bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(Aryl ethers) by nucleophilic aromatic substitution. II. Thermal stability
Authors: Hale W. F. , Farnham A. G. , Johnson R. N. , Clendinning R. A. 
Published: April 2003

AbstractThe thermal stability and degradation process for a specific poly(aryl ether) system have been studied. In particular, the polymer which is available from Union Carbide Corporation as Bakelite polysulfone has been examined in detail. Polysulfone can be prepared from 2,2‐bis(4‐hydroxyphenyl)propane and 4,4′‐dichlorodiphenyl sulfone by nucleophilic aromatic substitution. Because of a low‐temperature transition at − 100°C. and a glass transition at 195°C., polysulfone retains useful mechanical properties from −100°C. to 175°C. A number of experimental methods were utilized to study the thermal decomposition process for this polymer system. Polysulfone gradually degraded in vacuum above 400°C. as demonstrated by mass spectrometry. Thermogravimetric analysis in argon, air, or high vacuum indicated that rapid decomposition began above 460°C. From gas chromatography, mass spectrometry and repeated laboratory pyrolyses, a number of products from polymer decompositions were identified. The most important degradation process in vacuum or inert atmosphere was loss of sulfur dioxide. Several model compounds representative of portions of poly(aryl ether) molecules were synthesized and the relative thermal stabilities determined. Possible mechanisms for pure thermal decomposition of polysulfone were derived from the product analyses, model studies, and consideration of bond dissociation energies.
New high temperature polymers. VI. Ordered heterocycle copolymers
Authors: Preston J. , Black W. B. 
Published: April 2003

AbstractA new class of linear, thermostable polymers is reported. The compositions are ordered heterocycle copolymers in which two different heterocycles alternate regularly along the polymer chain. Examples of combinations studied are: oxadiazole–benzimidazole, oxadiazole–pyromellitimide, and thiazole–pyromellitimide. The heterocycle copolymers, or alternatively, the corresponding precursor polymers, were prepared by condensing preformed di‐or tetrafunctional blocks which contain one type of heterocycle with a second di‐ or tetrafunctional monomer under such conditions that no rearrangement of bonds occurred. The polymers are characterized in general by neither melting nor decomposing below 500°C. when heated in an inert atmosphere at a rate of about 10°C./min. Some of the copolymers are readily soluble in organic solvents; many, however, are soluble only in solvents such as concentrated sulfuric acid. In the case of the more intractable polymers, soluble precursor polymers can usually be prepared. In such precursor polymers only one of the heterocycles is preformed; the second heterocycle is formed by post‐treatment after the polymer has been fabricated into an end product. All of the polymers yielded self‐supporting films, some having very high strength; films of several of the polymers were hot‐drawable. Drawn film of an ordered oxadiazoleimide copolymer was shown to be well oriented and moderately crystalline.
Stereospecific polymerization of methacrylonitrile. III. Some new catalysts for isotactic polymethacrylonitrile
Authors: Joh Yasushi , Yoshihara Toshio , Kotake Yahide , Imai Yoshikatsu , Kurihara Seiki 
Published: April 2003

AbstractSome classes of organometallic catalysts what induce stereospecific polymerization of methacrylonitrile have been found. They include organolithium aluminum compounds of the type LiAlR4, Li[R3AlOAlR2], and Li[R3AlN(R)AlR2], organosodium aluminum compounds of the type NaAlR4, organolithium zinc compounds of the type LiZnR3 and Li2ZnR4, organomagnesium aluminum compounds of the type RMg[AlR4] and Mg[AlR4]2, and organomagnesium compounds containing an MgN bond, such as magnified image and their related compounds. One of the features of the polymerization with these catalysts was that the crystalline polymers were formed at moderately high temperatures. Total conversion, solubility index, and molecular weight of the polymer increased with increasing polymerization temperature, as observed in the case of polymerization with diethylmagnesium catalyst. Catalysts with an MgN bond were found to be highly effective for the stereospecific polymerization. The acetone‐insoluble fractions of the polymers gave x‐ray diagrams identical to the crystalline polymer produced with diethylmagnesium. This indicates that the acetone‐insoluble crystalline polymers produced with these catalysts have an isotactic structure. The viscosity–molecular weight relationship for crystalline polymer was conveniently determined in Cl2CHCOOH at 30°C.; [η] = 2.27 × 10−4 M0.754.
Gel permeation properties of cellulose. I. Preliminary comparison of unmodified and crosslinked, decrystallized cotton cellulose
Authors: Martin L. F. , Rowland S. P. 
Published: April 2003

AbstractDecrystallized cotton cellulose was found to be have gel permeation properties comparable to those of the highly crosslinked dextran and polyacrylamide gels used in chromatography. Partial separations of pairs of sugars, ranging in molecular weight from 120 to 738, were studied by determining the optical rotations of fractions eluted from chromatographic columns, employing a sensitive automatic polarimeter. The elution volumes of individual sugars of known molecular weights provide a quantitative measure of changes produced in the cellulose polymer structure by crosslinking. A significant difference was found between unmodified cellulose and the same material crosslinked by formaldehyde treatment; although crosslinking reduced permeability to larger molecules, the crosslinked material was found to be more permeable than the untreated cellulose to compounds having molecular weights below approximately 1000.
On the chromophore of polyacrylonitrile
Authors: Peebles L. H. 
Published: April 2003

AbstractFurther evidence is presented to show that the chromophore of polyacrylonitrile is formed by polymerization of the nitrile groups, rather than by dehydrogenation of the polymer backbone. The polyimine structure formed is resistant to hydrolysis; hence, the nitrogen content of hydrolyzed polymer increases with increased chromophore formation.
Diels‐Alder polymers. III. Polymers containing phenylated phenylene units
Authors: Mukamal H. , Harris F. W. , Stille J. K. 
Published: April 2003

AbstractThe Diels‐Alder reaction of biscyclopentadieneones with diacetylenes produces colorless, soluble, phenylated polyphenylenes of high molecular weight (M̄n≃ 40,000) in nearly quantitative conversions. The polymers are noncrystalline, form clear films, and are stable in air to 550°C. Under nitrogen, the polymers lost approximately half the phenyl groups attached to the phenylene main chain to give brown‐black insoluble polyphenylenes of very low crystallinity.
Effect of oxygen on the γ‐radiation‐induced polymerization of ethylene
Authors: Mitsui Hiroshi , Machi Sueo , Hagiwara Miyuki , Hosoi Fumio , Kagiya Tsutomu 
Published: April 2003

AbstractThe effects of oxygen on the γ‐radiation‐induced polymerization of ethylene were studied at a temperature of 30°C.; the pressure was 400 kg./cm.2, the dose rate was 1.9 × 105 rad/hr.; and oxygen content was from 1–2000 ppm. The main product was solid polymer, and no liquid product was found. The gaseous products were hydrogen, acetylene, higher hydrocarbons, carbon dioxide, aldehydes, and acids. Several kinds of carbonyls similar to those formed in γ‐ray oxidized polyethylene were observed in the polymer. The polymer yield and the degree of polymerization decreased markedly with increasing oxygen content, while the amount of carbonyls in the polymer increased. The number of moles of polymer chain and the amounts of hydrogen and acetylene were found to be almost independent of the oxygen content. The polymerization of pure ethylene was not affected by carbon dioxide and formic acid. On addition of acetaldehyde, the polymer yield and the degree of polymerization decreased markedly, while the number of moles of polymer chain increased. In the polymerization of ethylene containing oxygen, both the rate of oxygen consumption and the carbonyl content of the polymer increased, while the inhibition period decreased by the addition of acetaldehyde. It was found that the degree of polymerization after the inhibition period is almost independent of the reaction time in the presence of acetaldehyde, while it increases with the time in the absence of acetaldehyde.
Effects of carbonyl and aldehyde groups in the graft copolymerization of methyl methacrylate on cellulose with a ceric salt
Authors: Ogiwara Yoshitaka , Ogiwara Yukie , Kubota Hitoshi 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate on cellulosic materials of various carbonyl and aldehyde contents with the use of a ceric salt as an initiator was studied. It was found that the concentration of the ceric salt which gives the maximum per cent grafting is in good agreement with the equivalent of total carbonyl content in the cellulosic material, and the number of grafted chains in copolymers is roughly proportional to it. However, the molar ratio of the number of grafted chains to total carbonyl content is quite small, being approximately 1:50, and the graft copolymerization can be explained kinetically on the assumption that the number of radicals produced on cellulose by the ceric salt leading to branching is very much smaller than the number of radicals destroyed by the ceric salt, and growing radicals can be stabilized by the termination reaction with the ceric salt or with a cellulose radical. Although both aldehyde and carbonyl groups contribute to the formation of grafted chains, the former are effective mainly at low concentrations of the ceric salt; both groups participate in the production of graft copolymers showing the maximum per cent grafting.
Role of para‐substituted phenols in curing resole‐type phenolic resins
Authors: Rodia Jacob S. 
Published: April 2003

AbstractCertain para‐substituted phenols, namely, those phenols without ortho substituents and containing an electron‐attracting atom or group in the para position, e.g. p‐nitro‐, p‐bromo‐, and p‐chlorophenol, hasten gelation of etherified phenolic resoles. A mechanism involving cleavage of dibenzyl ether linkages in these resins is proposed to explain gelation.
Kinetics of γ‐ray polymerization of formaldehyde in the presence of carbon dioxide
Authors: Yokota Hisao , Otsuka Yozo , Kagiya Tsutomu , Fukui Kenichi 
Published: April 2003

AbstractA kinetic study of the γ‐ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to −17°C. Two modes of the polymerization, spontaneous and γ‐ray polymerization, occur in this system. The γ‐ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ‐ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ‐ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ‐radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ‐ray polymerization were also investigated.
Stereoregularity of polyacrylonitrile determined by NMR
Authors: Svegliado G. , Talamini G. , Vidotto G. 
Published: April 2003

AbstractThe NMR spectrum of polyacrylonitrile is interpreted and the tacticity of three polyacrylonitrile samples prepared at different temperatures in the range from −78 to 120°C. determined. The ratio between isotactic and syndiotactic units is about 50:50 for all the three samples examined.
Copolymerization of trans‐2,6‐diazido‐hexaphenylcyclophosphonitrile tetramer with 1,4‐bis(diphenylphosphino)butane or 4,4′‐bis(diphenylphosphino)biphenyl
Authors: Bilbo Andrew J. , Sharts Clay M. 
Published: April 2003

AbstractPolymers [N(PN)4(C6H5)6NP(C6H5)2(CH2)4P(C6H5)2]x and [N(PN)4(C6H5)6NP–(C6H5)2C6H4C6H4P(C6H5)2]x have been formed by thermal copolymerization of trans‐2,6‐diazidohexaphenylcyclophosphonitrile [N3(PN)4(C6H5)6N3] with either 1,4‐bis‐(diphenylphosphino)butane [(C6H5)2P(CH2)4P(C6H5)2] or 4,4′‐bis(diphenylphosphino)‐biphenyl [(C6H5)2C6H4C6H4P(C6H5)2]. The maximum molecular weights obtained were about 10,000. A polymer endcapped with triphenyl phosphine was stable to 400°C.
Changes in concentration of tetraoxane produced during the solution polymerization of trioxane catalyzed by BF3·O(C2H5)2
Authors: Miki T. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractThe behavior of tetraoxane produced during the polymerization of trioxane was investigated kinetically. In the polymerization of trioxane, a short induction period for the formation of methanol‐insoluble polymer was observed and during the induction period a certain amount of tetraoxane, depending on the polymerization conditions, was produced. This amount was independent of the initial concentration of catalyst but increased with an increase in the polymerization temperature and in the initial concentration of trioxane. So this amount was found to be determined by the equilibrium between the formation and consumption of tetraoxane. On the other hand, in the early stage of polymerization of trioxane, the formation of an appreciable amount of soluble polymer was estimated. Consequently the formation of tetraoxane was explained in terms of the “back‐biting” reaction of the soluble growing chain with depolymerization.
Effect of solvent on the amount of tetraoxane produced in the solution polymerization of trioxane catalyzed by BF3·O(C2H5)2
Authors: Miki T. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractThe amounts of tetraoxane produced in the polymerization of trioxane catalyzed by BF3·O(C2H5)2 were measured in various solvents. The maximum amount of tetraoxane produced depends on the nature of solvent used. This amount was independent of the initial concentration of the catalyst in ethylene dichloride and in nitrobenzene. On the other hand, in benzene, the amount of tetraoxane produced decreased slightly with increasing initial catalyst concentration. This result was explained by the reaction of tetraoxane produced with the residual catalyst as well as with the active center. The maximum amount of tetraoxane produced decreased, other conditions being similar, in the order, nitrobenzene > ethylene dichloride > benzene solvent. This order may be explained in terms of a longer lifetime of the active center in the more polar solvent, leading to the formation of tetraoxane.
Transition of nylon 6 γ‐phase crystals by stretching in the chain direction
Authors: Miyasaka Keizo , Makishima Kunio 
Published: April 2003

AbstractA crystal transition was found in nylon 6 fibers from the γ‐phase to α‐phase on stretching in the chain direction. The γ‐phase fiber prepared by iodine treatment was stretched under constant load and the crystal deformation was observed by an x‐ray method. The critical stress for the transition was estimated as 4 × 103 kg./cm.2 at room temperature. For this crystal transition the following conditions must be satisfied: (1) extension of the γ‐phase chain to untwist the chain around the amide groups, (2) translational mobility of the chain to change the stacking in the crystallite. At the critical stress, the chain in the crystal is extended to nearly the same length as that of α‐phase. The translational movement occurs under stress higher than about 3 × 103 kg./cm.2, and the pseudohexagonal cell is deformed into a monoclinic form. However, the monoclinic crystallites present at a stress lower than the critical value estimated above are unstable and may be brought back to the original form by head treatment at 100°C. No crystal transition occurs at low temperature.
Hydrodynamics of a porous sphere molecule
Authors: Seely Truman 
Published: April 2003

AbstractA mathematical model is proposed which treats a hypothetical polymer molecule as a porous sphere. Fluid flow within the sphere obeys Darcy's law while the creeping motion equations are used outside the sphere. Equations are derived relating the permeability and radius of the sphere to hydrodynamic properties of dilute solutions of the polymer. In checking against experimental data, it is found that the model, despite its simplicity, may be useful in explaining the hydrodynamic behavior of molecules which are highly branched or crosslinked.
Viscosity of polydimethylsiloxane blends
Authors: Kataoka Tadao , Ueda Shigeyuki 
Published: April 2003

AbstractZero shear viscosities of two‐component blends of polydimethylsiloxane with different molecular weights were measured over the whole range of composition. Results are analyzed on the basis of the conventional treatments for the viscosity of polymer blends and some comments are made on such treatments of data. After that, an empirical equation is derived:

where η is the viscosity, v the volume fraction, subscripts 1, 2, and bl denote the lower and higher molecular weight component and the blend, respectively, and a is a constant independent of composition. The equation is not only applicable to all series of blends of polydimethylsiloxane but also to other polymers.
Hydrophobic interaction in poly(2‐hydroxyethyl methacrylate) homogeneous hydrogel
Authors: Refojo Miguel F. 
Published: April 2003

AbstractHomogeneous poly(2‐hydroxyethyl methacrylate) (PHEMA) hydrogel exhibits a narrow range of swelling at equilibrium in water (% H2O, 41.09 ± 0.15 standard error of the mean of 24 samples), regardless of the dilution of the monomer solution and relatively low level of crosslinking. It is postulated that PHEMA hydrogel has, in addition to its covalently linked network structure, a secondary structure stabilized by hydrophobic bonding. The addition of microsolutes to the hydrogel seems to confirm this hypothesis. The hydrogel swells beyond its swelling equilibrium in water in presence of urea and its methyl derivatives. Swelling is also induced by organic solvents like alcohol and acetone, and by anions like iodide, acetate, trichloroacetate, and thiocyanate. Chlorides and sulfates produce a less swollen hydrogel than pure water, while bromides and cetylpyridinium chloride, in the concentrations tested, induce only a slight deswelling of the gel. When PHEMA gel prepared in organic solvent–water solutions is placed in water, the gel passes through an opaque state before becoming transparent again. This phenomenon is interpreted as being caused by the inability of water to solvate the hydrophilic ends of the unorganized polymer segments. Homogeneity returns to the gel after a rearrangement of the chains, directed by the interaction of the hydrophobic portions of the polymer segments, exposing to the solvent–water most of the hydrophilic sites in the network.
A redox‐initiated xylan–poly(sodium acrylate) graft copolymer
Authors: Church John A. 
Published: April 2003

AbstractAn aspen 4‐O‐methylglucuronoxylan was grafted with poly(sodium acrylate) (PSA) in 3.4N NaOH at 25–30°C. with the use of a persulfate–thiosulfate redox initiator system. The formation of a true graft copolymer was indicated by fractional precipitation and light‐scattering studies, physical mixtures of the two pure polymers being used as references. A grafted fraction was isolated, containing no ungrafted xylan but possibly some PSA homopolymer, which contained 96.5% PSA and 3.5% xylan, or an average of 3.2 PSA chains of M̄n approximately 90,500 per xylan chain of M̄n approximately 10,500.
Reactive fiber. V. Preparation and polymerization of p‐styrenesulfonyl (β‐chloroethyl)amide
Authors: Iwakura Yoshio , Uno Keikichi , Nakabayashi Nobuo , Chiang Wen‐Yen 
Published: April 2003

Abstractp‐Styrenesulfonyl(β‐chloroethyl)amide (III) was prepared and copolymerized with styrene (M1). The monomer reactivity ratios were determined (r1 = 0.25 = 0.1, r2 = 1.25 ± 0.25), and Q and e values were calculated (1.69 and 0.28, respectively). The polymer reacts with nucleophilic reagents such as amines and phenols in the presence of pyridine to the extent of 15–98%. Fibers from copolymers of acrylonitrile and III react with Congo Red in the presence of pyridine.
Dilute solution studies on a polycarbonate in good and poor solvents
Authors: Berry G. C. , Nomura H. , Mayhan K. G. 
Published: April 2003

AbstractLight‐scattering, viscometric and osmometric studies have been carried out on dilute solutions of polycarbonate fractions both in a good solvent and in theta solvents. The data span the molecular weight interval 5 < 10−3M < 760. It has been concluded that: (1) the overall behavior in dilute solution is consistent with a flexible chain conformation; (2) the ratio of the unperturbed mean‐square radius to the molecular weight, or to the number of chain elements, is larger than commonly observed for vinyl polymers; (3) the ratio of the unperturbed radius to the radius calculated for a chain with free rotation about valence bonds has the unusually small value 1.3; and (4) the hydrodynamic behavior of the chain may reflect partical draining affects.
Microstrain investigation of polyethylene
Authors: Rabinowitz Stephen , Brown Norman 
Published: April 2003

AbstractThe small‐strain mechanical behavior of crystalline polyethylene has been studied by using a microstrain technique with strain resolution on the order of 10−6. The strain rate was varied from 10−6 to 10−4 sec.−1, and a temperature range of 17–28°C. was investigated. A strong dependence on strain rate and temperature has been observed for the following parameters which characterize the mechanical response of polyethylene in the microstrain region: the initial modulus of the stress–strain curve, the deviation in strain from ideal linear elastic behavior at a given stress amplitude, and the energy dissipated in a deformation cycle. The Young's moduli that were observed by means of tensile tests in the microstrain region were only about 20% lower than the values reported in other investigations at kilocycle and megacycle frequencies. The experimental method made it possible to isolate a deformation process which was attributed to a crystallographic shear mechanism corresponding to a yield point of 27 psi. This shear mechanism is discussed in terms of the various shear processes, such as slip, twinning, and the orthorhombic–monoclinic phase change.