bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phenylated polyimides: Diels‐Alder reaction of biscyclopentadienones with dimaleimides
Authors: Harris Frank W. , Norris Steve O. 
Published: April 2003

AbstractA series of phenylated polydihydrophthalimides has been synthesized by the Diels‐Alder reactions of 3,3′‐(oxydi‐p‐phenylene)bis(2,4,5‐triphenylcyclopentadienone) and 3,3′‐(p‐phenylene)bis(2,4,5‐triphenylcyclopentadienone) with N,N′‐o‐, ‐m‐, and ‐p‐phenylenedimaleimide. The polydihydrophthalimides were soluble in dimethylformamide (DMF) and had intrinsic viscosities that ranged from 0.33 to 1.01, the polymers were dehydrogenated thermally and chemically to afford the corresponding phenylated polyphthalimides. The totally aromatic polyimides were also soluble in DMF but had intrinsic viscosities only as high as 0.41. The thermogravimetric analyses of the polyphthalimides showed breaks near 530°C in air and in nitrogen atmospheres.
Effect of oxygen on the polymerization of vinyl chloride. I. Kinetic features
Authors: Garton A. , George M. H. 
Published: April 2003

AbstractThe effect of oxygen on the liquid‐phase polymerization of vinyl chloride at 55°C in the presence of an added initiator, bis(4‐tert‐butylcyclohexyl) peroxydicarbonate (Perkadox 16), has been studied by the technique of tumbled dilatometry. With this method, at constant initiator concentration, the induction period showed a half‐order dependence on the initial oxygen concentration. At a constant initial oxygen concentration, the induction period varied inversely as the square root of the initiator concentration. Under the experimental conditions empolyed, the polyperoxy radicals with chloroalkyl (∼CH2ĊHCl) endgroups were not wholly scavenged by molecular oxygen but could undergo various decomposition reactions. The degree of conversion of the initial oxygen to peroxidic compounds did not exceed 30% by weight and was dependent on the shape of the reaction vessel empolyed. The existence of other oxidation products has been demonstrated. At 55°C, the average velocity constant for decomposition of the peroxide products from vinyl chloride, measured in dichloromethane solution, was found to be 8 × 10−5 sec−1. A kinetic scheme involving a predominant cross‐termination reaction is proposed to explain the experimental results.
Copolymerization of epichlorhydrin with maleic anhydride catalyzed by Zn(acac)2
Authors: Akimoto Akira 
Published: April 2003

AbstractCopolymerization of epichlorhydrin (ECH) with maleic anhydride (MA) was investigated under several conditions. Zinc acetylacetonate [Zn(acac)2] was found to catalyze the alternate copolymerization of ECH with MA at a mild temperature, resulting in the formation of polyester, the structure of which was confirmed with the aid of infrared, NMR, and elemental analysis. From kinetic studies of copolymerization an apparent first order of reaction with respect to catalyst concentration and to monomer concentration with 1:1 mole mixture was established.A possible initiation mechanism was discussed, and Zn(acac)2–MA complex was suggested to be an initiating species.
Friedel‐Crafts acylation reactions in copolymers of methyl methacrylate and styrene and in mixtures of the homopolymers
Authors: Grassie N. , Gilks J. , Moodie T. , Quietsch P. , Riordan P. 
Published: April 2003

AbstractIn the presence of SnCl4 in 1,2‐dichloroethane solution, copolymers of styrene and methyl methacrylate undergo a Friedel‐Crafts acylation reaction between the ester groups and the ortho position of adjacent styrene units to form a partial ladder polymer. This has been confirmed by infrared and ultraviolet spectral analysis and by observing the influence of substituted styrenes on the rate of the reaction. A similar reaction can be induced to occur between polystyrene and poly(methyl methacrylate). Thermal analysis measurements demonstrate that the degradation properties of copolymers of styrene and methyl methacrylate are profoundly changed by this treatment.
Four‐center type photopolymerization in the crystalline state. VI. Kinetic and structural study of the polymerization ofp‐phenylenediacrylic acid diethyl ester
Authors: Nakanishi Hachiro , Nakanishi Fusae , Suzuki Yasuzo , Hasegawa Masaki 
Published: April 2003

AbstractThe effect of temperature on the four‐center type photopolymerization has been investigated forp‐phenylenediacrylic acid diethyl ester over a wide temperature range including crystal transition point (56°C) and melting point (96°C) of monomer. With the elevation of temperature between −50 and 15°C, the polymerization rate in the initial stage increased and the degree of polymerization decreased monotonously, while the rate in the later stage decreased above −25°C. With irradiation at above 25°C, the monomer crystals became sticky, and the polymerization was suppressed at the stage of oligomerization with low conversion. This tendency was enhanced above the crystal transition point, giving mainly dimer in low yield. Above the melting point, only radical polymerization occurred with the aid of oxygen. The steric configuration of the products in the crystalline state was 1,3‐transwith respect to the cyclobutane ring. Peaks in NMR spectra of all products were assigned to the protons involved in four compounds up to tetramer. Various results obtained have been interpreted in terms of the change, as a function of temperature, from a topochemical polymerization which proceeds under a control of the monomer lattice to a photoinitiated vinyl‐type polymerization in the disordered state. It is concluded that a rigid crystal lattice is indispensable for the four‐center type photopolymerization to proceed smoothly.
Preparation and properties of poly(imide‐oxoisoindolobenzothiadiazine dioxides)
Authors: Imai Yoshio , Koga Hiroshi 
Published: April 2003

AbstractNew thermally stable poly(imide‐oxoisoindolobenzothiadiazine dioxides) (PIOD) have been prepared by the three‐step cyclopolycondensation reaction of diaminobenzenesulfonamides with aromatic tetracarboxylic dianhydrides. The polymerization proceeded through the formation of poly(amic acid‐sulfonamides) (PAAS), followed by cyclodehydration to yield polyimide‐sulfonamides (PIS), which were subsequently converted to PIOD at 300°C. PAAS having inherent viscosities in the range of 0.1–0.5 in N‐methyl‐2‐pyrrolidone (NMP) were obtained in approximately quantitative yield. PIOD were insoluble in most organic solvents, whereas PAAS and PIS were soluble in NMP and dimethyl sulfoxide. Differential thermal analysis and thermogravimetric analysis indicated that PIOD began to decompose at 460°C in air. The cyclodehydration of the model compounds was also investigated.
Polymerization mechanism of vinyl chloride with titanium tetrabutoxide–ethylaluminum sesquichloride catalyst and some physical properties of poly(vinyl chloride) prepared at low temperature
Authors: Mitani Katsuo , Ogata Takayuki , Awaya Hiroshi 
Published: April 2003

AbstractThe mechanism of vinyl chloride polymerization by titanium tetrabutoxide–ethylaluminum sesquichloride catalyst system was investigated from the view of the stereoregularity of poly(vinyl chloride). The samples were prepared at a selected temperature in the range from 23 to −78°C. The tactic triads, obtained from 220‐MHz NMR spectra, show clearly the adequacy of Bernoullian statistics in describing the mechanism for stereochemical propagation. The chain propagation proceeds according to Bernoullian statistics with syndiotactic placements favored by 550 cal/mole. These results suggest that vinyl chloride polymerizes by a free‐radical mechanism under the action of the present catalyst system.
Development of free radicals in sulfonated polystyrene ion‐exchange resins upon drying
Authors: Von Goldammer E. , Conway B. E. , Paskovich D. H. , Reddoch A. H. 
Published: April 2003

AbstractOn exhaustive drying of sulfonated polystyrene‐based ion‐exchange resins, it is shown that free‐radical centers develop. These have been examined by electron‐spin resonance spectroscopy. The formation of the free radicals is largely reversible with respect to desorption and sorption of water which was measured by means of a quartz spiral microbalance. The spin‐concentration isotherm as a function of sorbed water concentration is obtained. The presence of free radicals, dependent on water content in the resins, interferes with proton magnetic relaxation studies of hydration of ionized resins by providing a faster electron‐spin coupled nuclear magnetic relaxation mechanism.
Aging and degradation of polyolefins. I. Peroxide‐initiated oxidations of atactic polypropylene
Authors: Niki Etsuo , Decker Christian , Mayo Frank R. 
Published: April 2003

AbstractEfficiencies of polymer radical production by thermal decomposition of di‐tert‐butylperoxy oxalate (DBPO) have been measured in bulk atactic polypropylene (PP) at 25–55°C; they range from 1 to 26%, depending on [DBPO], temperature, and presence of oxygen. Most of the polymer radicals thus produced disproportionate in the absence of oxygen but form peroxy radicals in its presence. Most of the pairs of peroxy radicals interact by a first‐order reaction in the polymer cage. The fraction that escapes gives hydroperoxide in a reaction that is half order in rate of initiation. In interactions of polymer peroxy radicals, in or out of the cage, about one‐third give dialkyl peroxides and immediate chain termination, two‐thirds give alkoxy radicals. About one‐third of the later cleave at 45°C; the rest abstract hydrogen to give hydroxy groups and new polymer and polymer peroxy radicals. The primary peroxy radicals from cleavage account for the rest of the chain termination. Cleavage of alkoxy radicals and crosslinking of PP through dialkyl peroxides nearly compensate. Up to 70% of the oxygen absorbed has been found in hydroperoxides. The formation of these can be completely inhibited, but cage reactions are unaffected by inhibitors. Concentrations of free polymer peroxy radicals have been measured by electron spin resonance and found to be very high, about 10−3M at 58–63°C. Comparison with results on 2,4‐dimethylpentane indicate that rate constants for both chain propagation and termination in the polymer are much smaller than those for the model hydrocarbon but that the ratio, kp/(2kt)½, is about the same.
Aging and degradation of polyolefins. IV. Thermal and photodecompositions of model peroxides
Authors: Mill Theodore , Richardson Harold , Mayo Frank R. 
Published: April 2003

AbstractThere appear to be no unusual effects of phase change or near‐ultraviolet radiation on the reactions of alkoxy radical models for atactic polypropylene. The oxidation of purified atactic polypropylene by singlet oxygen is not an important process at 50°. Photochemical and thermal cleavages of tert‐amyloxy radicals, a model for polypropylene oxy radicals, give nearly the same ratio of ka/kd at 50°C. Photochemical cleavage of the model compound 1,1‐dinonylethyl hydroperoxide (10‐methyl‐10‐nonadecyl hydropenoxide) gives exclusive cleavage of a nonyl group both in solution and in polypropylene film at 50°C.
Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). IV. Influence of solvent type
Authors: Buter R. , Tan Y. Y. , Challa G. 
Published: April 2003

AbstractMethyl methacrylate (MMA) was polymerized by radical initiation at 25°C or 35°C in various solvents in the presence of stereoregular poly(methyl methacrylate) (PMMA). The occurrence of stereospecific replica polymerization appeared to be related to the capability of stereoassociation of isotactic and syndiotactic PMMA. The solvents can be roughly divided into three types. Type A solvents are polar solvents, which promote stereoassociation resulting in gelation and precipitation. Examples are dimethylformamide, dimethyl sulfoxide, and acetone. Type B solvents are nonpolar aromatic solvents like benzene and toluene, wherein stereoassociation is weaker but still leads to gelation. Type C solvents are very good solvents, in which stereoassociation does not occur. Chloroform and dichloromethane belong to this class. In solvents of type A as well as type B, polymerization in the presence of i‐PMMA as a polymer matrix was syndiospecific. However, in the presence of s‐PMMA as a polymer matrix the polymerization was isospecific only in type A solvents. The syndiotactic or isotactic triad contents of the polymer formed could be as high as ca. 90% at low conversions. In solvents of type C, polymerization in the presence of stereoregular PMMA proceeds according to a normal radical mechanism. Syndiotacticity was always less than 70%. Stereocomplexes formed in situ during replica polymerization were partly crystalline as detected by x‐ray diffraction. The highest crystallinity was detected in those formed in type A solvents.
γ‐Radiolysis of ketone polymers. I. Studies of symmetrical aliphatic ketones as model compounds
Authors: Slivinskas J. A. , Guillet J. E. 
Published: April 2003

Abstractγ‐Radiolysis of model ketones of the general structure R(CO)R, neat and in hydrocarbon solution, show that the radio‐chemical degradation of these aliphatic ketones can be explained by mechanisms analogous to those generally accepted for the photochemical decompositions of the same compounds. The G (type I) and G (type II) yields are found to decrease with increasing total chain length of the ketone as monitored by the products (RH) and (CH3COR), respectively. Differences in the relative yields of type I and II products are attributed to the higher incident energies involved in γ‐radiolysis as compared to ultraviolet photolysis. Evidence is presented for energy transfer from paraffinic solvents to aliphatic ketonic solutes. Solid‐ and condensed‐phase studies show the importance of rotational and diffusional mobility to the yields of the type II and I processes, respectively.
Organoaluminum–cyclic ether‐cyclic imide catalysts for the polymerization of epoxides
Authors: Masuda Yasushi , Hani Hiroshi 
Published: April 2003

AbstractA catalyst for the polymerization of epoxides consisting of trialkylaluminums, cyclic ethers, and cyclic imides has been investigated. Various catalyst components were examined to reveal that the combination of triisobutylaluminum, dioxane, and succinimide gives the most active catalyst. The catalytic activity is greatly enhanced with aging in which the change in color from pale yellow to dark red takes place. The polymerization data show that the dioxane provides a pathway for the catalyst components to form an active species. The dioxane‐containing catalyst is likely to be different in structure from that of the dioxane‐free catalyst. It was shown that the catalyst solution is electrically conductive. A parallel correlation seems to exist between the electrical conductivity and the catalytic activity, suggesting that the catalytic species may be of an ionic character.
NMR analysis of Ti(NEt2)4–AlMe3 catalyst system and its polymerization activity
Authors: Koide Naoyuki , Iimura Kazuyoshi , Takeda Masatami 
Published: April 2003

AbstractStudies have been made by NMR and ESR spectroscopy to elucidate the reaction mechanism in which the Ti(NEt2)4–AlMe3 catalyst system is involved. The two reaction products of Ti(NEt2)3Me and Al(NEt2)Me2 have been confirmed by NMR spectroscopy when Ti(NEt2)4 is reacted with AlMe3, and two kinds of paramagnetic species have been noted by ESR spectroscopy. It has been found that Ti(NEt2)3Me plays an important role as an active species for the polymerization of styrene.
Radiation‐induced grafting in the polyethylene–styrene system and differential thermal analysis of the grafted samples
Authors: Imai Masahiko , Shimizu Harumichi 
Published: April 2003

AbstractThe graft polymerization of styrene onto high‐density polyethylene films was carried out by γ‐irradiation in the vapor phase. Two methods were used for grafting in these experiments: a preirradiation method and a simultaneous irradiation method. The effects of these grafting methods on the reaction mechanism of grafting and on the properties of the grafted samples were investigated. The amounts of styrene homopolymer in the grafted samples is under 2% in the case of the preirradiation method and above 10% in the case of the simultaneous irradiation method. The activation energies were calculated to be 18 kcal/mole for grafting in the preirradiation method and 15 kcal/mole for weight increase of polyethylene films in styrene vapor. The difference in the dimensional expansion between in the direction of stretching and the direction prependicular to it is smaller with preirradiation grafting than with grafting by the simultaneous irradiation method. Differential thermal analysis of the grafted films shows an endothermic peak due thermal decomposition which decreases gradually from 450°C to 415°C with increase in degree of grafting from 30 to 60%. The lowering of this peak temperature appears at a lower degree of grafting when the preirradiation method is used. On the basis of these results, it is concluded that the reaction rate of radiation‐induced grafting in the vapor phase depends closely upon the processes of adsorption, dissolution, and diffusion of styrene monomer in polyethylene films; in the case of simultaneous irradiation method, the reaction proceeds comparatively uniformly in the amorphous region, while in the case of the preirradiation method, the reaction proceeds mainly at the boundary of the crystalline and amorphous regions.
Analyses of synthetic resins by application of 13C NMR
Authors: Mukoyama Y. , Tanno T. , Yokokawa H. , Fleming J. 
Published: April 2003

AbstractIn a study of synthetic resin analysis, 13C NMR spectra of phenol resins were measured, and the chemical shifts of the various carbon sites compared with the resins' reactivity with formaldehyde. Measurements were made with phenol, para‐substituted phenols, chlorophenols, hydroxytoluenes, dimethyl(hydroxy)benzenes, dihydroxybenzenes, and dihydroxytoluenes. The chemical shifts of these phenols were compared with calculated shifts obtained by using a simple summing rule. These chemical shifts are closely related in magnitude to the reactivity of the phenols with formaldehyde. For example, resorcin has the greatest reactivity with formaldehyde of the above‐mentioned phenols and this experimental result agrees well with the measured large 13C chemical shifts for resorcin.
Electron spin resonance studies of propagating radicals in polymerization. I. Methacrylate propagating radicals
Authors: Harris James A. , Hinojosa Oscar , Arthur Jett C. 
Published: April 2003

AbstractFerric chloride‐photosensitized free‐radical initiation was used to generate propagating radicals in polymerization of methacrylic acid (MAA), allyl methacrylate (AMA), methyl methacrylate (MMA), 1,3‐butylene dimethacrylate (1,3‐BDMA), hydroxypropyl methacrylate (HPMA), lauryl methacrylate (LMA), hexyl methacrylate (HMA), and methacrylamide (MA) in rigid glasses of methanol or acetone at near liquid nitrogen temperatures. The formation and conformational changes of these propagating radicals at different temperatures were studied by electron spin resonance (ESR) spectroscopy. When methanol was the rigid glass, ·CH2OH radicals were formed initially and were stable below −160°C. As the temperature of the rigid glass was increased, the ·CH2OH radicals reacted with monomer to yield propagating radicals. With the exception of the propagating radical for methacrylamide, the propagating radicals of the methacrylates examined initially generated five‐line ESR spectra which gradually changed to nine‐line spectra, as temperature of the rigid glass was increased. It was concluded that one type of propagating radical was formed in all cases. However, when the temperature of the rigid glass was increased, the single structural conformation that initially allowed one of the methylene hydrogens and methyl group to interact with the unpaired electron to generate only a five‐line spectrum was changed to yield a second conformation that allowed interaction to generate an additional four‐line spectrum. Finally, a mixture of the propagating radical for methacrylate monomer in two structural conformations was obtained, and an ESR spectrum consisting of nine lines (5 + 4 lines) was generated. In the case of the propagating radical for methacrylamide this change to yield two structural conformations evidently was hindered, so that only an ESR spectrum consisting of five lines was generated.
Solution properties and unperturbed dimensions of poly‐p‐fluorostyrene and poly‐m‐fluorostyrene
Authors: Matsuo K. , Stockmayer W. H. 
Published: April 2003

AbstractMolecular weights and solution viscosities are reported for unfractionated free‐radical polymers of m‐fluorostyrene and p‐fluorostyrene in several solvents. The estimated unperturbed dimensions lead to characteristic ratios C∞ at 25°C of 12.2 ± 0.5 and 11.6 ± 0.4 for the meta and para polymers, respectively. These are similar in magnitude to those of other polystyrenes.
Cyclization equilibrium constants and the conformations of polydimethylsiloxane chains
Authors: Wright P. V. 
Published: April 2003

AbstractExperimental molar cyclization equilibrium constants for dimethylsiloxane cyclics having from 8 to ca 400 skeletal bonds are presented. The results for an undiluted equilibrate, an equilibrate in toluene solution, and an equilibrate in diglyme solution are compared. The increases in the equilibrium concentrations of cyclic oligomers, previously found to be large in good solvents (e.g., toluene) are found to be small in the poor solvent (diglyme). For macrocyclics, the cyclization equilibrium constants in the undiluted equilibrate and in diglyme (theta conditions) are found to be in good agreement with calculations which were carried out by assuming that chains are unperturbed and by using the rotational isomeric state model of Flory, Cresenzi, and Mark for polydimethylsiloxane. However, with chain polymer in dilute solution in a good solvent (toluene), the macrocyclization equilibrium constants are found to be lower than in the other two equilibrates. This result confirms the work of other authors who suggested that in this case the chains were expanded by excluded‐volume effects.
Light scattering from tilted two‐dimensional spherulites
Authors: Hashimoto Takeji , Todo Akira , Kawai Hiromichi 
Published: April 2003

AbstractThe theory of small‐angle light scattering was developed for oblique incidence of the light beam on the surface of a two‐dimensional spherulite. Results of the theory were compared with previously reported results of light scattering from two‐dimensional and three‐dimensional spherulites for normal incidence, and with some experimental patterns. The comparisons suggest that the scattering intensity distributions of two‐dimensional spherulites deviate from those of three‐dimensional spherulites when the sample surface is tilted with respect to the propagation direction of the incident beam, although they are almost identical when the sample surface is normal to the incident beam. Observation of the change of scattered intensity distributions upon tilting the samples thus provides a method of distinguishing between two‐dimensional and three‐dimensional spherulites. Moreover, this observation makes it possible to determine the degree of planar orientation of the optic axes of optically anisotropic scattering elements within two‐dimensional spherulites. The calculations were carried out for special cases of two‐dimensional spherulites with the optic axis orientation confined to the two‐dimensional plane and randomly or helicoidally rotated around the spherulite radii.