bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ziegler–Natta catalysts on silica for ethylene polymerization
Authors: Nowlin T. E. , Mink R. I. , Lo F. Y. , Kumar T. 
Published: April 2003

AbstractThe amount of dibutylmagnesium (DBM) or triethylaluminum (TEAL) that reacted with silica at 55–60°C depended on the silica calcining temperature. Lower silica calcining temperatures resulted in more Mg or Al fixed to the silica surface, indicating greater amounts of DBM or TEAL reacting with the silica. The amount of the metal alkyls butyl(octyl) magnesium ethoxide, ethylaluminum dichloride, tri‐n‐hexylaluminum, and diethyl(ethyldimethylsilanolato) aluminum that reacted with 600°C calcined silica was also determined. The metal alkyl can react with the silica at two sites, a surface hydroxyl group and a siloxane group. The silica surface hydroxyl groups can be chemically converted to trimethylsilyl groups so that only the siloxane groups are available for attack. After the metal alkyl was reacted with silica, the resulting intermediate was treated with titanium tetrachloride to yield an ethylene polymerization catalyst in the presence of TEAL. When no metal alkyl was employed, titanium tetrachloride reacted only with the silica surface hydroxyl groups to yield a weakly active ethylene polymerization catalyst.
Emulsion copolymerization of styrene and methyl methacrylate. II. Molecular weights
Authors: Forcada Jacqueline , Asua José M. 
Published: April 2003

AbstractA mathematical model for the time evolution of both number‐average molecular weight and weight‐average molecular weight is described. The model results in a set of ordinary differential equations and its application is not limited by the maximum number of radicals per particle. The model was used to analyze the effect of the monomer molar ratio in the initial charge on the weight‐average molecular weight during the emulsion copolymerization of styrene and methyl methacrylate in a batch reactor.
The preparation, characterization, and application of cellulose–MMA graft copolymers. I. The aqueous‐based preparation of cellulose–MMA graft copolymers
Authors: Guthrie J. T. , Tune P. D. 
Published: April 2003

AbstractCellulose‐MMA graft copolymers have been produced using aqueous‐based, Ce(IV)‐initiated and periodate‐initiated systems and also photochemical initiation. The reaction variables studied include the effect on grafting of varying the MMA monomer concentration, the initiator type and concentration, and also the reaction time. Of the three initiator types examined, the Ce (IV)‐initiated and the photochemically‐initiated systems are comparable in their effects on graft copolymer formation. Concurrent homopolymer formation was in the region of 50% by weight. Periodate‐initiation leads to less efficient grafting of MMA onto cellulose, although homopolymer formation is also lower (typically <20% by weight). The characterization of the copolymeric products through their properties as solids and, as their carbanilated derivatives, through their solution properties has been undertaken. Values of the activation onergy of decomposition (EA) of the cellulose‐MMA graft copolymers decrease with increasing MMA content, ranging between 227 and 155kJ mol−1. There is also a dependence on initiator type and grafting reaction conditions used (EA (cellulose wood pulp) = 239 kJ mol−1; EA (PMMA) = 115 kJ mol−1). Quantitative zeta‐potential (ζ) determinations for cellulose‐MMA graft copolymer samples produce negative surface charge density (σ) values. At a comparable MMA grafting level of 70–80%, values are of the order: photochemical (−730 esu/cm2) > periodate (−470 esu/cm2) > Ce (IV)‐initiation (−351 esu/cm2). Characterization of carbanilate solutions (by rheological examination) and of dry, carbanilate films (by study of surface wetting behavior) highlighted differences in the physical conformation of copolymers prepared by the different initiation routes. The highly degradative effect on cellulose of a periodate initiator, in comparison with the Ce (IV)‐initiation system, is reflected in significantly reduced molar mass values (typically, Mn 65,000 as opposed to 130,000 for Ce (IV)‐initiated graft copolymer carbanilates).
Synthesis of poly(benzylidene phthalide)s: A new class of polymers
Authors: Cassidy Patrick E. , Johnson C. Greg , Neef Charles J. , Jhingree Isaac , Aminabhavi Tejraj M. 
Published: April 2003

AbstractPyromellitic dianhydride (PMDA) was condensed with different aromatic diacetic acids via a Perkin reaction to produce new polymers containing the benzylidenephthalide group in the backbone. Yields ranged from 50 to 90% with inherent viscosities ranging from 0.07 to 0.37 dL/g. Polymerizations at 275°C for 4 h using p‐phenylenediacetic acid and PMDA gave the polymer with highest inherent viscosity. However, polymerization under identical conditions of p,p′‐diphenyl ether diacetic acid, each with PMDA, yielded poor results. For these two monomers the best polymerization conditions were 250°C for 8 h. In general, the most thermally stable polymer was derived from the diphenyl ether diacetic acid monomer (308°C). This polymer was obtained in highest yields and gave the greatest amount of pyrolytic residue in argon (67%).
Synthesis and NMR study of amide and imide derivatives of PMR‐15 monomeric units
Authors: Milhourat‐Hammadi A. , Chayrigues H. , Levoy R. , Merienne C. , Gaudemer A. 
Published: April 2003

AbstractVariations in PMR‐15 composite properties could be due to by‐products formed during the polymerization cycle. In order to identify these compounds, various condensation products derived from the three monomeric constituents of the resin: NE, BTDE, and MDA, have been synthesized and fully characterized by spectroscopic methods, mainly by 1H‐ and 13C‐NMR. In these products, one or two MDA amino groups are replaced by amido or imido groups, leading to mono‐ and di‐substituted MDA derivatives. Monosubstituted derivatives were obtained by first protecting one MDA amino group with a terbutoxycarbonyl group (Boc). The MDA's CH2 bridge of these molecules gives rise, in their 1H NMR spectra, to a characteristic resonance singlet, the position of which can be correlated to the nature of the amino substituents through 1H chemical shift increments. The latter provide a useful tool to predict the CH2, shifts in other compounds. Similar substituent increments are proposed for the chemical shifts of the MDA aromatic protons and carbon atoms.
Synthesis of organotin polymers from diallylidenepentaerithritol (DAPE) and organotin monohydrides having an alkenyl substituent
Authors: Moriya Osamu , Urata Yoshikiyo , Endo Takeshi 
Published: April 2003

AbstractTri‐n‐butyltin hydride (Bu3SnH) and modified organotin monohydrides which had an allylic ether group were employed for polymerizations of diallylidenpentaerithritol (DAPE) to prepare crosslinked polymers containing both organotin and acetal groups. The use of the latter monohydrides having a terminal unsaturated bond was particularly effective for introduction of various contents of the organotin moieties into the polymers, althought they did not undergo homopolymerizations.
Olefin copolymerization with metallocene catalysts. I. Comparison of catalysts
Authors: Chien James C. W. , He Dewei 
Published: April 2003

AbstractA number of metallocene/methylaluminoxane (MAO) catalysts have been compared for ethylene/propylene copolymerizations to find relationship between the polymerization activities, copolymer structures, and copolymerization reactivity ratio with the catalyst structures. Stereorigid racemic ethylene bis (indenyl) zirconium dichloride and the tetrahydro derivative exhibit very high activity of 10 7 g (mol Zr h bar)−1, giving copolymers having comonomer compositions about the same as the feed compositions, molecular weights increasing with the increase of ethylene in the feed, random incorporation of comonomers, and narrow molecular weight distribution indicative of a single catalytic species. Nonbridged bis (indenyl) zirconium behaved differently, favoring the incorporation of ethylene over propylene, producing copolymers whose molecular weight decreases with the increase of ethylene in the feed, broad molecular weight distribution, and a methanol soluble fraction. This catalyst system contains two or more active species. Simple methallocene catalysts have much lower polymerization activities. CpTiCl2/MAO produced copolymers with tendency toward alternation, whereas Cp2HfCl2/MAO gave copolymer containing short blocks of monomers.
Olefin copolymerization with metallocene catalysts. IV. Metallocene/methylaluminoxane catalyzed olefin teropolymerization
Authors: Chien James C. W. , He Dawei 
Published: April 2003

AbstractEthylene, propylene, and ethylidene norbornene (D) were terpolymerized by Et [Ind]2ZrCl2/MAO in solution and supported on silica. The presence of D decreases the rate of polymerization. EPDM containing between 3 and 22 wt % of D were synthesized which have narrow MW distribution. The supported catalyst produces EPDM with E/P ratio which are similar to the ratio in the feed.
Free‐radical distributions in emulsion polymerization which employs oil‐soluble radical generators
Authors: Brooks Brian W. 
Published: April 2003

AbstractThe use of oil‐soluble radical generators for emulsion polymerization is considered. When radicals are formed in pairs within particles of a seed latex, the occurrence of radical desorption leads to complex kinetics. Use of radical balances and realistic simplifications produce a method for a relatively simple calculation of radical populations in the particles. Examples are restricted, for illustration purposes, to cases where the average number of radicals per particle, n, is less than one. Very low rates of radical desorption cause a substantial increase in n. As the desorption rate increases, the value of n decreases. n increases slowly with radical generation rate. Large decreases in the chain termination rate coefficient (which may accompany a gel effect) can have a negligible effect on the value of n. Radical distributions obtained from oil‐soluble initiators can be slightly broader than those expected from the use of water‐soluble initiators. The kinetics of emulsion polymerization will be similar for the two types of radical generator when radicals from oil‐soluble generators can desorb from the polymer particles.
Novel benzyl sulfonium salt having an aromatic group on sulfur atom as a latent thermal initiator
Authors: Hamazu Fumio , Akashi Sumio , Koizumi Tatsuya , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractThree benzyl p‐hydroxyphenyl methylsulfonium salts with different counter anions were synthesized as novel latent thermal initiators. Syntheses of the sulfonium salts (2) were performed by the reaction of p‐hydroxyphenyl methyl sulfide with benzyl chloride followed by exchange of the counter anion (Cl−) with SbF−6 (2a), PF−6 (2b), or BF−4 (2c). In the bulk polymerization of glycidyl phenyl ether (PGE) with 2, initiator activity of the sulfonium salts was evaluated by comparison with that of benzyl tetramethylenesulfonium hexafluoroantimonate (1, R = H). Among the initiators, 2a showed the highest activity, and was much more active than 1 (R = H). Since the polymerization of PGE with 2a proceeded efficiently at more than 80°C but not at all at less than 60°C, 2a was suggested to be a good latent thermal initiator.
Characterization of plasma polymerized hydrocarbons using CP–MAS 13C‐NMR
Authors: Gambogi Robert J. , Cho D. L. , Yasuda H. , Blum Frank D. 
Published: April 2003

AbstractPlasma polymerized hydrocarbons made from ethane and methane were produced under different reactor conditions and probed by solid‐state carbon‐13 nuclear magnetic resonance (13C‐NMR) with cross‐polarization and magic‐angle sample spinning. NMR experiments provided structural information about the plasma polymers. The conditions of low power, high hydrocarbon gas flow rate, and no added hydrogen gas appeared to give the highest amount of nonprotonated sp3 hybridized carbons in the films for the reactor design used. The use of methane or ethane as reactor gas did not affect plasma polymer structure significantly.
Synthesis and activity of aryl benzyl methyl sulfonium salts as cationic initiators: Effect of substituent on aryl group
Authors: Hamazu Fumio , Akashi Sumio , Koizumi Tatsuya , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractBenzyl o‐, m‐, and p‐substituted phenyl methyl sulfonium salts (2b–2g) were synthesized and their activities as cationic initiators were evaluated in the bulk polymerization of phenyl glycidyl ether (PGE). Especially, their activities were estimated with respect to the effect of substituents on the aryl groups. In the polymerizations of PGE with a series of benzyl p‐substituted phenyl methyl sulfonium salts, the order of their activities was found to be 2c (CH3OCOO) > 2b (CH3COO) > 2d (CH3O) ∼ 2a (HO). In particular, 2c was the most active initiator of all, capable of initiating the polymerization of PGE even at room temperature. In the polymerizations with 2a, 2e (m‐Cl), 2f (o‐CH3), and 2g (m‐CH3), the activity of 2e was the highest of all while those of 2a, 2f, and 2g were almost the same. These results strongly suggested that the electron‐withdrawing group placed on the aryl group undoubtedly enhanced the activity of the sulfonium salts as the cationic initiators.
Addition curing thermosets endcapped with 4‐amino [2.2] paracyclophane
Authors: Waters John F. , Sutter James K. , Meador Mary Ann B. , Baldwin Larry J. , Meador Michael A. 
Published: April 2003

AbstractA new family of addition curing polyimides were prepared that contained 4‐amino [2.2]‐paracyclophane as the endcap. An improved synthesis of the endcap 4‐amino‐[2.2] cyclophane was accomplished increasing the yield to 60% and simplifying the procedure. DSC and rheological analysis of endcapped polyimide oligomers confirmed that the onset for polymerization of the ethylene bridge was 250°C. 13C CP/MAS NMR was used to determine the structural changes of the oligomers after thermal treatment. The cyclophane capped polyimides were successfully compression molded to from void free neat resin specimens. T'gs as high as 353°C were obtained by thermomechanical analysis for postcured samples. Preliminary thermal stability studies (TGA) suggest that these resins have a high onset of decomposition ranging from 549 to 567°C.
Synthesis and properties of aromatic polyamide‐benzoxazoles from trimethylsilyl‐substituted 2,4‐diaminophenol and aromatic dicarboxylic acid chlorides
Authors: Tanaka Yuji , Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractAromatic poly(o‐hydroxy amide)s having inherent viscosities of 0.6–2.2 dL/g were readily synthesized by the low‐temperature solution polycondensation of N,N′,O‐tris(trimethylsilyl)‐substituted 2,4‐diaminophenol with aromatic dicarboxylic acid chlorides in various organic solvents. The viscosity values were much higher than those of the polymers obtained by a conventional method using parent 2,4‐diaminophenol. Subsequent thermal cyclodehydration of the poly(o‐hydroxy amide)s at 280°C under vacuum afforded the corresponding aromatic polyamide‐benzoxazoles. Most of the poly(o‐hydroxy amide)s dissolved readily in amide‐type solvents, whereas the polyamide‐benzoxazoles were quite insoluble in organic solvents. The polyamide‐benzoxazoles, which gave yellow, transparent, and tough films, had glass transition temperatures of 260–300°C and were stable up to 400°C in air.
Synthesis of halogenated monodispersed telechelic oligomers. III. Bistelomerization of allyl acetate with telogens which exhibit α, ω‐di(trichloromethyled) end groups
Authors: Améduri Bruno , Boutevin Bernard , Lecrom Christophe , Garnier Laurent 
Published: April 2003

AbstractThe redox bistelomerization of allyl acetate with telogens which exhibit α, ω‐di(trichloromethyled) end groups catalyzed by copper, iron salts, or a ruthenium complex led to monoadducts and telechelic oligomers. These diacetates were quantitatively changed into diols. Such compounds have been characterized by both 1H‐ and 13C‐NMR. A reactivity series has been determined and shows that both end groups must be activated to obtain the expected telechelic products in satisfactory yields.
Synthesis of poly(alkylene phosphate)s bearing uracil moiety in the main chain
Authors: Łapienis Grzegorz 
Published: April 2003

AbstractPoly(alkylene phosphate)s bearing regularly distributed uracil moiety in the main chain have been obtained. The synthetic procedure consists of condensation of bis(diethylamino)‐methoxyphosphine with N1,N3‐bis(2′‐hydroxyethyl) uracil followed by oxidation, dealkylation, and transformation to the resulting sodium polysalt. The final polymer (\documentclass{article}\pagestyle{empty}\begin{document}$\bar M_n \approx 10^4 $\end{document}) as well as the intermediate products were characterized by 1H‐, 13C‐, and 31P‐NMR spectroscopy.
Facilitated transport of molecular oxygen in cobaltporphyrin/poly(1‐trimethylsilyl‐1‐propyne) membrane
Authors: Nishide H. , Kawakami H. , Sasame Y. , Ishiwata K. , Tsuchida* E. 
Published: April 2003

AbstractThe combination membrane of poly(1‐trimethylsilyl‐1‐propyne) with enormously high permeability and poly(vinylimidazole)‐bound porphinatocobalt with selective oxygenbinding ability was prepared. Oxygen transport through the membrane was facilitated in terms of oxygen transport via the latter domain as a fixed oxygen‐carrier, and this oxygen permeability maintained for a month.
Synthesis and diels–alder polymerization of furfurylidene and furfuryl‐substituted maleamic acids
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractThe reactions of monomaleamic acid derived from an aromatic diamine with furfural afforded a novel class of furfurylidene‐substituted maleamic acids 2a–2d. The latter were cyclodehydrated to yield maleimides 3a–3d which are AB‐monomers for a Diels–Alder polymerization. In addition, N‐furfurylmaleamic acid (4) was synthesized by reacting furfurylamine with maleic anhydride at ambient temperature. Cyclodehydration of 4 afforded N‐furfurylmaleimide (5). The polymer precursors were characterized by IR and 1H‐NMR spectroscopy. Their curing behavior was investigated by DTA and correlated with chemical structures. Diels–Alder polymerization of monomers occurred at the temperature range of 113–210°C. Thermal stability of monomers was evaluated by TGA and isothermal gravimetric analysis (IGA). It was shown that thermal stability of the polymer derived from maleamic acid 4 was dramatically improved upon curing at high temperatures due to the formation by dehydration of a stable aromatic structure.
Synthesis, characterization, and blends of high temperature poly(arylether sulfone)s
Authors: Andrews S. M. 
Published: April 2003

AbstractThe preparation of poly(4‐oxy‐1,4‐phenylenesulfonyl‐4,4′‐biphenylene‐4‐sulfonylphenylene) (PBP) has been accomplished by the base mediated, polycondensation reaction between two biphenyl containing monomers. The bisphenol, 4,4′‐bis[(4‐hydroxyphenyl) sulfonyl]biphenyl (HSB), was reacted with 4,4′‐bis[(4‐chlorophenyl)sulfonyl]‐biphenyl (CSB) in tetramethylene sulfone solvent. The highest mechanical properties and glass transition temperature was observed for polymer PBP with a reduced viscosity around 1.0 dL/g. Consequently, the current synthesis route provides polymer with higher properties than other historical preparative routes. Blends of PBP with a different poly(ether sulfone) were miscible based on the observance of a single glass transition temperature. The Tgs of the polymer blends exhibited an unusual positive deviation from the weighted linear averages of the components.
Solid‐State polymerization of the binary mixture of methacrylate and liquid‐crystalline compound by electron beam
Authors: Shindo Tadafumi , Uryu Toshiyuki 
Published: April 2003

AbstractSolid‐state polymerization of a binary mixture of nonliquid‐crystalline monomer and liquidcrystalline compound was carried out using electron beam. The monomers were benzoic acid containing 4‐[ω‐(meth)acryloyloxyalkyloxy] benzoic acids, in which the alkylene spacer was ethylene, hexamethylene, or undecamethylene. The conversion yield of monomer to polymer to a large extent increased with increasing content of a liquid‐crystalline compound with a terminal carboxylic group, such as 4‐n‐alkyloxybenzoic acid, while the addition of a liquid‐crystalline compound without terminal carboxylic group did not affect polymerization of the monomer. Phase diagrams of the mixture of monomer and liquid‐crystalline compound were examined using cross‐polarizing microscopy and differential scanning calorimetry (DSC). All mixtures of monomer and 4‐n‐alkyloxybenzoic acid or liquid‐crystalline compound without terminal carboxylic group showed liquid‐crystallinity in a broad composition range. It was concluded that liquid‐crystalline compounds with terminal carboxylic acid may form hydrogen bondings with methacrylate or acrylate monomer having terminal carboxylic acid which enhance polymerizability of the mixture. The stereoregularity of polymers determined by NMR depended on increasing irradiation dose and temperature rather than the content of the added liquid‐crystalline 4‐n‐decanoxybenzoic acid.
Modification of polyolefin surfaces with iron cluster oxidants
Authors: Bergbreiter David E. , White Nicole , Zhou Jing 
Published: April 2003

AbstractModification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe3O(OCOCH3)6(C6H5N)3.5 and FeCl3 • 6H2O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.
Plasma polymerization using pulsed microwave power
Authors: Hwu Wen‐hwa , Zurawsky W. P. 
Published: April 2003

AbstractPulsed microwave power was used to polymerize a variety of monomers containing different functional groups. We examined the effects of pulse frequency and duty cycle on the deposition rates and the composition of the polymers. For monomers that do not contain oxygen we find that there is an increase in deposition rate with increasing pulse frequency and that the pulsed deposition rate is always less than the continuous power deposition rate. For monomers that contain oxygen, or for co‐depositions of hydrocarbon monomers with O2 or CO, we find that there is a decrease in deposition rate with increasing frequency, however the deposition rate using pulsed power is greater than the rate using continuous power. This result is shown to be related to the amount of etching that takes place during the deposition process. Infrared studies reveal that pulsed power can alter the composition of plasma polymers of some oxygen‐containing monomers. The presence or absence of vinyl unsaturation, nitrile groups, or a cyclic structure have no effect on the polymerization process.
Spectroscopic studies of new model compounds for poly[N,N′‐bis(phenoxyphenyl)pyromellitimide]
Authors: Saini Ajay K. , Carlin Clifford M. , Patterson Howard H. 
Published: April 2003

AbstractNew model compounds for poly[N,N′‐bis(phenoxyphenyl)pyromellitimide] have been synthesized in order to investigate the formation of imine bonds which are proposed to form during the curing process and lead to crosslinking in the bulk polymer. Raman studies show that terminal amines can react with imide carbonyls during curing to form CN bonds. The Raman band due to CN appears at 1656 cm−1 and the band due to CO closest to the imine bond is observed at 1742 cm−1. These results are in agreement with previously published results on vapor deposited polyimide films.