bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative characterization of deformation in polypropylene fibers
Authors: Samuels Robert J. 
Published: April 2003

AbstractA modus operandi is developed for characterizing, in quantitative morphological terms, the structural changes occurring during the preparation (spinning, drawing, and heat setting) and testing (tensile modulus) of isotactic polypropylene fiber. This involves the application of the following eight different physical techniques: wide‐angle x‐ray diffraction, birefringence, density, sonic modulus, small‐angle x‐ray diffraction, dark‐field microscopy, small‐angle light scattering, and tensile modulus. Structural changes on several organizational levels, the spherulitic, the interlamellar, and the molecular, are determined in this manner and related to the processes involved.
Thermostable organic polymers devoid of hydrogen and other pendent groups
Authors: Hirsch Stephen S. 
Published: April 2003

AbstractAromatic hydrogen atoms in thermostable polymers can be surprisingly labile at relatively low temperatures and may participate extensively in degradative reactions. If hydrogen were eliminated from the polymer chain, a number of degradative pathways would be excluded. Replacement of hydrogen with other pendent groups such as fluoride or trifluoromethyl still leaves a potential “handle” to enter into unwanted reactions, therefore, all bonds not required to create the chain were eliminated. The polyimide devoid of hydrogen from pyrazinetetracarboxylic dianhydride and 2,5‐diamino‐1,3,4‐thiadiazole was synthesized. This polymer exhibits extraordinary high temperature
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oxidation stability. Films of this composition support weight in air up to 592°C, and rupture at this temperature is accompanied by no charring whatever. By comparison, the corresponding polymer from pyromellitic dianhydride, with two hydrogen atoms per repeating unit begins to char at 320°C.
Synthesis, reactivity, and polymerization of vinylureas
Authors: Overberger C. G. , Montaudo G. , Ishida S. 
Published: April 2003

AbstractThe syntheses of N,N′‐divinylureas and some related compounds are reported. Polymerization of these monomers and determination of the structures of the resulting polymers are described. Evidence is presented which supports the tendency of vinylureas to react through their tautomeric form.
Triptycene polymers
Authors: Hoffmeister E. , Kropp J. E. , McDowell T. L. , Michel R. H. , Rippie W. L. 
Published: April 2003

AbstractNew, bifunctional, bridgehead‐substituted triptycenes were synthesized and used to prepare a series of triptycene polymers, including polyesters, polyamides, polyurethanes, and a polyoxadiazole. Certain of these partially aliphatic polymers were thermally stable. Clear and colorless films were obtained in some instances.
Synthesis of 4‐vinylbiphenyl–isoprene block copolymers and their characterization by gel‐permeation chromatography
Authors: Heller J. , Schimscheimer J. F. , Pasternak R. A. , Kingsley C. B. , Moacanin J. 
Published: April 2003

Abstract4‐Vinylbiphenyl–isoprene ABA block copolymers were prepared by initiating 4‐vinylbiphenyl with n‐butyllithium in benzene, adding isoprene, and coupling the resulting AB anion with phosgene. Preliminary coupling experiments with a polyisoprene anion have shown that virtually quantitative coupling could be achieved provided the phosgene was added extremely slowly. The block copolymers could be quantitatively analyzed by gel‐permeation chromatography from a knowledge of the ratio of the refractive index increments of the two homopolymers and the overall composition.
Polymerization of aromatic nuclei. XV. Polymerization of 2,5‐di‐ and 2,3,5‐trichlorothiophenes with aluminum chloride–cupric chloride
Authors: Ramsey J. S. , Kovacic Peter 
Published: April 2003

Abstract2,5‐Dichlorothiophene was polymerized to a solid in 93% yield on treatment with aluminum chloride–cupric chloride in carbon disulfide under mild conditions. The product is believed to be poly‐5‐chloro‐2,3‐thienylene on the basis of elemental analysis and infrared and NMR spectral data. Hydrogen chloride was collected in 90% of the theoretical amount. Dimer‐ and tetramer‐type fractions were isolated from the polymer. 2,3,5‐Trichlorothiophene underwent an analogous transformation in trichlorobenzene at 90–100°C. Polythienylenes coupled through the 2,3‐positions have not been reported previously. The net effect of the reaction is nuclear coupling by dehydrohalogenation. We believe that the mechanism involves cationic polymerization accompanied by loss of hydrogen chloride. 2‐Chlorothiophene and thiophene gave products of complex make‐up.
Molecular structure parameters in certain semiconducting polymers
Authors: Kho J. H. T. , Pohl Herbert A. 
Published: April 2003

AbstractThe condensation polymers formed by condensing aromatic hydrocarbons or their derivatives with aromatic acids are quite conductive. The room temperature resistivities of 42 polymers studied here range from 102 to 1012 ohm‐cm. It is found that the resistivities are inversely related to the number of fused rings in the hydrocarbon portion of the monomer for either the homopolymers or copolymers. The resistivities are strongly dependent, inversely, upon the acid strength of the acid monomer reactants. For all the polymers studied, the conductivity σ depended upon the pressure P as ln(σ/σ0) = (b*/k)P1/2 where b* is seen to be an inverse function of the number of fused rings in the monomer in accord with theory. The resistivity ρ varied with absolute temperature T, as ln ρ ∞ (1/T) for all polymers. Thermoelectric powers were determined, and the various relationships established among energy interval, resistivity at “infinite temperature,” carrier concentrations and mobility ratios, number of fused rings, and pressure coefficients are discussed. The polymers are p‐type. Doping by Be++ or Cu++ has a small effect, increasing the conductivity slightly. Electron spin concentrations and carrier concentrations are directly related among the polymers, being found nearly equal for the most conductive but differing by up to nine orders of magnitude in the least conductive polymers.
Synthesis and properties of self‐protecting polyarylates
Authors: Korshak V. V. , Vinogradova S. V. , Siling S. A. , Rafikov S. R. , Fomina Z. Ya. , Rode V. V. 
Published: April 2003

AbstractSelf‐protective polyesters were synthesized in two ways: by polymer analog transformations on polymers obtained and by introduction of inhibiting groups into the polymer during synthesis. It is shown that the Fries rearrangement takes place in the aromatic polyesters in the presence of the Friedel‐Crafts catalysts and on ultraviolet irradiation as well. Thermogravimetric analysis of the rearranged polymers and investigations of the influence of the ultraviolet irradiation on their properties show that the rearrangement markedly increases the photochemical and thermal stability of the polymers. Photostabilization may also be accomplished by the introduction of inhibiting groups, such as hydroxyl, sulfur, or phosphorus into the polymer molecule.
Free‐radical copolymerizations of 1,2‐dichloroethylenes. Evidence for chain transfer by chlorine atom elimination
Authors: Dawson T. L. , Lundberg R. D. , Welch F. J. 
Published: April 2003

AbstractTrialkylboron–oxygen, an active, low‐temperature free‐radical initiator, has been employed to investigate the effects of very low temperatures on the copolymerizations of vinyl acetate with cis and trans‐1,2‐dichloroethylenes. The low temperatures favor the propagation rate relative to the transfer rate, such that high molecular weight copolymers containing substantial quantities of 1,2‐dichloroethylene can be prepared. The molecular weights of the copolymers depend only on the amounts of 1,2‐dichloroethylene in the copolymers, regardless of the isomer which takes part in the copolymerization. Since the double bond of the trans isomer is about six times as reactive as that of the cis isomer, this indicates that the dominating chain transfer reaction occurs by chlorine atom elimination subsequent to the addition of the dichloroethylene unit to the growing free radical chain. It is suggested that a similar chain‐transfer mechanism occurs in the polymerization of vinyl chloride, wherein an infrequent head‐to‐head placement of monomer unit is followed by ejection of a chlorine atom to form an olefinic bond and termination of that growing chain. The presence of the 1,2‐dichloroethylene unit in the copolymer increases the glass transition temperature approximately 1°C per weight per cent copolymerized with the vinyl acetate.
Polymerization by crystallization of trioxane from cyclohexane solutions in presence of 1,3‐dioxolane
Authors: Baccaredda M. , Giorgini M. , Lucchesi A. , Morelli F. , Tartarelli R. 
Published: April 2003

AbstractTrioxane–1,3‐dioxolane copolymers of high molecular weights and good thermal stability are obtained with high yields by a crystallization‐polymerization method. The feed consists of concentrated solutions of trioxane in cyclohexane in the presence of dissolved 1,3‐dioxolane. The 1,3‐dioxolane/trioxane molar ratio in the feed lies in the range 2 to 10%. The results are compared with those obtained from isothermal copolymerizations.
Proton magnetic resonance investigation of structure of ω‐alkyl‐α‐olefin/SO2 copolymers
Authors: Bacskai R. , Lindeman L. P. , Ransley D. L. , Sweeney W. A. 
Published: April 2003

AbstractThe 100 MHz proton magnetic resonance (PMR) spectra of free radical alternating ω‐alkyl‐α‐olefin/SO2 copolymers has been investigated. The data obtained from the quantitative evaluation of the spectra are consistent with a copolymer structure containing unrearranged olefinic monomer units. The 4‐methyl‐1‐pentene/SO2 copolymer shows a quadruplet resonance in the CH3 proton region. This multiplicity, observed also in the analogous 1,2‐dichloro‐4‐methylpentane and 1,2‐dibromo‐4‐methylpentane, arises from the presence of magnetically nonequivalent CH3 protons located in the vicinity of the asymmetric carbon atoms of the main chain. There is no detectable nonequivalency of CH3 protons in the 5‐methyl‐1‐hexene/SO2 copolymer, probably because the center of asymmetry is further removed from the isopropyl group. In poly‐4‐methyl‐1‐pentene, prepared with Ziegler‐Natta catalyst, the polymer structure around the main chain tertiary carbons is fairly symmetrical; and, as expected, the CH3 protons of the isopropyl group are magnetically equivalent.
Poly(Vinyl 2‐furylacrylate), a new photosensitive polymer
Authors: Tsuda Minoru 
Published: April 2003

AbstractPoly(vinyl 2‐furylacrylate), a new photosensitive polymer, was prepared, and its photosensitivity was investigated. The polymer cannot be synthesized by the usual procedure, condensation of poly(vinyl alcohol) and 2‐furylacrylyl chloride in hot pyridine, but is easily prepared by the aqueous alkaline process, regardless of the degree of polymerization. Poly(vinyl 2‐furylacrylate) is remarkably highly photosensitive and is spectrally sensitized by aromatic nitro compounds and aromatic carbonyl compounds. The mechanism of photochemical reaction is considered to involve the dimerization of the furylacrylyl group, and the quantum yield appears to be constant.
New high‐temperature polymers. VIII. Ordered benzoxazole‐ and benzothiazole‐imide copolymers
Authors: Preston J. , Dewinter W. F. , Black W. B. 
Published: April 2003

AbstractOrdered heterocycle copolymers of high thermal stability were prepared from aromatic dianhydrides reacted with aromatic diamines containing preformed benzoxazole or benzothiazole units. These ordered benzoxazole‐imide and benzothiazole‐imide copolymers were prepared in the form of their soluble precursor polyamic‐acids, which, after fabrication to desired shapes, were converted to the thermally stable polymer. In general, these polymers are more resistant to air oxidation at elevated temperatures than are simple aromatic polyimides, and their thermoöxidative stability is equal to or greater than that reported for benzoxazole or benzothiazole homopolymers. Unlike the o‐hydroxyamide precursors to simple polybenzoxazoles, the amic acid precursors to benzoxazole‐imide ordered copolymers do not require temperatures above 300°C to complete ring closure nor inert atmospheres to prevent polymer degradation during ring formation. Excellent self‐supporting films and film coatings for metals were prepared. Selected compositions were readily spun to excellent fiber.
Dielectric properties of stereoregular poly(methyl methacrylates)
Authors: Shindo Heisaburo , Murakami Ichiro , Yamamura Hitoshi 
Published: April 2003

AbstractTo obtain more useful information about the effect of the degree of stereoregularity on the motion of the polymer chain, the dielectric and dilatometric measurements were made for a series of stereoregular poly(methyl methacrylates) (PMMA). The α‐ and β‐absorptions were observed in each sample, of which the dielectric behaviors of the α‐process are discussed. The temperature dependence of the relaxation time of the α‐process was sufficiently represented by the WLF equation and the resulting values of the parameters fg and B in the modified WLF equation were found smaller for isotactic‐rich PMMA than those values for syndiotactic PMMA. It may be deduced from these results that the chain mobility of the isotactic PMMA is larger than that of the syndiotactic. The dielectric increment of the α‐process in the isotactic PMMA is much larger than that in the syndiotactic PMMA, increasing rapidly with temperature, and taking its maximum in the temperature range of 55 to 60°C. The dielectric transition was clearly observed in the case of isotactic‐rich PMMA.
Nature of the active component in the catalytic system prepared from titanium(III) chloride(AA), ethylaluminum dichloride, and tetrakis(dimethylamino)silane, in the polymerization of propylene
Authors: Matsumura Kiichiro , Atarashi Yuji , Fukumoto Osamu 
Published: April 2003

AbstractThe chemistry of the titanium(III) chloride(AA)–ethylaluminum dichloride–tetrakis‐(dimethylamino)silane system for the polymerization of propylene was studied. A complex of ethylaluminum dichloride with tetrakis(dimethylamino)silane was isolated. It was shown that this complex contains ethylaluminum dichloride and tetrakis(dimethylamino)silane in the ratio of 2:1. This complex with titanium(III) chloride is responsible for the polymerization activity.
The cupric sulfate–hydrazine system as an initiator of vinyl polymerization. I. The polymerization of methyl methacrylate in aqueous solution in the presence of oxygen
Authors: Bond Joan , Lee P. I. 
Published: April 2003

AbstractThe cupric sulfate–hydrazine system has been used to initiate the aqueous solution polymerization of methyl methacrylate at pH 9.25 in the presence of oxygen. At cupric sulfate concentrations greater than the saturation solubility of cupric hydroxide, hydrazine is adsorbed on, and decomposes on, the surface of the hydroxide. The kinetics of the decomposition are zero‐order both in the absence and the presence of monomer. The initiation of the polymerization occurs both at the surface of the cupric hydroxide on to which some monomer is adsorbed and also in solution. Below the saturation solubility of cupric hydroxide, the initiation reaction between cupric ions and hydrazine occurs in solution.
Polycondensation rate of poly(ethylene terephthalate). II. Antimony trioxide–catalyzed polycondensation in static thin films on metal surfaces
Authors: Stevenson Robert W. 
Published: April 2003

AbstractIn the catalyzed polycondensation reaction of poly(ethylene terephthalate), defined by

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rates of polymerization in thin films under vacuum are orders of magnitude greater than those observed in an equilibrating system. Such behavior is consistent with a mechanism in which a volatile component of the reaction mixture reacts reversibly with the catalyst to render it unreactive in polycondensation; removal of this component is facilitated as polymerizing melt thickness is decreased. In accord with such a mechanism polycondensation rates for polymerizations carried out on metal surfaces at thicknesses of 1 to 5 mils of polymerizing melt are observed to increase with decreasing thickness, provided a catalyst is present. In the absence of a catalyst there is no tendency of rate to increase with decreasing thickness. A number of metal surfaces were found to dissolve in the polymerizing melt. On rhodium and silver, which were found to be inert to such dissolution, uncatalyzed polycondensation rate constants kp of 0.03 and 0.04 liter mol−1 min−1 were found. These values of kp are low and identical within experimental error. This behavior is in accord with the assumption that no catalysis occurs at the interface of the polymerizing melt and the metal surface. A typical value for the catalyzed rate constant kp (uncorrected for catalyst concentration) was 0.6 liter mol−1 min−1 in a 1‐mil thickness of polymerizing melt at 275°C and in the presence of 0.025 wt‐% antimony trioxide. The activation energy for the antimony trioxide–catalyzed polycondensation was found to be 14 kcal; for the uncatalyzed polycondensation it was 45 kcal.
Determination of the number of particles/unit volume of latex during the emulsion polymerization of styrene
Authors: Robb I. D. 
Published: April 2003

AbstractThe variation of the number of particles/unit volume of latex (N) with conversion was determined during the emulsion polymerization of styrene. The results showed that, contrary to what is required by the Smith‐Ewart theory, N increased during the constant rate period. This conclusion was supported by the variation of the particle size distribution with conversion. Further evidence that latex particles could form in the absence of micelles was given by using systems in which the soaps were below the CMC. The chain length of the soaps used had a marked effect on the rate of polymerization. This effect was shown not to be due to the variation of the CMC with chain length, but possibly to the stronger adsorption of the longer chain length soaps at the polymer–water interface.
The preparation and characterization of some cellulose graft copolymers. V. ESR study of preirradiation grafting of styrene to cellulose acetate
Authors: Campbell D. , Williams J. L. , Stannett V. 
Published: April 2003

AbstractPrevious studies have shown a two‐peak molecular weight distribution of the grafted polystyrene side chains from preirradiation‐grafted cellulose acetate. ESR has been used to investigate this grafting system in further detail. It was found that the rate of decay of the trapped radicals on adding the monomer solution was quite slow and a substantial proportion remained after 3 days at 25°C. The G value for radicals lost was, however, in good agreement with the G (grafted side chains) produced during the same period. The ESR spectrum does not change on addition of the monomer solution. The explanation offered is that the side chains grow and terminate rapidly compared with the slow overall rate of decay. The grafting yield and the molecular weight of the grafted side chains continue to grow until the reaction is terminated, leading perhaps to the high molecular weight narrow distribution fraction.
Copolymerization of butadiene and styrene by initiation with alkyllithium and alkali metal tert‐butoxides
Authors: Wofford C. F. , Hsieh H. L. 
Published: April 2003

AbstractCombinations of the various alkali metal tert‐butoxides with organolithium initiators give homogeneous copolymers of butadiene and styrene. The unprecedented flexibility of this initiator system allowed preparation of random copolymers with various amounts of vinyl unsaturation and various degrees of randomness. The butyllithium–potassium tert‐butoxide initiator system was more efficient than phenylpotassium.
Polymerization of aromatic aldehydes. II. Cationic cyclopolymerization of phthalaldehyde
Authors: Aso Chuji , Tagami Sanae , Kunitake Toyoki 
Published: April 2003

AbstractPhthalaldehyde was found to undergo cyclopolymerization with ease by several cationic catalysts and by γ‐ray irradiation. The polymer was composed entirely of the dioxyphthalan unit, as confirmed by infrared spectroscopy and ready decomposition to monomer. The enhanced polymerizability of phthalaldehyde as compared with other aromatic aldehydes was explained in terms of the intermediate‐type or, preferably, concerted propagation scheme. The conversion reached a saturation value of 87% in about 1 hr in methylene chloride at −78°C, indicating an equilibrium polymerization. The ceiling temperature of the polymerization was −43°C, as estimated from the relation between the saturation yield and polymerization temperature. The enthalpy and entropy of propagation were −5.3 kcal/mole and −23.0 eu, respectively. Since the molecular weight of the polymer was proportional to conversion, the propagating chain end was considered to be “living” in this system. The rate constant for propagation was calculated to be 0.18 1/mole‐sec in methylene chloride at −78°C with BF3OEt2 catalyst.
γ‐Ray‐induced copolymerization of ethylene and vinyl chloride in liquid carbon dioxide
Authors: Hagiwara Miyuki , Miura Takeshi , Kagiya Tsutomu 
Published: April 2003

AbstractThe γ‐ray‐induced copolymerization of ethylene and vinyl chloride with the use of liquid carbon dioxide as a solvent was studied under a total pressure of 400 kg/cm2, with a dose rate of 2.5 × 104 rad/hr at 30°C. A rubberlike, sticky polymer is obtained when the molar concentration of vinyl chloride is less than 30% in the monomer mixture, and the polymer is a white powder at higher concentrations of vinyl chloride. Infrared, x‐ray, and differential thermal analyses confirm that the polymerization products are noncrystalline, true random copolymers. The rate of copolymerization decreases markedly when a small amount of vinyl chloride is added to ethylene monomer. In the range of vinyl chloride concentration higher than 5%, however, the rate and the molecular weight of copolymer increase with increasing concentration of vinyl chloride. It has been concluded from kinetic considerations based on these results that the rate of initiation increases proportionally with the concentration of vinyl chloride. Further, the growing chain radicals are shown to be deactivated by the cross‐termination reaction between the radicals with terminal unit of ethylene and vinyl chloride, and no transfer reaction occurs.
Epoxide polymers: Synthesis, stereochemistry, structure, and mechanism
Authors: Vandenberg E. J. 
Published: April 2003

AbstractEpoxide polymerization studies have yielded technically important catalysts and polymers. The polymers were studied by cleaving them with Group IA organometallics to monomer, dimer, and trimer glycol fragments. The identification of these glycol fragments has established that the crystalline polymers from the cis‐ and trans‐2,3‐epoxybutanes are respectively racemic and meso‐diisotactic and that the amorphous polymer from the cis‐oxide is disyndiotactic. These studies also showed that the amorphous fraction from propylene oxide polymerization with coordination catalysts contains substantial head‐to‐head and tail‐to‐tail segments. This work has led to a much better understanding of the mechanism of epoxide polymerization. These facts were established: (1) epoxides polymerize with inversion of configuration of the ring‐opening carbon atom; (2) monosubstituted epoxides polymerize largely by attack on the primary carbon with a coordination catalyst; and (3) two or more metal atoms must be involved in the coordination polymerization of epoxides.