bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionic thermal current study of the α′ process in poly(hexamethylene adipamide)
Authors: Chatain D. , Gautier P. , Lacabanne C. 
Published: April 2003

AbstractThe ionic thermoconductivity (ITC) method has been used to study the α′ transition in the polyamide \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \hbox{--}\rlap{--} [NH(CH}_{\rm 2} )_6 {\rm NH}\hbox{---} \rm CO(CH_2 )_4 {\rm CO\hbox{--}\rlap{--} ]}_{{\rm x}} $\end{document} (nylon 66). Depending on the thermal history of the sample, the maximum of the thermocurrent peak attributed to the α′ relaxation is found somewhere between ca. 45°C and ca. 66°C; on one heating, it shifts to higher temperatures. The high sensitivity and resolving power of the ITC method permit resolution of this peak into four elementary “pure” activated processes, with constant activation energies in the relevant temperature range. Each of the four corresponding relaxation times follows an Arrhenius law, with a well‐defined characteristic temperature T0 = 83°C at which all these relaxation times are equal. When this last result is interpreted in the light of Eyring's or Bauer's theory, it gives a linear relation between “apparent” activation entropy and activation enthalpy of the elementary processes. The characteristic temperature T0 is independent of the thermal history of the sample, and the temperature shift of the thermocurrent maximum can be interpreted by the observed variation of the relative intensities of the elementary processes, without modification of their other characteristic features.
Lamellar thickening in polyethylene single crystals annealed under low and high pressure
Authors: Roe Ryong‐Joon , Gieniewski C. , Vadimsky R. G. 
Published: April 2003

AbstractSingle crystals of linear polyethylene, prepared from a dilute xylene solution, were annealed below their melting temperature under atmospheric and 6 kbar pressure. In order to preserve the identity of the single crystals, they were suspended in an inert solvent medium, silicone oil and ethanol, during annealing. Examination of the annealed crystals under an electron microscope revealed development of numerous reorganization centers consisting of a central, elongated hole surrounded by a raised edge. Characteristics of these holes, especially their location and orientation, were interpreted in terms of the molecular packing that existed prior to the annealing and the mechanism of molecular reorganization that occurred during the annealing. The effect of high pressure was primarily to flatten out the crystals and to increase the number of reorganization centers, but the height of the raised edges remained about the same irrespective of the applied pressure. The present study also showed examples pointing to the importance of differentiating the annealing behavior of monolayer crystals from that of multilayer crystals.
Stress relaxation upon cessation of steady flow and the overshoot effect of polymer solutions
Authors: Stratton Robert A. , Butcher Allan F. 
Published: April 2003

AbstractThe basis for obtaining the steady‐state compliance from stress relaxation upon cessation of steady flow (SRUCSF) data is derived. Measurements on three polymer solutions of differing molecular weight, polydispersity, and degree of entanglement coupling show good agreement between results from SRUCSF and creep‐recovery experiments in both linear and nonlinear viscoelastic regions. The stress overshoot phenomenon is interpreted in terms of a change in entanglement spacing upon imposition of a shearing field. The phenomenon is analyzed in terms of a relaxation time for re‐entanglement, which is found to be much longer than the relaxation time of the shear stress upon cessation of steady flow.
Morphology of uniaxially oriented poly(ethylene terephthalate)
Authors: Mocherla K. K. , Bell J. P. 
Published: April 2003

AbstractThe morphological character of uniaxially oriented poly(ethylene terephthalate) (PET) films was investigated as a function of draw ratio. Dynamic mechanical, infrared, and crystallite‐size measurements were made on the samples. In addition, selective degradation experiments and molecular weight determinations were employed. The dynamic mechanical measurements indicated a sharp decrease in irregular folds for draw ratios of 3.0 and higher, which also coincided with the essentially complete disappearence of regular folds (from the 988 cm−1band in the infrared spectra) in unannealed samples. Infrared studies of drawn samples annealed under different conditions gave evidence in support of a structure in which the chains are stretched out. Apparent crystallite‐size measurements showed a sudden increase in length of the crystals in the direction of the draw beyond a draw ratio of 3.0. Molecular weight measurements showed a large increase in average chain length in the residue after selective degradation of amorphous material and folds; undrawn and slightly drawn samples gave a much lowerMn. Based on these observations, it is postulated that for higher draw ratios and present drawing conditions, the crystals are of the straight chain type, somewhat similar to the fringed‐micelle crystal concept.
Determination of copolymer composition by Raman spectroscopy
Authors: Boerio F. J. , Yuann J. K. 
Published: April 2003

AbstractThe application of laser‐Raman spectroscopy to the analysis of copolymers of glycidyl methacrylate (GMA) with methyl methacrylate (MMA) and styrene is discussed. For both copolymer systems the line near 1451 cm−1, assigned to the methylene bending mode, was found to be a useful reference. Lines characteristic of each monomer were identified. The intensities of these lines were found to be linearly related to the composition of the copolymers when normalized against the 1451 cm−1 reference. The line near 1730 cm−1, assigned to the carbonyl stretching mode, was also found to be a useful reference for the copolymers of methyl methacrylate and glycidyl methacrylate.
Vapor sorption by filled/reinforced resins. I. General behavior and interpretation
Authors: Clark‐Monks Colin , Ellis Bryan 
Published: April 2003

AbstractThe sorption behavior of particulate‐filled resin composites is discussed and related to several different models. A thermodynamic analysis of the sorption is presented in the form of a cycle for the changes in Gibbs free energy. From such an analysis it is possible to set up a scale of relative adhesion between filler and resin matrix. It is shown that the scale depends on the sorbate, but use of this scale will rate the adhesion between resin and filler in the correct relative order.
Molecular energetics of the epitaxial crystallization of polyethylene on alkali halide substrates
Authors: Mauritz K. A. , Baer Eric , Hopfinger A. J. 
Published: April 2003

AbstractA series of energy calculations have been carried out in order to describe the epitaxial crystallization of polyethylene from solution in terms of molecular interactions. The total energy has been computed as the sum of electrostatic, dispersion, and repulsion contributions. The potential energy associated with a section of a planar‐zigzag polyethylene chain has been determined for various orientations and positions above three different planar alkali halide substrates. Inspection of the energy surfaces as a function of the spatial degrees of freedom reveals that the minimum energy orientation of the chain is that for which it is parallel to the substrate [(001) cleavage plane] and aligned in the 〈110〉 direction on the surface, a result in accordance with available experimental evidence. Specifically, the chain preference is to position itself along rows of positive ions, whereas alignment along rows of negative charge appears energetically unfavorable. The mode of chain orientation is virtually independent of lattice matching criteria. Dispersionrepulsive forces have been found to be most sensitive to orientation and greater in magnitude than the electrostatic forces.
Inorganic coordination polymers. XIV. Chromium(III) phosphinate perfluorocarboxylate polymers
Authors: Nannelli Piero , Gillman H. D. 
Published: April 2003

AbstractA series of polymers, {Cr(OH)(OPRR′O)[OOC(CF2)nCF(CF3)2]}x has been prepared and studied. The polymers with R = R′ = C6H5 are soluble in CCl2FCClF2, whereas those with R = CH3 and R′ = C6H5 and with R = R′ = C8H17 are insoluble in all solvents. Attempts to prepare similar materials without hydroxyl groups gave the polymers {Cr(OH)r(OPRR′O)p[OOC(CF2)nCF(CF3)2]q}x with 0 < r < 1. The latter polymers are much more tractable than the former; however they are also less thermally stable. The perfluoro‐carboxylate groups in these materials can either be chelating or bridging, depending on the other ligands present.
Polymerization of vinyl acetate retarded by 4‐methyl‐2,6‐di‐tert‐butylphenol: Kinetic and ESR studies
Authors: Parnell R. D. , Russell K. E. 
Published: April 2003

Abstract4‐Methyl‐2,6‐di‐tert‐butylphenol strongly retards the free radical polymerization of vinyl acetate initiated by azobisisobutyronitrile. The chain transfer constant, estimated from rate data, is 0.020 ± 0.004 at 35°C and does not vary significantly with temperature. Molecular weight data lead to transfer constants of 0.023, 0.020, and 0.024 at 35, 45, and 55°C, respectively. A mean kinetic isotope effect of 9.8 ± 1.0 is observed for the phenol deuterated at the OH group, showing that the main attack of poly(vinyl acetate) radicals on the phenol involves hydrogen abstraction from this group. The activation energy for hydrogen abstraction is estimated to be 7.8 kcal/mole, and the rate constant at 50°C is 160 ± 40 1./mole‐sec. The stationary concentration of 4‐methyl‐2,6‐di‐tert‐butylphenoxyl in the polymerization mixture is proportional to the phenol concentration and is independent of the initiator concentration, as shown by electron spin resonance studies. Cross termination of poly(vinyl acetate) and phenoxy radicals occurs to a greater extent than mutual termination of these radicals. The rate constant for cross termination is close to 1 × 108 1./mole‐sec at 50°C; the activation energy for cross termination is 2.9 ± 1.3 kcal/mole.
Photopolymerization of methyl methacrylate with the use of iodine as the photoinitiator
Authors: Ghosh Premamoy , Banerjee Amar Nath 
Published: April 2003

AbstractKinetics of photopolymerization of MMA at 40°C with the use of iodine as the photoinitiator was studied. At low range of iodine concentration (< 0.0004M), the rate of polymerization was proportional to square root of iodine concentration and the monomer exponent was 2.5, while at a higher range of iodine concentration, (0.0005–0.002M) the initiator exponent and monomer exponent were zero and 3.6–3.8 (i.e., close to 4), respectively. The chain‐transfer constant of iodine at 40°C was found to be 6.0. Polymerization was found to be largely inhibited in the presence of relatively high concentrations of iodine (> 0.005M) and also in presence of hydroquinone. Kinetic and other data indicate a radical mechanism of polymerization involving complexation of monomer molecules with iodine prior to radical generation, and termination is believed to take place bimolecularly at low iodine concentrations and unimolecularly, involving reaction with iodine, at high iodine concentrations (initiator termination).
Synthesis and characterization of phenylated pyrazino‐benzimidazophenanthroline polymers
Authors: Kovar Robert F. , Arnold F. E. 
Published: April 2003

AbstractNovel phenylated quinoxaline tetraamines have been prepared and polymerized with 1,4,5,8‐naphthalenetetracarboxylic acid in polyphosphoric acid solution. The resulting BBB‐type polymers with pendant phenyl groups along the polymer backbone are soluble in m‐cresol. The polymers, with inherent viscosities ranging from 0.3 to 0.6 dl/g in sulfuric acid, exhibited thermal stabilities near 500°C under nitrogen and near 400°C in air.
Cationic copolymerization of phenyl propenyl ethers
Authors: Yamamoto Kenji , Higashimura Toshinobu 
Published: April 2003

AbstractRing‐substituted phenyl propenyl ethers were found to form homopolymers without any rearrangement by metal halides. Phenyl propenyl ethers were less reactive than the corresponding phenyl vinyl ethers in cationic polymerization. In order to study the electronic effect of a substituent on the reactivity, cis‐p‐Cl,p‐CH3, and p‐CH3O‐phenyl propenyl ethers were copolymerized with phenyl propenyl ether in methylene chloride at −78°C with stannic chloride–trichloroacetic acid, and their 1H‐ and 13C‐NMR spectra were measured. The reaction constant ρ against Hammett σp was −2.1. The cis‐phenyl propenyl ethers were slightly more reactive than the corresponding trans isomers. On the other hand, an o‐methyl group decreased the reactivity of phenyl propenyl ether. The low reactivity of o‐methyl phenyl propenyl ether was attributed to the steric hindrance between the propagating carbocation and the monomer.
Polymers from intermediates obtained from hydrogen cyanide
Authors: MacDonald Robert N. , Cairncross Allan , Sieja J. B. , Sharkey W. H. 
Published: April 2003

AbstractThe recent demonstration of an easy synthesis of diiminosuccinonitrile (DISN) from hydrogen cyanide and cyanogen, the reduction of DISN to diaminomaleonitrile (DAMN), and the use of these compounds to form difunctional heterocycles has made several new polyamide intermediates accessible. The 1‐ and 2‐methyl‐1,2,3‐triazole‐4,5‐dicarbonyl chlorides have been polymerized interfacially to form high‐melting polyamides of good heat stability. Interfacial polymerization of 1‐methylimidazole‐4,5‐dicarbonyl chloride and trans‐2,5‐dimethylpiperazine has given a polyamide that is water‐soluble. The 2,6‐ and 2,3‐pyrazinedicarbonyl chlorides have been similarly converted to high‐melting polyamides. 2,6‐Dicyano‐3,5‐dipiperazinylpyrazine has been prepared from tetracyanopyrazine and piperazine and reacted with toluene diisocyanate to form a strong, stiff polyurea. Polyamides were also made from 2,3‐diaminoquinoxaline, 1,4,5,6‐tetrahydro‐5,6‐dioxo‐2,3‐pyrazinedicarbonitrile, and DAMN.
Organometallic polymers. XXIX. Synthesis and characterization of ferrocene‐containing siloxane polymers from bis(dimethylamino)silane–disilanol condensation
Authors: Patterson William J. , McManus Samuel P. , Pittman Charles U. 
Published: April 2003

AbstractA new monomer, 1,1′‐bis(dimethylaminodimethylsilyl)ferrocene, was synthesized by two routes and polymerized with three aryl disilanols: dihydroxydiphenylsilane, 1,4‐bis(hydroxydimethylsilyl)benzene, and 4,4′‐bis(hydroxydimethylsilyl)biphenyl, yielding three different polysiloxanes. Melt polymerizations carried out at 1 torr pressure and 100°C resulted in the highest molecular weight polymers. Intramolecular cyclization competed with intermolecular chain extension in polymerization of the bis(aminosilane) with dihydroxydiphenylsilane, resulting in isolation of a bridged derivative, 1,3,5‐trisila‐2,4‐dioxa‐1,1,5,5‐tetramethyl‐3,3‐diphenyl[5]ferrocenophane. Cyclization did not compete significantly during the formation of polymers from this bisaminosilane and the two remaining diols, as evidenced by higher yields and greater molecular weights. These polymers could be cast as tough flexible films, and fibers could be drawn from their melts. TGA and DSC data showed the polymer formed from 1,1′‐bis(dimethylaminodimethylsilyl)ferrocene and 1,4‐bis(hydroxydimethylsilyl)benzene to be at least as thermally stable as an arylene siloxane polymer which differed from the ferrocenylsiloxane structure only in the replacement of the ferrocene moiety with a p‐substituted phenylene linkage. The ferrocene‐containing polymers were generally hydrolytically stable under conditions of refluxing THF–H2O(10 : 1) for 1 hr. The polymer‐forming reaction was found to follow second‐order kinetics, and the specific rate constants for formation of two of the polymers were measured.
Synthesis and characterization of isomeric polyesters based on sebacic acid and hexanediols
Authors: O'Malley James J. , Stauffer Walter J. 
Published: April 2003

AbstractIsomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6‐hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a Tg of −62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2‐methyl‐2‐ethyl‐1,3‐propanediol and 2,5‐hexanediol were amorphous tacky fluids with glass temperatures of −69 and −66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6‐diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point.
Copolymerization of acrylonitrile. III. Copolymerization with α‐cyanocinnamamide
Authors: Liebersohn Aharon , Kohn David H. 
Published: April 2003

AbstractAcrylonitrile was copolymerized in solution with α‐cyanocinnamamide up to low conversions. The conventional scheme of copolymerization fitted this copolymer. The basic properties, such as solubility, viscosity, and thermal behavior, of the copolymer prepared in bulk and in solution were determined.
Cationic polymerization of styrene by acetyl perchlorate: Molecular weight distribution of polystyrene and nature of the propagating species
Authors: Higashimura Toshinobu , Kishiro Osamu 
Published: April 2003

AbstractTo clarify the nature of the propagating species in cationic polymerization of styrene catalyzed by acetyl perchlorate, the molecular weight distribution of the polymer was investigated under various conditions. The molecular weight distribution curve for the polymer obtained in methylene chloride at 0°C showed a double peak phenomenon. This suggests that two or more kinds of propagating species participate simultaneously in the propagation reaction. The weight fraction W(H) of the polymer corresponding to the higher molecular weight peak increased with increasing polarity of the solvent. W(H) decreased when the concentration of the ionic species was increased either by an increase of the catalyst concentration or by the addition of the common salt such as tetra‐n‐butylammonium perchlorate. On the other hand, the position of the peak in the molecular weight distribution curve was independent of polymerization conditions. It was concluded that the higher molecular weight part of the polymer was produced under conditions for conductive to dissociation of the propagating species and the less dissociated propagating species was responsible for the lower molecular weight part of the polymer.
Isothermal crosslinking studies on polyquinoxalines by dynamic mechanical methods
Authors: Augl Joseph M. , Duffy James V. , Wentworth Stanley E. 
Published: April 2003

AbstractTorsional braid analysis was used to investigate the crosslinking behavior of linear quinoxaline polymers with and without reactive side groups. The kinetic parameter followed was the glass transition temperature during isothermal exposure in an inert atmosphere. With high molecular weight polyamide‐quinoxaline copolymers (PPAQ), an initial decrease in Tg was observed during heat exposure which was followed by a subsequent increase in Tg. This was attributed to simultaneous chain scission and crosslinking reactions. Since the effect of random chain scission on the initial change in Tg of the highest molecular weight polymer samples is much stronger than on low molecular weight analogues, a Tg minimum was observed only on the highest molecular weight polymers. Because of the complexity of the reactions occurring one must consider the activation energies obtained from the Arrhenius plots as “apparent” activation energies. No attempt was made to elucidate the mechanisms of these reactions. It has been shown that isothermal heat exposure of high‐temperature aromatic polymers in an inert atmosphere leads to crosslinking. In general, however, linear polymers that have reactive side groups such as methyl or carboxyphenyl groups along the polymer chain crosslink more rapidly than the analogs without these groups.
New routes for copolymerization of carbon monoxide with styrene or vinyl chloride and photodegradation of these copolymers in solutions
Authors: Kawai Wasaburo , Ichihashi Taichi 
Published: April 2003

AbstractNew routes for copolymerization of carbon monoxide with styrene or vinyl chloride were found by emulsion polymerization (nonionic or ionic emulsifier). These procedures yielded copolymers containing carbonyl groups even at high conversion. These carbonyl‐containing polyketones were photoirradiated in solvent. In carbon monoxide—styrene copolymer of high molecular weight, the viscosity change produced by photoirradiation was especially remarkable, while in carbon monoxide—vinyl chloride copolymer no pronounced change in viscosity was observed, even at high contents of carbonyl group.
Anionic polymerization of 2,2,5,5‐tetramethyl‐1‐oxa‐2,5‐disilacyclopentane
Authors: Suryanarayanan B. , Peace B. W. , Mayhan K. G. 
Published: April 2003

AbstractIn the first of a two‐part series, a study has been made of the anionic polymerization of a five‐membered cyclocarbosiloxane, 2,2,5,5‐tetramethyl‐1‐oxa‐2,5‐disilacyclopentane. The polymerization was initiated by lithium n‐butyldiphenylsilanolate in the presence of tetrahydrofuran. The chemical shifts of the protons of the cyclic monomer and the polymer were found to be different, and therefore the rate of polymerization was obtained in an NMR spectrometer. The effects of varying the concentrations of THF, initiator, and water upon the rate of polymerization and upon the molecular weight and the molecular weight distribution were investigated. At a constant concentration of monomer and initiator, the rate of polymerization increased when the THF concentration was increased. At a constant concentration of monomer and THF the rate of polymerization reached a constant value when the initiator concentration was varied. The molecular weight and the molecular weight distribution were dependent upon the initiator to water ratio, whereas water concentration had little effect on the rate of polymerization. Essentially monodispersed polymers were obtained when the concentration of initiator was in large excess to that of water or vice versa. A bimodal distribution in molecular weight was obtained when the concentration of initiator was approximately equal to that of water. The apparent activation energy of polymerization was 12.7 kcal/mole.
Crystallite orientation effects in the 720/730 cm−1 doublet of transcrystalline polyethylene
Authors: Luongo J. P. 
Published: April 2003

AbstractTranscrystalline films of polyethylene were studied by polarized infrared spectroscopy with varying angles of incidence. The average orientation of the unit cells in the transcrystalline structure was shown to be such that the a axes were predominantly parallel to the surface of the films, and the b axes were predominantly perpendicular to the surface.