bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferrocene‐terephthalaldehyde copolymerizations and analogous polyferrocenylene crosslinking processes
Authors: Bilow N. , Rosenberg H. 
Published: April 2003

AbstractFerrocene has been copolymerized with terephthalaldehyde and 1,1′‐ferrocenedicarboxaldehyde to produce thermosetting polymers suitable for the fabrication of reinforced structural composites. Both the terephthalaldehyde and 1,1′‐ferrocenedicarboxaldehyde were also found to be useful curing agents for polyferrocenylenes formed by other methods. Glass‐reinforced laminates have been fabricated from both types of copolymers and from both types of cured polyferrocenylenes. Laminate flexural strengths have been in the range of 35 000 psi.
The polymerization of pyromellitic dianhydride with diphenylmethane diisocyanate
Authors: Meyers R. A. 
Published: April 2003

AbstractA novel polyimide forming reaction is reported. Pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt‐fusion conditions to give polydiphenylmethanepyromellitimide (II) and carbon dioxide. Polymer II was characterized by inherent viscosity, infrared spectrum, and thermogravimetric analysis. An intermediate Polymer I was isolated which appeared to contain seven‐membered rings in the backbone. It is postulated that these rings eliminate carbon dioxide to form polyimide II.
γ‐ray‐induced copolymerization of carbon monoxide with cyclic hydrocarbons
Authors: Kagiya Tsutomu , Kondo Masatsune , Fukui Kenichi , Yokota Hisao 
Published: April 2003

AbstractThe γ‐ray‐induced copolymerization of carbon monoxide with saturated or unsaturated cyclic hydrocarbons, such as cyclohexane, cyclohexene, 4‐vinyl‐1‐cyclohexene, and cyclopentadiene was studied at 30°C. Resinous or powdery polymers were obtained in the copolymerization. The results of elementary analysis, infrared spectra, and NMR spectra showed that copolymers containing ketone and ring structures were produced. The copolymers were confirmed to be partially crystalline by the x‐ray diffraction diagram. Further, the influence of the addition of ethylenimine on the copolymerization of carbon monoxide with cyclohexane or cyclohexene was examined. A powdery polymer formed in the copolymerization was concluded to be a terpolymer of carbon monoxide with cyclic hydrocarbon and ethylenimine. On the basis of the experimental results, a mechanism of the copolymerization is proposed.
Thermal polymerization of levoglucosan
Authors: Houminer Yoram , Patai Saul 
Published: April 2003

AbstractThe uncatalyzed polymerization of neat levoglucosan (1,6‐anhydro‐β‐D‐glucopyranose) was studied at 190–210°C under argon, and the course of the reaction was followed by analyzing samples at various reaction times; the residual levoglucosan was determined by GLC, and the optical rotation of the mixture was also measured. The plots of percentage reaction versus time were sigmoid, indicating the occurrence of an autocatalytic reaction. A. kinetic equation of the form, dA/dt = k2[A1]2 + k1[At] ([A0] − [At]), where [A0] and [At] denote the concentrations of levoglucosan at zero time and time t, was found to fit the results. A reaction scheme is proposed, consisting of a slower dimerization (k2) followed by a faster reaction between levoglucosan and the dimers and other oligomers formed (k1). This scheme results from the mechanistic assumption that axial hydroxyl groups in the unchanged levoglucosan are less reactive than equatorial hydroxyl groups present only in the oligomers, while the highest reactivity is ascribed to the primary hydroxyl at C6, again only present in the oligomers. The relation between the mechanisms of the reactions occurring and the structure of the product are discussed.
Polythiazolines
Authors: Iwakura Yoshio , Kurita Keisuke , Hayano Fusakazu 
Published: April 2003

AbstractPolythioureas having pendant hydroxyl groups were prepared by the polyaddition reaction of bisaminoalcohols and diisothiocyanates. The polythioureas had inherent viscosities in the range of 0.22–1.08 dl/g and gave transparent films by solution casting. These polythioureas were converted to polythiazolines by treatment with poly(phosphoric acid) or to poly(thiazoline–oxazolines) by treatment with a mixture of poly(phosphoric acid) and a polar solvent.
Radiation‐induced polymerization of styrene in the presence ofn‐dibutyl disulfide
Authors: Miller L. A. , Stannett V. 
Published: April 2003

AbstractThe γ‐radiation‐induced polymerization of pure styrene and styrene‐n‐dibutyl disulfide mixtures has been studied at a number of temperatures and dose rates. Up to 0.04 Mrad/hr the rates were proportional to the square root of the dose rate. By measuring the rates at a number of disulfide concentrations and at three different dose rates, the relative rates of radical formation were determined by kinetic analysis. Considerable energy transfer from the styrene to the disulfide was found. The relative contributions of energy transfer and radical formation were separated by using the kinetic scheme of Nikitina and Bagdasaryan. Values of 8.5 and 3.1 were found for the relative rates of radical production and energy transfer, respectively. This leads to aG(radical) value of 3.1 forn‐dibutyl disulfide. With azobisisobutyronitrile as the initiator, the chain transfer constant to the disulfide was determined at 55°C. Finally, the sulfur content of a number of the polymers were determined, an average of two sulfur atoms per polymer chain was found. In general, the rate of polymerization was found to increase in the presence of dibutyl disulfide.
Acid‐catalyzed polycondensation of bisdiazoalkanes
Authors: Koninck L. De , Smets G. 
Published: April 2003

AbstractDimerization reactions of diphenyldiazomethane have been applied to the polycondensation of six bisdiazobenzyl arylenes, namely 1,4‐ and 1,3‐bis(α‐diazobenzyl)‐benzenes C6H5CN2(C6H4)CN2C6H5; 1,4‐ and 1,3‐bis(α‐diazo‐p‐methoxybenzyl)‐benzenes, p,p′‐MeOC6H4CN2(C6H4)CN2C6H4OMe; 4,4′‐bis(α‐diazobenzyl)‐diphenylmethane, C6H5CN2(C6H4CH2C6H4)CN2C6H5; and 4,4′‐bis(α‐diazobenyl)‐diphenyl ether, C6H5CN2(C6H4OC6H4)CN2C6H5. Depending on the nature of the catalysts, polyene‐arylenes (C(Ar)C(Ar)C6H4)n, and polyazine‐arylenes, (C(Ar)NNC(Ar)C6H4)n, can be obtained selectively by acid‐catalyzed decomposition of these bisdiazoalkanes at room temperature. With perchloric acid and with arylsulfonic acids in strong polar media, polyene‐arylenes are formed. On the other hand, boron trifluoride and arylsulfonic acids in solvents of low dielectric constant afford polyazine‐arylenes. Less selective is the thermal decomposition at 75°C in toluene solution; it gives a polymer containing about 90% azine and 10% olefinic groups. All these polymers are soluble in common solvents. Their molecular weight vary from 3 200 to 5 000, i.e., X̄n from 12 to 20. The polyene‐arylenes are very stable and decompose only around 500°C; the polyazine‐arylenes are less stable and decompose around 370°C by losing nitrogen.
Determination of degree of crystallinity of drawn polymers by means of density measurements
Authors: Fischer E. W. , Goddar H. , Schmidt G. F. 
Published: April 2003

AbstractThe well known procedure of determining the degree of crystallinity by means of measuring the density presupposes the knowledge of both the densities ρc and ρa of the crystalline and of the noncrystalline regions. By combination of small‐angle and wide‐angle x‐ray scattering and of density measurements it can be shown that this method is not justified in the case of drawn polyethylene if the values of ρc and ρa known from isotropic material are used. Both ρc and ρa depend considerably on annealing and drawing conditions. In addition the effective density ρc* of the more densely packed phase in a two‐phase structure is much lower than the value ρc calculated from the positions of the x‐ray reflections due to a large number of lattice defects. This conclusion is based on the results of three independent sets of experiments: determination of the mean‐square fluctuation of density 〈η2〉 by means of x‐ray small‐angle scattering; x‐ray wide‐angle measurements of the positions of the crystal reflections and of the halo arising from the noncrystalline regions; and comparison of densities and long periods of samples treated at various annealing temperatures.
Determination of branching distribution by concurrent GPC and sedimentation velocity experiments
Authors: Tung L. H. 
Published: April 2003

AbstractA method of determining the distribution of branching in polydisperse polymer samples is proposed. This method uses data from concurrent gel permeation chromatography and sedimentation‐velocity experiments. Tedious fractionation, which must precede other methods of determining long‐chain branching, is eliminated. An example of use of the method on the data of a sample of styrene–divinylbenzene copolymer is given.
Effect of annealing conditions on the structure of drawn nylon 66 yarns
Authors: Buchanan D. R. , Dumbleton J. H. 
Published: April 2003

AbstractDifferences in structural parameters, shrinkage, and retractive forces have been compared for nylon 66 tire yarns annealed at several temperatures in silicone oil and in air. It is found that significantly different structural changes occur for oil‐annealing and air‐annealing. Retractive forces measured in hot oil are characterized by a high initial force, followed by a rapid decay and a second, more gradual, increase which is also followed by a decay at sufficiently high temperatures. In heated air, the first, short‐term, retractive force is absent. It is postulated that these differences are due to the different rates of heat transfer at gas–solid and at liquid–solid interfaces, and that rapid heat transfer (as in the case of oil‐annealing) promotes two mechanisms of molecular change which are characterized by different degrees of structural parameter change, and by different amounts of shrinkage.
Formation of spherulities in polyamides. IV. Even–odd polyamides and poly(ω‐aminocarboxylic acids)
Authors: Magill J. H. 
Published: April 2003

AbstractIsothermal and nonisothermal spherulitic crystallization in even–odd and poly(ω‐aminocarboxylic acids) has been studied for a range of fusion conditions and solidification temperatures. The variety of spherulites so formed are classified mainly by optical microscopy. It is found that polyamides with similar types of repeat units generally exhibit similar morphological features under corresponding crystallization conditions. The basic patterns are illustrated in the text. Changes in spherulitic birefringence with temperature are also discussed. In some cases, at temperatures not far below the polymer melting point, platelet‐like crystalline aggregates are formed in thin film preparations. These platelets exhibit properties characteristic of single crystals.
Resolution of GPC columns
Authors: Smith W. V. , Feldman G. A. 
Published: April 2003

AbstractA resolution index for gel‐permeation chromatograph (GPC) columns is defined by the relation log (RI) = αW, where RI is the resolution index, α is the slope of the calibration curve of logarithm of molecular weight against peak position for narrow polymer fractions, and W is the width of the GPC curves for narrow fractions. This resolution index is calculated approximately for several GPC columns individually and in series combinations by using data obtained on narrow fractions of polystyrene. The index increases with number of columns and with flow rate over a limited range of flow rate, does not vary much with solvent, and does not correlate well with plate count obtained with low molecular weight molecules. It is believed that the resolution index provides an improved indication of the performance of GPC columns.
Rheo‐optical studies of high polymers. XIV. Study of the deformation mechanism in polymer blends of polypropylene with ethylene–propylene rubber
Authors: Onogi Shigeharu , Asada Tadahiro , Tanaka Akira 
Published: April 2003

AbstractTo clarify the deformation mechanism in polyblends of polypropylene with ethylene–propylene rubber having different compositions, simultaneous measurements of the infrared dichroism with stress and strain under a constant rate of strain of 1.64%/min have been carried out. The orientation function of the crystallographic c axis of polypropylene in the blends has been obtained as a function of strain ranging from 0 to 20% and of polypropylene content ranging from 0.3 to 1.0. These results have been compared with the temperature dependences of the dynamic Young's modulus and of the loss modulus, as well as of stress–strain curves for the same blends. The modulus data analyzed by Kerner's equation reveal the occurrence of phase inversion at polypropylene contents higher than about 0.5, and this is supported by the infrared dichroism data. The strong effect of quenching on crystalline structure and mechanical properties of pure polypropylene has also been elucidated.
Crystallite orientation in stretched polychloroprene networks. II
Authors: Krigbaum W. R. , Dawkins J. V. , Via G. H. 
Published: April 2003

AbstractThe orientation of crystallites grown isothermally in several drawn trans‐polychloroprene networks is studied as a function of crystallization temperature tx, degree of crystallinity ω, and elongation ratio α. The orientation distribution is particularly simple for this polymer since the crystallographic c axis (chain axis) orients preferentially along the stretching direction, while a and b are randomly arranged about c. Hence the parameter cos2 χc adequately characterizes the distribution, where χc is the angle between the c axis and the fiber axis, and the average is taken over all crystallites. A treatment due to Krigbaum and Roe is utilized to obtain values of v (the number of statistical segments comprising the crystallization nucleus of critical size) through comparison of the average orientation of crystallites and amorphous statistical segments. The behavior observed falls into two categories. First, if the initial amorphous network is well oriented, 〈cos2 χc〉 is independent of crystallinity during both crystallization and melting, and v varies with tz (or the degree of supercooling) as predicted by nucleation theory. If different networks are to have the same crystallite orientation distribution, they must not only be crystallized at the same supercooling, but must also have the same distribution of amorphous segment orientations. Both the relative elongation and the network crosslink density affect the latter distribution. Next, we consider the second category. If the initial amorphous orientation is poor, 〈cos2 χc〉 decreases linearly during crystallization and increases along approximately the same path during melting. Further, 〈cos2 χc〉 for a given tz yields v values which are too large. These two behaviors can be explained if, in the former case, nucleation involves the best oriented statistical segments of all network chains, while in the latter there is a selection according to the chain displacement vector orientation. Thus, if the amorphous orientation is poor, both the orientation and thermodynamic stability of the crystallites decreases with further crystallization. If this decreased stability is reflected in shorter fold lengths, the reversible variation of long period spacing with temperature reported earlier for an oriented polychloroprene network can also be explained as a preferential melting process.
Gel‐permeation chromatography of polydimethylsiloxanes
Authors: Kendrick T. C. 
Published: April 2003

AbstractThe molecular weight distributions of three polydimethylsiloxanes (PDMS) have been determined by gel‐permeation chromatography (GPC), by gas–liquid chromatography (GLC), and by precipitation fractionation. The GPC data are greatly improved by correction for band spreading. For a high molecular weight polymer the corrected distribution agrees closely with the theoretical molecular weight distribution calculated from polymerization kinetics.
Mechanical relaxation in polypropylene as a function of polymorphism and degree of lamella orientation
Authors: Crissman J. M. 
Published: April 2003

AbstractMechanical relaxation data as a function of temperature (ca. 1 Hz) have been obtained for several samples of isotactic polypropylene crystallized from the melt, which exhibit both α and β forms as well as varying degrees of lamella orientation. The samples ranged in morphology from an unoriented sample showing only the α form to one highly oriented having approximately 90 per cent the β form. Results for the logarithmic decrement Δ and loss modulus G″ are that the low temperature (ca. −75°C) and glass temperature (ca. 0°C) relaxations show little or no sensitivity to orientation in the α form, but that the intensity of the two processes is different in the α form than in the β form for samples of nearly equal overall per cent crystallinity. In both Δ and G″, the low‐temperature peak decreased and the glass temperature peak increased in intensity as the fraction of β form crystallinity present increased. Data for the high‐temperature relaxation (ca. 80°C) indicate a dependence upon orientation and/or crystal form in addition to a dependence upon per cent crystallinity.
Polymerization of cyclic imino ethers. VI. X‐ray study of some polyaziridines
Authors: Litt Morton , Rahl Forrest , Roldan Luis G. 
Published: April 2003

AbstractPolymers of poly(N‐acyl and N‐aroyl aziridines) were studied by x‐ray diffraction. All the crystalline polymers studied have a triclinic unit cell with two monomer units per unit cell. The a and c (fiber direction) parameters (4.9 and 6.5 A, respectively) are essentially the same for all the cells. The b parameter for the N‐acyl polymers, however, increases steadily by a factor of 2 A per methylene group added to the lateral chains. The densities calculated for the unit cells are in agreement with the experimental values obtained. The most probable structure is one in which the molecules assume a planar configuration with the main chain not fully extended. The lateral groups are tilted from the c axis by an angle of 54° in a parallel configuration and alternate on each side of the main chain. This permits these lateral groups to assume packing similar to that of polyethylene. A brief description of the techniques used in this interpretation is included.
Steric exclusion and lateral diffusion in gel‐permeation chromatography
Authors: Yau Wallace W. 
Published: April 2003

AbstractThe peak separation in gel‐permeation chromatography (GPC) is attributed to the contributions of the steric exclusion and the lateral diffusion processes. The advantage of using the distribution coefficient KGPC of the solute molecule in interpreting the GPC separation mechanism is assessed. The physical significance of KGPC and its relation to measurable GPC parameters are examined in detail. A simple mixing experiment for determining the exclusion effect is described. The results of this experiment, as well as those of the flow rate study, show that the exclusion effect plays the primary role in GPC peak separation. For a column packed with Bio‐Rad porous glass of 200 Å designation, the diffusion effect does not contribute significantly to peak separation. However, for the case of a Waters Associates column packed with polystyrene gel of 104 Å designation, both the exclusion and the diffusion effects are shown to be important. A diffusion theory which includes the concept of a restricted diffusion coefficient is proposed to interpret the diffusion effect observed in the polystyrene gel column. The results of the theoretical calculation are found to agree with the observed flow rate dependence of the calibration curve.
Structure of poly(N‐butyl isocyanate)
Authors: Shmueli U. , Traub W. , Rosenheck K. 
Published: April 2003

AbstractAn x‐ray study of poly(N‐butyl isocyanate) (PBIC) was undertaken with the aim of providing the structural information required for the calculation of its ultraviolet absorption spectrum. Well defined diffraction patterns are obtained from powder samples and oriented films of the polymer cast from cyclohexane solution. All the reflections can be satisfactorily indexed in terms of a pseudo‐hexagonal unit cell with a = 13.3 Å and c = 15.4 Å. This indexing and the intensity distribution lead to the conclusion that PBIC has a helical structure with a translation of 1.94 Å and a rotation of 135° per monomeric unit (i.e., the c axis corresponds to 8 units in 3 helical turns). In the absence of single‐crystal data on closely similar model compounds, a range of possible bond lengths and angles was assumed. The atomic coordinates of the chromophoric group of PBIC were then computed using the restrictions imposed by the helical parameters. From an investigation of all the assumed range of bond lengths and angles, a few closely similar structures having no unacceptably short van der Waals contacts were found. A comparison of calculated and measured densities indicates that there are two molecules per unit cell. Construction of space‐filling models of PBIC supports this conclusion.
Light scattering and intrinsic viscosity investigation of polymethyl‐3, 3, 3‐trifluoropropylsiloxamer
Authors: Buch Robert R. , Klimisch Helen M. , Johannson O. K. 
Published: April 2003

AbstractSolution parameters for the polymer poly‐γ‐trifluoro‐propylmethylsiloxamer has been determined in cyclohexyl acetate, methyl hexanoate, and ethyl acetate. Interpretation of data follows the theory of Fox and Flory. In contrast to poly‐dimethylsiloxane, an increased steric hindrance to rotation about the siloxane bond occurs as evidenced by the characteristic ratio of root‐mean‐square end to end dimensions, (r02/r0f2)1/2, found to be 1.90 and 1.96 at 25.0 and 72.8°C, respectively. This increase is considered to be primarily due to nearest‐neighbor interaction of the polar substituent on the silicon atom. The relation, [η]θ ∝ M1/2, was observed to hold for this polymer system. The hydrodynamic model appropriate for the polymer is a random coil considerably more permeable to solvent flow than is generally reported for linear polymers. The universal parameter ϕ was determined to be 1.5 × 1021. The effect of temperature on polymer configuration is indicated to be negligible.
Temperature dependence of secondary crystallization in linear polyethylene
Authors: Schultz J. M. , Scott R. D. 
Published: April 2003

AbstractA specimen of linear polyethylene was subjected to isothermal secondary crystallization at a series of temperatures below the primary isothermal crystallization temperature, the melting and primary crystallization stages being held constant throughout the investigation. Dilatometric measurements exhibit an S–character at low values of undercooling Tp − Ts, where Tp and Ts are, respectively, the primary and secondary crystallization temperatures; at larger undercoolings, however, an initial very rapid crystallization is followed by a very slow stage. When corrected for thermal contraction of the polymer, the net degree of secondary transformation is seen to peak at a temperature in the range 109–113°C. The S‐character of the isotherms and the peaked temperature variation of degree of transformation lead to the conclusion that a large portion of the secondary crystallization consists of the nucleation and growth of the new crystallites. Johnson‐Mehl‐Avrami analysis leads to a model of heterogeneous nucleation within the remaining amorphous zones, followed by one‐dimensional, diffusion‐controlled growth.
Chain folding in oriented poly(ethylene terephthalate)
Authors: Dumbleton J. H. 
Published: April 2003

AbstractDrawn poly(ethylene terephthalate), PET, yarns have been heated for 1 min in silicone oil. The resulting samples were studied by x‐ray diffraction and mechanical properties were measured. The results suggest that drawn PET consists of highly extended molecules essentially parallel to one another, with few folds present. On heating, chain folding occurs. This model is very similar to that proposed by Dismore and Statton for drawn nylon 66 yarns.