bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oligomerization of phenylacetylene on fe‐catalysts
Authors: Voicechovsky Y. P. , Slivinsky E. V. , Fichte B. B. , Loktev S. M. 
Published: April 2003

AbstractUsing a low activity system as a catalyst gives additional opportunities for study of polymerization mechanism. We made an attempt using phenylacetylene as a monomer to synthesize, separate, and identify oligomers of this alkyne on melting iron catalyst—“naked” metal. Four components with the lowest molecular weight were identified as: (compound 1) isomers of 1,2‐diphenylcyclobutadiene, (compound 2) 1,3‐diphenylcyclobutadiene, (compound 3) 1,4‐diphenylbuten‐1‐yne‐3, and (compound 4) triphenyl substituted Dewar benzene. It was shown, that in the presence of iron catalysts the phenylacetylene oligomerization proceeds as a linear polymerization through a 2 + 2 cycloaddition.
Copoly(amide—ester)s from p‐aminobenzoic and hydroxybenzoic acids by the direct polycondensation with diphenyl chlorophosphate and LiCl
Authors: Higashi Fukuji , Ozawa Michihide , Hoshio Atsushi , Mochizuki Akihiko 
Published: April 2003

AbstractThe reaction promoted by diphenyl chlorophosphate (DPCP) and LiCl was found to be effectively used for the preparation of aromatic polyesters with high molecular weights directly from hydroxybenzoic acids when the condensing agent was added dropwise. The reaction was successfully to the direct polycondensation reaction of p‐aminobenzoic and hydroxybenzoic acids, giving high‐molecular‐weight copoly(amide—ester)s soluble in amide or phenolic solvents. Copolycondensations of isophthalic and terephthalic acids with bisphenols and aromatic diamines were also examined by adding the DPCP solution to a mixture of these monomers or by initial reaction of DPCP with the acids followed by dropwise addition of a mixture of bisphenols and the diamines. The latter stepwise reaction gave random copolymers soluble in amide and phenolic solvents. Thermal properties of these copolymers were studied.
Grafting onto polypropylene. I. Effect of solvents in gamma radiation‐induced graft copolymerization of poly(acrylonitrile)
Authors: Misra B. N. , Sood D. S. , Mehta I. K. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) onto isotactic polypropylene (PP) fiber has been studied by using gamma rays from a 2100 Ci 60Co source as initiator by preirradiation technique. The preirradiated PP was treated with AN and the mixture was graft copolymerized by heating to 100°C for different time periods. The percentage of grafting is determined as a function of total dose, reaction time, and monomer concentration. The effect of different solvents such as H2O, CH3OH, and dioxane upon percentage of grafting has been studied. The maximum effect was observed in water and the minimum in CH3OH. PP—g—PAN was characterized by IR spectroscopic and thermogravimetric methods. A plausible mechanism of gamma radiation induced grafting of AN onto PP in the absence and in the presence of solvents has been proposed. An attempt has been made to compare the relative abilities of different solvents to influence grafting.
Synthesis and characterization of soluble aromatic polyamides derived from 2,5‐bis‐(4‐chloroformylphenyl)—3,4‐diphenylthiophene and aromatic diamines
Authors: Kakimoto Masa‐Aki , Negi Yuvraj Singh , Imai Yoshio 
Published: April 2003

AbstractA new polymer‐forming monomer, 2,5‐bis(4‐carboxyphenyl)—3,4‐diphenylthiophene, was synthesized either by the Friedel—Crafts reaction of tetraphenylthiophene with oxalyl chloride directly, or by the Friedel—Crafts acetylation of tetraphenylthiophene, followed by oxidation. The low temperature solution polycondensation of 2,5‐bis(4‐chloroformylphenyl)—3,4‐diphenylthiophene with various aromatic diamines in N,N‐dimethylacetamide (DMAc) afforded tetraphenylthiophene‐containing aromatic polyamides with inherent viscosities of 0.5–1.0 dL/g. Copolyamides were obtained from a mixture of the diacid chloride and isophthaloyl or terephthaloyl chloride. Except for two polyamides, all the others were readily soluble in amidetype solvents including DMAc, and were cast into transparent and flexible films. These polymers had glass transition at around 300°C. Thermal stability of the polymers was evaluated by thermogravimetry which showed no weight loss below 390°C in both air and nitrogen atmospheres.
Syntheses of copolymers containing pendant cyclic iminoethers and crosslinking reactions of these copolymers with dithiols and dicarboxylic acids
Authors: Nishikubo Tadatomi , Tōkairin Atushi , Takahashi Makoto , Nosaka Waichi , Iizawa Takashi 
Published: April 2003

AbstractCopolymers containing pendant cyclic iminoethers were prepared by radical copolymerizations of 2‐vinyl‐2‐oxazoline (VOZO), 5‐methyl‐2‐vinyl‐2‐oxazoline (MVOZO), 4,4‐dimethyl‐2‐vinyl‐2‐oxazoline (DMVOZO), 4,4‐dimethyl‐2‐vinyl‐5,6‐dihydro‐4H‐1,3‐oxazine (DMVOZI), and 4,4,6‐trimethyl‐2‐vinyl‐5,6‐dihydro‐4H‐1,3‐oxazine (TMVOZI) with styrene, methyl methacrylate (MMA), and ethyl acrylate (EA) using AIBN as an initiator. In addition, the monomer reactivity ratios of VOZO, MVOZO, DMVOZO, and DMVOZI with styrene and MMA were determined. The crosslinking reactions of these copolymers with polyfunctional thiols such as 6‐(N,N‐dibutyl)amino‐1,3,5‐triazine‐2,4‐dithiol (DBDT), 4,4′‐oxydi(benzenedithiol) (OBDT), and pentaerythritol tetrathioglycolate (PETT), and dicarboxylic acids such as succinic acid, adipic acid, and sebacic acid were carried out at several reaction temperatures. From these results, it was found that the order of reactivity of pendant cyclic iminoethers to the thiols was VOZO > DMVOZO ≥ DMVOZI > MVOZO > TMVOZI, and that of the cyclic iminoethers to the carboxylic acids was VOZO > MVOZO ≥ DMVOZI > TMVOZI ≥ DMVOZO. Furthermore, the order of reactivity of the thiols to the cyclic iminoethers was DBDT > OBDT > PETT, and that of the dicarboxylic acids to the cyclic iminoethers was succinic acid > adipic acid > sebacic acid.
Polymerization of perfluoro‐2‐alkynenitriles by π‐bis(benzene)chromium(O)
Authors: Huang Yaozeng , Li Jis En , Zhou Qilin , Zhou Jianqiang 
Published: April 2003

AbstractPerfluoro‐2‐alkynenitriles can be polymerized into soluble polymers at low temperatures by π‐bis(benzene)chromium(O) in benzene/pyridine (10:1) solution. The degree of polymerization is 7.4 for perfluoro‐2‐butynenitrile, 6.5 for perfluoro‐2‐pentynenitrile, and 11 for perfluoro‐2‐hexynenitrile. These polymers were examined by UV and IR spectra. Their thermal stability and the electrical conductivity of nondoped polymers were also studied. The conductivities of polyperfluoro‐2‐butynenitrile(PPFBN) and polyperfluoro‐2‐pentynenitrile are found to be 4.8 × 10−8 and 6.6 × 10−8Ω−1 cm−1, respectively.
Cyclopolymerization of N,N′‐methylene bisacrylamide initiated by S2O82−–Fe2+ redox system
Authors: Gopalan A. , Paulrajan S. , Subbaratnam N. R. , Rao K. Venkata 
Published: April 2003

AbstractPolymerization of the symmetrical nonconjugated diolefin, N,N′‐methylene bisacrylamide, was carried out using peroxodisulphate ion ‐Fe2+ as redox initiator. The rate of polymerization is found to depend on [M]3/2 and [S2O82−]1/2 and independent of [Fe2+] over a range. A polymerization mechanism involving cyclopolymerization in the propagation step is suggested. Evidence in favor of the cyclopolymerization mechanism is discussed. Evaluation of the rate parameters indicates that the deactivation of the primary radical SO4− by Fe2+ ion is a factor to be reckoned with.
Kinetics of the surfactant‐free emulsion polymerization of styrene:‐The post nucleation stage
Authors: Hearn J. , Wilkinson M. C. , Goodall A. R. , Chainey M. 
Published: April 2003

AbstractThe kinetics of the surfactant‐free emulsion polymerisation of styrene have been studied. Reactions were sampled at several stages throughout their course, and the samples characterized by electron microscopy, gravimetric weights analysis and gel permeation chromatography, After an initial period of particle nucleation and coagulation, the reaction proceeds at a constant number density. The theories developed for emulsion polymerisation in the presence of surfactant above its critical micelle concentration might be expected, in Interval II, to apply to the surfactant‐free system if due regard is taken of the lower number densities and larger particle sizes developed. The results are in best accord with theories invoking a surface phase polymerisation mechanism. None of these theories predict a bimodel molecular weight distribution as found here and which is ascribed to polymerisation in two loci. The activation energy was found to be the same as for surfactant containing emulsion polymerisations.
Preparation of polyamides via the phosphorylation reaction. X. A study of higashi reaction conditions
Authors: Krigbaum W. R. , Kotek R. , Mihara Y. , Preston J. 
Published: April 2003

AbstractWe report a study of the conditions of the phosphorylation reaction for the preparation of aromatic polyamides using the Higashi reaction medium. For poly(p‐phenylene terephthalamide) (PPD‐T), the optimum conditions are: reaction temperature, 115°C; monomer concentration, C = 0.083 mol/L; and ratio of triphenyl phosphite (TPP) to monomer, 2.0. These optimum conditions produce PPD‐T having ηinh = 6.2 dL/g. At temperatures of 120°C and above PPD‐T precipitates from the reaction mixture, leading to lower molecular weights. At lower temperatures the reaction mixture gels, and the gel time decreases with increasing reaction temperature. However, polycondensation continues in the gel state. Monomer concentrations C = 0.10 mol/L and above produce precipitation and yield polyamides of lower molecular weight. For the preparation of poly(p‐benzamide) (PBA), the optimum ratio of TPP to monomer is 0.6 for either p‐ aminobenzoic acid or N‐4‐(4′‐aminobenzamido)benzoic acid. In the former case the inherent viscosity of polymer prepared at 115°C showed little dependence upon the concentration of the monomer. The highest value, ηinh = 1.8 dL/g, was obtained with C = 0.40 mol/L and a TPP/monomer ratio of 0.6. However, for the same TPP/monomer ratio, the monomer containing a preformed amide linkage, N‐4‐(4′‐aminobenzamido)benzoic acid, gave PBA with ηinh = 4.6 dL/g when the monomer concentration is 0.33 mol/L. This is the highest value reported for PBA using the phosphorylation reaction. In A−A + B−B polycondensation, examples in which one of the monomers contained one or two preformed amide linkages produced polyamides having ηinh = 7.8 and 8.9 dL/g, respectively.
Syntheses of 2‐phenyl‐3‐vinyloxirane derivatives that undergo radical ring‐opening polymerization
Authors: Endo Takeshi , Kanda Naoki 
Published: April 2003

Abstract2‐Phenyl‐3‐vinyloxirane derivatives that undergo radical ring‐opening polymerization were prepared from allyl bromide and corresponding aldehydes. The difunctional monomers containing vinyloxirane structure were also synthesized from dialdehydes such as isophthalaldehyde and terephthalaldehyde. The obtained monomers undertook the radical isomeric polymerization to obtain the corresponding polymers.
Microscopic appearance of fractured surfaces and mechanical properties of starch–extended poly(vinyl alcohol)
Authors: Nwufo Bethrand T. , Griffin Gerry J. L. 
Published: April 2003

AbstractMixtures of Mowiol [an industrial plasticized poly(vinyl alcohol)] and corn starch have been examined by scanning electron microscopy (SEM); their impact and crossbreaking strengths, as well as their flexural moduli, measured. The results show fracturing as well as pitting with increased corn starch in Mowiol. The starch granular sizes (determined randomly for a number of samples) fluctuated between 10 and 22 μm, without some definite trend in the distribution. However, a certain degree of uniformity of granular size distribution appears to be achieved with an increase in the starch content of Mowiol. Both the impact and crossbreaking strength decreased with increase in starch, while the flexural modulus increased as the starch content increased. The impact of these observations on the resultant Mowiol/starch composites has been discussed. That transformed poly(vinyl alcohol) is likely to be an invaluable engineering material is not in doubt.
Aqueous polymerization of acrylonitrile by ascorbic acid–peroxodisulfate redox system
Authors: Ariff Mohamed , Jainuddin Md. , Gopalan V. , Rao K. Venkata 
Published: April 2003

AbstractThe polymerization of acrylonitrile initiated by an ascorbic acid–peroxodisulfate redox system was studied in an aqueous solution at 35°C in the presence of air. Molecular oxygen was found to have no effect on the polymerization reaction. An increase in ionic strength slightly increased the rate. The overall rate of polymerization, Rp, showed a square dependence on [monomer] and a half‐order dependence on [peroxodisulfate]. A first‐order dependence on [ascorbic acid] at low concentrations (<3.0 × 10−3 mol L−1) followed by a decrease in Rp at higher concentrations of ascorbic acid (>3.0 × 10−3 mol L−1) was also noted. Rp remained unchanged up to 40°C and showed a decline thereafter. Addition of catalytic amounts of cupric ions decreased the rate whereas ferric ions were found to increase the rate. Added sulfuric acid in the range (6.0−50.0) × 10−5 mol L−1 decreased the Rp.
Homogeneous Ziegler–Natta catalysis. II. Ethylene polymerization by IVB transition metal complexes/methyl aluminoxane catalyst systems
Authors: Giannetti Enzo , Nicoletti Giuseppe Martino , Mazzocchi Romano 
Published: April 2003

AbstractHomogeneous Ziegler‐Natta systems for the ethylene polymerization, deriving from R2R2′M complexes (R = cyclopentadienyl; R′ = alkyl, aryl; M = Ti, Zr, Hf) and oligomeric oxoalane compounds, were studied. Further results concerning the methyl aluminoxane synthesis and the related chemistry are reported. On the basis of spectroscopic data a delocalized electronic structure could be inferred for these compounds. Results from polymerization experiments showed that the highest productivities are obtained only by oxoalane cocatalysts having a high degree of oligomerization. The catalytic activity of the systems under investigation was strongly affected also by changing both the σ‐alkyl and the π‐cyclo‐pentadienyl ligands. Furthermore, it was found that in the presence of methyl aluminoxane, the homoleptic σ‐alkyl derivatives of IVB transition metals, such as Zr(CH2C6H5)4, are also able to polymerize ethylene with a fairly high productivity. Active species containing ZrOAl bonds have been postulated.
Ionomeric interpretation of thickening of polyesters by alkaline earth metal oxides
Authors: Rao K. Balakoteswara , Gandhi K. S. 
Published: April 2003

AbstractFour resins of poly(propylene glycol adipate) were mixed with different amounts of MgO and their viscosities were measured after a month. The viscosities increased by several thousand but the increase was less for resins containing more water. The existing explanations of the thickening behavior, namely the polymerization and the coordinate complex formation theories, were found to be inadequate in accounting for the observations. Small‐angle x‐ray scattering (SAXS) and transmission electron microscopy (TEM) of the thickened resins revealed formation of aggregates of magnesium ions, much like those observed in other ionomers. It is postulated that domain formation is the cause of observed thickening. A correlation between the viscosity of thickened resins and the amount of metal oxide reacted, the water content, and other properties of resin was obtained.
Polyaromatic ether‐ketones and polyaromatic ether‐ketone sulfonamides from 4‐phenoxybenzoyl chloride and from 4,4′‐dichloroformyldiphenyl ether
Authors: Litter Marta I. , Marvel C. S. 
Published: April 2003

AbstractPolyaromatic ether‐ketones possessing high thermal stabilities were prepared by Friedel—Crafts polymerizations from 4‐phenoxybenzoyl chloride and from 4,4′‐dichloroformyldiphenyl ether and diphenyl ether. Sulfonation and subsequent sulfamidation of these polymers afforded polyaromatic ether‐ketone sulfonamides with different degrees of substitution depending on the reaction conditions. Sulfonation reactions with chlorosulfonic acid did not cause much degradation on the polymers. The polysulfonamides were soluble in various organic solvents such as N,N‐dimethylformamide, dimethylsulfoxide, or chloroform, and could be cast into transparent films. These polymers may be used as desalination membranes.
Sulfone/ester polymers containing pendent ethynyl groups
Authors: Jensen B. J. , Hergenrother P. M. 
Published: April 2003

AbstractSulfone/ester polymers containing pendent ethynyl groups were prepared by multistep and direct routes. Hydroxy‐terminated sulfone oligomers(Mn = 2650 and 8890 g/mol) were reacted with diacid chlorides to yield high‐molecular‐weight polymers. In the multistep route, a pendent bromo group on the polymer was converted to an ethynyl group. In the direct route, the hydroxy‐terminated sulfone oligomers were reacted with a stoichiometric amount of 5‐(4‐ethynylphenoxy)isophthaloyl chloride to yield high polymers. The pendent ethynyl groups on the sulfone/ester polymers were reacted in the 200 to 300°C range to provide branching and crosslinking. The resultant polymers exhibited higher Tgs and better resistance to chloroform than comparable polymers void of ethynyl groups. Films of the cured polymers displayed good mechanical properties. The synthesis and characterization of the monomer, oligomers, and polymers are discussed.
Combinations of hydroxyl‐terminated polybutadiene and boron
Authors: Sandén, Roland 
Published: April 2003

AbstractMixing and curing experiments with suspensions of boron in hydroxyl‐terminated polybutadiene (HTPB) have been performed. In kneading experiments on a plastograph very high viscous masses with bad curing properties were obtained. The experiments indicated that HTPB is attached with its OH groups to acidic impurities on the surface of the boron powder. By adding a basic substance, such as octadecyl amine, mixing and curing were undertaken with much less difficulty.
The use of ylide (4‐picolinium 4‐chloro phenacyl methylide) as an initiator for the polymerization of methyl methacrylate
Authors: Tewari R. S. , Bajpai Anita , Srivastava A. K. 
Published: April 2003

AbstractThe thermal polymerization of methyl methacrylate [MMA] was carried out using ylide (4‐picolinium 4‐chloro phenacyl methylide) as an initiator. The rate of polymerization (Rp) increases with increasing monomer and initiator concentrations; The exponent value has been computed to be 1 ± 0.02 and 0.5, respectively. The reaction was carried out at four different temperatures and the overall activation energy has been computed to be 16.01 kcal/mol. The polymerization was inhibited in the presence of hydroquinone as a radical scavanger. Kinetic studies indicates that the overall polymerization takes place by a radical mechanism.
Multinuclear (13C, 15N) NMR study of polyethyleneimine‐based polymers
Authors: Axelson D. E. , Blake S. L. 
Published: April 2003

AbstractRepresentative polyethyleneimine‐based polymers have been studied by 13C‐ and 15N‐nuclear magnetic resonance spectroscopy and an extensive set of chemical shift assignments has been proposed for the complex spectra obtained. The samples in question represent a complex mixture of both protonated and nonprotonated primary, secondary, and tertiary as well as quaternary monomeric units.
Polymerization of tert‐alkylacetylenes by Mo‐ and W‐based catalysts
Authors: Okano Yoshimichi , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractPolymerization of three tert‐alkylacetylenes (3,3‐dimethyl‐1‐pentyne, 3,3‐dimethyl‐1‐nonyne, 1‐adamantylacetylene) by Mo‐ and W‐based catalysts provided new polymers in virtually quantitative yields. In contrast, Ziegler catalysts did not polymerize these monomers. Every polymer had a form of white solid, and had alternating double bonds along the main chain. Though some of poly(3,3‐dimethyl‐1‐pentyne)s contained a toluene‐insoluble fraction, the polymer was totally soluble when proper polymerization conditions were chosen. The molecular weights of soluble fractions were as high as 3 × 105. Poly(3,3‐dimethyl‐1‐nonyne) was also partly insoluble in toluene, and the quantity of soluble fraction was less than that of poly(3,3‐dimethyl‐1‐pentyne). The geometric structure of these two polymers could be controlled by the choice of suitable polymerization conditions. Poly(1‐adamantylacetylene) was insoluble in any organic solvents. Copolymerization of 1‐adamantylacetylene with suitable comonomers afforded soluble copolymers.
Thermal degradation of vinyl alcohol/vinyl acetate copolymers V. Study of the reaction products of statistical copolymers
Authors: Vasile Cornelia , Odochian Lucia , Paţachia Silvia Florica , Popoutanu Mercedes 
Published: April 2003

AbstractBy coupling the evolved gas detection method with various analysis methods, the thermal decomposition products of the statistical vinyl alcohol/vinyl acetate copolymers were analysed.The data are presented comparatively with those obtained for the corresponding block copolymers of the same composition.The differences in the nature and amounts of the reaction products are explained by the structural characteristics of the copolymers.
Thermal decomposition of cyclolinear and cyclic methylsiloxane polymers
Authors: Blazsó M. , Székely T. , Makarova N. M. 
Published: April 2003

AbstractA series of branched‐chain methylsiloxane polymers built up of four‐membered siloxane cycles and linear segments of zero to four siloxy units, and another series consisting only of siloxane cycles of five to eight members were investigated. The samples were pyrolyzed at temperatures increased stepwise from 300 to 800°C. The pyrolysate was analyzed online by gas chromatography and mass spectrometry. In the pyrolysates, series of cyclic, bicyclic, and polycyclic methylsiloxane compounds were found. Quantitative analysis of the pyrolysates shows that their composition reflects the composition and structure of the pyrolyzed polymethylsiloxane. The amount of the cyclic dimethylsiloxanes is related to the length of the linear siloxane segments between the branching points. The amount of bicyclic and polycyclic dimethylsiloxane oligomers in the pyrolysates is related to the average frequency and vicinity of the branching points.
Kinetics and mechanism of emulsifier‐free emulsion polymerization: Styrene/surface active ionic comonomer system
Authors: Chen Show‐An , Chang Herng‐Show 
Published: April 2003

AbstractThe emulsifier‐free emulsion polymerizations of styrene in the presence of the surface active comonomer, undecylenic isethionate sodium salt (at concentration below its critical micelle concentration), and of the initiator, potassium persulfate, indicate that the number of polymer particles and the rate of polymerization at steady state is dependent on 1‐power of the comonomer concentration and 1/2‐power of the initiator concentration. This result suggests a homogeneous nucleation mechanism by which particles are formed from coiled‐up oligomeric radical chains originally dissolved in the aqueous phase. Size distribution of the particles is rather narrow and has a uniformity very close to one (ca. 1.02) after 30% conversion. Addition of salt such as sodium sulfate to increase the ionic strength in the aqueous phase results in a formation of micelles (which can grow to become polymer particles) in addition to the formation of polymer particles through the homogeneous nucleation mechanism. Variation of the ionic strength leads to a variation in the number of polymer particles due to a competition between these two nucleation mechanisms and gives a minimum of the number of polymer particles and a maximum of the average particle diameter.