bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation of the thermolysis mechanism of model urethanes
Authors: Voorhees K. J. , Hileman F. D. , Einhorn I. N. , Futrell J. H. 
Published: April 2003

AbstractThe products of pyrolysis in a helium atmosphere of a model urethane foam based on PAPI and propoxylated trimethylol propane were investigated by using GC/MS and GC/CIMS. Chemical‐ionization mass spectrometry was used because it produces primarily protonated molecular ions (M + 1) with little fragmentation which facilitated the identification of the polyol decomposition products. Identification of the polyol pyrolysis fragments has led to the formulation of a detailed polyol thermolysis mechanism. This mechanism shows the polyol to decompose by a systematic route of reactions rather than by a random breakdown.
Distribution of polymer deposition in plasma polymerization. I. Acetylene, ethylene, and the effect of carrier gas
Authors: Yasuda H. , Hirotsu Toshihiro 
Published: April 2003

AbstractFactors which influence the distribution of polymer deposition in an electrodeless glow‐discharge system were investigated for acetylene and ethylene. Under the conditions in which “full glow” is maintained, the distribution of polymer deposition from pure monomer flow systems is nearly independent of flow rate of monomer or of the system pressure in discharge, but is largely determined by the characteristic (absolute) polymerization rates (not deposition rate) of the monomers. Acetylene has a high tendency to deposit polymer near the monomer inlet, whereas ethylene deposits polymer more uniformly in wider areas in the reactor. The addition of carrier gas such as argon or partially copolymerizing gas such as N2, H2, and CCl2F2 was found to narrow the distribution of polymer deposition. The distribution of polymer deposition is also influenced by a glow characteristic which is dependent on flow rate and discharge power.
Dipole moment characterization of phenol–, o‐cresol–, and p‐cresol–formaldehyde resins
Authors: Tobiason Fred L. , Cain Greg H. , Anderson Jack W. 
Published: April 2003

AbstractDipole moments and their temperature dependence have been measured in p‐dioxane for fractionated novolac phenol–, o‐cresol–, and p‐cresol–formaldehyde polymers. The phenol–formaldehyde fractions covered a molecular weight range of 200 to 6100, and the limiting dipole moment ratio 〈μ2〉/xm2 is 1.48. The p‐cresol–formaldehyde dipole‐moment ratio at a DP of 4 is 2.47, whereas the phenol–formaldehyde dipole‐moment ratio is 1.40. That for o‐cresol–formaldehyde is intermediate in value. The dipole‐moment temperature coefficients are positive for p‐cresol chains and negative for the phenol–formaldehyde chains. These results indicate that the hydroxyl groups along the p‐cresol–formaldehyde polymer are highly ordered, with the aromatic rings closer to the sterically hindered planar position than in the phenol–formaldehyde polymers.
Poly‐α‐ester degradation studies. VII. Thermal degradation of poly(cycloalkylidene carboxylates)
Authors: Norton G. P. , Tighe B. J. , Molloy R. 
Published: April 2003

AbstractThe thermal degradation of poly(cyclopentylidene carboxylate) and poly(cyclohexylidene carboxylate) has been studied over the temperature range 200–500°C by using a combination of kinetic and analytical techniques. The results obtained indicate the simultaneous operation of mechanisms previously observed with different compounds in the series. Thus kinetic studies by thermogravimetric analysis and characterization of the products formed suggest the occurrence of an essentially first‐order hydrogen abstraction process with superimposed random scission reactions in the early stages. The main products are cyclopenten‐1‐carboxylic acid and cyclohexen‐1‐carboxylic acid, respectively. This corresponds to the behavior previously observed in the degradation of poly(3‐pentylidene carboxylate). On the other hand, in‐line pyrolysis directly linked to a gas chromatograph clearly indicates the production of cyclopentanone and cyclohexanone and, more importantly in the case of poly(cyclopentylidene carboxylate), the formation of dicyclopentyl glycollide. The appearance of these products in addition to the unsaturated acids suggests that some degradation occurs by the intramolecular ester‐interchange process previously postulated for poly(methylene carboxylate) and poly(isopropylidene carboxylate). The associated thermodynamic parameters and relative quantities of the different products observed by gas‐chromatographic methods indicate that the hydrogen‐abstraction process predominates.
Aqueous polymerization of acrylonitrile initiated by the bromate–thiourea redox system
Authors: Pati Nrusingha C. , Lenka Subasini , Nayak Padma L. , Mohanty Trijama R. 
Published: April 2003

AbstractThe aqueous polymerization of acrylonitrile initiated by an acidified bromate–thiourea redox system has been studied under nitrogen atmosphere. The rate of polymerization is independent of thiourea concentration over the range 2–9 × 10−3M and reaches maximum at 9 × 10−3M. The rate varies linearly with [monomer]. The initial rate of polymerization as well as the maximum conversion increases within the range of 4–22.5 × 10−3M KBrO3, but beyond 22.5 × 10−3M the rate of polymerization decreases. The initial rate and the limiting conversion increases with increasing polymerization temperature in the range 30–45°C; and beyond 45°C they decrease. The effect of certain neutral salts, water‐soluble solvents, and micelles of cationic, anionic, and nonionic surfactants on the rate of polymerization has been investigated.
Study of the mechanism of polysulfone decomposition by pyrolysis/gas chromatography and pyrolysis/gas chromatography/mass spectrometry
Authors: Gritter R. J. , Seeger M. , Gipstein E. 
Published: April 2003

AbstractBoth co‐ and terpolysulfones have been flash‐pyrolyzed at high temperature followed by separation and identification of the products by gas chromatography and/or gas chromatography/mass spectrometry. As expected, most of the products were the corresponding olefin and SO2. Additionally, higher molecular weight products, including aromatics, and olefin isomerization products, were produced. Mechanisms for initiation and formation of the higher molecular weight products are presented which include the back reaction of intermediate free radicals to abstract hydrogen or to form CC bonds followed by expulsion of SO2. The free‐radical intermediates formed by the SO2 expulsion undergo transformations to give the aromatic products. No breakdown products were found with either O or S present, nor was SO2H found.
Some aspects of plasma polymerization of fluorine‐containing organic compounds. II. Comparison of ethylene and tetrafluoroethylene
Authors: Yasuda H. , Hsu T. S. , Brandt E. S. , Reilley C. N. 
Published: April 2003

AbstractPlasma polymerizations of ethylene and tetrafluoroethylene are compared. In the plasma polymerization of ethylene and of tetrafluoroethylene, glow characteristics play an important role. Glow characteristic is dependent on a combined factor of W/Fm, where W is discharge power and Fm is monomer flow rate. At higher flow rates, higher wattages are required to maintain “full glow.” In the plasma polymerization of tetrafluoroethylene, simultaneous decomposition of the monomer competes with plasma polymerization. Above a certain value of W/Fm, decomposition becomes the predominant reaction, and the polymer deposition rate decreases with increasing discharge power. ESCA results indicate that the plasma polymer of tetrafluoroethylene that is formed in an incomplete glow region (low W/Fm) is a hybrid of polymers of plasma polymerization and of plasma‐induced polymerization of the monomer. Polymers formed under conditions of high W/Fm to produce “full glow” are similar, regardless of the extent of decomposition of the monomer. They contain carbons with different numbers of F(CF3, CF2, >CF, >C<) and carbons bonded to other more electronegative substituents.
Catalytic activity of Cu(II)–poly(vinyl alcohol) complex for decomposition of hydrogen peroxide
Authors: Hojo Nobumasa , Shirai Hirofusa , Chujo Yoshiki , Hayashi Sadao 
Published: April 2003

AbstractDecomposition of hydrogen peroxide was examined was examined by using Cu(II)–poly(vinyl alcohol) (PVA) as catalyst. The rates of decomposition were measured. Electronic spectra and infrared spectra of Cu(II)–PVA complex systems were determined at various stages of decomposition. Effect of addition of various amines to the Cu(II)–PVA system on catalytic action was considered. The relation between the initial rate and the initial concentration of hydrogen peroxide varied in accordance with the rate expression of Michaelis‐Menten type. Cu(II)–PVA complex was found to have a large catalytic activity, while the polymeric PVA ligand and copper(II) ion exhibited less activity than Cu(II)–PVA complex. For hydrogen peroxide decomposition, Cu(II)–PVA complex showed catalytic activity when a stable complex of planar structure formed, while many other polymer complexes reported by other authors showed the catalytic activity when they were in unstable complex forms. An amine substituent has a critical influence on the rate of hydrogen peroxide decomposition. The mechanism in the first step of reaction for hydrogen peroxide decomposition is discussed.
Block copolymers of styrene, isoprene, and ethylene oxide prepared by anionic polymerization. I. Synthesis and characterization
Authors: Koetsier D. W. , Bantjes A. , Feijen J. , Lyman D. J. 
Published: April 2003

AbstractAnionic polymerization has been used as a technique for the synthesis of five‐block copolymers of polystyrene (PS), polyisoprene (PI), and poly(ethylene oxide) (PEO). Two types of such polymers, PEO‐PI‐PS‐PI‐PEO and PEO‐PS‐PI‐PS‐PEO with varying PEO block length, have been prepared, using potassium naphthalene as the initiator and tetrahydrofuran as the solvent. The polymers were purified by extraction with ethyl acetate, diethyl ether, and water. After the addition of each monomer, a sample from the living polymer solution was taken and analyzed by spectroscopy (infared (IR) and proton magnetic resonance (PMR)), osmometry, and gel‐permeation chromatography (GPC) to obtain information about composition, molecular weight and molecular weight distribution of the intermediate polymers. The five‐block copolymers have also been characterized by the same techniques and by elemental analysis.
Polypivalolactone grafts on EPDM
Authors: Thamm Richard C. , Buck Warren H. 
Published: April 2003

AbstractRandom copolymers of ethylene, propylene, and 1,4‐hexadiene (EPDM) were carboxylated by reaction with thioglycolic acid or with maleic anhydride. Treatment of these polymers in tetrahydrofuran solution with tetrabutylammonium hydroxide generated carboxylate anions, which initiated the graft polymerization of pivalolactone. Conversion and grafting efficiencies approached 100%. Polypivalolactone chains had an estimated DPn of 3 to 20 and the average distance between graft sites varied from 3000 to 7700 molecular weight units. On cooling from the melt, highly crystalline domains of polypivalolactone formed, which melted at 120–200°C depending on DPn. Electron microscopy and x‐ray analysis verified the presence of these domains, which serve as reinforcing tiepoints for thermally reversible network formation. The resultant thermoplastic elastomers have excellent elasticity and strength, and their compression set resistance is equivalent to that of conventionally cured and reinforced EPDM. This paper details the synthesis, morphology, and structure–property relationships of these elastomers.
Ionic polymerization of 1,2‐butylene oxide: GPC, NMR, and IR characterization of the reaction products
Authors: Malhotra Shadi Lal , Leborgne Alain , Blanchard Louis‐Philippe 
Published: April 2003

AbstractThe triphenylmethyl hexafluoroarsenate‐initiated cationic polymerization of 1,2‐butylene oxide in dichloroethane between −25 and +25°C and its sodium‐initiated anionic polymerization in bulk at 20°C have been carried out. Gel permeation chromatography (GPC) molecular weight distribution curves of the reaction products are multinodal. Nuclear magnetic resonance (NMR) and infrared (IR) analyses show that the cationically prepared polymers are composed of cyclic oligomers and linear high‐molecular‐weight products, while the anionically prepared polymers contain only linear products some of which include double bonds. NMR analyses further reveal that the cationically prepared polymers consist of monomer repeat units, while the anionically prepared polymers are essentially made of side products originating from the reaction of 1,2‐butylene oxide with the sodium mirror used as the anionic initiator.
Effect of homologous series of alkyl sulfate surfactants on the emulsion polymerization of styrene. I. Equal total concentrations
Authors: Al‐Shahib W. A. G. R. , Dunn A. S. 
Published: April 2003

AbstractThere is evidence in the literature that the rates of emulsion polymerization increase by a large factor as the alkyl chain length increases for a homologous series of surfactants. However, the area occupied by a surfactant molecule in a saturated monolayer at the polystryene/water interface is independent of chain length for alkyl sulfates so that, on the basis of Gardon's theory, equal rates of polymerization would be expected when equal concentrations of surfactants are used. There is a large increase in the number of polymer latex particles formed and in the rate of emulsion polymerization as the surfactant concentration is increased through the critical micelle concentration; this accounts for the large increases reported, because the lower members of the homologous series are below their critical micelle concentrations in most of the published studies. When a common concentration is chosen that is above the critical micelle concentration even for the lowest member of the series, only a relatively small increase in latex particle number and rate of emulsion polymerization with alkyl chain length of the surfactant is observed. This is attributable to an increase in the concentration of surfactant micelles. Good agreement with Gardon's theory is obtained when the concentration of micellar surfactant is used instead of the total surfactant concentration.
Application of mass spectrometry to copolymers of ethylenes and propylene oxides. I. Structural analysis
Authors: Lee A. K. , Sedgwick R. D. 
Published: April 2003

AbstractMass spectra of linear copolymers of ethylene and propylene oxides show features which are characteristic of the two monomers. Interpretation of the spectra of samples with and without modified end groups allows them to be classified as either random or blocked in structure and, in the latter case, permits determination of the order in which blocks are incorporated. Within a limited molecular weight range, the method can lead to a full determination of the distribution of molecular weights in the samples.
Vinylation and polymerization with trivinylaluminum. I. Vinylation of organic halides as a model for termination in cationic polymerization leading to vinyl end groups
Authors: Mandal Broja M. , Kennedy Joseph P. , Kiesel Rodney 
Published: April 2003

AbstractAn improved synthesis of trivinylaluminum (V3Al) is described. The proton magnetic resonance (PMR) spectrum of V3Al was recorded and analyzed. A new vinylation method involving the use of V3Al as the vinylating agent has been developed, and the vinylation of organic halides by V3Al was studied at −30, −50 and −70°C. Primary alkyl chlorides, such as methyl and methylene chloride, do not react with V3Al and were used as solvents. Secondary chlorides such as 2‐chloropropane also do not react. t‐Butyl chloride gives rise to t‐butylethylene (70–98%), depending on reaction conditions, and the allylic chlorides, 3‐chloro‐1‐butene, and 3‐chloro‐3‐methyl‐1‐butene, yield the expected vinylated products and their isomers (∼90%). Allyl and benzyl chloride do not react under the conditions tried. The reaction between V3Al and the ditertiary dichloride 2,6‐dichloro‐2,6‐dimethylheptane yields several isomeric C13H24 and C11H20 hydrocarbons; however, surprisingly, C9H16 does not form. The C13 hydrocarbons arise by divinylation at the termini of the dichloride, while the C11 hydrocarbons are formed by vinylation at one and proton elimination at the other terminus of the dichloride. The presence of unsaturated C13H24 and C11H20 isomers is most likely due to proton induced isomerization. These results are explained by a proximity effect involving vinylation at one end of the dichloride by V3Al followed by rapid reaction of the second chlorine (mostly) by V2AlCl generated in situ during the first vinylation in the proximity of the chloride. At the other chlorine terminus V2AlCl causes either a second vinylation (leading to C13 hydrocarbons) or a proton elimination (leading to C11 hydrocarbons). The absence of C9H16 among the reaction products indicates that V3Al exclusively effects vinylation. The RCl + V3Al ← RV + V2AlCl reaction may be regarded as a model for initiation followed by immediate termination in cationic olefin polymerization, a process leading to vinyl‐ended polymers.
Photochemical addition of maleic anhydride derivatives and related compounds to benzene and polystyrene sensitized by low‐ and high‐molecular carbonyls
Authors: Hrdlovič P. , Záhumenský L. , Lukáč I. , Sláma P. 
Published: April 2003

AbstractThe photochemical addition of maleic anhydride to benzene initiated by radiation with λ > 340 nm is sensitized by low and high‐molecular carbonyls. Only those copolymers of para‐substituted acrylophenones with methyl methacrylates are effective sensitizers that have a triplet energy ET higher than 276 kJ/mole. The efficiency of maleic anhydride addition was found to be higher for copolymers of acrylophenone with styrene (ET > 276 kJ/mole) than that with polystyrene in the presence of low‐molecular ketone. The copolymer 4‐phenylacrylophenone–styrene exhibits maleic anhydride addition in solution and in film, although ET < 276 kJ/mole, possible caused by energy transfer from higher triplet level. The derivatives of maleic anhydride and structurally related compounds react under the conditions of sensitized photoaddition in a different way from the parent compound. Vinylene carbonate is added to polystyrene sensitized by acetophenone; 2,3‐dichloromaleic anhydride and 1,2‐dichlorovinylene carbonate initiated crosslinking of polystyrene in solution and in film; 2,3‐dimethylmaleic anhydride mainly underwent dimerization (88% w/w); dimethyl maleate does not react at all. Maleic anhydride and other related compounds take part in these reactions in the lowest triplet state. Addition of maleimide and its derivatives to polystyrene proceeds as a nonsensitized reaction from the singlet state and is more effective than maleic anhydride addition to polystyrene in solution and in film. 2,3‐Dichloromaleimide dimerized (15% (w/w)) as well as undergoing addition to polystyrene.
Singlet oxygen and photooxidation of polymers
Authors: Ivanov V. B. , Shlyapintokh V. Ya. 
Published: April 2003

AbstractThe rates of accumulation of oxygen‐containing species in photooxidation have been determined for a series of polymers such as polystyrene, polyisoprene, and polybutadiene in a wide range of singlet oxygen stationary concentrations in the polymers. An increase in singlet oxygen (1O2) concentration was achieved by introducing a dye which is a 1O2 donor into a polymer and by irradiating a sample with an additional source of light absorbed by the dye only. To decrease 1O2 concentration, 1,2,5‐trimethyl‐4‐hydroxyphenylpiperidine, which is a quencher of 1O2, was introduced into a sample. The 1O2 stationary concentration in an oxidized polymer was measured via singlet oxygen oxidation of 2,2,6,6‐tetramethyl‐4‐oxypiperidine which leads to the formation of the corresponding nitroxyl radical. The photooxidation rate has been found to vary only slightly with 1O2 concentration, even when the concentration changes 10–25‐fold. Thus, 1O2 does not participate appreciably in the process of polymer photooxidation. It may be due to the lowering of 1O2 reactivity toward unsaturated groups in the polymer matrix as compared with that in solution.
ESCA applied to polymers. XVIII. RF glow discharge modification of polymers in helium, neon, argon, and krypton
Authors: Clark D. T. , Dilks A. 
Published: April 2003

AbstractThe crosslinking of an ethylene–tetrafluoroethylene copolymer by exposure to a variety of inert gas plasmas, excited by an inductively coupled radiofrequency (RF) field, has been studied. The rates for direct and radiative energy‐transfer processes are determined within the framework of a kinetic model of the system and are shown to have a strong dependence on the sustaining gas, as do the average depths of penetration of the ions and metastable species. Helium is found to be the most efficient gas for the crosslinking of the outermost few monolayers whereas the crosslinking of the subsurface and bulk polymer is best effected by neon. Madelung charge potential calculations have been performed to simulate the experimentally determined x‐ray photoelectron spectroscopy (ESCA) spectra to elucidate several features of the mechanisms involved.
A pronounced ortho effect in the polymerization of o‐substituted β‐nitrostyrenes
Authors: Carter Mary E. , Drueke Joseph W. , Nash James L. , Schwietert James W. , Butler George B. 
Published: April 2003

AbstractIt was shown in a previous paper that a number of m ‐ and p‐substituted β‐nitrostyrenes would readily undergo polymerization via anionic initiation with alkoxide ions to yield high polymers, whereas, in all cases, the corresponding o‐substituted isomers could not be induced to produce polymers under any conditions tried. This article reports a systematic study of this unexpected “ortho effect” based on the initial postulate that the effect was the result of steric inhibition of the propagation step that would ordinarily lead to polymer. Since the fluorine atom is only slightly larger than the hydrogen atom, the series o‐, m‐, and p‐fluoro‐β‐nitrostyrenes was synthesized and its alkoxide ion‐initiated polymerization studied. Although it was shown in all cases of o‐substituted β‐nitrostyrenes studied that initiation was rapid, only in the case of o‐fluoro‐β‐nitrostyrene was a substantial amount of polymer obtained. With up to 3 mole % initiator a maximum of 26% polymer was obtained, whereas polymerization was rapid in cases of the meta and para isomers. The values of the propagation rate constants kp were found to be 1.1 liters/mole‐sec for the para isomer as compared with 4.8 × 10−2 liter/mole‐sec for the ortho isomer for a ratio kp(p)/kp(o) = 23, the magnitude of this ortho effect for the fluorine atom.
The kinetics of polyesterification. II. Succinic acid and ethylene glycol
Authors: Lin Chen Chong , Yu Ping Chang 
Published: April 2003

AbstractThe polyesterification of succinic acid with ethylene glycol in both equimolar and nonequimolar ratios was investigated at the reaction temperature of 195°C. The experimental results agreed quite well with the kinetic equations proposed in our previous paper for the adipic acid–ethylene glycol system, except in the case of acid‐catalyzed equimolar reaction, where a shift of kinetic behavior from reaction control to diffusion control would appear. The apparent rate constants for uncatalyzed and acid‐catalyzed reactions were evaluated by using the method of least squares for various values of initial molar ratio between [OH] and [COOH]. The dissociation effect of hydrogen ion from dibasic acid in glycol, as proposed in the adipic acid–ethylene glycol system, could also be applied in the succinic acid–ethylene glycol system to explain the kinetic behavior observed. The kinetic equations previously proposed for polyesterification were again confirmed.