bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR observations of drawn polymers. IX. Chain mobilization and water mobility in nylon 66
Authors: Olf H. G. , Peterlin A. 
Published: April 2003

AbstractWide‐line NMR spectra of nylon 66 fibers have been obtained at different alignment angles between the fiber axis and the magnetic field, at varying water contents (H2O and D2O), and at different temperatures. At 28°C the spectrum of the dry fibers consists of a nearly structureless broad line. At water regains of 1.4% by weight (dry basis) and higher a sharp line appears which originates from highly mobile water molecules. The width of this line decreases with increasing water content, implying an increase of water mobility. Moreover, the width is a function of the alignment angle; this shows that the water is not reorienting isotropically owing to specific water‐polymer interaction. The amount of mobile water is always smaller than the amount of water absorbed. At water contents close to saturation, a mobile polymer line appears with a width intermediate between the broad line (immobile polymer) and the sharp water line. This line, most clearly observed at an alignment angle of 0°, is due to a shift of the αa process to lower temperatures in the presence of water. A similar line is observed in the dry fibers at 120°C. It is shown that the αa process decreases the NMR second moment only slightly. The shift of the high temperature drop in second moment to lower temperatures in the presence of water is therefore interpreted as due to a shift of the αc process, and not of the αa process, to lower temperatures.
Growth and morphology of single crystals of linear aliphatic polyesters
Authors: Kanamoto T. , Tanaka K. , Nagai H. 
Published: April 2003

AbstractIn order to elucidate the relations between morphological habits and chemical structure of polymers, poly(ethylene sebacate), poly(hexamethylene sebacate) and poly(decamethylene 1,16‐hexadecanedicarboxylate) were crystallized from dilute solutions in n‐hexanol, isoamyl acetate etc., and were studied with the electron microscopy and x‐ray diffraction. The crystal structure of these polyesters are tentatively determined. Morphological “regularity” and “simplicity” of the single crystals are correlated with the chemical structure of the polymers. The crystallization conditions under which “regular” and “simple” single crystals are obtained are relaxed with increase of methylene sequence length in chemical repeat unit. The Bragg extinction bands in the single crystals of poly(hexamethylene sebacate) and poly(decamethylene 1,16‐hexadecanedicarboxylate) suggest nonplanar nature of these crystals. The molecular chains in the poly(ethylene sebacate) single crystals are inclined from the normal of the basal plane; the fold surface corresponds to the (001) plane.
Fractionation of linear polyethylene during bulk crystallization under high pressure
Authors: Kardos J. L. , Li H.‐M. , Huckshold K. A. 
Published: April 2003

AbstractTwo linear polyethylene fractions (Mη, 11,260 and 100,000) and mixtures of these fractions have been isothermally crystallized from the melt under pressures up to 3000 atm. Characterization of individually crystallized fractions with transmission electron microscopy indicates that pressure can be used to produce a crystallite whose thickness is a measure of the chain length within it. Although the high molecular weight fraction yields spherulites containing individually varying lamellae thicknesses, the maximum thickness of each lamella is a measure of the chain length within it. Both electron micrographs and differential thermal analysis results show that crystallization of homogeneous mixtures of the high and low molecular weight fractions under high pressure results in a distinct fractionation and segregation according to molecular weight.
Statistical thermodynamics of networks at large deformations
Authors: Smith K. J. 
Published: April 2003

AbstractA general theory of non‐Gaussian elasticity is presented for real polymeric chains having fixed bond angles and restricted internal rotations. The theory contains the displacement‐vector distribution given by Nagai, and the Flory‐Wall‐Hermans procedure is used for the calculation of network properties. Whereas the treatment is valid for all types of polymer chains, it is not totally satisfactory from a practical standpoint because of a slow series convergence if the chains are stiff. It is best utilized for flexible polymers under conditions of light crosslinking. Detailed network behavior is investigated only for polyethylene type chains having uncorrelated internal rotations. In this instance the fractional contribution fe/f of the internal energy of the total force f is found to be a function of elongation at high degress of stretching. It may decrease, or increase, depending upon the sign of fe/f at low elongations. Furthermore, the variation of fe/f with elongation is independent of the fixed bond angle of the chain backbone. Stress–strain behavior and energy–strain behavior are in opposition, i.e., when the non‐Gaussian contribution to the stress is greatest, it is the least for the ratio fe/f, and vice versa. The presence of correlated internal rotations would not be expected to greatly alter these general conclusions.
Oxidation of polypropylene in benzene solution
Authors: Van Sickle Dale E. 
Published: April 2003

AbstractThe oxidation of both amorphous and crystalline polypropylene in benzene solution was studied at 100–130°C. tert‐Butyl peroxide was used as an initiator. The kinetic behavior of the amorphous and crystalline forms differs slightly; the oxidation rate of the amorphous type is slower for a given polymer and initiator concentration. The oxidation rate of solutions of the crystalline form can be simply described by the expression: R0 = 1.87 × 1013 exp {−29,000/RT} [t‐Bu2O2]0.58[polypropylene]0.73, mole/l.‐min. Product analyses of the oxidized solutions are incomplete, but the results do show that only ∼40% of the absorbed oxygen is present as hydroperoxide. Further, much of the hydroperoxide is present in low molecular weight polar fragments which are acetone‐soluble. These results show that oxidized polypropylene cannot be regarded simply as “polypropylene hydroperoxide” with repeating hydroperoxide groups attached to the polymer chain in 1,3,5… (tertiary) positions.
Polymerization of complexed monomers. II. Alternating copolymers of indene with methyl acrylate and methyl methacrylate
Authors: Hecht Jeffrey K. , Dix Don T. 
Published: April 2003

AbstractIndene has been copolymerized with polar monomers in the presence of ethylaluminum sesquichloride. The polymers have molecular weights in the 7,000–10,000 range and soften at temperatures above 150°C. The NMR spectra of the copolymers are discussed with reference to polymer structures and chain conformations. Indene is comparable to cyclopentene in reactivity in copolymerizations with methyl acrylate but is much more reactive than cyclopentene toward methyl methacrylate.
Photodegradation of urethane model systems
Authors: Beachell H. C. , Chang I. L. 
Published: April 2003

AbstractThe photo‐oxidation products of ethyl N‐phenyl‐carbamate (EPC) were identified as ethyl o‐aminobenzoate, ethyl p‐aminobenzoate, aniline, water, carbon dioxide, azo compounds, and other colored material. The ethylaminobenzoates, formed by intramolecular rearrangement of EPC, were precursors of the azo and colored products. Diethyl 4,4′‐azobenzenedicarboxylate was produced by the ultraviolet irradiation of the precursor, ethyl p‐aminobenzoate, in the presence of oxygen. Benzophenone and anthraquinone, as the triplet donors, sensitized the photo‐oxidation of EPC. Quantum yields of photolysis of EPC were measured. The photorearrangement reaction was inhibited by the polar solvent (ethanol). The presence of metal ions and phenyl isocyanate in EPC showed no effect on the oxygen consumption rate.
Effect of chelation on the polycondensation of monomers having an active ester group
Authors: Ogata N. , Sanui K. , Ikari T. , Okouchi K. 
Published: April 2003

AbstractVarious amino acid esters and dicarboxylic acid esters having a β‐thioether group have been synthesized and their polycondensation with diamine was found to occur at room temperature to form polyamide thioether. The effect of solvents or chelating agents on their polycondensation reaction was investigated. Metal acetylacetonates or inorganic salts had a great influence on the rate of the polycondensation reaction, and the catalytic activity of metal acetylacetonates M(AcAc)n or inorganic salts decreased in the following order: Mg(AcAc)2≫Th(AcAc)4>Cu(AcAc)2>Li(AcAc)>None>Zr(AcAc)4, MgCl2·6H2O>CuCl2·.2H2O>ZnCl2>MgCl2>None. It was also found that the amount of polyamide thioether was dependent on solvents or the presence of chelating agents because the polycondensation rate and the apparent equilibrium between ring and chain structures were both greatly influenced by solvents or chelating agents.These effects of solvents or chelating agent on the polycondensation may be attributable to formation of a complex with the thioether group which enhances the reactivity of ester.
Electron paramagnetic resonance study of thermal‐oxidative degradation of nylon 6
Authors: Chiang T. C. , Sibilia J. P. 
Published: April 2003

AbstractElectron paramagnetic resonance studies were conducted on thermally degraded nylon 6 polymers. A nitroxide radical was observed from nonterminated and amineterminated nylon 6 samples heat‐treated in the persence of air. The nitroxide concentration in the latter was about twice that of the former under the same conditions. The nitroxide radical was not observed in acid‐terminated nylon 6 samples. A mechanism of nitroxide radical formation was proposed based on the oxidation of secondary amines. A one‐line EPR signal was also observed from nonterminated, amine‐terminated, and acid‐terminated nylon 6 samples heated in the presence of air. This singlet signal was attributed to conjugated systems with unpaired electrons.
Theoretical reaction kinetics of reversible polymerization
Authors: Huang Ching‐Rong , Wang Huei‐Hsiung 
Published: April 2003

AbstractThe kinetics of reversible polymerization of a polymer system without transfer and termination reactions is investigated theoretically. An analytic solution is obtained that enables one to predict the variation of monomer concentration with respect to time in a closed system. When the polymer system reaches equilibrium, three different relationships are derived between the equilibrium monomer concentration and the ceiling temperature under different conditions. The classical relationship by Dainton and Ivin is a special case of the three derived cases.
Degradation of chlorinated polyethylene. I. Effect of antimony oxide on the rate of dehydrochlorination
Authors: Abu‐Isa Ismat A. 
Published: April 2003

AbstractThe degradation of two chlorinated polyethylene compounds CPE 25 (45% chlorine) and CPE 16 (36% chlorine) was studied by following their rates of dehydrochlorination at two temperatures, 150°C and 180°C in pure nitrogen and pure oxygen atmospheres. Studies on the powdered polymers showed that the dehydrochlorination rate of CPE 25 is about fourteen times faster than that of CPE 16 in nitrogen atmospheres and only three to four times faster in oxygen. The molded polymers gave a lower rate of dehydrochlorination than when in the powdered form. This effect is attributed to diffusion factors. The antimony oxide brought about an induction period in the dehydrochlorination reaction during which only a small amount of HCl is evolved, followed by a very fast rate of dehydrochlorination both in oxygen and nitrogen atmospheres. The duration of the induction period increases with increase in the Sb2O3 concentration, but is followed by an accelerated HCl loss which is faster when Sb2O3 concentration is higher. This work provides supporting evidence that SbCl3 was formed and lost during degradation. Mechanisms of dehydrochlorination are suggested for the reaction in the case of pure chlorinated polyethylene and for the polymer containing antimony oxide.
Synthesis of some vinyl‐substituted pyrylium salts and their intermediates
Authors: Petropoulos Constantine C. 
Published: April 2003

AbstractThe preparation of vinyl‐substituted pyrylium salts and their intermediates is described. These monomers and intermediates have been derived from syntheses based onp‐2‐hydroxyethoxybenzaldehyde and 4‐methoxypyrylium salts. Treatment of the hydroxybenzaldehyde with acetophenone gives a hydroxypyrylium intermediate which, when methacrylated, gives a pyrylium methacrylate. Methacrylation of the hydroxy‐benzyldehyde followed by condensation with methylpyrylium salts gives styryl‐pyrylium methacrylates. Displacement of the methoxy group in methoxypyrylium salts with ethanolamine derivatives followed by methacrylation yields a series of aminopyrylium methacrylates. The preparation of a divinylpyrylium urethane and a pyrylium‐type copolymer is also described.
Radical polymerization of methyl methacrylate in the presence of isotactic poly(methyl methacrylate)
Authors: Buter R. , Tan Y. Y. , Challa G. 
Published: April 2003

AbstractMethyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed isotactic PMMA (iMA) with about 90% isotactic triads and different M̄v's, viz., iMA‐1: 7.2 × 105; iMA‐2, 5.0 × 105; iMA‐3, 3.5 × 105; iMA‐4, 1.25 × 105; and iMA‐5, 1.15 × 105. The MMA:iMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. It is found that the M̄v of the polymer formed ran parallel to the M̄v of iMA. In all cases syndiotactic PMMA (s‐PMMA) was produced which associated with the isotactic substrate to form acetone‐insoluble stereocomplexes. The syndiotactic polymers probably consist of long syndiotactic and heterotactic sequences. The syndiotacticity decreased with conversion and was generally highest in the presence of iMA‐1. With iMA‐1 even the formation of some additional i‐PMMA (in the acetone‐insolubles) was indicated, especially in the later stages of the polymerization. Characterization of the acetone‐soluble fractions indicated that i,s‐stereoblock polymers were also produced, of which the persistence ratios ρ increased with the M̄v of iMA. From these results it is concluded that this reaction differs from the conventional radical polymerization and can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i‐ and s‐PMMA to associate. The formation of i,s‐stereoblock polymers and additional i‐PMMA indicates that s‐PMMA in its turn can also act as a polymer matrix.
Synthesis of polyimides by photoaddition of bismaleimides to alkylbenzenes
Authors: Kardush Nabil , Stevens Malcolm P. 
Published: April 2003

AbstractBismaleimides undergo successive 2 + 2 and 2 + 4 cycloadditions to alkylbenzenes to form polyimides. For the series toluene, ethylbenzene, cumene, tert‐butylbenzene, highest yields of polymer are obtained with toluene and tert‐butylbenzene with three different bismaleimides. This is explained in terms of inductive and steric effects of the alkyl substituents.
Polymerization of vinyl monomers with chlorosilane compounds and metal halides
Authors: Minoura Yuji , Toshima Hiroyuki 
Published: April 2003

AbstractIt was found that styrene was polymerized with chlorosilane compounds and metal halides in 1,2‐dichloroethane. The rate of polymerization of styrene was proportional to the concentration of styrene, trimethylchlorosilane, and mercuric chloride. The overall activation energy of polymerization was −2.9 kcal/mole. The polymer yield decreased markedly on addition of ether into the polymerization system, and the infrared spectrum showed evidence of silicone fragments in the polymer. From the results, it was considered that the polymerization was initiated by a siliconium cation. The formation of a complex between trimethylchlorosilane and metal halides (i.e., ferric chloride) was confirmed by the continuous variation method of ultraviolet and visible absorption spectra.
Equilibrium anionic polymerization of the isopropenyl monomers containing aromatic heterocycles
Authors: Yagi Kohji , Miyazaki Tatsuru , Okitsu Hiroyuki , Toda Fujio , Iwakura Yoshio 
Published: April 2003

AbstractThe anionic polymerization of three monomers, 2‐isopropenyl‐4,5‐dimethyloxazole(I), 2‐isopropenylthiazole(II), and 2‐isopropenylpyridine(III), was studied in THF. These monomers produced red‐colored living polymers on addition of sodium naphthalene or living α‐methylstyrene tetramer as an initiator. It was observed that a considerable amount of monomer remained in the respective living polymer–monomer system, indicating that an equilibrium between the polymer and the monomer existed as in the case of α‐methylstyrene. At lower temperatures, the conversion of the monomer to the polymer increased. The equilibrium monomer concentrations [Me] were determined at different temperatures, and the heats (ΔH) and the entropies (ΔS°) of polymerization were obtained by plotting In(1/[Me]) against 1/T as ΔH = −9.4, −6.8, and −6.2 kcal/mole, ΔS°S = −22.9, −16.5, and −16.6, eu for I, II, and III, respectively.
Synthesis of polysulfonates and polysulfonamides from 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene‐5,9‐disulfonyl chloride
Authors: Wilson John C. , Hamb F. Lynn 
Published: April 2003

AbstractTreatment of 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene with chlorosulfonic acid leads to the formation of the mono‐, di‐ and tetrasulfonyl chloride derivatives. The 5 and 9 positions of 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene were found to be most active toward electrophilic sulfonation. Polysufonates and polysulfonamides prepared from 7,7‐dimethyl‐7H‐dibenzo[c,h]xanthene‐5,9‐disulfonyl chloride exhibit glass transition temperatures above 200°C and show little weight loss at temperatures to 350°C.
Asymmetric selective copolymerization of propylene oxide with d‐camphoric acid anhydride
Authors: Yamaguchi Hidemasa , Nagasawa Masayuki , Minoura Yuji 
Published: April 2003

AbstractThe ring‐opening copolymerization of propylene oxide with d‐camphoric acid anhydride [α]D −3.4° was carried out with diethylzinc and triethylamine as catalysts. It was found that the products were alternating copolymers which were optically active. The optical rotatory dispersion curves were found to fit a simple Drude equation having a λc value of 201 mμ. The specific rotation increased with increasing intrinsic viscosity of the product. The propylene oxide recovered from the polymerization system was optically active. Its specific rotation increased with increasing polymerization time. It is thought that the asymmetric selective copolymerization of propylene oxide is caused by the influence of the optically active camphoryl group of the polymer end.
Hydrogen‐transfer polymerization of acrylamide and methacrylamide with optically active basic catalysts
Authors: Yamaguchi Koichi , Minoura Yuji 
Published: April 2003

AbstractHydrogen‐transfer polymerization of acrylamide and Methacrylamide with an optically active amyl alcoholate or n‐amyl alcoholate (sodium, calcium, magnesium, barium, and aluminum) was investigated to 100°C in toluene. The initiation ability of the metal ion of the initiator increased in the order, sodium > barium > calcium > magnesium > aluminum. The optically active polymer was obtained by the polymerization of methacrylamide with an optically active alcoholate (barium or calcium), but was not obtained by the other alcoholates and by the polymerization of acrylamide with the optically active alcoholate. The specific rotation of the optically active polymer obtained was about +1.1° ∼ +1.3°. The hydrolyzed product of the optically active polymer was α‐methyl β‐alanine having optical activity (+1.0°). The initiation mechanisms of the polymerization were thought to be the dehydrogenation of the monomer of the negative ion and the Michael addition reaction with the monomer of the negative ion and the catalyst, and it was confirmed that the optically active polymer was prepared by intermolecular hydrogen transfer mechanism. In the polymerization of MMA with menthol barium and borneol barium as the optically active catalyst, the optically active polymer was obtained.
Branching of anionic poly(methyl methacrylate)
Authors: Trekoval J. , Kratochvíl P. 
Published: April 2003

AbstractA viscometric determination of the degree of branching γ, of poly(methyl methacrylate) obtained by anionic polymerization proved the reaction of the growing center of poly(methyl methacrylate) with the ester group of another polymer molecule, accompanied by the formation of a trifunctional branch point. This reaction occurs if the solution polymerization of methyl methacrylate is initiated: (1) with butyllithium at −78°C only on attaining 100% conversion and after a long time or at +20°C immediately after the polymerization has set in; (2) with lithium tert‐butoxide at +20°C after a long time. The degree of branching of poly(methyl methacrylates) obtained under similar conditions in the presence of tetrahydrofuran reaches higher values than for polymers prepared in toluene. The tacticity of polymers does not affect the experimentally determined γ values.
Anionic polymerization of caprolactam. XLIII. Relationship between osmometric molecular weight, viscosity, and endgroups of a polymer
Authors: Goebel C. V. , Čefelín P. , Stehlíček J. , Šebenda J. 
Published: April 2003

AbstractFor unfractionated anionic polymers, the following relationship between the osmometric molecular weight and intrinsic viscosity is valid: M̄n = 13200[η]1.115 (cresol), or M̄n = 13000[η]1.021 (93.8% H2SO4). A comparison of the osmometric and viscometric data with the number of endgroups of a polymer confirmed the finding that under certain conditions, moderately branched molecules can be formed; the above parameters depend on the type of the activator used.
Polybenzodipyrroloquinoxalines
Authors: Janović Z. , Higgins Jerry 
Published: April 2003

AbstractThree polymers have been prepared by the condensation of benzo[1,2‐b;5,4‐b ′]‐dipyrrolo‐2,3,4,5‐tetraone (I) with 1,2,4,5‐tetraaminobenzene (II), 3,3 ′‐diaminobenzidine (III), and 3,3 ′,4,4 ′‐tetraaminodiphenyl ether (IV) in polyphosphoric acid (PPA) solution. The polymer structures were substantiated by comparison of their infrared and ultraviolet spectra with spectra of the model compounds and elemental analysis. The polymers had inherent viscosities of 0.86‐0.90 (H2SO4) and thermal stabilities of 460°C and up to 700°C in air and nitrogen atmospheres, respectively.
Fluorine‐containing poly(vinyl alcohol): A helix or a random coil
Authors: Haas Howard C. , MacDonald Ruby L. 
Published: April 2003

AbstractSubstitution of several mole per cent of the hydroxyl groups of poly(vinyl alcohol) by fluorine results in marked changes in polymer properties. These fluoro poly(vinyl alcohols) (PVAF) form thermally reversible gels in water at low polymer concentrations. In solution, a helical conformation or a random coil containing helical sequences is more in accord with the experimental observations than the random coil structure of poly(vinyl alcohol). This helical hypothesis is supported by high heats of crosslinking of the aqueous thermally reversible gels, the difficult solubility of PVAF in H2O, the insolubility of the PVAF–iodine complex under conditions where the PVA–iodine complex remains soluble, the temperature‐independent high value for the Huggins k ′ slope constant, the greater stability of the PVAF–iodine complex, the shear dependence of the solution viscosity and our inability to form thermally reversible gels by the introduction of fluorine into other water‐soluble polymers which are capable of hydrogen bond formation. Infrared dichroism and deuteration measurements do not differentiate between PVA and PVAF. If this conclusion is correct, PVAF is the first vinyl polymer of which we are aware that maintains a helical conformation in solution.