bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of benzylidene‐pendant polyphthalimidines from flexible bisphthalides and various diamines
Authors: Imai Yoshio , Takahashi Takeyoshi , Nan Renzhi , Ueda Mitsuru 
Published: April 2003

AbstractNew polyphthalimidine‐forming monomers, 5,5′‐(oxydi‐p‐phenylenedicarbonyl)bis(3‐benzylidenephthalide) and the 6,6′‐derivative, were synthesized by the Friedel–Crafts reaction of diphenyl ether with 5‐ and 6‐chloroformyl‐3‐benzylidenephthalide, respectively. The direct polycondensation of these bisphthalides with both aliphatic and aromatic diamines in o‐phenylphenol at 200–250°C afforded polyphthalimidines having inherent viscosities of 0.2–1.2 dL/g in almost quantitative yields. Syntheses of aliphatic polyphthalimidines with higher inherent viscosities were also achieved by a two‐step procedure involving ring‐opening polyaddition and subsequent thermal cyclodehydration. All the polymers were amorphous and readily soluble in N‐methyl‐2‐pyrrolidone (NMP), m‐cresol, nitrobenzene, pyridine, and chloroform. Tough and flexible films could be cast from NMP solutions of the polymers. Glass transition temperatures of the polyphthalimidines were in the range of 158–246°C. The thermogravimetry of the aromatic polymers showed 10% weight loss in air and nitrogen at 445–515 and 500–520°C, respectively. The crosslinking reaction of some benzylidenependant polyphthalimidines took place at 300°C through double‐bond addition to afford cured polymers with improved thermal stability.
Photopolymerization reactions initiated by copper (II)–amino acid chelates: Investigation of the initiating species by flash photolysis. I
Authors: Namasivayam C. , Natarajan P. 
Published: April 2003

AbstractFlash photolysis of copper (II)–bis(amino acid) complexes (amino acids: glutamic acid, serine, or valine) in deaerated aqueous solution produces transient species having absorption maxima at around 350 nm. The transient species are identified as copper (II)–alkyl complexes. In the case of Cu(valine)2 at pH > 6.5 formation of Cu(II)‐alkyl complex is not observed; this is interpreted to be due to the presence of two bulky methyl groups of the coordinated valine ligand, which hinders the rearrangement. Pseudo‐first‐order rate constants for the decay of the transients are determined at different pH with varying concentration of amino acid ligand. The free‐radical species of the complexes responsible for the initiation of the vinyl polymerization reactions are identified as Cu(I)‐coordinated amino acid radicals which are formed in the primary photochemical reaction of the complex. A mechanism for the secondary reactions involving the initiating species consistent with the nature of the product formed and the pH dependence of the decay of the transients is proposed.
Synthesis of monomers that expand on polymerization. Synthesis and polymerization of 2,6,7‐trioxabicyclo[2.2.2]octanes with phenyl groups
Authors: Saigo Kazuhide , Bailey William J. , Endo Takeshi , Okawara Makoto 
Published: April 2003

Abstract2,6,7‐Trioxabicyclo[2.2.2]octanes with phenyl group were prepared to obtain monomers which expand on polymerization. 1‐Phenyl‐4‐ethyl‐2,6,7‐trioxabicyclo[2.2.2]octane (I) could expand 0.2% during polymerization at a temperature slightly higher than the melting point. 1,4‐Diphenyl‐2,6,7‐trioxabicyclo[2.2.2]octane (II) also expanded as much as 1.4% on polymerization. Further, the hydrolysis of 2,6,7‐trioxabicyclo[2.2.2]octanes with p‐substituted phenyl groups were investigated to estimate the stability in water.
Mechanism of imidazole catalysis in the curing of epoxy resins
Authors: Ricciardi Fiore , Romanchick William A. , Joullié Madeleine M. 
Published: April 2003

AbstractThe mechanism of imidazole catalysis in the curing of epoxy resins was studied using the PGE/1‐methylimidazole, 2‐methylimidazole, and 1,2‐dimethylimidazole model systems and another model system based on trichloromethylethylene oxide. It was demonstrated that imidazolium systems, generated in the curing reaction, show an inherent instability leading to cleavage of an NC bond or the 2‐CH bond (2‐unsubstituted imidazoles). Fourier‐transform infrared spectroscopy was used to follow specific changes in the IR spectrum of the curing mixture during polymerization. The identification of carbonyl absorptions occurring during the polymerization led to the conclusion that ketone formation is a general occurrence in the cure of epoxides with nitrogen compounds. We have also shown that imidazoles are regenerated during the curing process by at least two routes. One pathway for the regeneration of the catalyst involves N‐dealkylation of the imidazole via a substitution process. Another route, β‐elimination, afforded carbonyl compounds, which account for the previously unexplained appearence of infrared bands in the 1650–1770 cm−1 region during the curing process. These investigations demonstrated the true catalytic function of the imidazole. Possible mechanisms for the regeneration of the catalyst are also suggested.
Enantioselective polymerization of γ‐benzyl‐DL‐glutamate N‐carboxy anhydride in the presence of poly(γ‐benzyl‐L‐glutamate)
Authors: Oguni Nobuki , Kuboyama Hiroaki , Nakamura Akira 
Published: April 2003

AbstractThe polymerization of γ‐benzyl‐DL‐glutamate NCA in the presence of poly(γ‐benzyl‐L‐glutamate) was investigated. At the initial stage the D‐enantiomer was preferentially polymerized (ca. 35% ee) by using triethylamine as an initiator. Enantioselectivity was independent of the molecular weight of preformed poly(γ‐benzyl‐DL‐glutamate).
Synthesis and solution properties of poly(trans‐5‐ethylproline). A slow mutarotating substituted polyproline
Authors: Ahn Kwang‐Duk , Overberger C. G. 
Published: April 2003

AbstractAn optically active polypeptide, poly(trans‐5‐ethylproline) (PT5EP) was synthesized and its solution properties were observed to investigate the conformational changes with various conditions. The trans‐5‐ethyl substitution on polyproline showed noticeable perturbed effects on the conformations of the polypeptide as well as mutarotation of the polypeptide in solution. Circular dichroism (CD) spectra suggested that the polypeptide existed in a poly(L‐proline) form‐I‐type helix and mutarotated slowly to an intermediate conformation in which some of the amide bonds had rotated to a trans conformation. In trifluoroethanol (TFE) solution the polymer took more than 20 days to change from a form‐I‐type helix conformation, in which CD bands for D‐PT5EP are at 199.5 ± 1.0 (positive), 115.5 ± 0.5 (negative), and around 238 nm (positive), to an intermediate conformation. Upon addition of trifluoroacetic acid (TFA) to a TFE solution, the polymer was transformed to form‐II‐type polymers. Even a greater change in conformation was observed in a solution of TFA or in LiClO4‐TFE. The overall change of the intensity ratio RCD of positive to negative CD bands of D‐PT5EP was from 0.6–0.7 to 30. Reverse mutarotation toward the original form I was observed when n‐butyl alcohol, water, or THF was added to a solution containing the form II polymer. A blue shift of the UV spectra and a change in the NMR spectrum also supported the concept of this conformational change.
Glow discharge polymerization of tetramethylsilane investigated by infrared spectroscopy and ESCA
Authors: Inagaki N. , Kishi A. 
Published: April 2003

AbstractThe influence of operating conditions (W/FM parameter: W input energy of rf power; F flow rate of monomer; M molecular weight of monomer) on glow discharge polymerization of tetramethylsilane (TMS) was investigated by infrared spectroscopy and ESCA. Elemental analyses showed that the compositions of the polymers formed strongly depended on the level of the W/FM parameter, i.e., whether the W/FM value was more or less than 190 MJ/kg. The infrared spectra indicated that these polymers were composed of SiH, SiO, SiC, SiCH3, and SiCH2 groups, and that there was no significant difference in structural features between polymers prepared at W/FM parameters of more or less than 190 MJ/kg. ESCA spectra (C1s and Si2p core‐level spectra) showed that the polymers included carbonized carbon, aliphatic carbon SiC, CO, SiO, and SiO2 species, and that the sum of carbonized and aliphatic carbons reached more than 50%. Raising the W/FM value increased the formation of the carbonized carbon but did not influence the formation of Si units such as SiC and SiO groups.From this evidence the rupture of SiCH3 bonds in the polymer forming process is emphasized. The magnitude of the W/FM parameter may be related to the detachment of hydrogen from the aliphatic carbon units.
Synthesis, characterization, and properties of novel poly(ether urethanes)
Authors: Ghatge N. D. , Jadhav J. Y. 
Published: April 2003

AbstractNovel poly(ether urethanes) were synthesized by homo‐ and random copolymerization of the m‐ and p‐hydroxyethoxy benzoyl azides. Polymerization proceeded by decomposition and rearrangement of the acid azide group to the isocyanate group, which immediately reacted intermolecularly with the hydroxyl group to produce polyurethanes. These polymers were characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), x‐ray diffraction, scanning electron microscopy (SEM), viscosity, and solubility. The thermal stability of these polymers was also studied by TG and DTG (derivative TG).
Adsorption layers of surface‐active substances and their influence on polyurethane network formation
Authors: Lipatova T. E. , Vengerovskaya Sh. G. , Feinerman A. E. , Sheinina L. S. 
Published: April 2003

AbstractThe study of polyurethane systems cured in the presence of surface‐active substances (SASs) proves that surfactants call forth the structural and kinetic changes in the reaction system. It is shown that surfactant decreases the viscosity of these systems in the early stages of reaction, shifting the beginning of structural gel formation to the higher degrees of NCO‐group conversion. The reaction rate is shown to be a complex function of surfactant concentration. The binary polyether‐surfactant system was studied by IR spectroscopy and surface tension measurement. The data prove that intermolecular and intramolecular H bonds in the system are redistributed at all surfactant concentrations but 0.03 and 0.15%. According to our calculations for surfactant adsorption layers at the polyether‐air interface, ΔS values do not depend on temperature at surfactant concentration 0.03% whereas at 0.15% ΔS and ΔH values are maximum. The results obtained by different methods are well correlated and suggest that kinetic effects are due to redistribution of H bonds under the influence of conformational changes in surfactant structure.
Polyaromatic ether‐ketones from o,o′‐disubstituted diphenyl ethers
Authors: Lee Jasun , Marvel C. S. 
Published: April 2003

AbstractPolyaromatic ether‐ketone resins with potentially open structures which are possibly useful as membranes were prepared from diphenyl ethers with alkyl substitutions in the ortho positions and isophthaloyl or terephthaloyl chloride by Friedel–Craft‐type polymerization. These polymers are soluble in such solvents as DMF, DMA, and CHCl3, and can be cast into colorless transparent films.
Interaction of crosslinked polyethylenimine with a homologous series of methyl orange derivatives in aqueous solution
Authors: Takagishi Toru , Sugimoto Takeo , Hayashi Akiyo , Kuroki Nobuhiko 
Published: April 2003

AbstractPolyethylenimine (PEI) was crosslinked with dichloroethane, glyoxal, or glutaraldehyde and polymers of various degrees of crosslinkage were made. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl, ethyl, propyl, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. PEI crosslinked with glutaraldehyde showed markedly increased binding affinity toward these cosolutes compared with the polymers crosslinked with dichloroethane or glyoxal. The extent of the binding increased with an increase in the degree of crosslinkage. These results suggest that the enhancement of the binding by the crosslinking is due mainly to a dual effect, introduction of hydrophobic moieties and proximity of neighboring polymer chains. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. The thermodynamic data show that the binding process is athermal and is stabilized entirely by the entropy term. Water‐soluble PEI exhibited stronger cooperative interactions than the crosslinked polymer because the mobilities of the chains of the former are greater than those of the latter.
Ignition of poly(methyl methacrylate) slabs using a small flame
Authors: Clark Ferrers R. S. 
Published: April 2003

AbstractWhen exposed to a lean hydrogen‐oxygen flat flame, slabs of poly(methyl methacrylate) ignited to flaming combustion after a delay, the length of which depended on the gas temperature and the separation between the slab and the igniting flame. The delay obeyed an Arrhenius‐type expression, giving an activation energy of 96 ± 8 kJ mol−1. By the end of the delay the surface of the sample was pitted if the delay was long and almost unchanged if the delay was short. The rates of flame development measured immediately after the ignition were proportional to the ignition delay, the proportionality constant varying with the separation between slab and flame. These rates decreased as temperature increased; the slope of the linear Arrhenius plots was independent of slab‐flame separation. During the delay, carbon dioxide was formed within the boundry layer and a blue preignition glow was visible at its outer edge. These data were explained by a model in which ignition delay is governed by the induction period of gas‐phase reactions in or near the boundry layer. Models in which delay is governed by the time taken to heat the polymer to a critical ignition temperature did not satisfactorily explain the data.
Preparation and photolysis of polyamides having coumarin dimer component
Authors: Hasegawa Masaki , Saigo Kazuhiko , Katsuki Hirokazu , Yonezawa Noriyuki , Kanoe Toshio 
Published: April 2003

AbstractThe ring‐opening polyaddition reaction of anti and syn head‐to‐head Coumarin dimers with diamines and the photocleavage behavior of the resulting polyamides were investigated. Anti head‐to‐head Coumarin dimer successfully reacted with aliphatic and aromatic diamines in an aprotic polar solvent to give corresponding high molecular weight polyamides. The polyamides showed good film forming ability and exhibited solubility behavior typical of polyelectrolytes. Furthermore, these polyamides were found to undergo exclusively asymmetric photocleavage on the cyclobutane rings in the polymer main chain to give a fumaramide unit with elimination of 2,2′‐dihydroxystilbene. On the other hand, syn head‐to‐head Coumarin dimer gave only low molecular weight polyamides. These polymerization and photocleavage behaviors were elucidated in comparison with those of model reactions.
Ultra‐fast polymerization of epoxy‐acrylate resins by pulsed laser irradiation
Authors: Decker Christian 
Published: April 2003

AbstractThe 337.1‐nm emission of a pulsed nitrogen laser was shown to initiate the crosslinking polymerization of epoxy‐acrylate photoresists effectively. We evaluated the extent of curing from the amount of insoluble polymer formed and by the decrease in infrared (IR) absorption of the reactive double bond at 810 cm−1. With the large power density available in the laser pulse (0.5 MW cm−2) rates of polymerization as high as 108 mol L−1 s−1 were observed in the presence of air. Quantum yield measurements indicated that each photon absorbed can create as many as 450 crosslinks; the kinetic chain length was calculated as ca. 4000 double bonds polymerized per initiating radical. During the induction period due to oxygen inhibition each photoinitiator radical consumed 1 O2 molecule. The influence of the monomer and photoinitiator used on the sensitivity of the resin was examined; the best performing formulation contained the epoxy‐acrylate oligomer, pentaerythritol triacrylate, as monomer and 2,2 dimethoxy‐2‐phenyl‐acetophenone as photoiniatior. All the formulations studied can be cured by a single 500‐kW laser pulse of 8 ns duration, provided that the irradiation is carried out in an inert atmosphere or with a focused laser beam.
Gamma radiation‐initiated polymerization of styrene at high pressure. IV. Emulsion polymerization with nonionic emulsifier
Authors: Moore P. W. , Clouston J. G. , Chaplin R. P. 
Published: April 2003

AbstractThe effects of pressure, irradiation dose rate, and emulsifier concentration on the rate of polymerization of styrene emulsions stabilized with a nonionic surfactant, Teric GX13, were investigated. Results differed from those previously obtained with anionic surfactants and did not follow Smith–Ewart kinetics. The controlling influence of the surfactant at the particle–water interface on the reaction was demonstrated and results could be interpreted in terms of the Medvedev equation. Using this equation, we determined a value for the activation volume for chain propagation, ΔV, as −18.7 cm3 mol−1. This value is the same as that for pure styrene and emulsions that follow Smith–Ewart kinetics.
Polybromostryl macromers and their anionic polymerization
Authors: Königsberg Itzhak , Jagur‐Grodzinski Joseph 
Published: April 2003

AbstractThe decomposition of polybromostyryl carbanions (PBS−), obtained by anionic polymerization of 4‐bromostyrene in tetrahydrofuran (THF), was investigated in the dark in a temperature range of −6–−21°C. It was accompanied by the evolution of bromine anions and by the formation of polymeric allylic carbanions (λmax = 575 nm; εmax = 6800 eq−1·L·cm−1). The reaction mechanism was elucidated. The rate constant of the unimolecular rate‐determining step of the process was 1.3 × 10−5 s−1 and 9.7 × 10−5 s−1 at −21 and −6°C, respectively. Its apparent energy of activation Eapp = 18.38 Kcal/mol. The polybromostyrenes with allylic carbanions at their ends may decompose further. Their “dark” decomposition yielded 1,3‐butadiene‐1,3‐diphenyl‐macromers. The mechanisms of decomposition of the PBS− carbanions and the dark decomposition of the polybromostyryl allylic carbanions are analogous. The rate constant of the latter process was 2.5 × 10−6 s−1 at −6°C. The anionic polymerization of prepared macromers can be initiated in THF at −78°C by α‐methylstyryl carbanions, which do not react, however, with PBS− carbanions. “Comblike” polymacromers were prepared in which each branch had a molecular weight of about 50,000. The overall molecular weight of the polymacromer was estimated to be about 1 × 106. It has been assumed that the 2–1 mode of addition to the diene group of the macromer is predominant during its polymerization. The 3–4 mode of addition followed by proton shift represents the termination step. The 4–3 mode of addition was ruled out on the basis of spectroscopic evidence.
Radical polymerization in the presence of complexing agents. VI. Effect of low concentrations of ZnCl2 on the overall rate of copolymerization of methyl methacrylate with ethyl acrylate
Authors: Madruga E. L. , Román J. San , Rodriguez M. J. 
Published: April 2003

AbstractOverall rates for the free‐radical copolymerization of methyl methacrylate with ethyl acrylate in the presence of low concentrations of ZnCl2 have been determined at 50°C. The rate of copolymerization Rp depends on both the ZnCl2 concentration and the monomer feed composition. Relative copolymerization rates Rp/R where R is the rate of copolymerization in the absence of complexing agent in the reaction mixture, show a minimum for intermediate feed compositions, independently of the ZnCl2 concentration. On the basis of the results obtained, a conventional copolymerization mechanism is proposed for this system in which free and complexed species of both acrylic monomers participate.
Kinetics and mechanism of acetylene polymerization
Authors: Schen M. A. , Karasz F. E. , Chien James C. W. 
Published: April 2003

AbstractThe kinetics of acetylene polymerization initiated by Ti(OBu)4/4AlEt3 catalyst was studied by radioquenching with C*O to count the number of active sites [C] and by CH3OT* to determine the total metal polymer bonds [MPB] and M̄n of the polymer. The amount of quenching agent and time of reaction required and the kinetic isotope effect for CH3OT* were determined. The effects of Al/Ti ratio, catalyst aging, catalyst concentration, temperature, and monomer pressure on the polymerization were investigated. Detailed kinetic data on the variation of rate of polymerization, Rp, [C] [MPB], and M̄n with time were obtained at 298 and 195°K. The results required the assumption that the catalytic species C, is initially active and within less than 30 min all are converted by bimolecular kinetics to a far less active species. Analysis of the data yielded rate constants of propagation and termination and their energies of activation. Estimates of chain transfer efficiency were obtained. The mechanisms for the propagation, termination, and transfer processes were discussed. By drawing on our earlier EPR results we propose probable structures for the catalytically active species.
Correlation of fine structural characteristics and textile properties of silk fiber
Authors: Padhi R. C. , Labischinski H. , Patel A. 
Published: April 2003

AbstractThe small‐angle, x‐ray scattering method was applied to evaluate macromolecular parameters of defated proteinous silk fibers like Eri, Muga, Tussah, and raw silk. For the experimental measurement of scattering intensities the small‐angle Kratky camera, coupled with an automatic‐step scanning device, pulse‐height discriminator, and counter attachment was used. Macromolecular parameters like specific inner surface, percentage of void, length of coherence, range of inhomogeneity, and transversal length were evaluated by using the theories of Kratky, Porod and Debye, and Bueche. The physical properties of these defated fibers were also evaluated with Scott's IP2‐inclined plane tester. The correlation of the tertiary structural parameters with textile properties like average breaking strength of the proteinous fibers indicated a dependence of physical properties on certain macromolecular parameters.
Curing epoxy resins with anhydrides. Model reactions and reaction mechanism
Authors: Matějka L. , Lövy J. , Pokorný S. , Bouchal K. , Dušek K. 
Published: April 2003

AbstractThe mechanism of acid curing of epoxy resins catalyzed with tertiary amines was investigated by using model systems composed of phenylglycidyl ether and benzoic acid or acetic acid anhydrides in the presence of benzyldimethylamine. The reaction was studied by NMR spectrometry, liquid chromatography, and ozone absorption. The main findings are that (1) the tert‐amine is bound chemically and irreversibly during the reaction under the formation of a quaternary ammonium salt
magnified image
and (2) 1‐phenyloxypropanediol‐2,3‐dibenzoate or diacetate is the main reaction product. The suggested reaction mechanism involves initiation in which the tertiary amine reacts with the epoxy group, giving rise to a zwitterion that contains a quaternary nitrogen atom and an alkoxide anion; the latter immediately reacts with the anhydride and quaternary salt is formed. In a later stage the carboxy anion of the quaternary salt reacts first with the epoxy group, then with the anhydride. By this reaction diester is formed and the carboxy anion is regenerated.