bluuebunny/crossref_metadata_2025_split huggingface dataset:
ESCA applied to polymers. XXXI. A theoretical investigation of molecular core binding and relaxation energies in a series of prototype systems for nitrogen and oxygen functionalities in polymers
Authors: Clark D. T. , Harrison A. 
Published: April 2003

AbstractNonempirical LCAO MO SCF computations (in the ΔSCF formalism) were performed on the ground and core‐hole states of a range of nitrogen‐containing model systems which encompass most of the common functionalities of interest in the study of polymers. The data complement those previously presented on oxygen functionalities and show that for specific functionalities (e.g. nitrate esters and nitriles) substituent effects can be substantially different than normally anticipated on the basis of a simple additivity model. A comparison was drawn in appropriate cases with experimental data on simple model systems and polymers.
Fracturing silica‐based catalysts during ethylene polymerization
Authors: McDaniel M. P. 
Published: April 2003

AbstractThe rate and extent to which silica‐based catalysts fracture during the polymerization of ethylene in a slurry process were examined. Reactions were stopped at various times to yield as little as 20 g of polymer per gram of catalyst to more than 20,000 g/g. The catalyst residue was then collected and analyzed. Fragmentation of the catalyst was complete within the first minute or two of polymerization, whereas the rate of reaction continued to increase for more than an hour. Therefore fragmentation cannot be the rate‐controlling step. A comparision of the kinetics of Cr/silica and Ti‐Mg/silica led to the same conclusion. The most active silica gels also tended to be the most porous, which suggests fragility as a necessary requisite. Although 98% of their surface was internal, their activity was comparable to that of nonporous silicas, in which all the surface was external. This suggests that long polymer chains can diffuse out of the pores.
Radiation‐induced polymerization at high dose rate. VI. Butadiene in n‐hexane solution
Authors: Hayashi Kanae , Kagawa Kazunori , Okamura Seizo 
Published: April 2003

AbstractPolymerization of butadiene by electron‐beam irradiation was studied in n‐hexane solution. Kinetic features of the polymerization and microstructure of the product were similar to those in bulk polymerization, which indicated a cationic mechanism. Both the rate of polymerization and average molecular weight of the product decreased by about 20% in the solution system. Soluble polymer was obtained up to ca. 40% conversion at the monomer concentration of 50 mol%, whereas in the bulk system the gel formed in polymer conversion exceeded 10%. A kinetic equation was proposed to explain the change in rate of polymerization with the monomer concentration.
Reactions of cationic living poly(tert‐butyl aziridine)
Authors: Munir Arshad , Goethals Eric J. 
Published: April 2003

AbstractThe cationic polymerization of N‐tert‐butyl aziridine (TBA) can be conducted in such a way that the rate of termination is much slower than the rate of propagation, thus permitting preparation of a corresponding polymer which is “temporarily living”. Reactions of N‐methyl‐N‐tert‐butyl aziridinium triflate (which is the model for the active species of the living polymer) with different nucleophiles show that, at room temperature, the aziridinium ring reacts almost instantaneously with nucleophiles to form the corresponding ring‐opened product. Analogous reactions with the aziridinium end group of living poly‐TBA lead to polymers with varying end groups such as hydroxy, ester, primary, secondary or tertiary amino, halogen, and others. End group analysis by means of 360‐MHz 1H‐NMR nuclear magnetic resonance spectroscopy showed that the concentration of the end groups was in all cases equal to the concentration of the methyl head group, originating form the initiation reaction, if the terminating nucleophile was added five minutes after initiation (at 15°C). Under these conditions the polymerization is quantitative for initiator concentrations down to 0.01 mol L−1.
Anionic polymerization of styrene sulfonic acid derivatives
Authors: Whicher S. J. , Brash J. L. 
Published: April 2003

AbstractAs a preliminary to the preparation of block copolymers of p‐styrene sulfonic acid and isoprene, anionic polymerization of several derivatives of the former was investigated. Radical anions of naphthalene were used as the initiator for this study, in which the effects of polymerization variables including counterion, temperature, monomer and initiator concentrations, and solvent were investigated. Synthesis techniques were modified to obtain monomers of sufficient purity for anionic polymerization of n‐propyl, isopropyl, and methyl styrene sulfonates were successfully initiated, but only a limited degree of polymerization could be achieved under a wide variety of polymerization conditions. It is tentatively suggested that the living polymeric anions become dormant owing to a complexation between the anion and nearby sulfonate groups on the polymer coil.
Degradation of low‐density polyethylene in the presence of water and deuterium oxide
Authors: Sedgwick R. D. , Al‐Sultan Y. Y. , Abushihada A. M. 
Published: April 2003

AbstractThe degradation of low‐density polyethylene in the presence of water as the degradative agent was studied at a temperature of 450°C and a pressure greater than 160 atm. The experimental work was conducted in an autoclave of 333‐mL capacity. The products (gases, liquids, and solids) were analyzed by microanalytical methods and GC‐spectroscopic techniques. The results indicate the presence of paraffins, olefines, dienes, and aromatics in the degradation products. The occurrence of aromatics in the products demonstrates the importance of this degradation procedure for obtaining these valuable materials. The present work (Part 1) is believed to be the first publication to discuss the production of aromatics from polyethylenes degradation.
Studies of carbazole‐based polyarylates
Authors: Biswas Mukul , Das Sukhendu K. 
Published: April 2003

AbstractA low temperature solution condensation method with pyridine as acceptor‐catalytic reagent was applied to the synthesis of polyarylates from carbazole and bisphenol A/phenolphthalein. The polyarylates were classified with respect to their structure, thermal stability, and dielectric behavior.
Degradation of lignin by ozone. I. The kinetics of lignin degradation of ozone
Authors: Mbachu R. A. D. , Manley R. St. John 
Published: April 2003

AbstractThe ozonolysis of spruce periodate and cuoxam lignins and protolignin in spruce wood has been studied in 45% aqueous acetic acid at room temperature. Stirring affected the rate of reaction and a tentative explanation is given. Degradation followed first‐order kinetics characterized by a rate constant K with values of 6.96 × 10−4s−1 for periodate lignin, 5.10 × 10−4s−1 for cuoxam lignin, and 5.09 × 10−4s−1 for protolignin in spruce wood. The similarity of the rate constants shows (1) that periodate and cuoxam lignins are good models for wood lignin and (2) that the carbohydrate matrix has an insignificant effect on the rate of delignification of the protolignin by ozone. The average rate of ozone consumption per C9 unit for periodate lignin was determined as 0.12 mol/min and 0.08 mol/min for cuoxam lignin. The implications of the various results are discussed.
Degradation of lignin by ozone. III. The fate of the carbohydrate matrix during the degradation of spruce protolignin by ozone
Authors: Mbachu R. A. D. , Manley R. St. John 
Published: April 2003

AbstractSolvent‐extracted spruce wood meal was ozonized in 45% aqueous acetic acid at room temperature. The ozone‐treated wood meal was then extracted with dilute alkali at 65°C for 1 h. Lignin, α‐cellulose, and hemicellulose content and the viscosities of the pulped wood‐meal samples were measured as a function of the time of ozonization. Results indicate that although the attack on the wood components by ozone is not selective in this medium cellulose and hemicelluloses are degraded slowly compared with lignin. Lignin degraded approximately four times faster than the carbohydrates. At the fiber liberation point the pulp retained 78% of the original hemicelluloses and about 90% of the α‐cellulose compared with 25% of the lignin. The pulp samples obtained during ozonization of the wood meal showed a slow decrease in the average degree of polymerization (DP); the limit reached near 350 was attributed to the inaccessibility of the ordered regions in native cellulose to ozone.
Synthesis of polyamides from active O,O′‐diacyl derivatives of N‐hydroxy compounds and diamines under mild conditions
Authors: Lu Chengxun , Liu Peigang , Hu Chang 
Published: April 2003

AbstractTwo new routes to polyamides were established, based on the polycondensation of two new typical active diesters: the active diester of N‐hydroxy‐5‐norbornene‐2,3‐dicarboximide, such as N,N′‐(terephthaloyldioxy)bis(5‐norbornene‐2,3‐dicarboximide), and the active diester of 3‐hydroxy‐4‐oxo‐3,4‐dihydro‐1,2,3‐benzotriazine, such as 3,3′‐(isophthaloyldioxy)bis(4‐oxo‐3,4‐dihydro‐1,2,3‐benzotriazine) with diamines. The polycondensation occurred at room temperature in solution without added catalyst. Dipolar aprotic solvents which included dimethyl sulfoxide and N‐methyl‐2‐pyrrolidone were used as solvents for polymerization. Before polymer synthesis the aminolysis of two active monoesters was carried out as a model compound study.
Polymerization of cyclohexene oxide with Al(acac)3‐ silanol catalyst
Authors: Hayase S. , Ito T. , Suzuki S. , Wada M. 
Published: April 2003

AbstractThe polymerization of cyclohexene oxide was investigated with a new catalyst system of Al(acac)3‐ silanol compounds. Catalyst activity varied with the ratio of silanol/Al(acac)3 and the structure of silanol compounds. Catalyst deactivation appeared to be caused by self‐condensation of silanol and the addition of silanol to the epoxy ring. Polymer structure was investigated by 13C‐NMR spectroscopy and x‐ray diffraction. The mechanism of the polymerization appears to be cationic.
Water‐soluble copolymers. III. Dextran‐g‐poly(acrylamides) control of grafting sites and molecular weight by Ce(IV)‐induced initiation in homogeneous solutions
Authors: McCormick Charles L. , Park Lee Soon 
Published: April 2003

AbstractModel graft copolymers were synthesized by grafting acrylamide onto dextran (Mw = 500,000) utilizing an initiation method in which a Ce(IV)/HNO3 solution was added to the dextran solution in order to allow coplexation prior to monomer addition. Three synthetic reaction parameters were optimized on the basis of conversion and solution viscosity: monomer concentration, dextran concentration, and nitric acid concentration. Molar ratios of [Ce(IV)]/[dextran] were changed systematically to affect the number and length of the acrylamide grafts. The number of grafting sites and graft chain lengths, determined by selective hydrolysis of the carbohydrate backbone, were in good agreement with those theortically predicted from knowledge of initiation efficiency and monomer conversion. Rheological studies of the model graft copolymers were conducted in aqueous solutions as a function of temperature, added salt, and copolymer concentration.
Autocatalysis and equilibrium in polyimide synthesis
Authors: Kaas Roger L. 
Published: April 2003

AbstractModel compounds have been used to determine the mechanism of the reaction of aromatic diamines with aromatic cyclic dianhydrides to form poly(amic acids). Phthalic anhydride was used to model the anhydride functionality, while either 4,4′‐diaminodiphenyl ether or aniline was used for the amine functionality. The reaction between these materials was shown to follow second‐order, autocatalytic, and reversible kinetics. The rate constants for the mechanism were determined using a Runge–Kutta numerical integration of the rate equation and a Fibonacci technique to determine the reverse rate constant which minimzed the sum of squared deviations of the experimental data from the predicted line. Autocatalytic reversible kinetics are also followed by the formation of the poly(amic acid) precursor to a thermoplastic polyimide. In this polymerizing system, pyridine shifts the equilibrium to higher degrees of conversion to give higher molecular weights, while the opposite effect is obtained with acetic acid. Similarly, low temperatures favor higher equilibrium conversion and higher molecular weights. Thus the molecular weight of polyimides can be systematically controlled by manipulating factors which control the equilibrium conversion during the original formation of the poly(amic acid) precursor.
Post‐irradiation grafting of tetrafluoroethylene at low temperatures
Authors: Barkalov I. M. , Kiryukhin D. P. , Muydinov M. R. 
Published: April 2003

AbstractLow‐temperature postirradiation grafting of tetrafluoroethylene (TFE) to polyolefines and silicone elastomers was the subject of study. After preliminary dissolution of TFE in the polymer at 273°K the system was slowly cooled to 77°K. In this process a certain part of TFE in polyolefines (ethylene‐propylene copolymer and polypropylene) is retained by the vitreous polymer matrix. When slowly heated after radiolysis at 77°K this system shows graft polymerization of dissolved TFE after Tg. The graft copolymer is soluble and its IR spectra contain absorption bands characteristic of polytetrafluoroethylene. In polydimethylsiloxane rubber (SKT) the dissolved TFE when frozen to 77°K remains sorbed between the SKT crystallites rather than in a separate phase. When these radiolyzed samples are heated the graft‐polymerization occurs primarily over the temperature range between the TFE and SKT melting points. The technique provedes for 100–150% grafting of TFE. This method also permits grafting to silicone rubbers and to several other polymers and elastomers.
Functional monomers and polymers. XCV. Photochemical reactions on synthetic polymers having pendant thymine bases in polymethyl methacrylate film
Authors: Kita Yasuo , Uno Taizo , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractThe photodimerization reaction of synthetic polymers which contain thymine bases was studied in polymethyl methacrylate film. The quantum efficiency for the photodimerization of the thymine bases of polyacrylate and polymethacrylate, fixed in the polymethyl methacrylate film was measured. The value of the film was higher than those measured in solution.
Head‐to‐head vinyl polymers. III. Preparation and characterization of head‐to‐head poly(acrylic acid) and its esters
Authors: Otsu Takayuki , Quach Loc 
Published: April 2003

AbstractHead‐to‐head (h‐h) poly(acrylic acid) (PAA) and some h‐h poly(alkyl acrylates) (PRA) with methyl, ethyl, n‐propyl, n‐butyl, isobutyl and 2‐ethylhexyl substituents were prepared by hydrolysis or esterifications of the alternating copolymer of ethylene with maleic anhydride. In general, these esterification reactions became increasingly difficult as the carbon chain in the alcohols lengthened or branched. The softening, glass transition, and degradation temperatures of the h‐h polymers obtained were somewhat higher than those of the corresponding head‐to‐tail (h‐t) polymers. The main degradation products of both h‐h and h‐t PRA were identified by pyrolytic gas chromatography as the alcohol and monomer. In addition, the relative ratios of the amounts of alcohol to monomer were larger for h‐h than for the corresponding h‐t polymers.
Head‐to‐head vinyl polymers. V. Preparation and characterization of alternating head‐to‐head copolymers of alkyl acrylates with alkyl methacrylates
Authors: Quach Loc , Otsu Takayuki 
Published: April 2003

AbstractAlternating head‐to‐head (h‐h) copolymers of methyl or n‐butyl acrylates with the corresponding methacrylates were synthesized by alternating copolymerization of ethylene with citraconic anhydride, followed by esterification and Characterization. The respective equimolar (1:) head‐to‐tail (h‐t) copolymers were also prepared by conventional radical copolymerization as comparison. The alternating, relatively low molecular weight h‐h copolymers obtained showed softening, glass transition, and degradation temperatures somewhat higher than those displayed by the 1:1 h‐t copolymers. After pyrolysis the main decomposition products from both h‐h and h‐t copolymers were alcohols, acrylates, and methacrylates. Furthermore, the ratios of alcohols to acrylates were larger for the h‐h than for the h‐t copolymers and smaller for the methyl than for the n‐butyl esters.
Calculation of molecular weight distribution of thermally polymerized polystyrene
Authors: Tung L. H. 
Published: April 2003

AbstractThe molecular weight distribution of thermally polymerized polystyrene prepared under steady‐state conditions is expected to obey the simple exponential distribution function. By integrating this simple distribution function with conversion the overall distribution of polystyrene prepared under more complex conditions can be predicted without invoking other kinetic constants. Good agreement between prediction and experiments has been obtained when a mercaptan compound was used to broaden the molecular weight distribution.
Effects of curing on the glass transition temperature and moisture absorption of a neat epoxy resin
Authors: Danieley Ned D. , Long Edward R. 
Published: April 2003

AbstractApparent glass transition temperature (Tg) measurements were made on smaples of a neat epoxy resin that had been cured at four different temperature and for four different times at each temperature. The apparent Tg data increase with cure time toward an asymptote that was dependent on cure temperature. The asymptotic dependence of Tg on cure temperature may be explained by the effect of cure temperature on the reaction rates and available reaction sites. The asymptotic increase with cure time may be understood in terms of the resin's extent of cure. Moisture‐conditioning studies were also made and the amount of moisture absorbed was correlated with the extent of cure. The absorbed moisture's interaction with the resin's molecular structure was deduced to by primarily at hydroxyl sites.
Functional monomers and polymers. XCVI. Photochemical reactions on oligo‐ and polyethyleneimines which contain pendant thymine bases
Authors: Inaki Yoshiaki , Suda Yasuo , Kita Yasuo , Takemoto Kiichi 
Published: April 2003

AbstractThe photodimerization reaction of oligo‐ and polyethyleneimine derivatives which contain pendant thymine bases in various amounts was studied in aqueous solution in a wide pH range and in N, N‐dimethylformamide solution. The photodimerization reaction of these derivatives in poly(methyl methacrylate) was also studied. It was found that its quantum efficiency tended to increase as thymine units were added to the oligomers and copolymers. This result is discussed in terms of the effect of the nearest neighboring thymine units and singlet energy migration, particularly in the polymers.
Further discussion of the cyclopolymerization of acrylic anhydride in terms of ring size control
Authors: Matsumoto Akira , Kitamura Takao , Oiwa Masayoshi , Butler George B. 
Published: April 2003

AbstractRadical cyclopolymerization of acrylic anhydride (AA) was conducted under various polymerization conditions to yield highly cyclized polymer, and the content of the five‐membered ring of cyclic poly‐AA obtained was examined in detail. Five‐membered ring formation was favored with increased solvent polarity, raised polymerization temperature, and decreased monomer concentration; the ring size of the cyclic structure could be controlled freely by choosing appropriate polymerization conditions. In addition to these results, the rate of polymerization and the molecular weight of the polymer were reduced under polymerization conditions where the five‐membered ring formation was favored. Finally, a mechanistic discussion is given in order to interpret these results; a reaction scheme for propagation based on polymerization equilibrium is proposed.
Solution properties of poly(4,4′‐oxydiphenylene)‐4‐amidophthalamic acid
Authors: Alvino William M. , Ray John R. 
Published: April 2003

AbstractA series of polymers based on 4‐chloroformyl phthalic anhydride (TMAC) and 4,4′‐diaminodi‐phenylether (DAPE) was prepared and shown to be soluble in N, N‐dimethylacetamide which contained 0.1N LiBr. These solutions were characterized by light scattering, membrane osmometry, and viscosity. A relationship between the viscosity and molecular weight was formulated and the nature of the polymer chain in solution was postulated.
Synthesis of vinyl polymers with pendant phenoxazinyl group
Authors: Kamogawa Hiroyoshi , Todo Yasuto , Nanasawa Masato 
Published: April 2003

AbstractVinyl monomers bearing phenoxazine units, were synthesized: 2‐vinyl‐phenoxazine starting with phenoxazine in a five‐step synthesis; 3‐acrylamido‐ or 3‐methacrylamido‐phenoxazines with or without 10‐PhCH2 or 10‐Me‐substituent starting with o‐benzylideneaminophenol or o‐anisidine via 3‐aminophenoxazines; and 3‐(p‐styrenesulfonamido)phenoxazines with or without 10‐PhCH2‐ or 10‐Me‐substituent, also via 3‐aminophenoxazines. Polymerizations of these noval monomers proceeded smoothly, except those having no 10‐substituent. Changes of the visible absorption spectrum of iodine in THF with addition of the polymers and oligomers thus prepared were considerable, with the appearance of new absorption peaks for polymers with 10‐Me‐substituent.
Polymerization of coordinated monomers. XVII. Alternating copolymerization of methyl methacrylate with styrene by boron compounds
Authors: Hirai Hidefumi , Takeuchi Kazuhiko , Komiyama Makoto 
Published: April 2003

AbstractBy the use of various boron compounds methyl methacrylate and styrene were copolymerized under photoirradiations at −20°C. The alternately regulating activities of the boron compounds in the copolymerizations were in the following order: boron trichloride > ethylboron dichloride > boron trifluoride > diethylboron chloride ≫ triethylboron (≃0). Boron trichloride and ethylboron dichloride exhibited such high regulating activities that their presence in 1 mol% in the charged methyl methacrylate was sufficient to complete equimolar alternating copolymerization. The alternating copolymerization proceeded in the steady state. The copolymerization rates decreased in the following order: boron trichloride ≫ ethylboron dichloride > diethylboron chloride ≫ triethylboron (≃0). The cotacticities of methyl methacrylate‐centered triads in the resulting copolymers were identical to those prepared with boron trichloride, ethylboron dichloride, and diethylboron chloride. The mechanism of the alternating copolymerization is discussed.
Polymers with improved flammability characteristics. I. Phenolphthalein‐related homopolymers
Authors: Lin M. S. , Pearce E. M. 
Published: April 2003

AbstractImproved fire resistance occurs for phenolphthalein‐related polycarbonates and polyesters compared to bisphenol‐A polymers and emphasizes the importance of polymer composition and polymer structure in affecting the flammability of a polymer. Phenolphthalein‐related polymers are able to produce a higher degree of crosslinking during pyrolysis which subsequently leads to higher char yields. The correlations between oxygen index and char yield for various polymers are obtained and discussed. Polycarbonates and polyamides usually show higher oxygen indices than the corresponding polyesters of related structures. This indicates that the nature of the pyrolysis products has a measurable effect on the flammability of a specific polymer. Among many factors, polycarbonates should release more CO2 from the breakdown of the carbonate group, and polyamides should produce relatively nonflammable nitrogen‐containing products during pyrolysis, thus accounting in part for these results.