bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallite size in highly drawn polyethylene
Authors: Glenz W. , Peterlin A. , Wilke W. 
Published: April 2003

AbstractThe size and distortion of crystallites in samples of linear polyethylene were determined before and after plastic deformation. A slowly cooled sample, a quenched sample, and highly drawn films (draw ratio 16) were investigated by different methods. Wide‐angle x‐ray patterns were analyzed to study the average size of the crystalline mosaic blocks and their distortion. In addition, the longitudinal crystal thickness (in the chain direction) was evaluated by two other approaches, determination of the long period, and the melting temperature of irradiated samples. The results show clearly that the size of the crystalline mosaic blocks changes substantially with drawing of polyethylene. Not only is the lateral crystal thickness affected, but the longitudinal crystal dimensions also change during the drawing process. By the three independent methods we find that the longitudinal crystal thickness after drawing is independent of the value for the undrawn samples, as was reported earlier by Peterlin. The change in crystallite size after drawing is accompanied by a large decrease in crystal volume to about 10% of the value for the undrawn sample. The degree of distortion in the crystals seems not to be affected by the deformation process. These experimental data can be considered evidence for high chain mobility and for the possibility of rearrangement of chain molecules during the process of plastic deformation.
Scattering of light by disordered spherulites. II. Effect of disorder in the magnitude of the anisotropy
Authors: Hashimoto T. , Stein R. S. 
Published: April 2003

AbstractThe contribution to the disorder scattering by imperfect spherulites resulting from fluctuations in the magnitude of the anisotropy is analyzed for two‐dimensional spherulites. The fluctuations are described in terms of a parameter characterizing the meansquare amplitude of the fluctuation and a correlation function describing the distance over which the correlation occurs. Cases considered are those where the correlation depends on either the radial or the angular separation of the scattering volume elements. As with the case of disorder in orientation, one finds that disorder in anisotropy may result in a nonzero value of intensity at μ = 0° and 90°, a decrease in the higher‐order variation of scattered intensity with θ, and an increase in the intensity of scattering at higher values of θ over that for a perfect spherulite. In addition, disorder in the angular direction leads to an increase in the scattered intensity at small values of θ as compared with the zero intensity of scattering from a perfect spherulite at θ = 0°.
Diffusion mechanisms in solid and molten polyethylene
Authors: Lowell P. N. , McCrum N. G. 
Published: April 2003

AbstractThe diffusion coefficient D and solubility coefficient k of small molecules [C3H6, C4H10, (CH3)4C] are determined at very low solute concentrations in annealed linear polyethylene over a wide range of temperature above and below the melting point Tm. For measurements above Tm the specimen was lightly crosslinked by irradiation from a 60Co source. The diffusion data fit equations of the form D = D0 exp {–ΔHD/RT}. An abrupt change in ΔHD occurs at Tm: representative values (for C4H10) are 4.53 and 14.9 kcal/mole above and below Tm. At Tm, D0 also changes abruptly: representative values (for C4H10) are log D0 = −2.65 above Tm and log D0 = +2.70 below Tm. The mechanism of diffusion therefore changes at the melting point. The melt exhibits typical liquidlike characteristics (negative values of activation entropy ΔSD). The ratio ΔSD/ΔHD = 4β (β denoting the isobaric coefficient of volume expansion) holds below but not above Tm. Equations of the form k = k0 exp {–ΔHk/RT} fit the solubility data. The log k versus T−1 plots above and below Tm are parallel but separated by a step at Tm. If crystallization followed by annealing is assumed to leave a weight fraction of polymer αk (the amorphous fraction) in which the solute can absorb and if the specific solubility coefficient of the amorphous fraction is identical to that of the melt, then log αk Equals the magnitude of the step at Tm. Values of αk determined from the observed step are very close to values of amorphous fraction determined by measurement of density. The solubility experiments support the concept of polyethylene as a two‐phase solid with the amorphous fraction of specific volume equal to the extrapholated specific volume of the melt. The passage of a solute molecule from one potential well to another, however, occurs by processes in the melt and the amorphous fraction which are entirely different.
Polymerization of α‐amino acid N‐carboxy anhydride. IX. Copolymerization of α‐amino acid N‐carboxy anhydride in heterogeneous system
Authors: Oya Masanao , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractCopolymerization of NCA's was undertaken in a heterogeneous system in acetonitrile, which is not a solvent of the polypeptides. The reactivity ratio was calculated by using the Lewis‐Mayo equation. Further, the conversion rate in the copolymerization and the configuration of the copolymer produced were compared with those of the copolymerization in the homogeneous system in nitrobenzene, in which the copolypeptides are swollen. The rate of copolymerization in acetonitrile was between the rates of polymerization of the individual monomers. It has been reported that the configuration of the copolymer obtained in dimethylformamide, in which the copolypeptides are swollen, is of the block type. On the other hand, many polypeptides obtained in acetonitrile, which is not a solvent of the copolypeptides, had a random configuration near to an alternating configuration.
Tractable polyfluoral
Authors: Temple S. , Thornton R. L. 
Published: April 2003

AbstractLow‐temperature polymerizations of fluoral with the use of ionic initiators in inert diluents have produced high molecular weight polyfluoral which is amorphous and tractable. The polymer can be end‐capped by standard techniques to give material which is thermally stable to 350–400°C. The stabilized polymer can be fabricated from solution or melt‐pressed at temperatures as low as 125°C to give clear films and coatings which are oil‐and water‐repellent but highly permeable toward oxygen and water vapor.
Radiation‐induced postpolymerization of trioxane in the solid state. IV. Copolymerization of trioxane with dioxolane
Authors: Ishigaki Isao , Ito Akihiko , Hayashi Koichiro 
Published: April 2003

AbstractThe radiation‐induced postpolymerization of trioxane with 1,3‐dioxolane has been investigated. Trioxane and 1,3‐dioxolane were carefully purified in a rigorously dry, high‐vacuum system. In the present study it was found that trioxane can be easily copolymerized with 1,3‐dioxolane to give a copolymer having high molecular weight and excellent thermal stability. Typically, the isothermal weight loss after heating for 60 minutes under nitrogen at 222°C was 3.5% for a copolymer of trioxane and 1.0 wt‐%1,3‐dioxolane preirradiated with a dose of 1.0 × 105 Rad. The thermal stability of the copolymer was scarcely affected by the polymerization temperature and time, although it decreased slightly with increasing preirradiation dose. The dependences of the yield and inherent viscosity of the polymer on the preirradiation dosage, polymerization temperature and time were quite similar to those found for the homopolymerization of trioxane. The results were analyzed by using the kinetic scheme previously reported, and it was found that no chain transfer reaction occurs in this system. These results are discussed in comparison with those of homopolymerization reported previously.
Surface changes during polypropylene photo‐oxidation: A study by infrared spectroscopy and electron microscopy
Authors: Blais P. , Carlsson D. J. , Wiles D. M. 
Published: April 2003

AbstractThe surface oxidation of polypropylene films which occurs during ultraviolet irradiation in air was found to result in extensive surface restructuring. This restructuring was detected by changes in surface infrared spectra, as measured by attenuated total reflection spectroscopy, and by electron microscopy. The 997 cm−1/974 cm−1 absorbance ratio of the film surfaces increased steadily during ultraviolet degradation and was interpreted as an increase in helical ordering which resulted from backbone scission during irradiation. This scission probably also results in the increase in crystallinity detected by density changes. Electron microscopy of direct surface replicas and replicas of material detached from the oxidized film surfaces showed that surface cracking resulted during photo‐oxidation, and that this oxidation penetrated selectively into the polymer structure. The replicas of detached, oxidized material showed periodic structures related to the interior morphology of the films. The observed restructuring is believed to be entirely responsible for the decrease in percentage elongation at break which results from photodegradation.
Amide–quinoxaline copolymers
Authors: Duffy James V. , Augl Joseph M. 
Published: April 2003

AbstractA series of new amide–quinoxaline ordered copolymers derived from phthaloyl, isophthaloyl, and terephthaloyl chlorides have been synthesized and characterized. The isophthaloyl and terephthaloyl polymers had decomposition temperatures between 445–495°C and were soluble in a variety of solvents. These high molecular weight polymers were prepared by reacting aromatic bis‐o‐diamines with bis(benzilyl)amides. Phthaloyl chloride yielded low molecular weight polymers due to competing side reactions.
Photopolymerization of methyl methacrylate in the presence of tertiary amines
Authors: Yokota Kenji , Tomioka Hideo , Ono Teruyuki , Kuno Fumimasa 
Published: April 2003

AbstractThe sensitization effect of tertiary amines on the photopolymerization of methyl methacrylate was studied. N,N‐Dimethylbenzylamine, triethylamine, and N,N‐dimethylaniline increased the rate of polymerization in this order, but pyridine did not show any effect. A free‐radical mechanism was confirmed by the tacticity of polymer, the retarding effect of hydroquinone, and the copolymer composition with styrene. On the basis of the detailed kinetics of the sensitized polymerization and the ultraviolet spectra of the reaction mixtures, a sensitization mechanism is proposed, in which the excited monomer and the amine form a complex and generate an initiating radical.
Radiation‐induced postpolymerization of trioxane in the solid state. V. Studies on copolymer composition
Authors: Ishigaki Isao , Ito Akihiko , Iwai Tadashi , Hayashi Koichiro 
Published: April 2003

AbstractStudies on the composition of copolymers obtained by the radiation‐induced solid‐state postpolymerization of trioxane with 1,3‐dioxolane have been carried out. Gas‐chromatographic analysis of the reaction mixtures showed that most of the 1,3‐dioxolane disappears rapidly from the reaction system in an early stage of polymerization, and that the fraction of ethylene oxide units in the copolymer chain [E] decreases markedly with increasing polymer yield. This finding was confirmed by NMR spectra of the copolymer. DSC thermograms of the copolymer indicated that the relationship between the melting point and the average composition of copolymers prepared in this study differed from that found for copolymers in which comonomer units are distributed statistically in the polymer chain. It was suggested that the copolymer formed by the radiation‐induced solid‐state postpolymerization of trioxane–1,3‐dioxolane is characterized by a heterogeneous distribution of ethylene oxide units in the copolymer chain. It was also found that, in the radiation‐induced solid‐state postpolymerization of trioxane–1,3‐dioxolane, the amount of tetraoxane formation increased linearly with increasing polymer yield. Although it is extremely small compared with that obtained in solution polymerization, it is slightly larger in the trioxane–1,3‐dioxolane system than in the trioxane system.
NMR and ESR studies of the solid‐state polymerization of vinyl monomers. I. Acrylamide
Authors: Chachaty C. , Forchioni A. 
Published: April 2003

AbstractThe kinetics of the solid‐state polymerization of acrylamide, γ‐irradiated at 77°K, has been studied by wide line NMR and by ESR at temperatures above 300°K. This reaction may be followed by the growth of a narrow line superimposed on the NMR spectrum of the monomer. The amplitude of this narrow line has been found to be proportional to the polymer yield. By long continued annealing, the conversion yield approaches a limiting value, generally lower than 50% under most of our experimental conditions. The activation energy of post‐polymerization is 19 ± 1 kcal/mole. The radiochemical yield of radicals, determined by ESR, is 0.27 ± 0.03 at 77°K before warming. In the course of annealing above 300°K, the overall concentration of radicals is reduced to about one tenth of its initial value at 77°K. However, the local concentration of the remaining radicals is constant and equal to 1.2 × 1019 spins/g, i.e., more than 100 times their overall concentration. The recombination of radicals does not seem to intervene in the kinetics of post‐polymerization, so that it may be assumed that only the radicals remaining after annealing, have actually contributed to the reaction.
Effects of trivalent phosphorus compounds on vinyl polymerizations. II. Photopolymerization of acrylonitrile in the presence of triphenylphosphite
Authors: Ogawa Takeshi , Taninaka Takumi 
Published: April 2003

AbstractIt was found that acrylonitrile is polymerized by UV irradiation in the presence of triphenylphosphite under conditions where acrylonitrile alone does not polymerize. The rate of polymerization was found to be proportional to the monomer concentration, the phosphite concentration, and the light intensity. It was thought that a donor‐acceptor complex formed between triphenylphosphite and acrylonitrile absorbs light and initiates the radical polymerization.
Graft modification of poly(vinyl chloride) and related reactions
Authors: Thame N. G. , Lundberg R. D. , Kennedy J. P. 
Published: April 2003

AbstractCationically polymerizable olefins can be efficiently grafted onto poly(vinyl chloride) in the presence of alkylaluminum compounds. The substitution of labile chlorines in PVC by various branches yields a product of improved thermal stability as compared with unmodified PVC. Thus the grafting of a few per cent of polyisobutylene or poly‐butadiene onto PVC gives graft copolymers superior in thermal stability to the PVC backbone, as determined by thermogravimetric and differential thermal analyses as well as color development of molded films. At advanced stages of thermal degradation the thermal stability of poly(vinyl chloride)‐g‐isobutylene) (PVC‐g‐PIB is some 40°C superior to the unmodified PVC. In addition to grafting of polymer chains onto the PVC backbone, other methods are also available to achieve improved thermal stability. In pentane suspension, alkylaluminum compounds efficiently alkylate labile chlorines in PVC, and the product exhibits improved thermal stability. Alternatively, PVC carbonium ions can alkylate aromatic compounds, and these products also exhibit high heat stability. Based on the assumption that certain alkylaluminums quantitatively react with labile chlorines in PVC, it was estimated that 2–3% of the chlorines present in suspension‐grade PVC are labile.
Morphological study of crystals formed in films obtained by evaporation and deposition of polyethylene
Authors: Satou M. , Watanabe Y. , Hayashi H. 
Published: April 2003

AbstractFrom thin films produced by vacuum evaporation and condensation of polyethylene, single crystals were grown by subsequent heat treatment of the films in xylene. Extended molecular chains composing the crystals are approximately 150 Å in length, i.e., about 1.5 times the thickness of the crystal layers. Electron microscopic examination of the crystals revealed that they were morphologically similar to ordinary polyethylene and paraffin single‐crystals, e.g., they sometimes exhibited a hollow pyramidal shape or typical spiral growth.
Melting behavior of polyethylene crystallized in a pressure capillary viscometer
Authors: Southern John H. , Porter Roger S. , Bair H. E. 
Published: April 2003

AbstractThe Melting of various polyethylene structures is compared by using data obtained on the Perkin‐Elmer differential scanning calorimeter (DSC). Transparent, high‐density samples crystallized under both orientation and pressure in the Instron capillary rheometer are compared with samples crystallized from dilute solution by stirring and with samples crystallized under high pressure. The latter two structures are assumed to contain extended‐chain crystallites. By comparison, the melting points and the superheatability of the Instron samples are consistent with the presence of an extended‐chain crystal component. The melting of irradiated samples crystallized in the rheometer is also observed to be consistent with this conclusion. In addition, DSC data are compared with the melting points defined with a polarized light microscope equipped with a hot stage.
Polymer photoprotection by copolymerized triplet quenchers
Authors: George G. A. 
Published: April 2003

AbstractFrom a model of delocalized triplet energy in an aromatic vinyl polymer, the relative efficiency of triplet‐energy transfer to either an added or copolymerized quenching molecule is determined. It is found that copolymerization can increase the photoprotective efficiency only if the quenching rate is determined by the final energy transfer step. A study of the quenching of polystyrene phosphorescence by added or copolymerized naphthalene indicates that there is no enhancement of quenching efficiency by copolymerization.
Temperature dependence of the conformation of isotactic polystyrene in toluene
Authors: Helms J. B. , Challa G. 
Published: April 2003

AbstractIn order to obtain information about a possible helix–coil transition of isotactic polystyrene (i‐PS) at 80°C in toluene, as has been reported in other solvents, solution properties were examined at temperatures between 10 and 110°C. Use was made of viscometry, high‐resolution nuclear magnetic resonance, infrared spectroscopy, calorimetry, and light scattering. No distinct transition was found at 80°C but rather a second‐order transition between 62 and 65°C. A similar transition occurred in toluene solutions of atactic polystyrene. The transition may be attributed to a sudden change in the mobility of the phenyl side‐group of the polymer. From this study it is concluded that i‐PS has a helical conformation in toluene, the mean helix length decreasing smoothly with increasing temperature.
Alkylated polypyrazines
Authors: Biehle Richard P. , Higgins Jerry 
Published: April 2003

AbstractThe syntheses of four new monomers and two new polyaromatic pyrazines are described. The monomers; bis‐p,p′‐(octanoyl)diphenyl ether (Ia), bis‐p,p′‐(hexadecanoyl)diphenyl ether (Ib), bis‐p,p′‐(α‐bromooctanoyl)diphenyl ether (IIa), and bis‐p,p′‐(α‐bromohexadecanoyl)diphenyl ether (IIb), were produced by Friedel‐Crafts acylation of diphenyl ether with the corresponding acyl chloride and subsequent α‐bromination. Prepolymers were synthesized by the condensation of (IIa) and (IIb) with ammonia in N,N‐dimethylformamide (DMF), and polymers were prepared by subsequent melt condensation of the prepolymer to produce poly[2,5‐(oxydiphenylene)‐3,6‐(dihexyl)pyrazine] (IIIa), and poly[2,5‐(oxydiphenylene)‐3,6‐(ditetradecyl)pyrazine] (IIIb). Polymer IIIa was thermally (stable at >400°C while polymer IIIb was a tacky substance). The inherent viscosity of IIIa produced by 12 hr of melt condensation was 0.30 dl/g in formic acid. Additional heating in excess of 24 hr gave a slightly soluble polymer. The inherent viscosity of IIIb produced by 40 hr of melt condensation was 0.37 dl/g in formic acid.
Radiation‐induced copolymerization of tetrafluoroethylene with vinyl ethers
Authors: Hikita Tomoji , Tabata Yoneho , Oshima Keichi , Ishigure Kenkichi 
Published: April 2003

AbstractRadiation‐induced copolymerization of tetrafluoroethylene with various vinyl ethers has been studied. It was found that tetrafluoroethylene can be copolymerized with vinyl ethers to give alternating copolymers over a wide range of the initial monomer concentration in the monomer mixture. The monomer reactivity ratios were determined for the copolymerization of tetrafluoroethylene with n‐butyl vinyl ether as 0.005 (rTFE) and 0.0015 (rNBVE). The rate of copolymerization is extremely high and has a maximum at an equimolar concentration of two monomers. The alternating structure of the copolymers was confirmed by the analysis of NMR spectra. Some thermal properties of the copolymers were measured by DSC and DTA.
Polymers having stable radicals. I. Synthesis of nitroxyl polymers from 4‐methacryloyl derivatives of 2,2,6,6‐tetramethylpiperidine
Authors: Kurosaki Toshikazu , Lee Kyu Wan , Okawara Makoto 
Published: April 2003

AbstractPolymers having stable nitroxyl free radicals, poly‐4‐methacryloylamino‐ and poly‐4‐methacryloyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyls, were synthesized from their precursor polymers by oxidizing them in a methanolic solution of hydrogen peroxide. The precursor polymers were prepared by radical polymerization of 4‐methacryloyl‐amino/oxy‐2,2,6,6‐tetramethylpiperidines in various solvents. These polymerizations in acetic acid were found to yield polymers of high molecular weight. The copolymers of the precursor monomers with styrene and methyl methacrylate were also prepared as precursor copolymers. These precursor polymers of a piperidine type were converted to the polymers having stable nitroxyl free radicals by the hydrogen peroxide method. In this report, it was assumed that the post‐oxidation reaction introduced a nitroxyl group smoothly and quantitatively at room temperature. Elucidations of the stable radical formation and the electron spin behavior of the stable radical polymers were made in terms of elemental analyses, infrared, ultraviolet, and ESR spectroscopy.
Syntheses of polyurethanes derived from oximes and their photodegradation
Authors: Hong Sung Il , Kurosaki Toshikazu , Okawara Makoto 
Published: April 2003

AbstractPolyoxime‐urethanes have been synthesized from dioximes and diisocyanates, and their structures have been ascertained by elemental analysis and infrared spectroscopy. They can be represented by the general formula:
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These polymer films were photolyzed by using a high‐pressure 100‐W mercury lamp, and the rate of decomposition of the NO bond was determined by use of ultraviolet and infrared spectra, or comparing the photochemical behavior with that of corresponding model compounds. Upon irradiating these polymers in the presence or absence of sensitizers or a hydrogen donor, there were obtained photolyzed polymers of low molecular weight, of which the molecular weights were estimated by observing the viscosity changes. To deduce the mechanism of photodegradation of polyoxime‐urethane, photolysis of benzophenone oxime‐phenyl urethane was investigated as a model compound.