bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. I. Single crystals
Authors: Williams T. , Blundell D. J. , Keller A. , Ward I. M. 
Published: April 2003

AbstractThis paper describes the application of gel permeation chromatography to the morphology of polymer single crystals. Various types of single crystals of polyethylene were etched with fuming nitric acid, and the molecular weight distributions of the degraded fragments determined. The crystal preparations studied were monolayer crystals grown from xylene solution at 85°C and multilayer crystals grown at 84°C and 70°C. In all cases peaks in the molecular weight distribution were observed corresponding to single and double transverses of the molecular chains through the lamellae. By using the chromatograph calibration described in a previous paper, the position of these peaks were compared and correlated with previous estimates of lamellar thickness from low‐angle x‐ray measurements. The relative positions of the peaks provide information regarding the nature of the fold surface. The results are found to be consistent with a model in which the majority of the molecules are tightly folded.
Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. II. Bulk polyethylene
Authors: Williams T. , Keller A. , Ward I. M. 
Published: April 2003

AbstractPreliminary results are reported on the use of gel permeation chromatography in morphological studies of bulk polymers and fibres. Several samples of bulk isotropic and drawn polyethylene were analyzed by gel permeation chromatography following nitric acid oxidation. In all cases suitable samples showed two peaks in the molecular weight distribution, suggesting a qualitative similarity with results for single crystals. It is concluded that the present data are consistent with chain folding in bulk polymers, both in the isotropic and oriented states, with a less degree of regularity than exists in single crystals.
Extrapolation procedures for intrinsic viscosity and for Huggins constant k′
Authors: Sakai Tsukasa 
Published: April 2003

AbstractConventional extrapolation procedures for the calculation of intrinsic viscosities and the Huggins constant k′ have been critically examined. A condition which must be satisfied by the basic equation for viscosity–concentration relations of dilute solutions of nonelectrolytic polymers has been clarified. On the basis of the comparison of the curvatures for empirical equations and for the basic equation, it is proposed to use arithmetic averages of the values calculated from a Huggins plot and those from a Martin plot for good‐solvent systems, and to employ the averages of values from the former and those from a Schulz‐Blaschke plot for poor‐solvent systems as approximations to the correct values. Failure to confine approximations in the usual statistical treatment of experimental points to the given range of the variables as well as neglect of the fact that curvatures for the empirical and basic equations do not necessarily coincide are the usual sources of error in the conventional extrapolation procedures.
Shearing of oriented polyethylene and polypropylene
Authors: Robertson Richard E. , Joynson Catherine W. 
Published: April 2003

AbstractTo learn more about the out‐of‐plane deformation of polymer lamellae during drawing, we have measured the resistance to shear along various planes in uniaxially oriented polyethylene and polypropylene. Fissures parallel to the orientation axis in oriented materials always cause too small an experimental value for the resistance of crystal glide parallel to the chain axes, but a rough estimate for the resistance to crystal glide is obtained using the elastic anisotropy. Also, the results suggest that kinking can be easier than glide when glide is inhibited by tie molecules.
High‐temperature mechanical behavior of unplasticized poly(vinyl chloride)
Authors: Crugnola A. , Pegoraro M. , Danusso F. 
Published: April 2003

AbstractWe studied the high‐temperature mechanical behavior of unplasticized poly(vinyl chloride) by stress relaxation experiments covering a temperature range of 100–180°C and a time interval of 0.01–3600 sec at an elongation of 40%. The polymer was observed to respond elastomerically within these set temperature limits. The molecular basis for this behavior is linked to the partial crystalline nature of this material. The crystalline phase is postulated to be the seat of the relaxation process taking place in the rubbery response region, and evidence is presented supporting this point of view. A comparison is made between free volume variations arising from thermal expansion and those originating instead from uniaxial straining. It is also pointed out that, following linear viscoelastic theory, the viscosity is a time‐dependent quantity, and it is shown that for this polymer its variation with temperature at short times is ninefold less than the corresponding variations in its limiting value. Finally it is noted that the measured high‐temperature tensile strength corresponds to a chain bond strength approximately 1/300 of the theoretical value.
Crystallization kinetics of isotactic polystyrene. I. Spherulitic growth rate
Authors: Boon J. , Challa G. , Van Krevelen D. W. 
Published: April 2003

AbstractThe spherulitic growth rate of isotactic polystyrene has been measured in a wide range of temperature by means of a polarizing microscope provided with a hot stage. It was possible to fit the experimental data to theory by choosing a value of 75 for the constant C2 of the WLF equation. The growth rate parameters were compared with those of polyethylene and polychlorotrifluoroethylene. The slowness of crystallization of isotactic polystyrene is mainly a consequence of the lower mobility of the molecules caused by the bulky phenyl groups.
Basic gel permeation chromatography studies. III. Mathematical analysis of peak spreading
Authors: Hendrickson J. G. 
Published: April 2003

AbstractPeak spreading in gel permeation chromatography has been studied with a range of gels including those whose permeation limit corresponded to about 103, 106, 108, and 109 molecular weight polystyrene. Peak spreading conformed to the equation YV2 = YM2 + YA2 + YI2 + YD2 + YS2, where YV is the peak width of a normal chromatogram, YM is the contribution due to the true molecular weight of the sample, YA is due to peak spreading in the apparatus, YI is spreading in the interstitial volume, YD is diffusional spreading due to time spent in the gel, and YS is due to sorption. Evaluating the appropriate parts of the equation leads to measures of the true molecular weight distribution and the contribution due to diffusion into and out of the gel. The data also allowed estimates as to the diffusional spreading with small molecules. With polystyrene having 100 000 molecular weight, diffusional spreading accounts for 80% of YV,2 but with small molecules the contribution due to diffusion was not detected.
Flow birefringence of short‐chain molecules: Cellulose tricarbanilates in benzophenone
Authors: Janeschitz‐Kriegl H. , Burchard W. 
Published: April 2003

AbstractMeasurements of flow birefringence of cellulose tricarbanilates were carried out on nine fractions (0.27 × 105 < M ≤ 12 × 105) in a temperature range of 55–110°C, with benzophenone as a matching solvent (dn/dc = 0). The ratio of Maxwell constant to intrinsic viscosity, which has been found to be independent of molecular weight for the limiting case of Gaussian molecules, is successfully interpreted as a function of molecular weight in terms of the recent theory of Gotlib and Svetlov (based on the wormlike chain model of Kratky and Porod). From the measurements at 55°C a number of 36.6 monomer units per random link is deduced. This is in accord with results of small‐angle x‐ray scattering. For the extinction angle curves a clear transition is observed from rodlike to statistical molecules when the molecular weight is increased. At high molecular weights the master curves obtained for anionic polystyrenes and cellulose tricarbanilates coincide. Implications of this observation on the kinetic stiffness of the cellulose tricarbanilate chain are discussed. The intrinsic viscosity‐molecular weight relationship is considered. From a comparison with the results of the theory of Eizner and Ptitsyn it is concluded that the cellulose tricarbanilate chain must be highly solvated in benzophenone.
Normal stress effect of molten polyethylene
Authors: Sakamoto Kunisuke , Ishida Nobuhiro , Fukasawa Yoshiaki 
Published: April 2003

AbstractA brief description is given of a new parallel‐plate rheogoniometer for normal stress measurements on polymer melts as functions of the rate of shear. A wire‐resistance strain gauge is used as the pressure gauge. Measurements are reported on high‐density polyethylene. It is found that the time‐temperature superposition principle is applicable to the normal stress data as well as to shear stress in steady flow.
Microstructure of ethylene–vinyl chloride copolymers. I. Direct verification of terminal radical effects on copolymerization by a simplified NMR approach
Authors: Wilkes Charles E. , Westfahl J. C. , Backderf Richard H. 
Published: April 2003

AbstractThe sequence distributions of monomer units in a series of high‐pressure, bulk ethylene–vinyl chloride copolymers have been determined by high‐resolution NMR spectroscopy. The concentrations of EE, VV, and EV (VE) monomer pairs or diads were used with NMR‐determined compositions to calculate, in addition to the sequence distribution parameters, the reactivity ratio product for the system. Inclusion of feed data allowed the calculation of individual reactivity ratios. Well within experimental error, the reactivity ratio product (r1r2 = 0.7) determined from microstructure analysis—independent of monomer feed data—was equal to that determined by the standard Fineman‐Ross technique. Terminal monomer unit effects on the copolymerization were observed. The nonrandom structures result from a copolymerization described by first‐order Markoffian statistics.
Studies in some new initiator systems for vinyl polymerization. III. Amine–halogen systems as redox initiators
Authors: Pramanick Dinabandhu , Palit Santi R. 
Published: April 2003

AbstractAmine–halogen redox systems are very efficient initiators of polymerization of a number of vinyl monomers in benzene media and are rather inefficient initiators in aqueous media. A large number of aliphatic amines and a few aromatic amines have been used. Among the halogens, chlorine and bromine are very effective. Iodine initiates with a few amines only. Endgroups incorporated are halogen and amine totalling an average of nearly one per chain in the case of polymerization in benzene media and 0.5–0.7 per chain in polymerization in aqueous media. In the light of endgroup results, a mechanism of initiation through halogen and amine radicals has been suggested.
Unit cell dimensions of isotactic polyvinylcyclopropane
Authors: Noether H. D. , Overberger C. G. , Halek G. 
Published: April 2003

AbstractThe unit cell dimensions of isotactic polyvinylcyclopropane were determined, based on crystalline, oriented fiber and film samples. Two structures were found: (1) a hexagonal structure with a = 13.6 Å, c = 6.48 Å, 31 helix, space group P31 and P32, ρ(calc) = 0.9805 g/cm3, ρ(obs) = 0.975 g/cm3; (2) a tetragonal structure with a = 15.21 Å, c = 20.85 Å, 103 helix, space group I4, ρ(calc) = 0.926 g/cm3.
Photo‐oxidation of the 2,4‐dichloropentanes and PVC
Authors: Kwei Kwei‐Ping Shen 
Published: April 2003

AbstractThe photo‐oxidation of PVC and its model compounds, the dl‐ and meso‐2,4‐dichloropentanes, were studied by high‐resolution NMR spectroscopy. The structure, CHClCH2COCH2 was found to be present in PVC after photo‐oxidation. Two peaks, which corresponded to the CHCl and CH2 groups next to the carbonyl group, were observed in carbon disulfide–acetone‐d5 mixture, at 6.15 and 7.25τ, respectively. From the NMR spectra, the ratio of the CH2 to CHCl protons in PVC and the model compounds were found to increase linearly with the time of photo‐oxidation after induction periods. The initial rates of the model compounds were comparable with that of PVC; i.e., 1.6 × 10−2 hr−1, at 30°C. Since similar gaseous products were also detected by mass spectrometry in the initial stage, their photo‐oxidation probably assumed the same rate‐determining step. According to the results that the dl‐2,4‐dichloropentane was photo‐oxidized 1.5 times faster than the meso‐compound, it would be likely that the syndiotactic sequences in PVC might be more easily photo‐oxidized than the isotactic sequences.
Aromatic polyimide‐co‐amides. I
Authors: Wrasidlo W. , Augl J. M. 
Published: April 2003

AbstractA series of aromatic polyimide‐co‐amides of high thermal stability were synthesized. Low‐temperature solution condensation involving aromatic diamines of varying basicity and bifunctional carboxylic acid chlorides containing performed imide rings was empolyed. This approach offers several advantages over the conventional polyamic acid route. The final polymers obtained are linear, soluble, and of high molecular weight. Solution of the final polymers are stable in contrast to polyamic acid solutions, which depolymerize hydrolytically due to the neighboring‐group effect. Tough, flexible films were cast from solution and required no heat cure. The properties of one polymer made by the preformed ring approach were compared to its structurally related amide and imide homologs.
Cationic graft copolymerization of polystyrene onto poly‐2,6‐dimethoxystyrene by the termination reaction
Authors: Overberger C. G. , Burns C. M. 
Published: April 2003

AbstractPoly‐2,6‐dimethoxystyrene (P26) was used as the polymeric backbone and was obtained by a new synthetic route involving the Wittig reaction. The grafting reaction was studied by polymerizing styrene with stannic chloride as catalyst in the presence of various concentrations of preformed P26 in solution with carbon tetrachloride and nitrobenzene at 60, 45, 30, and 0°C. The product was fractionated with cyclohexane and the fractions were analyzed by ultraviolet absorption spectroscopy and density‐gradient ultracentrifugation. The molecular termination constant of P26 at 30°C was 0.106 much larger than the value of 0.016 which had been obtained for poly‐p‐methoxystyrene at 0°C. The amount of grafting and grafting efficiency generally increased with increasing temperature, contrary to results using the cationic initiation reaction. Anomalous results were obtained at 0°C as the product was no longer completely soluble. The ratio of grafted to ungrafted polystyrene chains was proportional to the concentration of P26 and generally increased with temperature. The grafting reaction was competitive with the normal termination reaction, and the energy of activation of the grafting reaction was estimated to be larger by ca. 7 kcal/mole.
Contributions au fractionnement des copolymères. II. Copolymères ternaires acrylonitrile–acétate de vinyle–α‐méthylstyréne
Authors: Feldman Dorel , Uglea Constantin , Simionescu Natalia 
Published: April 2003

AbstractAcrylonitrile, vinyl acetate, and α‐methyl styrene copolymers, were synthesized in aqueous solution, and the resulted products were studied viscometrically by fractionation and by cloud‐point titration. The values of the intrinsic viscosities of the polymers in DMF at 20°C are not influenced by the overall composition of the copolymers and the distribution mode of the comonomers. The solubility of the products is directly dependent on the composition, namely, it increases as the acrylonitrile content decreases. The differential fractionation curves are influenced by the chemical composition and by the mode of distribution of the monomers along the macromolecular chain. The successive precipitation method for the fractionation of the ternary copolymers is recommended.
Alkyllithium and alkali metal tert‐butoxide as polymerization initiator
Authors: Hsieh H. L. , Wofford C. F. 
Published: April 2003

AbstractWe have shown that the presence of other alkali metal alkoxides in the alkyllithium‐initiated polymerization drastically increases the rate of polymerization and vinyl unsaturation in polybutadiene. Mechanistically, the propagating center is the dynamic equilibriums between carbon–metal bonds and oxygen–metal bonds. With potassium, rubidium, and cesium salts it reaches a limiting anionic behavior.
Polymerization and copolymerization of some epoxides by potassium tert‐butoxide in DMSO
Authors: Price Charles C. , Atarashi Yuji , Yamamoto Ryuzo 
Published: April 2003

AbstractCopolymerization of tritiated PGE with analogs and with propylene oxide by potassium tert‐butoxide in DMSO shows that this anionic polymerization is favored by electron‐withdrawing groups. The homopolymerization of PGE and its p‐chloro and p‐methoxy analogs gives polymer with molecular weight limited by chain transfer. For PGE, where this limit is about 7000, some of the polymer is insoluble, crystalline isotactic material.
Direct metalation of poly(2,6‐dimethyl‐1,4‐phenylene ether)
Authors: Chalk A. J. , Hay A. S. 
Published: April 2003

AbstractPoly(2,6‐dimethyl‐1,4‐phenylene ether) (I) was metalated with butyllithium in tetrahydrofuran and with the N,N,N′,N′‐tetramethylethylenediamine complex of butyllithium in a variety of solvents. In these cases, metalation occurred at both the ring and side chain positions, the former being preferred initially. Subsequently, there was an isomerization in favor of the side chain.magnified imageAt 25°C, there is no significant amount of polymer scission or crosslinking during metalation, but some crosslinking occurs on derivatizing with dimethyl sulfate and trimethylchlorosilane for high extents of ring metalation. With sodium and potassium alkyls, only side‐chain metalation was observed. The metalated polymer reacts as a typical organometallic, allowing polymer modification by a wide variety of reactions.
Thermal decomposition products of polyisobutylene
Authors: Tsuchiya Yoshio , Sumi Kikuo 
Published: April 2003

AbstractPolyisobutylene was decomposed at 325, 345, and 365°C under vacuum, and the volatile products were trapped by using liquid nitrogen. The products, C1–C24 hydrocarbons, were analyzed by gas chromatography. The formation of the main products is discussed on the basis of a free‐radical mechanism. Intramolecular radical transfer can account for the production of most fragments including dimers, trimers, tetramers, and so on, of isobutylene.
Relationship between structures and activities of silver salt–organic halide catalyst systems for styrene polymerization
Authors: Kagiya Tsutomu , Izu Masatsugu , Maruyama Hitoshi , Fukui Kenichi 
Published: April 2003

AbstractThe rate of bulk polymerization of styrene initiated by silver salt–organic halide systems was measured at 0°C. Neither of the catalyst components initiated the polymerization when used alone, while combined catalysts containing both components initiated the polymerization in the case that the components reacted with each other with precipitation of silver halide. The rate in the early stage of the polymerization increased with an increase in reaction time. Plots of yield against the second power of time gave a linear relation in the early stage of the polymerization. The slope of the line was taken as a measure of catalytic activity. The catalytic activity was markedly influenced by the kinds of the components. The activities of silver perchlorate–organic halide systems increased in the following order of halides: chloride < bromide < iodide in most cases. The activities of silver perchlorate–organic chloride systems increased with a decrease in ionization potentials of the organic groups of the chlorides. The activities of silver salt–benzyl bromide systems increased with a decrease in the pKa values of conjugate acids of silver salts. From these results, it was concluded that the facility of ionic dissociation of the catalyst components determined the activities.
Polymerization of β‐cyanopropionaldehyde. III. Polymerization by organoaluminum and by organoaluminum–titanium chloride complexes
Authors: Kobayashi Kazukiyo , Sumitomo Hiroshi 
Published: April 2003

AbstractThe mechanism of formation and stereoregularity of poly(cyanoethyl)oxymethylene have been studied. The polymerization was carried out at −78°C with use of aluminum compounds [Al(C2H5)3, Al(C2H5)2Cl, Al(C2H5)Cl2, and AlCl3] and complex catalysts [Al(C2H5)3–TiCl4, Al(C2H5)3–TiCl3, and Al(C2H5)2Cl–TiCl3] as initiators. The stereoregularity of poly(cyanoethyl)oxymethylene was estimated from the optical density ratio, D1258/D1270, in the infrared absorption spectrum. Polymer yields were observed to depend upon the aluminum compound used as initiators, while the stereoregularity of the polymer was nearly independent of the particular aluminum compound used. As the catalyst ratio of titanium chloride to aluminum compound increased, the polymer yield was found to increase to a maximum and then to decrease with further increase of the ratio. It is supposed that titanium chlorides themselves increase the acid strength of aluminum compounds through chlorination, resulting in the change of the polymer yield. The highest stereoregularity of poly(cyanoethyl)oxymethylene was attained by increasing the molar ratio of titanium trichloride to aluminum and by treating β‐cyanopropionaldehyde (CPA) with titanium trichloride prior to the polymerization. Complex formation of the nitrile group of CPA with titanium is considered responsible for the increase in stereoregularity. A propagation mechanism is also proposed.
Poly‐as‐triazines
Authors: Hergenrother P. M. 
Published: April 2003

AbstractTwo high molecular weight (ηinh > 1.0) soluble poly‐as‐triazines have been prepared by the solution polycondensation in m‐cresol of 2,6‐pyridinediyl dihydrazidine with p,p′‐oxybis(phenyleneglyoxal hydrate) and with p,p′‐oxydibenzil. Thermal characterization of the poly‐as‐triazines by TGA showed polymer decomposition temperatures of ∼400°C after a 300°C cure in argon. Poly‐as‐triazines exhibited weight losses <8% after aging in static air at 316°C for 200 hr. Clear yellow films cast for m‐cresol solutions exhibited good flexibility and toughness even after aging at 316°C for 200 hr in air and after refluxing in 10% aqueous potassium hydroxide solution for 24 hr.
Polymers containing carbohydrate residues
Authors: Overberger C. G. , Takekoshi Tohru 
Published: April 2003

Abstract2,3,4,6‐Tetra‐O‐methyl‐D‐glucosyl methacrylate and acrylate were prepared and subsequently polymerized by radical initiation. The optical rotatory dispersions of the polymers in tetrahydrofuran and in chloroform obeyed a first‐order Drude equation.
Relationships for determining the rate constant of the polymerization growth reaction by means of the emulsion polymerization method
Authors: Hrabák František , Hynková Vlasta , Bezděk Milan 
Published: April 2003

AbstractSome simple equations for the emulsion polymerization system were derived on the basis of the Smith‐Ewart theory. These are used in calculating the molar monomer concentration and rate of polymerization in units of moles per liter per second for the zero‐order region with respect to the monomer as well as in calculating the rate constant of the growth reaction.