bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative spherulite of poly‐γ‐methyl‐L‐glutamate and effect of aging polymer solution on spherulite growth
Authors: Ishikawa Saburo , Kurita Toshio , Suzuki Eikichi 
Published: April 2003

AbstractPoly‐γ‐methyl‐L‐glutamate was obtained by the NCA method in a chloroform solution using trimethylamine as initiator. After polymerization, the solution was left alone for a long time at room temperature before spherulites formed. A film was casted very slowly from this aged solution in a desiccator at room temperature. We could then obtain spherulites in these thin films. This aging treatment was one of the main factors in making the spherulites. The morphological structure, optical properties, and the molecular orientation of the spherulites were examined by infrared spectroscopy, the x‐ray method, and electron microscopy. After short aging periods (1–6 months), we could obtain positive spherulites. After much longer aging periods (6–10 months), negative spherulites were obtained. The conformation of the molecules in both spherulites was the same—the so‐called α‐helical conformation, but the orientation of the α‐helical axis in the spherulites was just the opposite. In the positive spherulites, the helical axes oriented along the radius, but in negative spherulites, the helical axes oriented along the tangential direction. These positive and negative spherulites were constructed with microfibriles the diameters of which were about 45–67 A. The orientation of these microfibriles in the spherulites was just the same as the α‐helical axes' orientation. These microfibriles oriented by side‐by‐side association in making the layer structure in the spherulites so that the α‐helical axes were aligned parallel to these layers. Also, no evidence was observed of the presence of the so‐called folding orientation of these α‐helical molecules or microfibriles, as was pointed out in the case of polyethylene. From these results, we know that the crystallization habits of helical molecules, such as polypeptides, were different from those of polyethylene. The helical axes of the polypeptide molecules were not oriented perpendicular to the layer surface of the spherulites, but parallel to the layer surface. The crystallization mechanism of polypeptide was not by the so‐called folding mechanism, but by the side‐by‐side crystallization mechanism.
Acrylic anhydrides and polymers derived therefrom
Authors: Hwa Jesse C. H. , Fleming William A. , Miller Leon 
Published: April 2003

AbstractThe free‐radical polymerization of four acrylic anhydrides—methacrylic anhydride, acrylic anhydride, acrylic methacrylic anhydride, and acrylic propionic anhydride—under a variety of conditions has been studied. The polymers and their polyacid and polyester derivatives were characterized by solubility, infrared spectroscopy, and x‐ray diffraction. Methacrylic anhydride could be polymerized in bulk and in hydrocarbon solvents from −50°C. to 80°C. to give soluble, linear cyclopolymers in high conversions. In a polar solvent such as dimethyl sulfoxide, gelation would result at high monomer concentrations and at high conversions. Acrylic anhydride, however, appeared to become crosslinked more readily; soluble polymers could be obtained only by polymerization in nonpolar solvents. Most of the previous and somewhat conflicting results on the cyclopolymerization of these two monomers can now be reconciled by the present findings. The physical properties of cast poly(methacrylic anhydride) suggest that it has a stiff backbone with hindered functional groups and that the monomer itself was perhaps intramolecularly associated. Some improvements in the aqueous hydrolysis of poly(methacrylic anhydride) and in the esterification of the derived polyacid by diazomethane were described. By these refinements, poly(methyl methacrylate), derived from a −50°C. poly(methacrylic anhydride), had previously been shown to possess a novel, mixed syndiotactic and syndioduotactic (++−−++−−) configuration. Acrylic methacrylic anhydride could be cyclopolymerized very much like methacrylic anhydride. The polyacid and polyester derived from this unsymmetrical anhydride are expected to have unique structures; the acrylic or methacrylic units in the derivatives do not occur more than twice in succession. Acrylic propionic anhydride, when homopolymerized, readily changed to a soluble polymer and an unidentified, immiscible liquid. Its soluble copolymer with methyl methacrylate, however, could be crosslinked by heating. An intramolecular and intermolecular disproportionation reaction was postulated to explain these two interesting observations, respectively.
Electron exchange polymers. XXI. Polymerization behavior of 2,5‐dimethoxystyrene
Authors: Kamogawa Hiroyoshi , Cassidy Harold G. 
Published: April 2003

AbstractIt was shown that 2,5‐dimethoxystyrene polymerizes under free‐radical, cationic, and anionic initiation. The less bulky character of the ortho substituent in the benzene ring makes the behavior of this monomer more normal than that of the previously reported vinylhydroquinone dibenzoate. Thus, a linear relationship is observed between specific extinction coefficients of copolymers in the ultraviolet absorption spectra and copolymer compositions. Q‐e values are also normal (Q = 1.76, e = −1.04). The copolymerization behavior is well understood through these values.
Decomposition of asymmetric peranhydrides
Authors: Smets G. , Van Rillaer W. 
Published: April 2003

AbstractThe synthesis of a peranhydride copolymer was carried out in three steps: (a) copolymerisation of acrylyl chloride with methyl methacrylate, (b) reaction of the acid chloride copolymer with perbenzoic acid, (c) treatment with aqueous methanol and methylation with diazomethane, in order to avoid free carboxylic groups. The polymer contained 18.1 wt.‐% peranhydride groups. The stability of this peranhydride copolymer (PerBzO2) has been compared to that of acetylbenzoic peroxide AcBzO2; the overall energies of activation of thermal decomposition in toluene solution are 24.6 and 33.2 kcal./mole, respectively. The relative importance of first‐order decomposition with respect to the induced decomposition has been determined. The first‐order rate constants are 3.8 × 10−4 sec.−1 for PerBzO2 at 59.7°C. and only 5.8 − 10−5 sec.−1 for AcBzO2; consequently the peranhydride copolymer is much less stable than the low molecular weight anhydride. This unexpected result must be related to chain structural effects.
Graft copolymerization with peranhydride side groups
Authors: Van Rillaer W. , Smets G. 
Published: April 2003

AbstractSeveral copolymers of methyl acrylate, methyl methacrylate, and acrylyl perbenzoate of different peranhydride contents (5.35, 9.24, 12.6, 20.2, and 33.9 wt.‐%) were prepared and used for initiating the graft polymerization of styrene. The overall rate of polymerization and the grafting rate are proportional to the square root of the peranhydride concentration, while they are practically first order with respect to the monomer concentration. The graft copolymers were separated from both homopolymers by precipitation with methanol from the chloroform solution of the copolymer; the styrene content of the graft copolymer increases with monomer concentration e.g., 32.4 and 51.1% for monomer concentrations of 2.6 and 6.1 mole/l., respectively. The ratio of Rg/Rh, i.e., the weight of styrene bonded as graft to that as homopolystyrene has been taken as a conventional measure of the graft efficiency. At 80°C. this ratio never exceeds 0.46, independent of the composition of the initiating copolymer. It increases, however, markedly with decreasing grafting temperature; for a styrene concentration of 6.1 mole/l. it is equal to 0.64 and 1.27 at 72.1 and 55.6°C., respectively. The ratio Rg/Rh depends also strongly on steric effects: when the copolymer contains only methyl acrylate and acrylyl perbenzoate units with exclusion of methyl methacrylate, Rg/Rh is much larger than unity: at 74.9°C. it is equal to 1.68 and 2.31 for monomer concentrations of 2.6 and 4.35 mole/l., respectively, in the presence of a polymer containing 23.9 wt.‐% of peranhydride. This ratio is also enhanced by the viscosity of the solution. The results are compared to those obtained with similar copolymers containing tert‐butyl perester side groups.
Distribution of molecular weight and of branching in high molecular weight polymers from bisphenol a and epichlorohydrin
Authors: Myers G. E. , Dagon J. R. 
Published: April 2003

AbstractThe molecular weight distributions and long‐chain branching distributions of three samples of Bisphenol A poly(hydroxy ether) have been investigated. The samples were fractionated and the fractions characterized by solution viscosity and light‐scattering measurements. A log‐log plot of intrinsic viscosity and M̄w for fractions of all three resins yields a straight line up to molecular weights of about 70,000 (approximately 80% by weight of each polymer) described by [η] = 1.48 × 10−4 M̄w. Beyond this molecular weight the viscosities fall increasingly below the straight line whose constants are representative of those expected for linear fractions in a good solvent. It is evident that long‐chain branching does not occur appreciably in the lower fractions but does begin abruptly at 70,000 molecular weight and increases continuously above that point. Comparison of both the branching and molecular weight distributions with those predicted from Beasley's random branching mechanism confirms the nonrandom nature of the branching mechanism in these poly(hydroxy ethers). The numbers of branches calculated using the Zimm‐Kilb theory reach impossibly high values, while those calculated from the Zimm‐Stockmayer theory appear more reasonable. No correlation was found between the Huggins' k′ and molecular weight or branching. The highest molecular weight sample possesses a longer and more highly branched high molecular weight tail, which is reflected in differences in physical properties.
Free radical‐catalyzed reaction of the acrylamidomethyl ether of cotton
Authors: Gardon J. L. 
Published: April 2003

AbstractA limited number of acrylamidomethyl ether groups can be introduced into cotton. We can assume that the reactive groups form a lattice and that when two or more adjacent sites are occupied, these neighboring vinyl groups will react with each other when a free radical catalyst is applied to them. A monomer group isolated from others by empty neighboring sites will remain unconverted. If each site has Z neighbors, Z being the coordination number, the conversion can be calculated as a function of the fractional site occupancy and of Z. The expression derived from the lattice model is mathematically equivalent to an expression which is based on an excluded volume model. In the latter, it is assumed that each reactive monomer has a reactive shell around it. If another monomer is placed within this shell, the two can react with each other. In terms of this model the parameter Z is defined as the ratio between the volume of the reactive shell and of the volume occupied by the monomer. The latter model offers some mathematical advantages and allows the calculation of both conversion and degree of polymerization from Z and the fractional site occupancy. It is shown that the ultimately achievable conversion and the degree of polymerization increases with Z and with site occupancy. Acrylamidomethylated cotton samples were treated with increasing amounts of ammonium persulfate and the conversion was determined. The data could be extrapolated to infinite initiator concentration and Z was found to have a value of 3.5–4. Since the reaction between double bonds on neighborings sites of a single cellulose chain would have a coordination number equal to 2, the fact that Z > 2 indicates that reaction between double bonds attached to different cellulose chains must occur. The fraction of links which are intermolecular is (Z‐2)/Z, being 43–50%. This result is an excellent agreement with previous data showing that only 42% of the crosslinks contribute to the increased resilience of cotton. It is likely that the termination of the polymerization reaction involves the combination of two radicals. Consequently, each polymeric or oligomeric chain contains two sulfate groups when ammonium persulfate is used as initiator. The molecular weight of these chains can be calculated from the mole ratio between the converted monomers and sulfur. The molecular weights determined this way agreed reasonably well with the molecular weight values calculated from the theory with Z = 4.
Redox polymerization of unsaturated polyester resins. III. Catalytic properties of tertiary amine N‐oxides. Redox polymerization with the system, dimethylaniline N‐oxide with vanadyl acetyl acetonate
Authors: Svoboda Glenn R. 
Published: April 2003

AbstractCatalytic activity has been shown for both trialkyl and aryl dialkyl amine N‐oxides. Of the series, unsaturated polyester resins catalyzed with dimethylaniline N‐oxide exhibited complete polymerization in a practical length of time (24 hr.), when promoted with vanadyl acetyl acetonate. Such a resin system may also be heat cured without the addition of any promoter. A unique property of dimethylaniline N‐oxide‐catalyzed resins is the extraordinary stability exhibited by these resins systems. Up to two years precatalyzed resin and catalyst stability has been noted with resins stored at normal ambient temperatures. Lower storage temperatures are recommended.
Rubber elasticity in highly crosslinked systems: Crosslinked styrene, methyl methacrylate, ethyl acrylate, and octyl acrylate
Authors: Tobolsky A. V. , Katz D. , Takahashi M. , Schaffhauser R. 
Published: April 2003

AbstractStyrene, methyl methacrylate, ethyl acrylate, and octyl acrylate were each copolymerized with tetraethylene glycol dimethacrylate (TEGDM) over the complete range of copolymer compositions. Modulus‐temperature curves of these polymers were constructed and compared. The equation of state for rubber elasticity was applied to the rubbery plateau regions of these polymers.
Crystallization of polyethylene from o‐xylene
Authors: Wunderlich Bernhard , James Edward A. , Shu Tsao‐Wen 
Published: April 2003

AbstractThe upper limit of platelike growth of polyethylene from a 0.1% solution by weight in o‐xylene can be represented by the equation T′ = M × 103/(2.747M + 170.6). This equation was derived on kinetic and thermodynamic arguments. Dendritic growth occurs 8–10°C. below T′. Higher molecular weights give more irregular and more branched dendrites. The ratio of heterogeneously nucleated hedgehog dendrites is constant for any one preparation crystallized at different temperature. Polymethylene can crystallize in a different morphology above T′. Interference microscopy was used as a main tool in this research.
Carriers and unpaired spins in some organic semiconductors
Authors: Pohl Herbert A. , Chartoff Richard P. 
Published: April 2003

AbstractSemiconduction and electron spin resonance studies on a number of conjugated polymers representative of the polyacetylenes, the polybenzimidazoles, and the polyacene quinone radical polymers were made. Observed resistivities ranged from 270 to 1016 ohm‐cm. at room temperature. These and the spin concentrations, the relaxation times, and the energies of activation of conductance and spin concentration were found to be functions of the molecular structure. It was considered impressive evidence that impurity effects on the electronic properties of molecular solids are far less than those commonly observed with the covalently bonded semiconductors such as Ge and Si, for example. A detailed analysis was made of the carrier and free radical formation and life‐times in these ekaconjugated molecular solids using a simple model.
Incorporation of hydroxyl endgroups in vinyl polymer. Part II. Aqueous polymerization of methyl methacrylate initiated by salts or complexes of some metals in their higher oxidation states
Authors: Ghosh Premamoy , Mukherjee Ashish R. , Palit Santi R. 
Published: April 2003

AbstractHydroxyl endgroups have been incorporated in polymers of methyl methacrylate obtained by initiation with salts or complexes of Mn4+, Ce4+, Co3+, and Ag3+ with the monomer in aqueous solution. Hydroxyl and carboxyl endgroups in the respective polymer samples have been estimated with the help of the dye interaction technique. Initiation with Mn4+ and Ce4+ ions in dilute H2SO4 medium in the dark at room temperature has been found to incorporate an average of about 2 hydroxyl endgroups per polymer chain. Initiation with potassium trioxalato cobaltate (III) complex has been carried out both in the dark and in the presence of ultraviolet light at room temperature, and both carboxyl and hydroxyl endgroups have been characterized in the polymers formed. An average total of 1 endgroup (both COOH and OH combined) per polymer chain has been obtained in case of photoinitiation, and about 2 per polymer chain in the case of thermal initiation in dark. Polymerization in the dark at room temperature has been carried out in neutral medium with ethylene dibiguanidinium nitrate complex of tripositive silver as the initiator, and an average of 2 hydroxyl endgroups per polymer chain has been found to be incorporated in the process.
Radiation crosslinking of polyethylene–polyfunctional monomer mixtures
Authors: Odian George , Bernstein Bruce S. 
Published: April 2003

AbstractPolyfunctional monomers such as allyl methacrylate, allyl acrylate, and diallyl maleate have been found to greatly enhance the radiation crosslinking of polyethylene. The radiation dose for incipient gelation is decreased by a factor of approximately 25 by the presence of small amounts of these monomers. The ultimate scission/crosslinking ratio is unchanged by the presence of these monomers and the swelling behavior of the gels follows the Flory‐Rehner equation. The monomer‐crosslinking process is compared to the monomer‐free process as regards the physical properties (tensile strength, elongation, modulus) of the crosslinked materials. A mechanism is presented for the enhancement of polyethylene crosslinking by polyfunctional monomers.
Mechanisms of thermal degradation of phenolic condensation polymers. I. Studies on the thermal stability of polycarbonate
Authors: Lee Lieng‐Huang 
Published: April 2003

AbstractBisphenol‐A polycarbonate gradually degrades at temperatures above 310°C. as detected by differential thermal analysis. The first stage of degradation of the dry and purified resin is induced by oxygen. In connection with oxidation, zinc stearate causes a notable degradation. This compound may act partly as an oxidation catalyst. The initial site attacked by oxygen is presumably the isopropylidene linkage of the polymer. The second stage of degradation shows a characteristic endothermic peak between 340 and 380°C. This stage is chiefly associated with depolymerization since only a small amount of volatiles is detectable. Depolymerization can be caused by hydroperoxide cleavage, hydrolysis, alcoholysis and bisphenol cleavage. Bisphenol‐A can decompose in the presence of acid into phenol and isopropenylphenol. The latter compound is a color‐forming material. As temperature increases above 400°C., volatilization rate gradually increases. The last stage of degradation becomes uncontrollable above 500°C. At this stage, decarboxylation, dehydration, hydrolysis, hydrogen abstraction, ether cleavage, crosslinking as well as chain scission interact to yield aromatic hydrocarbons, phenolic compounds, and tar. The quantity of aromatic hydrocarbons is determined by the intensity of the thermal degradation.
Some graft copolymerizations at high pressure
Authors: Lamb J. A. , Weale K. E. 
Published: April 2003

AbstractSome graft copolymerizations of monomers with substrates previously irradiated in air to form polymeric peroxides have been studied at pressures up to 8000 atm. In the heterogeneous system styrene‐irradiated polyethylene, the rate of grafting increases considerably with pressure up to about 3000 atm. At higher pressures the reaction is retarded, and this is attributed to diffusion control of the propagation reaction. The rate of homopolymerization increases exponentially with pressure over the range 1‐4000 atm. Irreproducible results were obtained when methyl methacrylate was used in place of styrene, possibly because the substrate is not swollen by this monomer. No grafting was observed between five different chloro‐substituted ethylenes and irradiated polyethylene at pressures up to 5000 atm. The rate of grafting in the homogeneous system vinyl acetate‐irradiated polystyrene increases considerably with pressure up to 8000 atm., and there is no indication of diffusion control of the propagation reaction.
Some aspects of the photosensitivity of poly(vinyl cinnamate)
Authors: Tsuda Minoru 
Published: April 2003

AbstractA theoretical investigation of the relationships between the photosensitivity of poly‐(vinyl cinnamate) and various factors—the degree of esterfication, the average molecular weight, and the concentration of sensitizers—was made under the assumption that the main response of the polymer to light is the production of crosslinking by the dimerization of cinnamoyl groups. The obtained equations are S = k16C2 for the degree of esterification, S = k22M̄ for the average molecular weight, and S = k33 (1 − e) + k34 for the concentration of sensitizers, where S is the photosensitivity of the polymer, C is the degree of esterification, M̄ is the average molecular weight, c is the concentration of sensitizers, and kij is a constant. It was shown that these equations agree well with the experimental data obtained by other authors.
Peroxide crosslinking of ethylene–propylene rubber
Authors: Loan L. D. 
Published: April 2003

AbstractThe crosslinking of ethylene–propylene rubber by means of dicumyl peroxide has been followed in detail. The overall crosslinking efficiency has been found to be about 0.4 crosslinks per peroxide molecule, and this result has been shown by stress relaxation and permanent set experiments to result from a mixture of both scission and crosslinking reactions. The results obtained with two different rubbers are consistent with the view that scission results from abstraction of a tertiary hydrogen atom while crosslinking arises from attack at a secondary hydrogen. Such a scheme allows a relative reactivity of tertiary :secondary of 6:1 to be calculated. The action of sulfur in peroxide cures has been shown to be to introduce labile, presumably sulfur‐containing, crosslinks. Such labile crosslinks explain the increased tensile strength of such vulcanizates. Allyl compounds are effective in increasing the crosslinking efficiency of the peroxide.
Irradiation of polyethylene crystals: Gas evolution studies
Authors: Salovey R. , Malm D. L. , Beach A. L. , Luongo J. P. 
Published: April 2003

AbstractEqual radiation yields of hydrogen are obtained from bulk polyethylene and thin films of solution crystallized polyethylene, with a G value of 4.6. The corresponding value for very thick mats of the solution crystallized material is 3.4. Reasoning from material balance considerations indicates that the yield of radiation‐induced crosslinking for bulk and thin films is about twice that for thick mats of polyethylene. It is suggested that thin films and thick mats differ only in fold surface contact, and that crosslinking is preferential at the folds. The retention of xylene between fold surfaces following crystallization is compatible with the effect of irradiation on trapped solvent.