bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of polybenzimidazole: Synthesis and thermal stability of poly(N1‐methylbenzimidazole) and poly(N1,N3‐dimethylbenzimidazolium) salt
Authors: Hu Ming , Pearce Eli M. , Kwei T. K. 
Published: April 2003

AbstractPoly(N1,N3‐dimethylbenzimidazolium) (PDMBI) salt and poly(N1‐methylbenzimidazole) (PMMBI) were synthesized by methylation of commercial polybenzimidazole [poly‐2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole (PBI)]. First, the N‐lithium salt of polybenzimidazole was formed by treating polybenzimidazole solution of 1‐methyl‐2‐pyrolidinone (NMP) with lithium hydride at 80°C for 18 h. Ninety percent substitution of PMMBI was obtained by treating the N‐lithium salt of PBI with equimolar ratio of iodomethane at room temperature. Upon addition of excess iodomethane to the lithium salt of PBI at 80°C, a polymer was formed that showed 100% substitution on the N1 nitrogen and about 30% substitution of the methyl group on the N3 nitrogen in the form of N1,N3‐dimethylbenzimidazolium iodide salt [PDMBI (30%)]. The content of the benzimidazolium iodide salt was increased to about 90% by dissolving PDMBI (30%) in dimethyl sulfoxide (DMSO) and re‐treating with excess iodomethane at 80°C overnight. The modified PBI polymers were characterized by NMR and FTIR. The modified PBI differed in solubility from PBI. PMMBI could be easily dissolved in NMP and PDMBI in DMSO at room temperature. The solution of PDMBI could be mixed with water in all proportions without precipitation. PDMBI could be also dissolved directly in a mixture of DMSO and water (1 : 1). Typical polyelectrolyte behavior of viscosity was found in solution of PDMBI (30%) and PDMBI (90%) when DMSO and a mixture of DMSO and water were used as solvents. A salt effect on viscosity was also found in the mixed solvent solution. Thermogravimetric analysis (TGA) showed that the methyl group on the imidazole ring was unstable above 180°C under nitrogen. When PDMBI was heated under nitrogen, one of the methyl groups was lost with the counterion to result in a neutral PMMBI. © 1993 John Wiley & Sons, Inc.
Copolymers of PBT and nylon 4T
Authors: Gaymans R. J. , De Haan J. L. , Van Nieuwenhuize O. 
Published: April 2003

AbstractPolybutylene terephthalate–nylon 4T copolymers (PBT–PA 4T) are synthesized from the diamide of diaminobutane and dimethyl terephthalate (DMT) with butane diol and more DMT in a concentration range of up to 50% PA 4T. The polymerization conditions were similar to those for PBT: first, a melt polymerization, followed by solid‐state post‐condensation. The materials were studied by differential scanning analysis (DSC) (melting and crystallization behavior) and dynamic mechanical thermal analysis (DMTA) (glass transitions and torsion moduli). The water absorptions were determined at 100% RH. By increasing the PA 4T content in the copolymers, melting temperatures increased strongly, heats of fusion decreased slightly, and glass transition temperatures increased linearly. The torsion moduli above the glass transition temperature were higher. © 1993 John Wiley & Sons, Inc.
Synthesis, characterization, and curing of hyperbranched allyl ether–maleate functional ester resins
Authors: Johansson Mats , Malmström Eva , Hult Anders 
Published: April 2003

AbstractA model two‐step synthesis of a saturated hyperbranched hydroxyl‐terminated ester has been developed to show a synthesis route. Three different series of hyperbranched esters with different terminations have been synthesized to relate some of their properties to their structures. This route has then been used to synthesize three different allyl ethermaleate functional hyperbranched ester resins in a two‐step procedure. The resins have been characterized with respect to rheology, structure, and properties, and the differences are discussed. The allyl ether‐maleate functional resins have also been studied with respect to curing performance and final film properties. © 1993 John Wiley & Sons, Inc.
Curing reaction of o‐cresol novolac epoxy resin according to hardener change
Authors: Kim Whan Gun , Lee Ji Yoon , Park Kyung Y. 
Published: April 2003

AbstractThe investigations of cure kinetics and glass transition temperature (Tg) versus reaction conversion (α) of o‐cresol novolac epoxy resin with the change of hardener were performed. All kinetic parameters of the curing reaction such as the reaction rate order, activation energy, and frequency factor were calculated. The curing mechanisms were classified into two types. One was an autocatalytic mechanism and the other was a nth order kinetic mechanism. The constants related to the chain mobility of polymer segments were obtained by using the DiBenedetto equation. We have tried to correlate the relationships between curing mechanism and molecular structures of hardeners from these results. © 1993 John Wiley & Sons, Inc.
A systematic nomenclature for cascade polymers
Authors: Newkome George R. , Baker Gregory R. , Young James K. , Traynham James G. 
Published: April 2003

AbstractCascade (dendritic) polymers are discrete, highly branched, monodisperse polymers that possess branching patterns described by a mathematical progression. A systematic nomenclature that accurately represents these molecules is described. © 1993 John Wiley & Sons, Inc.
S‐benzoyl O‐ethyl xanthate as a new photoinitiator: Photopolymerization and laser flash photolysis studies
Authors: Ajayaghosh A. , Das S. , George M. V. 
Published: April 2003

AbstractA new sulfur‐containing photoinitiator, S‐benzoyl O‐ethyl xanthate (2) has been prepared and used for the photopolymerization of methyl methacrylate (MMA). The photoinitiation property of 2 has been examined by conventional polymerization methods and nanosecond laser flash photolysis studies. Upon 308 nm laser pulse excitation, 2 gave rise to transients with absorption maxima at 350 and 650 nm, assigned to the benzoyl radical (3) and (ethoxythiocarbonyl)thiyl radical (4), respectively, on the basis of their quenching by nitroxy radicals and spectral similarity to analogous species, reported in the literature. © 1993 John Wiley & Sons, Inc.
Thermal degradation behavior of polyamides having 2‐ and 4‐hydroxycinnamic acid dimer components
Authors: Yonezawa Noriyuki , Kanoe Toshio , Saigo Kazuhiko , Hasegawa Masaki 
Published: April 2003

AbstractTwo new types of polyamides having anti head‐to‐tail hydroxycinnamic acid dimer component in the main chain were synthesized. Their thermal degradation behavior was investigated by TG‐DSC analysis in comparison with those of their model compounds and the polyamides derived from anti head‐to‐head coumarin dimer. The key reactions in the thermal degradation were clarified to be lactonization and cyclic imide formation. The polyamide, derived from 4‐hydroxycinnamic acid dimer and hexamethylenediamine, showed good heat stability. © 1993 John Wiley & Sons, Inc.
Linear all‐ortho oligomers of phenol–formaldehyde resins. I. Preparations, characterizations, and solution properties
Authors: Yamagishi T. , Enoki M. , Inui M. , Furukawa H. , Nakamoto Y. , Ishida S. 
Published: April 2003

AbstractThree kinds of all‐ortho methylene‐linked phenolic oligomers, i.e., 4‐tert‐butylphenol (BP), phenol (AO), and O‐methylated BP (BPM), were prepared with good yields and their dilute solution properties were studied. In acetone, all of these oligomers are highly solvated and molecularly dispersed. In chloroform, however, AO and BP molecules strongly form hydrogen bonds among themselves. By intramolecular and intermolecular hydrogen‐bondings, a large portion of the dimers and the trimers of AO and BP associate to form bimolecular aggregates in chloroform, assuming pseudo‐cyclic conformations analogous to calix [4] arene and calix [6] arene, respectively. By intramolecular hydrogen‐bonding, the tetramers and the hexamers also form pseudo‐cyclic conformations by themselves in chloroform. © 1993 John Wiley & Sons, Inc.
Chemiluminescence of anhydride‐cured epoxy networks: Influence of the anhydride structure
Authors: Tcharkhtchi A. , Audouin L. , Verdu J. 
Published: April 2003

AbstractThe chemiluminescence of three epoxy networks based on diglycidyl ether of biphenol A (DGEBA) crosslinked by respectively the phthalic anhydride (PA), hexahydrophthalic anhydride (HHPA), and methyl tetrahydrophthalic anhydride (MTHPA), was studied in the 180–240°C temperature range. Isothermal stationary and nonstationary (perturbed) experiments revealed that the behavior depends sharply on the anhydride structure. The higher emissivity of cycloaliphatic systems (MTHPA and HHPA) is explained in terms of hydrogen abstractibility on the hardener's moiety. The main difference between MTHPA and HHPA (intensity initially decreases for the former, increases for the latter) is explained by the consumption of the MTHPA double bonds in oxidative crosslinking processes. The results of perturbed experiments were essentially attributed to changes of alkyl radical concentration during the exposure under nitrogen. These changes can be modelled by a simple kinetic model taking into account the observed differences between the systems under study. © 1993 John Wiley & Sons, Inc.
Copolymers of nylon 266 and nylon 66: Synthesis and characterization
Authors: Gonsalves Kenneth E. , Chen Xiaomao 
Published: April 2003

AbstractCopolymers of nylon 266 and nylon 66 were prepared by interfacial polymerization of N‐glycyl hexanediamine and hexanediamine with adipoyl chloride. According to the results of intrinsic viscosity measurements and GPC analysis, the molecular weights of the copolymers were relatively high. The structure of the copolymers was confirmed by FTIR, and the compositions were determined by 1H‐NMR spectroscopy. The copolymers have similar solubility features as nylon 66. Both melting and glass transition temperatures showed a minimum at around 20–30% nylon 66 content. The copolymers are semicrystalline. Copolymers with lower Tm could be melt‐spun into fibers without appreciable thermal degradation. © 1993 John Wiley & Sons, Inc.
Determination of the degree of N‐deacetylation in chitin and chitosan as well as their monomer sugar ratios by near infrared spectroscopy
Authors: Rathke Thomas D. , Hudson Samuel M. 
Published: April 2003

AbstractChitin and its derivative chitosan are rapidly becoming of commercial interest in the biomedical, wastewater treatment, and fiber industries. One of the most important properties of these copolymers is the degree of N‐acetylation. Presently there is no rapid accurate method to determine this value. We propose near infrared spectroscopy for such a method. Using a primary method such as hydrobromic acid titration or 1H‐NMR, standards can be established. Once a model calibration equation has been developed, unknown samples can be analyzed by near infrared spectroscopy in less than 5 min. This is demonstrated by examining representative structural monomers of chitosan, N‐acetyl‐D‐glucosamine and D‐glucosamine hydrochloride, as model compounds as well as actual chitin and chitosan samples. © 1993 John Wiley & Sons, Inc.
Electrophilic aromatic substitution in the curing of brominated poly(isobutylene‐co‐4‐methylstyrene): A mechanistic model study with zinc salts
Authors: Bielski R. , Fréchet J. M. J. , Fusco J. V. , Powers K. W. , Wang H. C. 
Published: April 2003

AbstractThe crosslinking chemistry of a new elastomer based on brominated poly(isobutylene‐co‐4‐methylstyrene) has been investigated using model compounds. In order to mimic the conditions that prevail within the highly allphatic rubber, the study was carried out in mineral oil using catalysts that are compatible with such low polarity media. Electrophilic aromatic substitution reactions occur in a system consisting of p‐isopropylbenzyl bromide and p‐isopropyl toluene in the presence of zinc oxide and zinc stearate. The reaction proceeds after a significant induction period while no induction period is seen for a similar reaction with zinc bromide as the catalyst. The in situ formation of reactive species containing ZnBr bonds appears to be an important step in the overall process. The stoichiometric ratio of zinc salt to benzylic bromide is important. High ratios lead to the accumulation of benzylic stearate or benzylic alcohol in the system which retards the alkylation reaction. The model study emphasizes the importance of stoichiometry of reagents in this reaction and provides insight into the crosslinking mechanism. © 1993 John Wiley & Sons, Inc.
Polymerization of coordinated monomers. XXII. Ab initio molecular orbital study on the binary radical complexes of 2‐methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride as a model of growing radical end
Authors: Sato Kota , Goto Tatsuo , Iwabuchi Susumu , Hirai Hidefumi 
Published: April 2003

AbstractThe geometrical and electronic structures of the binary radical complexes of 2‐methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride were determined by using an ab initio molecular orbital method. The 2‐methoxycarbonyl propyl radical complex was a model of the growing radical end in the copolymerization of methyl methacrylate in the presence of boron halides. The most stable structure of the binary radical complex composed of 2‐methoxycarbonyl propyl radical with boron trichloride was a twisted form in which the dihedral angle between the vinyl group and the ester group was 32°, while that of the binary radical complex composed of methyl methacrylate radical with boron trifluoride was a planar form as the free radical. The frontier orbital energy of 2‐methoxycarbonyl propyl radical was lowered by 0.06 au by the coordination of boron trichloride, while that was lowered only by 0.02 au by the coordination of boron trifluoride. The polymerization mechanism was elucidated on the basis of these predictions. © 1993 John Wiley & Sons, Inc.
Polymerization of ethylene at high temperature by vanadium‐based heterogeneous Ziegler–Natta catalysts. I. Study of the deactivation process
Authors: Adisson E. , Deffieux A. , Fontanille M. 
Published: April 2003

AbstractKinetics of the polymerization of ethylene initiated by heterogeneous vanadium‐based Ziegler‐Natta catalysts (VCI3‐1/3 AICI3) have been studied at high temperature (160°C, 5 bars) and compared with a titanium‐based system. For the V catalyst, the dependence of the polymerization activity versus time, with the nature and the concentration of the associated aluminum alkyl, has been investigated. Kinetic results have also been correlated with the oxidation state of vanadium in the polymerization conditions. Despite the relatively high initial activity a low productivity is obtained; it can be attributed to a very fast deactivation of the active sites due to the reduction of vanadium III into vanadium II. The effect of the nature of the alkyl aluminum component of the catalytic system on the reduction process is shown. A kinetic model for the polymerization is proposed. © 1993 John Wiley & Sons, Inc.
Hydrogenated polybutadiene–polymethyl methacrylate (HPB–PMMA) block copolymer. I. Synthesis of polybutadiene–polymethyl methacrylate (PB–PMMA) block copolymer
Authors: Ren Qin , Zhang Hong Jin , Zhang Xiao Kang , Huang Bao Tong 
Published: April 2003

AbstractTo get hydrogenated polybutadiene‐polymethyl methacrylate (HPB‐b‐PMMA) block copolymer to be used as a compatibilizer for blends of polyolefin/polar polymer, PB‐b‐PMMA was synthesized by anionic‐free radical mechanism transformation polymerization. Selective extraction, gradient elution thin layer chromatography, and oil‐oil emulsion separation techniques were tried to attempt to separate the copolymerization products. Hydrogenation of the PB sequence in PB‐b‐PMMA yielded HPB‐b‐PMMA. The compatibilizing function of PB‐b‐PMMA was shown in blending experiments. © 1993 John Wiley & Sons, Inc.
Synthesis and Ni(0)‐catalyzed oligomerization of isomeric 4,4‴‐dichloroquaterphenyls
Authors: Percec Virgil , Okita Shigeru 
Published: April 2003

Abstract4,4‴‐Dichloro‐1,1′ : 2′,1″ : 2″,1‴‐quaterphenyl (9), 4,4‴‐dichloro‐1,1′ : 3′,1″ : 3″,1‴‐quaterphenyl (10), and 4,4‴‐dichloro‐1,1′ : 4′,1″ : 4″,1‴‐quaterphenyl (11) were synthesized by Pd (0) catalyzed cross‐coupling reaction of 4‐chlorobenzeneboronic acid with 2,2′‐, 3,3′‐, and 4,4′‐bis (trifluoromethanesulfonyloxy)biphenyl respectively. 4,4‴‐Dichloro‐1,1′ : 2′,1″ : 2″,1‴‐quaterphenyl (9) and 4,4‴‐dichloro‐1,1′ : 3′,1″ : 3″,1‴‐quaterphenyl (10) were oligomerized by Ni(0) catalyzed homocoupling reaction to yield white and soluble oligophenylenes. © 1993 John Wiley & Sons, Inc.
Monomer‐isomerization radical polymerization of di‐tert‐butyl maleate and preparation of poly(fumaric acid) via pyrolysis
Authors: Otsu Takayuki , Shiraishi Kohei , Matsumoto Akikazu 
Published: April 2003

AbstractDi‐tert‐butyl maleate (DtBM) did not polymerize with 2,2′‐azobis(isobutyronitrile) as a radical initiator, but DtBM easily homopolymerized via a monomer‐isomerization radical polymerization mechanism to give a high molecular weight polymer when morpholine was added into the polymerization system as an isomerization catalyst. The feature of the monomer‐isomerization polymerization of DtBM was investigated in detail. The polymer obtained was confirmed to consist of a poly(tert‐butoxycarbonylmethylene) structure similar to that from di‐tert‐butyl fumarate. Subsequent pyrolysis of the resulting polymer at 180°C is a useful route to synthesis of a high molecular weight poly(fumaric acid). © 1993 John Wiley & Sons, Inc.
Investigation of the free radical polymerization of styrene in the presence of several 1,1‐disubstituted ethylenes
Authors: Dais Virginia A. , Priddy D. B. , Bell Bruce , Sikkema Kevin D. , Smith Pat 
Published: April 2003

AbstractA variety of 1,1‐disubstituted ethylenes, having an electron‐withdrawing (capto) and an electron‐donor (dative) substituent on the same carbon, were synthesized and added to styrene polymerizations. The dative substituents investigated were alkoxy or alkylcarbonate. After the addition of a polystyryl radical to a disubstituted ethylene, the resulting alkoxy or carbonate radicals could potentially fragment, resulting in chain termination and the formation of alkyl radicals. This process is called addition‐fragmentation chain transfer (AFCT). The polymers produced during this study were examined for evidence of copolymerization and AFCT. The relative stability of the radicals generated by the fragmentation process appears to be the predominant factor controlling the ratio of copolymerization versus AFCT. © 1993 John Wiley & Sons, Inc.
Effects of diamine monomer structure on the gas permeability of polyimides. I. Bridged diamines
Authors: Langsam Michael , Burgoyne William F. 
Published: April 2003

AbstractPermeability measurements for oxygen and nitrogen were carried out on a series of structurally similar polyimides in order to define structure/permeability relationships. The polyimides were prepared from 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl) ethylidene] bis‐1,3‐isobenzofuranedione (6FDA) and a variety of substituted methylene dianilines and benzidines. A correlation between the diamine monomer structure and polymer permeability was found, particularly with diamine monomer variations at the ortho positions of the diamine relative to the amino moiety. These correlations were semilogarithmic, relative to the summation of the substituent volumes. Direct correlations were observed between the measured properties of polymer density and interchaind‐spacings and the oxygen permeability value of each of these polyimides. In addition, we observed that the calculated values of fractional free volume were related to oxygen permeability in a manner which enabled us to identity a polar component in the effects of these ortho substituents. © 1993 John Wiley & Sons, Inc.
Nucleophilic substitution reactions of 1,4‐dichlorobenzene chromium tricarbonyl with mono‐ and diphenoxides
Authors: Percec Virgil , Okita Shigeru 
Published: April 2003

AbstractThe nucleophilic substitution reactions of 1,4‐dichlorobenzene chromium tricarbonyl (1) with the phenoxide anion were investigated. The substitution of the first chlorine was very fast and gave the mono‐substituted product in high yield. The substitution of the second chlorine group was significantly retarded by the presence of the phenoxy group incorporated during the first reaction and also due to the competing decomplexation reaction. The application of 1,4‐dichlorobenzene chromium tricarbonyl (1) to the synthesis of new monomers was demonstrated by the preparation of 2,2′‐bis[4‐(4‐chlorophenoxy)phenyl]propane (9). 2,2′‐Bis[4‐(4‐chlorophenoxyl)phenyl]propane (9) was synthesized by a nucleophilic substitution reaction of 4,4′‐isopropylidenediphenolate with 1,4‐dichlorobenzene chromium tricarbonyl (1) followed by decomplexation with I2. 2,2′‐Bis[4‐(4‐chlorophenoxy)‐phenyl]propane (9) was also synthesized via a three‐step reaction starting from the nucleophilic substitution reaction of 4,4′‐isopropylidenediphenol (7a) with 1‐chloro‐4‐nitrobenzene (10). 2,2′‐Bis[4‐(4‐chlorophenoxy)phenyl]propane (9) was polymerized by a Ni(0)‐catalyzed reaction to yield amorphous aromatic polyethers with number‐average molecular weights of up to 11,200 g/mol. © 1993 John Wiley & Sons, Inc.
Insoluble polystyrene‐bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide
Authors: Nishikubo Tadatomi , Kameyama Atsushi , Yamashita Jun , Tomoi Masao , Fukuda Wakichi 
Published: April 2003

AbstractThe addition reaction of oxiranes (26a—e) with carbon dioxide (CO2) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO2 proceeded smoothly catalyzed by 1–2 mol % of the polymer‐supported quaternary onium salts to give the corresponding cyclic carbonates (27a—e) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer‐supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back‐bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer‐supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer‐supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.
Radical polymerization of 3‐methylene‐5,5′‐dimethyl‐2‐pyrrolidinone: A cyclic analog of N‐substituted methacrylamide
Authors: Ueda Mitsuru , Honda Mutsumi , Sugiyama Jun‐ichi , Ito Hiroshi 
Published: April 2003

Abstract3‐Methylene‐5,5′‐dimethyl‐2‐pyrrolidinone (α‐MDMP), a cyclic analog of N‐substituted methacrylamide, was synthesized and polymerized with α,α′‐azobis (isobutyronitrile) (AIBN) in solution. Poly(α‐MDMP) is only soluble in dimethyl sulfoxide (DMSO) at room temperature. Thermogravimetry of poly(α‐MDMP) showed 10% weight loss at 355°C in air and 400°C under nitrogen, respectively. The kinetics of α‐MDMP homopolymerization with AIBN was investigated in DMSO. The rate of polymerization (Rp) can be expressed by Rp = k[AIBN]0.49[α‐MDMP]1.0 and the overall activation energy has been calculated to be 73.2 kJ/mol. Monomer reactivity ratios in copolymerization of α‐MDMP (M2) with methyl methacrylate (M1) are r1 = 0.71 and r2 = 0.71, from which Q and e values of α‐MDMP are calculated as 0.75 and ‐0.43, respectively. © 1993 John Wiley & Sons, Inc.