bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of new soluble aromatic polyimides from 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylpyrrole and aromatic tetracarboxylic dianhydrides
Authors: Jeong Hwa‐Jin , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractNovel aromatic polyimides containing tetraphenylpyrrole unit were synthesized from 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylpyrrole and various aromatic tetracarboxylic dianhydrides by the usual two‐step procedure that included ring‐opening polyaddition and subsequent thermal cyclodehydration. These polymers had inherent viscosities in the 0.20–0.65 dL/g range and were practically amorphous as shown by the X‐ray diffraction studies. All the polyimides except for polypyromellitimide were easily soluble in a wide range of organic solvents such as o‐chlorophenol, pyridine, 1,3‐dimethyl‐2‐imidazolidone, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrolidone at room temperature. These polyimides had high glass transition temperatures of 302–359°C and exhibited 10% weight loss at temperatures above 510°C in nitrogen.
Synthesis of substituted polymethylenes by radical polymerization of alkyl N,N‐dialkylfumaramates and maleamates: Relative reactivity of the isomers
Authors: Matsumoto Akikazu , Kotaki Ryuji , Otsu Takayuki 
Published: April 2003

AbstractBulk polymerization of alkyl N,N‐dialkylfumaramates (FAE) and maleamates (MAE) was performed in the presence of a radical initiator. It has been found that FAE is more reactive than MAE when the reactivity of the two geometrical isomers was compared for their homo‐ and copolymerizations. From investigation on the effect of ester and N‐substituents of these monomers, it has been found that the isopropyl ester shows a higher reactivity than the methyl ester and that N‐ethyl and n‐butyl substitution gives polymers with high molecular weight of more than several thousands. The resulting substituted polymethylenes from FAE and MAE were characterized and compared with each other. The isomerization of MAE to FAE with morpholine as an isomerization catalyst and monomer‐isomerization radical polymerization were also investigated.
Photochemistry of macromolecular metal complexes. II. Synthesis, thermal, and photochemistry of some polypyridyl complexes of chromium (III) bound to macromolecules
Authors: Anbalagan K. , Natarajan P. 
Published: April 2003

AbstractPolymer coordinated chromium(III) complexes [Cr(bpy)2(PAA)2]+, 1, [Cr(bpy)2‐(PMA)2]+, 2, [Cr(phen)2(PAA)2]+, 3, and [Cr(phen)2(PMA)2]+, 4, [where bpy, phen, PAA and PMA are, respectively, 2,2′‐bipyridine, 1,10‐phenanthroline, poly(acrylic acid), and poly(methacrylic acid)] were synthesized. The polymer–chromium(III) complexes were characterized by elemental and spectroscopic analyses. Thermal substitution reactions of these macromolecular chromium(III) complexes in basic solutions lead to the replacement of the polypyridyl ligand by hydroxide ion while in strong acidic solutions the polymer complexes precipitate out. The photochemical reactions are qualitatively similar to that of the thermal reactions and the quantum yields are dependant on the pH of the medium. Further, lower quantum yields were observed for the aquation of the polymer complexes in comparison with the monomeric chromium(III) complexes and the results are discussed in terms of the effect of the polymer environment. Flash photolysis of 1 and 3 results in the formation of transients with maxima at 480 nm for 1 and 470 nm, 580 nm for 3. The decay of the transients were found to obey first order kinetics and the rate constants were determined. The transients were suggested to be the alkyl‐chromium complexes. Flash photolysis of 2 and 4 does not produce transients which is interpreted to be due to the presence of a methyl group in the ligand which hinders the formation of the carbonchromium bond.
New polymer syntheses. 60. Thermostable polymers of 2‐(hydroxyaryl)benzoxazole‐5‐carboxylic acids
Authors: Kricheldorf H. R. , Thomsen Sven A. 
Published: April 2003

AbstractTristrimethylsilyl‐3‐amino‐4‐hydroxybenzoic acid was condensed with various aromatic acetoxy carboxylic acid chlorides in Marlotherms‐S® at 20–350°C. Under these conditions formation of an amide group, ring closure to benzoxazole groups and polycondensation occur step by step in a “one‐pot procedure”. The crude polyesters were hydrolyzed to yield pure 2‐(hydroxyaryl) benzoxazole‐5‐carboxylic acids which were acetylated and polycondensed. The pure polyesters obtained in this way were characterized by viscosity and DSC measurements, WAXS‐powder patterns, and thermogravimetric analyses. The polyester of 2‐(4‐hydrophenyl) benzoxazole‐5‐carboxylic acid has a degree of crystallinity > 90% and a short term in thermostability in air up to 500°C.
Polymerization of α‐methyleneindane: A cyclic analog of α‐methylstyrene
Authors: Ueda Mitsuru , Mano Motokazu , Mori Hideharu , Ito Hiroshi 
Published: April 2003

Abstractα‐Methyleniedane (MI), a cyclic analog of α‐methylstyrene which does not undergo radical homopolymerization under standard conditions, was synthesized and subjected to radical, cationic, and anionic polymerizations. MI undergoes radical polymerization with α,α′‐azobis(isobutyronitrile) in contrast to α‐methylstyrene, owing to its reduced steric hindrance, though the polymerization is slow even in bulk. Cationic and anionic polymerization of MI with BF3OEt2 and n‐butyllithium, respectively, proceed rapidly. The thermal degradation behavior of the polymer depends on the polymerization conditions. The anionic and radical polymers are heteortactic‐rich. Reactivity ratios in bulk radical copolymerization on MI (M2) with methacrylate (MMA, M1) were determined at 60°C (r1 = 0.129 and r2 = 1.07). In order to clarify the copolymerization mechanism, radical copolymerization of MI with MMA was investigated in bulk at temperatures ranging from 50 to 80°C. The Mayo–Lewis equation has been found to be inadequate to describe the result due to depolymerization of MI sequences above 70°C.
Synthesis of aromatic polyethers by Scholl reaction. V. Synthesis and polymerization of 1,3‐bis[4‐(1‐naphthoxy) benzoyl]benzene, 1,4‐bis[4‐(1‐naphthoxy)benzoyl]benzene, bis[4‐(1‐naphthoxy)phenyl]methane, 1,3‐bis[4‐(1‐naphthoxy) phenylmethyl]benzene, and 1,4‐bis‐[4‐(1‐naphthoxy)phenylmethyl]benzene
Authors: Percec Vergil , Wang James H. , Okita Shigeru 
Published: April 2003

AbstractThis article describes the synthesis and the cation‐radical polymerization (Scholl reaction) of 1,3‐bis[4‐(1‐naphthoxy) benzoyl] benzene (6) and 1,4‐bis[4‐(1‐naphthoxy) benzoyl]‐ benzene (7) initiated by FeCI3. This polymerization produced poly(ether ether ketone ketone)s (PEEKK) of number average molecular weight (M̄n) up to 5400 g/mol. The synthesis of bis[4‐(1‐naphthoxy) phenyl] methane (8), 1,3‐bis[4‐(1‐napthoxy) phenylmethyl] benzene (9), and 1,4‐bis[4‐(1‐naphthoxy) phenylmethyl] benzene (10) are also described. Polyethers of M̄n up to 15400 g/mol at a FeCl3/monomer molar ratio of 2/1 were obtained. An increased polymerizability of the monomers 9 and 10 containing two CH2 groups versus that of the corresponding monomers containing two carbonyl groups (6 and 7) was observed. This enhanced polymerizability was explained based on the increased nucleophilicity of monomers 9 and 10.
Solvay type VCl3 isospecific catalysts
Authors: Nozaki Takashi , Chien James C. W. 
Published: April 2003

AbstractSolvay type S–VCl3 catalyst has 7% of catalytically active vanadium sites ([C*]) with kp (rate constant of propagation) = 31 (M s)−1 for ethylene polymerization. Addition of a comonomer, propylene of 4‐methylpentene‐1 (4‐MP) significantly raised the ethylene polymerization activity. S–VCI3 catalyst has very small amounts of catalytically active vanadium for propylene polymerizations: [C] = 0.19% with kp,i = 857 (M s)−1 and [C] = 0.45% with kp,a = 23 (M s)−1 for isospecific and nonspecific sites, respectively. Addition of a conomer, ethylene or 4‐MP. lowered the propylene polymerization activity. S–VCI3 is more easily reduced to the divalent ion by AIR3 than S–TiCl3. Methyl‐p‐toluate moderates the reducting power of AIR3; it increase the productivity and stereoselectivity of the S–YiCl3 catalyst, VCI3 supported on MgCl2 (CW–V catalyst) has enhanced rate constant of propylene polymerization but has the opposite effects on the S–TiCl3 Catalyst. VCI3 supported on MgCl2 (CW–V catalyst) has enhances rate constant of propylene polymerization but only a minute fraction of the supported vanadiums are catalytically active: [C] = 0.019% and kp,i = 1580 (Ms)−1, [C] = 0.057% and kp,i = 58 (M s)−1. This is compared with far greater number of catalytically active titanium sites in the TiCl3 supported on MgCl2 catalyst: [C] = 6% and kp,i = 200 (M s)−1, [C] = 6% and kp,a = 16(M s)−1. Therefore, both the S–VCI3 and CW–V catalysts are highly stereoselective but low in efficiency with respect to the utilization of the vanadium ion in the catalysis.
Polymerization and copolymerization of α‐alkylacrylic acids and characterization of their polymers
Authors: Cheng Jin‐Shun , Yamada Bunichiro , Otsu Takayuki 
Published: April 2003

Abstractα‐Alkylacrylic acids (RAA's) bearing n‐alkyl groups were found to homopolymerize with slower rates than acrylic and methacrylic acids to number‐average molecular, weight (M̄n) of 104 or above. When the α‐substituent was a branched alkyl group, the polymerization rate and M̄n decreased further. Reactivities of RAA's in copolymerization were interpreted by steric and resonance effects of the alkyl group using Hancock's steric substituent constant. Comparison of the reactivities of RAA's with those of methyl α‐alkylacrylates revealed that replacement with the smaller carboxyl group facilitates polymerization and copolymerization. Preference of co‐syndiotactic propagation in the copolymerization of methacrylic acid with styrene changed to random fashion in the copolymerization of the α‐higher alkyl derivatives. After methylation with diazomethane, the homopolymers were shown to be thermally less stable than poly(methyl methacrylate). Tg's of poly(methyl α‐ethylacrylate) and poly(methyl α‐n‐propylacrylate) were 57 and 25°C, respectively.
Synthesis of polymer containing o‐nitrobenzyl ether structure in the main chain
Authors: Iizawa Takashi , Kudou Hiroshi , Nishikubo Tadatomi 
Published: April 2003

AbstractThe polycondensation of nitrated xylenedihalides with diphenols was carried out under various conditions. The polycondensation of 2‐nitro‐1, 3‐xylylenedibromide (NXDB) with 4,4′‐isopropylidenediphenol proceeded in competition with the decomposition of polymer in the mixed solvent of tetrahydrofuran (THF) and dimethylsulfoxide (DMSO). The viscosity of the resulting polymer was markedly affected by the concentration of aqueous sodium hydroxide, reaction time, and reaction temperature. When dibromomethane was used as a solvent, the polycondensation proceeded very smoothly without the decomposition to give a higher reduced viscosity polymer than that in THF‐DMSO at 60°C. The polymer obtained in dibromomethane contained a very small amount of formal bonds determined from the 1H‐NMR spectrum. The formation of formal bonds seems to cause the molecular weight in increase. Furthemore, the polycondensation of NXDB with 2,2‐bis (4‐hydroxyphenyl) hexafluoropropane afforded high molecular‐weight polyether in dibromomethane. However, either high reaction temperatures or the high concentrations of aqueous potassium hydroxide solution casused the viscosity of the resulting polymer to decrease during the polycondensation in dibromomethane. The obtained polyethers with o‐nitrobenzyl groups showed relatively good solubility, and decomposed smoothly upon the irradiation with UV light. Therefore, these polymers might be useful for positive type photoresists.
Synthesis of aromatic polyamide‐imides from N,N′‐bis(trimethylsilyl)‐substituted aromatic diamines and 4‐chloroformylphthalic anhydride
Authors: Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractThe polymerization of N,N′‐bis(trimethylsilyl)‐substituted aromatic diamines with 4‐chloroformylphthalic anhydride in various solvents at a temperature range between 10 and 70°C afforded polyamide‐amic acid trimethylsilyl esters having inherent viscosities of 0.8–1.4 dL/g. Transparent and flexible films of the silylated precursor polymers were obtained by casting directly from the polymer solutions. Desilylation of the silylated polymers with methanol resulted in the formation of the corresponding polyamide‐amic acids. Subsequent thermal imidization of the silylated precursor polymers with the elimination of trimethylsilanol afforded yellow, transparent, and tough films of the aromatic polyamide‐imides. The thermal conversion of the silylated precursor polymer to polyamide‐imide proceeded almost as rapidly as that of the corresponding polyamide‐amic acid prepared by a conventional method from the parent aromatic diamine and 4‐chloroformylphthalic anhydride.
Novel synthesis of aromatic polysulfides from S,S′‐bis(trimethylsilyl)‐substituted aromatic dithiols and activated aromatic dihalides
Authors: Hara Atsushi , Oishi Yoshiyuki , Kakikoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractA new method for the synthesis of aromatic polysulfides has been developed by the polycondensation of S,S′‐bis(trimethylsilyl)‐substituted aromatic dithiols with activated aromatic dihalides. The solution polycondensation of three S‐silylated aromatic dithiols with bis(4‐chloro‐3‐nitrophenyl) sulfone afforded readily aromatic polysulfides having inherent viscosities of 0.7 dL/g, and the polymerization with bis(4‐fluorophenyl) sulfone gave the polymers with viscosity values of 0.3 dL/g. The silylation method was compared advantageously with a conventional route using parent dithiols and activated aromatic dihalides.
The active species of the chromium (phillips type) catalysts for the polymerization of ethylene: A unifying approach
Authors: Rebenstorf Bernd 
Published: April 2003

AbstractFrom literature data it is concluded that the rate of the reduction, alkylation, polymer chain growth, and chain transfer reactions of three chromium(II) and one chromium(III) surface species all increase with decreasing electron density at the chromium ion. This electron density has previously been measured by the IR shift of the stretching vibration of one CO molecule terminally adsorbed on these chromium ions. It is observed that the reduction half time decreases proportional to the increasing Lewis acidity and that the rate of the polymer chain growth reaction increases exponentially for three chromium surface species with increasing CO stretching vibration. Due to the large difference of the polymer chain growth rates for the two chromium (II) species (Ad and Cd), common in the normal Phillips catalyst, both contribute almost equally to the polymer product, although the Ad species outnumbers the Cd one by more than 3 to 1.
Novel dialkylaminoalkyl‐ and dialkylaminoalcoxi‐benzophenones as photoinitiators of polymerization. I. Photochemical characteristics and radical efficiencies
Authors: Mateo J. L. , Bosch P. , Catalina F. , Sastre R. 
Published: April 2003

AbstractThe behavior of the nonconjugated aminated benzophenones—4‐[2′‐N,N‐(diethylamino)ethoxy]benzophenone (E4), 2‐[2′‐N,N‐(diethylamino)ethoxy]‐4‐methoxybenzophenone (E2), and 4‐N,N‐dimethylaminomethylbenzophenone (DM)—as photoinitiators of MMA polymerization has been studied and the results compared with those obtained with the conjugated aminobenzophenone 4‐N,N‐dimethylamino‐4′‐isopropyl‐benzophenone (CU—MI). Photoreduction behavior of these compounds in various solvents in the presence and absence of MMA has been also examined. The order of the polymerization reaction with respect to monomer and initiator concentrations has been investigated; values of initiation quantum yield (Φi), Kp/K1/2t and efficiencies of the different radicals have also been determined. Similar polymerization rates (Rp) of methyl methacrylate (MMA) were found when E4 and CU‐MI were used as photoinitiators under the same range of absorbed irradiation intensity. This fact results from a compensation between the higher rate of E4 radical production (n‐π* transition type) and the greater reactivity of the radicals generated from CU‐MI.
Novel regular network polyester films from aromatic tetracarboxylic acids and ethylene glycol
Authors: Tsutsumi Naoto , Chen Ying‐Hsien , Kiyotsukuri Tsuyoshi 
Published: April 2003

AbstractNovel regular network polyester films were prepared from pyromellitic (X), biphenyltetracarboxylic (U), and 3,3′,4,4′‐benzophenonetetracarboxylic (W) dianhydrides and ethylene glycol (2G). Prepolymers prepared by melt polycondensation were cast from DMF solution and successively post‐polymerized at 260°C for various times to form a network. The resultant films were transparent, flexible, and insoluble in any solvents. The structure and properties of these network polyester films were compared with those of previously reported network polyester film from trimesic acid (Y) and 2G. Two diffraction peaks appeared in X‐ray diffraction curves of 2GY, 2GX, and 2GU films. Peaks of 2GX and 2GU were broader than that of 2GY, suggesting less ordered structure of 2GX and 2GU by the less symmetric aromatic tetracarboxylic acid moieties. Densities of network films decreased with increasing the post‐polymerization time. The degree of reaction (the degree of network formation) was estimated by the change of infrared absorption of hydroxyl and methylene groups. The degree of reaction obtained was 95 and 87% for 2GY and 2GX films post‐polymerized for 12 h, respectively. Distortion temperature (Th) was measured by a penetration mode of thermomechanical analysis (TMA). Th, was 222 and 240°C for 2GY and 2GW films post‐polymerized at 260°C for 12 h, respectively, while it disappeared for 2GX and 2GU films post‐polymerized for more than 30 min and 1 h, respectively. Drastic decrease in TMA curves around 400°C corresponded to the rapid weight loss in TG curves due to the thermal decomposition. Young's modulus of network film was 2GX > 2GW = 2GU > 2GY, while the tensile strength and elongation were 2GY > 2GU > 2GW > 2GX. Water absorbing capacity was 2GX > 2GY > undrawn PET, while the alkali resistance was undrawn PET = 2GY > 2GX.
Electroinitiated polymerization of butadiene sulfone
Authors: Aybar S. P. , Hacioglu B. , Akbulut U. 
Published: April 2003

AbstractElectroinitiated polymerization of butadiene sulfone was achieved by direct electron transfer in acetonitrile—tetrabutylammonium fluoroborate system by controlled potential electrolysis technique. High conversions were obtained at reasonable temperatures and polymerization times. The polymer was found to be composed of linear segments along with some cyclic units. The effect of monomer concentration, temperature, and polymerization potential on the rate of polymerization was investigated. Temperature and polymerization potential have positive effects on the rate of polymerization. The effect of ultrasonic vibration was also investigated by conducting electrolyses at different monomer concentrations in the presence and absence of ultrasonic vibration. It was observed that the rate of polymerization increases significantly in the presence of ultrasonic vibration. The inverse relationship between the rate of polymerization and monomer concentration was observed in presence and absence of ultrasonic vibration.
Control synthesis of isocyanate and alkoxy‐silane terminated macromers
Authors: Surivet Françoise , Lam Thanh My , Pascault Jean‐Pierre 
Published: April 2003

AbstractThe kinetics of the reactions in bulk of 4,4′‐dicyclohexyl methane diisocyanate (H12 MDI) and 5‐isocyanato‐1,3,3‐trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI) with benzylic alcohol (BZA) and α‐hydroxy‐ω‐methyl ether‐terminated polyethylene oxide PEO (M̄w = 350) were studied by size exclusion chromatography (SEC) and 13C nuclear magnetic resonance (13C‐NMR). The substitution effect is exhibited in the case of H12 MDI reactivity. The kinetic constants were calculated by a numerical method. The second‐order kinetic mechanism was shown to be valid. In the IPDI case, the cycloaliphatic isocyanate group is shown to be more reactive than the aliphatic group in our conditions, without catalysis, in agreement with previous results from the literature, in our obtained by 1H‐and 13C‐NMR without any catalyst. The reactivity ratio is found to be on the order of 3. This difference in reactivity of the two isocyanate groups is used for the control synthesis of isocyanate and alkoxy‐silane‐terminated macromers.
Regioselective rhodium‐containing catalysts for ring‐opening polymerizations and hydrosilylations
Authors: Crivello J. V. , Fan M. 
Published: April 2003

AbstractOrganometallic rhodium complexes are described which are highly efficient initiators for the ring‐opening polymerization of expoxides and other heterocyclic compounds. A cocatalyst, consisting of a compound or polymer containing silicon–hydrogen bonds must also be present. These same catalyst–cocatalyst mixtures are also highly active for hydrosilylation reactions. Other complexes bearing phosphine ligands have been discovered, which while active for hydrosilylation, are not catalysts for epoxide polymerizations. Polymer supported rhodium catalysts are also described which permit the synthesis of epoxy‐functional silanes in high yields without competing ring‐opening polymerization.
Analysis of copolymerization systems involving multiple reaction pathways
Authors: Wood Kenneth B. , Stannett Vivian T. 
Published: April 2003

AbstractA method of analysis of copolymerization systems involving multiple reaction pathways is presented. The method involves fractionation and separate analysis of the individual product populations comprising each sample. Modification of the Kelen–Tüdos linearization techniques into the form necessary to deal with high conversion copolymerizations involving multiple reaction pathways is presented. The method is applied to the ionizing radiation initiated copolymerization of styrene derivatives in dichloromethane, in which case simultaneous copolymerization via cationic and free radical mechanisms is found to occur. Reactivity ratios corresponding to each mechanism are calculated and discussed.
Catalysis of ring‐opening and vinyl polymerizations by dicobaltoctacarbonyl
Authors: Crivello James V. , Fan Mingxin 
Published: April 2003

AbstractIn the presence of SiH containing cocatalysts, dicobaltoctacarbonyl has been found to very efficiently catalyze the ring‐opening polymerization of cyclic ethers, especially epoxides, as well as certain vinyl monomers. The reaction conditions employed are very similar to those used in Co2(CO)8 catalyzed hydrogenation and hydrosilylation reactions. Detailed investigations have been carried out to elucidate the nature of the active species for this catalytic system. A cationic mechanism is proposed based on the experimental results of those investigations.
New coordination catalysts based on rare earth compounds for polymerization of 1‐octene
Authors: Yang Mujie , Zhang Xiaojun , Li Jianfu , Shen Zhiquan 
Published: April 2003

AbstractThe study of rare earth coordination catalysts for polymerization of 1‐octene has been successfully carried out for the first time. Some features and kinetic behavior of polymerization of 1‐octene by Nd(naph)3–AIEt3 catalyst system in tetrachloro‐methane are described. The overall polymerization activation energy Ea measured was 74.5 kJ/mol and the rate equation could be expressed as Rp = kp [Nd] [M] (kp = 3.21 × 10−3 L/mol s, at 50°C). The catalytic activity of various rare earth elements in Ln (naph)3 and ligands in NdL3 for the polymerization was compared. A 1‐octene oligomer with double bonds was obtained. It is either a white or pale yellow waxy semi‐solid. Its number‐average molecular weight is about 103 and the molecular weight distribution is less than 2.