bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR observations of drawn polymers. VII. Nylon 66 fibers
Authors: Olf Heinz G. , Peterlin A. 
Published: April 2003

AbstractWide‐line NMR spectra have been obtained on an oriented sample of drawn nylon 66 fibers at temperatures between −196°C and 200°C and at alignment angles between the fiber axis and the magnetic field of 0°, 45°, and 90°. At −196°C, 20°C, and 180°C, the complete angle dependence of the NMR spectrum has been measured. The second moments of these spectra have been compared to theoretical second moments calculated for various models of chain segmental motion in an attempt to elucidate the mechanisms involved in the low‐temperature segmental motion (γ process) and the high‐temperature segmental motion (αc process). In agreement with earlier suggestions, the present results indicate that the γ process consists of segmental motion in noncrystalline regions. The overall decrease in second moment caused by the γ process is consistent with a model in which all noncrystalline segments rotate around axes nearly fixed in space. Furthermore, this decrease shows a pronounced dependence on the alignment angle. It is believed that this is due to tie molecules which become highly oriented along the fiber axis during drawing; their axes of rotation will therefore be nearly parallel to the fiber axis. The segments in noncrystalline entities such as chain folds and chain ends are less well oriented along the fiber axis and make an essentially isotropic contribution to the second moment decrease. The second moment at 180°C indicates the presence of considerable motion in the crystalline regions, and this motion is denoted the αc process. The second moment Sc of the crystalline regions is strongly dependent on the alignment angle, the predominant feature being a relatively high value of the second moment when the fiber axis is directed parallel to the magnetic field. This is in qualitative, but not quantitative, agreement with the motional model recently advanced by McMahon, which assumes full rotation of the chains around their axes. Excellent quantitative agreement with experiment has been obtained by superimposition of rotational oscillation around the chain axis of amplitude roughtly 50°, and torsion of the chains with neighboring CH2 groups oscillating around the CC bond with a relative amplitude of about 40°. A model in which the chains perform rotational jumps of 60° between two equilibrium sites has also been considered (60° flip‐flop motion). A distinction between this model and rotational oscillation has not been possible.
Single crystals of amylose V complexes. III. Crystals with 81 helical configuration
Authors: Yamashita Yuhiko , Monobe Kazuo 
Published: April 2003

AbstractSingle crystals of amylose V complexes with the 81 helical configuration can be obtained from aqueous solutions of amylose by using α‐naphthol as a complexing agent. Morphological observations suggest that the differences in crystallization behavior among the α‐naphthol complex and other complexes with alcohols are due to differences in solubility of the complexes in water. Electron diffraction studies indicate a two‐dimensional tetragonal unit cell with a = b = 22.9 Å. It is deduced that the space group providing a satisfactory arrangement of two helices is one of the enantiomorphs P41212 and P43212. From x‐ray diffraction it was found that the c axis spacing of the α‐naphthol complex is equivalent to that in 61 and 71 helical amylose crystals. Consequently, the geometry of the helical configuration requires an integral number of glucose residues per turn. The true helical diameters of the n‐butanol, isopropanol, and α‐naphthol complexes were calculated from experimental data. The ratio was 6:7:8 and indicated that the helix of the α‐naphthol complex has eight glucose residues per turn. The diversity of helical configurations in V amylose crystals is discussed.
Vibrational analysis of poly(vinylidene fluoride)
Authors: Boerio F. J. , Koenig J. L. 
Published: April 2003

AbstractA vibrational analysis has been carried out for the two crystalline forms of poly(vinylidene fluoride) (PVF2). The Raman spectrum of the planar form of PVF2 is also reported. The band assignments are made on the basis of the spectral properties including the infrared dichroism and Raman intensities. A force field is derived based on a force constant refinement procedure utilizing the frequency data for both crystal forms.
Salt rejection by polymer membranes in reverse osmosis. I. Nonionic polymers
Authors: Yasuda H. , Lamaze C. E. 
Published: April 2003

AbstractAn attempt is made to analyze the relationship between salt rejection and water flux of nonionic polymer membranes in reverse osmosis on the basis of the movement of water in the membranes. The salt rejection Rs is a consequence of transport depletion of salt in relation to water flux. The transport depletion can be quantitatively expressed through knowledge of the mode of water transport and by application of free‐volume theory to membrane transport phenomena. Water permeation can be characterized by a parameter ω = RTK1/P1v1, K1 denoting hydraulic permeability, P1 diffusive water permeability, v1 the molar volume of water. Thus polymer membranes can be classified in three categories: ω = 1 (diffusion membranes); ω > 1 (diffusion‐flow membranes); and ω ≫ 1 (flow membranes). Salt rejection Rs can be expressed in terms of P1, the diffusive salt permeability P2, and the effective pressure (Δp − Δπ):

Experimental results obtained with various hydrophilic polymers are presented as the dependence of Rs on the logarithm of water flux. Good agreement was found between the experimental data and the calculated curve. Excessive swelling of membranes results in bulk flow of water (high ω) with coupled transport of salt. Hence the salt rejection decreases quickly as water flux in creases beyond a threshold value above which water flux can be characterized as bulk flow.
Sorption properties of polypropylene
Authors: Ochiai Hiroshi , Gekko Kunihiko , Yamamura Hitoshi 
Published: April 2003

AbstractThe sorption properties of atactic polypropylene (APP) and isotactic polypropylene (IPP) were studied by equilibrium sorption of various organic solvents. The variation of the Flory‐Huggins interaction parameter χ for the APP‐CCl4 system at 25°C was expressed as a function of the volume fraction v2 of polymer by the relation: x = 0.113 exp {1.879 v2}. The average molecular weight Mc of the polymer chains between successive crystallites for IPP subjected to different thermal treatments was calculated to be 250 to 350 by the equation of Flory and Rehner. From the variation of Mc with solvent concentration, we estimated the number fraction of polymer chains actually contributing to elastic deformation. The clustering function for solvent in the polymer calculated by the method of Zimm and Lundberg decreased linearly from a positive value to −1 with increasing solvent concentration. Clustering of solvent molecules was found to occur more easily in APP than in IPP.
Catalysis of ionic reactions by polyelectrolytes. IV. Quenching of the quinine cation fluorescence by Fe++, Ag+, and Br− in solutions of poly(vinylsulfonic acid)
Authors: Taha Issam A. , Morawetz Herbert 
Published: April 2003

AbstractThe fluorescence quenching of the doubly charged quinine cation by Fe++, Ag+, and Br− was studied in the presence and absence of polyvinylsulfonate (PVS). The quenching by cationic species was greatly enhanced by PVS at low polyion concentrations; at higher concentrations of PVS, the fluorescence intensity increased owing to displacement of the quinine cations from the polyion domain. Quenching of quinine fluorescence by Br− was repressed by PVS. Interpretation of the data with the use of Fe++ as the quenching agent led to “effective concentrations” of counterions in the polyion domain similar to those calculated from the catalysis of the redox reaction of Co(NH3)5Cl++ with Fe++. This may indicate that the reagent ions are not rigidly bound to the polyion chain, since such binding would affect differently processes with high and low activation energies. The Stern‐Volmer constant for self‐quenching of the quinine fluorescence can also be obtained from fluorescence intensity data in PVS solution.
Crystal orientation in a semicrystalline polymer in relation to deformation of spherulites
Authors: Nomura Shunji , Asanuma Akira , Suehiro Shoji , Kawai Hiromichi 
Published: April 2003

AbstractA mathematical development interrelating the orientation distribution functions of three kinds of orientation units for a polymer spherulite (i.e., a crystal lamella, a crystallite, and a given reciprocal lattice vector of the crystallite) is formulated on the basis of series expansions of the distribution functions in generalized spherical harmonies. Two types of uniaxial deformation models of a polyethylene spherulite, taking account of micronecking and untwisting of crystal lamellae, and of chain tilting and untwisting of crystal lamellae, respectively, both in addition to affine deformation of the lamellae are discussed. The models are tested by comparison of the theoretical orientation distribution functions of some reciprocal lattice vectors of the crystallite with the results of x‐ray diffraction experiments.
Piezoelectricity in oriented films of poly(γ‐benzyl‐L‐glutamate)
Authors: Konaga Toshiyoshi , Fukada Eiichi 
Published: April 2003

AbstractOriented films of poly(γ‐benzyl L‐glutamate) (PBLG) were prepared by two methods. Films of PBLG cast from chloroform solutions were elongated by rolling at 70°C. A solution of PBLG in methylene bromide was placed in a magnetic field of about 7000 gauss and the solvent was slowly evaporated for a few days until an oriented film was obtained. The real and imaginary components of the complex piezoelectric strainconstant d25* = d25′ − jd25″ were determined over the temperature range from −180°C to +180°C at a frequency of 20 Hz. The constants showed dispersions at about 20°C and about 100°C, where dynamic viscoelastic dispersions were also observed. Degree of crystallinity Xc and degree of orientation IIa of crystallites were determined from x‐ray diffraction diagrams. The product XcIIα and the value of d25′ at room temperature were found to be linearly related, and both showed a maximum at an elongation ratio of 1.5 (the ratio of the final to initial length) for roll‐oriented films and at an initial solution concentration of 15% by weight for magnetically oriented films. The largest values of d25′ were approximately 2 × 10−12 and 4 × 10−12 coulomb/newton, respectively, at room temperature.
Terephthalamide‐nylon single crystals isolated from dilute solutions of hexafluoro‐2,2‐propandiol
Authors: Livingston H. K. , Gregory R. L. 
Published: April 2003

AbstractTerephthalamide nylons with two to five carbon atoms in the aliphatic portion of the chain have been crystallized from aqueous solutions of hexafluoro‐2,2‐propandiol. The 3T and 4T nylons in particular form rodlike crystals. Indications are that these are bundles of cylindrical structures about 50 nm in diameter. Electron diffraction shows the symmetry to be C2v. Films of the nylons were drawn with great difficulty. The x‐ray diffraction on the films is consistent with a monoclinic structure, though the crystal structure could not be positively established. There is some evidence for a polymer chain alignment perpendicular to the long axis of the rods.
Electron spin resonance of γ‐irradiated poly(ethylene 2,6‐naphthalene dicarboxylate)
Authors: Rogowski R. S. , Pezdirtz G. F. 
Published: April 2003

AbstractThe two types of radicals trapped in γ‐irradiated poly(ethylene 2,6‐naphthalene dicarboxylate) (PEN 2,6) have been identified by ESR as OCHCH2O (radical I) and a radical located on the naphthalene ring (radical II). The relative concentrations of radicals in the gross polymer are 10–20% radical I and 80–90% radical II. Similar trapped radicals have been identified in γ‐irradiated poly(ethylene terephthalate) (PET), a structurally related polymer which differs only in the aromatic moiety, but the relative radical concentrations are quite different. These results are discussed in relation to the radiation resistance of the two polymers.
Apparatus for instantaneously measuring ultraviolet, visible, or infrared dichroism from thin polymer during high‐speed stretching
Authors: Wilkes Garth L. , Uemura Y. , Stein Richard S. 
Published: April 2003

AbstractAn apparatus has been constructed for following changes in the dichroism of a polymer film undergoing rapid elongation. By means of a rapidly rotating mirror with evenly spaced open sectors, a beam of radiation is passed through the sample and then alternately polarized in the horizontal and vertical direction so that the horizontal and vertical absorbances may be rapidly compared in time as compared with the time of sample elongation (a few milliseconds). The apparatus utilizes reflection optics and a grating monochromator so that measurements may be made by using ultraviolet, visible, or infrared radiation. The transmitted intensity is detected by a photomultiplier or semiconductor infrared device, the output of which is amplified and displayed on an oscilloscope. A temperature‐controlled sample chamber is provided. The operation of the apparatus is illustrated by following the change in dichroism of a sample of dehydrohalogenated poly(vinyl chloride) with visible radiation during rapid extension.
Mechanism aspects of th e ring‐opening polymerization of the episulfides compared to epoxides
Authors: Vandenberg E. J. 
Published: April 2003

AbstractThe cis‐ and trans‐2‐butene episulfides polymerize with cationic catalyts differently than reported for the corresponding oxides. Where the cis‐oxide gave amorphous disyndiotactic polymer, the cis‐sulfide gives crystalline racemic diisotactic polymer since this polymer could be asymmetrically synthesized in optically active form. Also the same crystalline polymer was obtained with coordination catalysts. Where the trans‐oxide gave only crystalline, meso‐diisotactic polymer, the trans‐sulfide gives mainly amorphous polymer which, in one case, did slowly crystallize. The difference between the trans forms appears due to the longer CS bond which lowers steric hindrance and thus isomer selection in the attack of episulfide on the growing sulfonium ion to give less steroregular polymer. The difference in the cis forms may result from the sulfur atom in the last chain unit coordinating with the counterion. The greater hindrance around oxygen in the comparable oxide polymers may prevent the same mechanism from being utilized. The cationic polymerization of isobutylene sulfide gives both crystalline and amorphous polymer. NMR evidence indicates that the amorphous polymer results from substantial head‐to‐head, tail‐to‐tail polymerization, along with the expected head‐to‐tail polymerization. The same phenomenon occurs, but to a lesser extent, in cationic isobutylene oxide polymerizations. The preparation and properties of high molecular weight, head‐to‐tail isobutylene oxide and sulfide polymers from R2Mg‐NH3 coordination catalysis are described.
Comparative synthesis of oligomeric group IV polyesters
Authors: Carraher Charles E. , Dammeier Roger L. 
Published: April 2003

AbstractOligomeric group IV polyesters of the form: magnified image have been synthesized by using the interfacial technique. Polymerization rate follows the order Sn > Ge > Si as M is varied. Aliphatic‐substituted organometallic compounds exhibit higher polymerization rates than do aromatic‐substituted organometallic compounds. This may be the result of (p → d)π bonding between the vacant d orbitals of the metal and the p electrons of the phenyl rings.
Anionic polymerization of a fluorinated butadiene
Authors: Kaufman Martin H. 
Published: April 2003

Abstract1,1‐Bis(trifluoromethyl)‐1,3‐butadiene (I) is cleanly prepared in three steps. I produces an amorphous polymer by free‐radical catalysis. Crystalline poly‐I is produced by butyllithium catalysis in tetrahydrofuran at −78°C. Qualitative kinetic experiments indicate that the anionic polymerization proceeds by a “living polymer” process. An AB block copolymer may be formed by adding I to anionically propagating butadiene; however, the reverse does not occur.
Preparation of polyethylene in solution
Authors: Christman Donald L. 
Published: April 2003

AbstractPolyethylene was prepared in a homogeneous system at 120°C. Several catalytic systems were employed, all using a soluble vanadium compound. The first consisted of an alkylaluminum compound in conjunction with the vanadium compound and a “promoter.” This promoter, which is believed to act as an oxidizing agent to reactivate dead catalyst sites, was a polyhalo compound with esters of trichloroacetic acid preferred. The promoter was added continuously throughout the polymerization. Polyethylene so produced had a narrow M̄w/M̄n ratio close to the theoretical ratio of 2.0 for a single catalyst site. Up to 266 polymer chains were produced per vanadium atom. In the second system, the cocatalyst was an AlBr3(AlCl3)–(C6H5)4Sn[(C6H5)3Bi] combination. The continuous addition of a promoter such as methyl trichloroacetate was necessary, presumably to reactivate dead catalytic sites. By this procedure, yields up to 6.6 kg of polymer per millimole of vanadium and 30–60 chains per vanadium atom were achieved. The product had a narrow M̄w/M̄n ratio of 2.4 by gel‐permeation chromatography (GPC). A study of the interactions of the catalyst compounds indicated that CCl3COOR does oxidize di‐ and trivalent vanadium.
Synthesis of titanium polythioethers
Authors: Carraher Charles E. , Nordin Robert J. 
Published: April 2003

AbstractThe synthesis of polythioethers of the form magnified image was effected, where Cp denotes cyclopentadienyl. Four reaction systems were studied and evaluated. Two proved to be undesirable (the “reverse” interfacial and organic solution methods), while two proved acceptable (the “normal” interfacial and aqueous solution methods). A number of added bases were evaluated. Et3N and NaOH were found to be acceptable. Yield increases with reaction time for aqueous solution syntheses, while yield remains constant with reaction time for synthesis via the normal interfacial method.
Oxidative polymerization of aromatic hydrocarbons: A study of kinetics and mechanism
Authors: Mano Eloisa B. , Alves Luiz A. 
Published: April 2003

AbstractAromatic hydrocarbons were homopolymerized by means of an oxidative polymerization reaction with the use of the catalyst system anhydrous aluminum chloride–cupric chloride. The kinetics of the benzene homopolymerization carried out under different experimental conditions was followed by the determination of the amounts of cuprous ion and polymeric product formed in the reaction. Cuprous ion was spectrophotometrically titrated in the form of its complex with 2,2′‐biquinolyl (cuproine). The experimental results do not agree with cationic mechanism for this reaction previously proposed in the literature. Ethylbenzene was kinetically studied under the same experimental conditions. In view of the experimental evidences obtained in this work and on some literature data, a mechanism based on formation of cation‐radicals is proposed for the oxidative polymerization reaction when carried out under the studied conditions.
Cationic polymerization of α,β‐disubstituted olefins. XV. Stereospecific polymerization of butenyl ethers by cationic catalysts
Authors: Higashimura T. , Hoshino M. 
Published: April 2003

AbstractMethyl, ethyl, and isopropyl butenyl ethers, CH3CH2CHCHOR, were polymerized with homogeneous catalysts at −78°C. Toluene, methylene chloride, and nitroethane were used as solvents, and BF3O(C2H5)2 and SnCl4·CCl3CO2H were used as catalysts. The stereoregularity of the polymers were compared by x‐ray diagrams and infrared absorption ratios. The stereoregularity of polymers increased with increasing content of the trans isomer in the monomer and with increasing polarity of the solvent. In the polymerization of methyl and ethyl butenyl ethers, crystalline polymers were obtained from both the trans and cis isomers. The crystalline polymer prepared from the trans isomer and that from the cis isomer had the same steric structure. This behavior is quite different from that observed in the polymerization of propenyl ethers. It is concluded that the bulkiness of the group on the olefinic β‐carbon plays an important role in the stereospecific polymerization of α,β‐disubstituted olefins.
Theory of titration curves. VIII. A new interpretation of acid‐base titration curves for polymeric acids. The significance of the Kern‐equation parameters pKa and n
Authors: Meites Louis 
Published: April 2003

AbstractThe Kern equation, pH = pKa + n logf/(1 − f), has been widely used in interpreting the potentiometric titration curves obtained on titrating polymeric acids with bases, and various interpretations of its empirical parameters pKa and n have been advanced. Values of n similar to those generally obtained for polymeric acids are also obtained for dibasic and other monomeric polybasic acids for which the ratios of successive dissociation constants, Ki/K(i+1), exceed the corresponding statistical values by a constant factor. The dependences of n on this factor and on the basicity of the acid are described. It is argued that the traditional picture of a dissociation constant varying continuously with the fraction titrated cannot be correct, and that the data can be more properly interpreted in terms of a constant non‐statistical free‐energy contribution to the successive values of Ki/K(i+1).
Preparation and polymerization of a diisocyanate from the Diels‐Alder adduct of levopimaric acid and acrylic acid
Authors: Bingham John F. , Marvel C. S. 
Published: April 2003

AbstractStarting from tetrahydroabietic acid the model compounds tetrahydroabietoyl chloride, 2‐aminoethyltetrahydroabietate hydrochloride, and 2‐isocyanatoethyltetrahydroabietate have been prepared. Carbamate and urea derivatives of the isocyanate have been prepared. A Diels‐Alder adduct of levopimaric acid and acrylic acid has been prepared and converted to its diacid chloride. The β‐aminoethyl ester hydrochloride has been synthesized and converted to a diisocyanate which has been polymerized with poly(tetramethylene glycol) and also with p‐phenylenediamine. Dimerex resin, a technical polymerized rosin, has been similarly converted to a diisocyanate. This isocyanate has not proven to be useful as a polymer‐forming intermediate.
Polypyrazoles and polyisoxazole from polydiethynylbenzene
Authors: Bracke W. 
Published: April 2003

AbstractThe reaction of polydiethynylbenzene with hydrazine is described. The resulting polypyrazole has good tensile properties and good thermal stability. N‐Methylhydrazine and hydroxylamine react in a similar way but product properties are inferior. Polypyrazole polymers can easily be modified with acid chlorides or isocyanates.
Desorption reaction of ferric ions adsorbed on cellulosic materials by acids
Authors: Ogiwara Yoshitaka , Kubota Hitoshi 
Published: April 2003

AbstractFactors affecting the desorption reaction of ferric ions adsorbed on cellulose and oxidized poly(vinyl alcohol) fibers by acids were investigated. The desorbing effect generally increased with increasing acid concentration, treating temperature, and treating time, although the magnitude of this effect varied somewhat from one acid to another. Oxalic acid, hydrochloric acid, sulfuric acid, sulfurous acid, and phosphoric acid are examples of those acids which show large desorbing effects. Scission of the cellulose chain was also observed under the desorption conditions used for such acids. The desorption reaction may be divided into two stages, an initial fast reaction and a subsequent slow reaction; the activation energies were calculated for each reaction, and values of 7–10 kcal/mole and 5–6 kcal/mole were obtained for cellulose and oxidized poly(vinyl alcohol) fibers, respectively.