber spinning etc., cannot be explained in terms of experiments or theories concerning the shear flow (velocity field with perpendicular gradient):

as obtained in viscosity measurements in common types of viscometers (capillary, rotational, falling body), or investigations of flow birefringence in coaxial apparatus.
Water sorption of titanium dioxide–poly(vinyl acetate–vinyl chloride) copolymer films
Authors: Kumins Charles A. , Roteman Jerome , Rolle Clifford J. 
Published: April 2003

AbstractCrystalline solids, as exemplified by TiO2 incorporated within a film of a model polymer, poly(vinyl chloride–vinyl acetate) copolymer, have been shown to absorb relatively large amounts of water vapor on the surface. In some cases all of the crystal surface may participate in the sorption process, despite evidence that the polymer has been initially present on the surface of the former. This, coupled with anomalous density changes in the film, suggests the possibility of measuring crystal flocculation within the membranes as well as the displacement of adsorbed polymer segments by means of water vapor. The anomalous density determinations were correlated with water transport measurements, and an equation for calculation of the heat of wetting of a crystal with a solid polymer is presented.
Polymerization of acrylonitrile by electron transfer catalysts
Authors: Zilkha Albert , Avny Yair 
Published: April 2003

AbstractThe heterogeneous polymerization of acrylonitrile in tetrahydrofuran by chain transfer catalysts: monosodium anthracene, disodium anthracene, sodium naphthalene, monolithium anthracene, and lithium naphthalene was investigated. The free radical formed in the initiation was found to participate in the polymerization process only in the case of lithium naphthalene at low catalyst concentrations. Also, block copolymerization with styrene, which is more reactive in free radical polymerization than acrylonitrile and less in anionic, succeeded only with lithium naphthalene. The absence of dimerization of the free radicals is mainly due to their occlusion caused by the high rate of the anionic polymerization of acrylonitrile and the low polymerization temperature, and in the case of the anthracene catalysts also due to inhibition of the free radical dimerization by the liberated anthracene. The mechanism of the termination of the polymerization was found to depend on the catalyst concentration and the ratio [MI]/[C]. At high catalyst concentrations and relatively low [M]/[C] values, termination was by chain transfer to the monomer, as can be seen from the independence of the molecular weights on both monomer and catalyst concentrations. At low catalyst concentrations and relatively high [M]/[C] values, the molecular weights were found to increase with monomer concentration and decrease with catalyst concentration. This was found to be due to the anionic mechanism of the polymerization, and the results are similar to those obtained in a typical anionic polymerization of acrylonitrile with butyllithium.
Electron spin resonance study of radiation oxidation of polymers. IIIA. Results for polyethylene and some general remarks
Authors: Ohnishi Shun‐Ichi , Sugimoto Shun‐Ichi , Nitta Isamu 
Published: April 2003

AbstractThe effect of oxygen on ESR spectra of various kinds of irradiated polymers has been examined by using a saturation technique developed in the present investigation. The radiation oxidation of some polymers has been studied by means of ESR as well as infrared spectroscopy. Results for polyethylene (PE) are given in this paper, with some general remarks as introduction. In PE three kinds of radicals are produced on irradiation: CH2CHCH2 (FRVI), CHCHCH (FRVII), and CH(CHCH)nCH2(FRI). On introduction of air, FRVII gave the asymmetric singlet of the peroxide radical which showed anisotropy. Reversible oxygenation of FRVII took place even as low as −113°C. Radiation oxidation of PE proceeds mainly via FRVII, which produced eventually about 12 carbonyl groups and about 5 hydroxyl groups in the course of post‐oxidation, the trans‐vinylene group decreasing by an amount nearly equal to the amount of initial FRVII. FRVI played only a minor role in the oxidation. An oxidation mechanism involving chain reaction has been proposed. It suggests an intramolecular free‐back reaction of hydrogen to the peroxide radical of FRVII. FRI (polyenyl radicals of longer conjugations) is oxidized to form carbonyl and hydroxyl groups, although it does not give the spectrum of the peroxide radical. Polyenyl radicals of shorter conjugations reacted faster.
Electron spin resonance study of radiation oxidation of polymers. IIIB. Polypropylene and poly(vinyl chloride)
Authors: Ohnishi Shun‐Ichi , Sugimoto Shun‐Ichi , Nitta Isamu 
Published: April 2003

AbstractResults of ESR and infrared studies of radiation oxidation of polypropylene (PP) and poly(vinyl chloride) (PVC) are reported. The effect of oxygen on the free radicals, FRVIII (CH2Ċ(CH3)CH2) and FRIX (CH2Ċ(CH3)2), FRI′ (polyenyl radicals with shorter conjugations), FRI (polyenyl radicals with longer conjugations) in PP and FRI′, FRI in PVC was studied. On introduction of air, FRVIII and FRIX in PP and FRI′ in PP and PVC showed the asymmetric singlet spectrum of the peroxide radical. Oxygenation of the radicals began at low temperatures: −135°C. for FRVIII and FRIX, −144°C. for FRp in PP, and −170°C. for FRI′ in PVC. By reevacuation, the oxygen molecule could be removed from the peroxide radical of FRI′ in PP and PVC, while deoxygenation was impossible from FRVIII and FRIX. Oxidation of the radicals in PP and PVC gave carbonyl and hydroxyl groups. The number of carbonyl groups produced per radical was estimated as 3.4 and 1.6 for FRI′ in PP and PVC, respectively.