bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enthalpy of polymerisation of ethylene oxide and of copolymerisation of ethylene oxide with 7‐oxabicyclo[2.2.1]heptane
Authors: Andruzzi Fulvio , Suradi Sukiman , Pilcher Geoffrey 
Published: April 2003

AbstractThe enthalpies of combustion of poly(ethylene oxide), ΔH(c)=‐1178,7 ± 1,3 kJ . mol‐1, and of a random copolymer of overall molar composition 0,41 (poly(ethylene oxide)) + 0,59 (poly(oxy‐1,4‐cyclohexylene)), ΔH(c)=‐2566,4 ± 1,8 kJ . mol‐1, were measured at 298,15 K by high‐precision bomb calorimetry. The enthalpy of polymerisation of ethylene oxide was derived as ΔH (l → c) = ‐102,4 ± 1,6 kJ . mol‐1. The enthalpy of copolymerisation of ethylene oxide and 7‐oxabicyclo[2.2.1]heptane was ΔH (l → c) = ‐63,0 ± 2,1 kJ . mol‐1, compared with ‐68,1 ± 1,6 kJ . mol‐1 for producing the two homopolymers in the proportion in which the monomers were present in the copolymer. It is concluded that insertion of an ethylene oxide unit into a poly(oxy‐1,4‐cyclohexylene) chain does not affect the strain‐energy by a significant amount.
On the conformational characteristics of acrylamide polymers
Authors: Chiantore Oscar , Trossarelli Luigi , Guaita Marino 
Published: April 2003

AbstractThe effect of lateral substituents on the structure of the solutions and on the chain conformations of N‐substituted and N,N‐disubstituted poly(acrylamide)s is discussed. The water‐soluble polymers show solution properties influenced by the development of strong specific interactions between the chain molecules and the solvent, and by the hydrophobicity of the substituents. In non‐aqueous solvents the interactions between the polar groups of the structural units force the polymer chains to assume unusually large unperturbed dimensions, causing the chain flexibility to depend more on the overall polarity of the molecule than on the bulkiness of the substituent.
Polymere mit phosphor‐stickstoff‐bindungen, 7. Die polymerisation gemischt chlor‐ und trifluorethoxysubstituierter cyclotriphosphazene bei anwesenheit von bortrichlorid
Authors: Horn Hans‐Georg , Kolkmann Friedrich 
Published: April 2003

AbstractMixed chloro‐ and trifluoroethoxy substituted cyclotriphosphazenes 1a–d react with boron trichloride at elevated temperature to give mixed substituted polyphosphazenes of low molecular weight. The reaction was investigated by 31P NMR. Fractionation of the polymers was achieved by extraction with hexane/benzene. The low molecular weights are explained by a large amount of cyclophosphazenyl cations generated nearly simultaneously.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 10. Synthèse de poly(méthacrylate de méthyle)s par le rayonnement UV: étude de l'influence de la nature du solvant mutuel sur la polymolécularité
Authors: Brosse Jean‐Claude , Lenain Jean‐Claude , Gauthier Jean‐Marie 
Published: April 2003

AbstractMethyl methacrylate was polymerized under UV irradiation (254 nm) at room temperature by hydrogen peroxide in order to give hydroxytelechelic polymers. The polymerization was carried out in the presence of ethanol. An alcohol may be used as a diluent, as a mutual solvent of hydrogen peroxide and the monomer, and as a solvent or nonsolvent of the polymer. The influence of the alcohol is pointed out on the various characteristics of the polymerization; the results are compared with those obtained in methanol.
Effects of DNA and other polyanions on the EDTA induced photoreduction of thionine
Authors: Pal Medini Kanta , Manna Pravash Ch. 
Published: April 2003

AbstractThionine (7‐amino‐3‐imino‐3‐H‐phenothiazine) undergoes reversible photobleaching when exposed to visible light in the presence of ethylenediaminetetraacetic acid (EDTA) with the associated development of an electromotive force (emf). This photocreation between EDTA and thionine is inhibited in the presence of excess Mg+ +. Polyanions like DNA, RNA and polystyrenesulfonate also protect the dye from the EDTA induced photoreduction; this protective power of the polyanions depends on their nature and increases with their concentration. DNA, thought a weak chromotrope to form a metachromatic compound with thionine, protects the dye from photobleaching efficiently, presumbly due to the intercalation of the dye cations between base pairs of DNA; denatured DNA is relatively poorer in its ability to protect the dye and resembles RNA and polystyrenesulfonate in this respect. The results indicate that EDTA and thionine form a transient complex or are at least associated before electron transfer from EDTA to thionine in the excited‐triplet state takes place.
Metalloester, 9. Untersuchung des anfangsstadiums der anionischen polymerisation von methylmethacrylat. Reaktion von methyl‐2‐sodioisobutyrat mit methylmethacrylat
Authors: Adler H.‐J. , Lochmann L. , Pokorný S. , Berger W. , Trekoval J. 
Published: April 2003

AbstractIn the reaction of methyl methacrylate (2) with methyl 2‐sodioisobutrate (1) (a model of the active center in the anionic polymerization of 2) in a mole ratio of 2:1, the concentrations of all known initial compounds and reaction products were estimated. This reaction was studied in a flow reactor with reaction times between 0,02 and 1,4 s using GLC, LC and GPC as analytical methods. At the same time, a rise in temperature of the reaction mixture by 6°C was observed (for [2] = 0,2 mol/1); at a higher concentration of 2 (0,6 mol/1), this rise was 27°C and hence not negligible in the interpretation of the results. The concentration changes of the individual products were in accordance with the concept of a stepwise addition of 2, to the metalloesters. At the end of the reaction the mean molecular weight of the addition products corresponded roughly to the ratio 2/effective 1. The cyclization of Na‐trimer 4a to a cyclic trimer 9 was shown to be an important side reaction. The Na‐tetramer 5a and the higher Na‐oligomers 6a probably undergo a similar cyclization. 2 added 1 very quickly; the following approximate order of reaction rates (Scheme 1) is proposed: R1 > R2, R3, R4, … > Rc.
Synthesis and properties of block copolymers of polystyrene and poly(2‐acrylamido‐2‐methylpropanesulfonic acid)
Authors: Konishi Hisatoshi , Shinagawa Yoshinobu , Azuma Atsushi , Okano Tamon , Kiji Jitsuo 
Published: April 2003

AbstractA series of A‐B‐A triblock copolymers consisting of poly(2‐acrylamido‐2‐methylpropanesulfonic acid) as outer blocks and polystyrene as the middle block was synthesized by polymerizing 2‐acrylamido‐2‐methylpropanesulfonic acid at the ends of a diethyldithiocarbamate‐terminated polystyrene, in which the terminal diethyldithiocarbamate groups act as the radical initiator under photo‐irradiation. The heterogeneous character of the block copolymers in solutions is discussed on the basis of the solubility behavior and the 1H NMR spectra.
Synthèse et caractérisation de copolymères séquencés poly(vinyl‐2 pyridine)/poly(oxyéthylène)
Authors: Marie Pascal , Lingelser Jean‐Paul , Gallot Yves 
Published: April 2003

AbstractHydrophobic‐hydrophilic poly(2‐vinlypyridine)/poly(ethylene oxide) block copolymers were synthesized by anionic polymerization in tetrahydrofuran in vacuum with diphenylmethylpotassium as initiator. The resulting polymers were fractionated from benzene solution by progressive precipitation with 2,2,4‐trimethylpentane at 35°C. Gel permeation chromatography, light scattering, osmometry, and 1H NMR were used to characterize the fractions. The copolymers, thus prepared, were found to have a well defined structure and a low polydispersity in both molecular weight and chemical composition.
Nature et conséquence des interactions se développant lors de la mise en contact de polyéthylène avec des produits mouillants et non mouillants, 2. Cas des produits non mouillants polaires (eau) et apolaires (iodure de méthylène)
Authors: Escoubes Marcelle , Berticat Philippe , Chabert Bernard , Chauchard Jacques , Sage Daniel 
Published: April 2003

AbstractThe nature of interactions between polyethylene and a non‐wetting solute was analyzed to know if the interface can be characterized by the expression of the energy of wetting or if phenomena other than adhesion and wetting must be taken into account. In this way, the isotherms of sorption, the molar heats of interaction, the kinetic behaviour of the sorption, the permeation, and the changes of length during liquid immersion gave informations on the existence of a limited diffusion into the polymer. Two types of systems were investigated: polyethylene/water and polyethylene/methylene iodide. The formation of aggregates is discussed.
Synthesis of AB and BAB poly(styrene‐b‐4‐vinylpyridine) and solution properties of their quaternized compounds
Authors: Ishizu Koji , Kashi Yasuo , Fukutomi Takashi , Kakurai Toshio 
Published: April 2003

AbstractWell‐definded AB and BAB poly(styrene(S)‐b‐4‐vinylpyridine(4VP))s were prepared by anionic polymerization in tetrahydrofuran (THF) at −78°C. Quaternization of these block copolymers was carried out with methyl iodide and P4VP blocks were completely quaternized. The emulsifying effect, viscosity behavior, and binding of methyl orange to the quaternized compounds are discussed in detail from a view‐point of sequential arrangements.
Hochdruck‐hochtemperatur‐reaktionen in einem strömungsreaktor, 12. Thermische dimerisierung von acrylsäauremethylester, methylvinylketon und acrylnitril
Authors: Metzger Jürgen O. , Köll Peter 
Published: April 2003

AbstractThermal dimerization of methyl acrylate to dimethyl 2‐methyleneglutarate was performed in a high pressure‐high temperature flow apparatus at temperatures up to 420°C and pressures up to 200 bar. The head to head dimer dimethyl 2‐methyl‐3‐methylenesuccinate was observed, too. Methyl vinyl ketone and acrylonitrile are able to dimerize analogously.
Role of hydrophobic interaction in the enantioselective solvolyses of amino acid p‐nitrophenyl esters by optically active imidazole‐containing polymers
Authors: Cho Iwhan , Shin Jae‐Sup 
Published: April 2003

AbstractSolvolytic reactions of N‐benzyloxycarbonyl‐D‐phenylalanine p‐nitrophenyl ester and N‐benzyloxycarbonyl‐L‐phenylalanine p‐nitrophenyl ester by optically active imidazole‐containing polymers were performed at different temperatures and in aq. ethanol of different water contents. The catalyst polymers employed were homopolymers of N‐methacryloyl‐L‐histidine (1a) and N‐methacryloyl‐L‐histidine methyl ester (1b), as well as copolymers of 1a with dodecyl methacrylate (DMA) and 1b with DMA. In 30 vol. ‐% aqueous ethanol at pH 7,02 the homopolymers did not show any enantioselective catalysis. However, the copolymers did exhibit enantioselective catalysis, viz., kcat(L)/kcat(D) = 1,25 for poly (1b‐co‐DMA) containing 5,7 mol‐% of DMA. As the reaction temperature was lowered, the reaction rate increased and the enantioselectivity was enhanced (kcat(L)/kcat(D) = 1,67 for poly (1b‐co‐DMA) at 10°C). When the ethanol content was decreased, enhanced reaction rates and enantioselectivity (kcat(L)/kcat(D) = 1,65 for poly (1 b‐co‐DMA) in 20 vol.‐% aqueous ethanol) were observed. From these results it is concluded that hydrophobic interaction plays an important role in the enantioselective catalysis of optically active imidazole‐containing polymers.
OH Radical‐induced chemical reactions of polynucleotide complexes
Authors: Denk Otmar , Washino Komei , Schnabel Wolfram 
Published: April 2003

AbstractPoly(A + U), the 1:1 complex of poly(riboadenylic acid), poly A, and poly(ribouridylic acid), poly U, at pH 8 and self‐complexed poly A at pH 4 exist as double helices in dilute aqueous solution. These complexes exhibit a similar behavior as native calf thymus DNA upon irradiation with 16 MeV electron pulses. Thus time resolved Rayleight light scattering measurements showed that crosslinking and double strand breakage can be clearly separated, the former proceeding faster than the latter. The extent to which the two processes occur depends on the ionic strength of the solution. At ionic strenghts exceeding 10 −1 mol/l crosslinking is the dominant process indicating that hcrit, the critical length between two single strand breaks for the accomplishment of double strand breaks, is strongly reduced. The investigation of complexes of poly A and Mg2+ ions revealed that the destruction of salt bridges is the rate determining process for the decrease of the light scattering intensity due to mainchain scission. This implies that life‐times of salt bridges can be determined.
Synthesis and investigation of the properties of cardo‐copolyimides with different microstructure
Authors: Korshak V. V. , Vinogradova S. V. , Vygodskii Ya. S. , Nagiev Z. M. , Urman Ya. G. , Alekseeva S. G. , Slonium I. Ya. 
Published: April 2003

AbstractCopolyimides, their microstructure being determined by the method of synthesis, were prepared by copolycondensation of 4,4′‐oxydiphthalic anhydride (1a), 4,4′‐carbonyldipthalic anhydride (1b), or 1,8:4,5‐naphthalenetetracarboxylic anhydride with a mixture of two diamines, hexa‐, octa‐, or dodecamethylene diamine (5a, 6a, 7a) and cardo‐diamines 9,9‐bis(4′‐aminophenyl)fluorene (3a) and 3,3‐bis(4′‐aminophenyl)phthalide (4) or two aromatic diamines, 4,4′‐oxydianiline (9) and 2,2‐bis(4‐aminophenyl)hexafluoropropane (8), at various mole ratios of the comonomers. Blockcopolyimides with five‐membered imide cycles were formed by catalytic imidization of the intermediate polymers prepared by addition of the solid dianhydride to a solution of the mixture of the two diamines, whereas the thermal cyclization of such polymers and the one‐step high‐temperature synthesis led to random copolyimides. The thermal and mechanical properties of the copolyimides with various microstructure and their solubility in organic solvents were compared.
Preparation of poly[(3S)‐1,2,3,4‐tetrahydroisoquinoline‐2,3‐diylmethylene] and its use as chiral catalyst in the addition of arenethiols to 2‐cyclohexen‐1‐one
Authors: Yamashita Tetsushi , Kagigaki Eizo , Takahashi Nozomu , Nakamura Nobuo 
Published: April 2003

AbstractPoly[(3S)‐1,2,3,4‐tetrahydroisoquinoline‐2,3‐diylmethylene] (4) and (3S)‐3‐(1,2,3,4‐tetrahydroisoquinolin‐2‐ylmethyl)‐2‐methyl‐1,2,3,4‐tetrahydroisoquinoline (7) were prepared using (3S)‐1,2,3,4‐tetrahydro‐3‐isoquinolinecarboxylic acid (1) as starting material. The optically active amines 4 and 7 were used as asymmetric catalysts for the addition of thiophenol (8a), 4‐tert‐butylthiophenol (8b), or 4‐chlorothiophenol (8c) to 2‐cyclohexen‐1‐one (9). 4 yielded 3‐phenylthiocyclohexanone (10a) with the highest optical yield of 24% at −25°C, showing a marked polymer effect with respect to enantiomeric excess.
Functional metal‐porphyrazine derivatives and their polymers, 7. Synthesis and properties of metal‐2,9,16,23‐tetracarboxyphthalocyanine covalently bound to poly(2‐ or 4‐vinylpyridine‐co‐styrene)
Authors: Higaki Seigo , Hanabusa Kenji , Shirai Hirofusa , Hojo Nobumasa 
Published: April 2003

AbstractMetal‐2,9,16,23‐tetracarboxyphthalocyanines(Mt‐taPc's) [Mt = Fe(III), Co(II), Ni(II), Cu(II)] covalently bound to poly(2‐ or 4‐vinylpyridine‐co‐styrene) were synthesized by Friedel‐Crafts reaction of the styrene units of the copolymers with Mt‐taPc tetraacid chloride. The copolymers contain about 0,3 to 14,6 mol‐% Mt‐Pc rings and are soluble in methanol, ethanol, and N,N‐dimethylformamide. The coordination spheres around the Mt‐Pc rings were characterized by electronic as well as ESR spectra and by viscosity measurements. The dimerization of Mt‐taPc in the copolymers is sterically hindered by the polymer chain. The copolymer supported Fe(III)‐ or Co(II)‐taPc's are of the five coordinate high spin type in DMF solution. One coordination site at axial position of the Mt‐Pc ring may be occupied by an N atom of a pyridine group. The electronic structures of the metal atoms may be useful in catalytic reactions.
Kinetic determination of stereoselectivity in the anionic polymerization of α‐ethyl‐α‐phenyl‐β‐propiolactone
Authors: Biela Tadeusz , Penczek Stanislaw , Slomkowski Stanislaw , Vogl Otto 
Published: April 2003

AbstractThe kinetics of the anionic polymerization of optically active α‐ethyl‐α‐phenyl‐β‐propiolactone (optical purity 16,8%) initiated with bis(triphenylphosphine)iminium acetate was investigated and the rate constants for the homo‐(kph) and crosspropagation (kpc) (considering R and S enantiomers as comonomers) were determined. The knowledge of the values of kph and kpc, equal to 1,53·10−4 and 9,0·10−51· mol−1·s−1, respectively (25°C, CH2Cl2 solvent), allowed us to calculate the distribution of homosequences in the polymer prepared from racemic monomer. The concentration of homosequences was slightly higher than calculated for the process with random enchainment of enantiomers. Thus, the content of homodyads, homotriads, and homotetrads equals 63, 40, and 25%, whereas for the random process it was 50, 25, and 13%, respectively. This difference is, however, too small to create homoblocks which could be responsible for the observed crystallinity of these polymers.
Polymer conformation and NMR chemical shifts, 8. Monomer‐ and stereo‐sequence dependences of 13C NMR spectrum of poly(methyl acrylate‐co‐styrene)
Authors: Sato Kota , Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

AbstractThe 13C NMR spectra of poly(methyl acrylate‐co‐styrene) are interpreted by a theoretical procedure which consists of conformational analysis of the random copolymer chain and shielding calculation. The conformational probabilities of the diad sequences constituting poly(methyl acrylate‐co‐styrene) are calculated by a matrix method which is conducted by the statistical mechanics of polymer chains. All the elements of the matrices are determined by the force field method. As significant shielding factors for 13C nuclei, paramagnetic, diamagnetic, and anisotropic terms are taken into account. The calculation is used to assign the observed split peaks for the carbonyl carbon and methoxyl carbon in the copolymer. A good agreement between calculation and observation of the peak splittings due to the distribution of the monomer sequence as well as that of the stereo sequence was obtained by considering the feasibility of rotational isomerization at the side chain ester group in two successive MA units.
Solution properties of ultrahigh molecular weight polymers, 1. Methyl methacrylate‐styrene 50:50 random copolymers
Authors: Simionescu Cristofor I. , Simionescu Bogdan C. , Ioan Silvia 
Published: April 2003

AbstractThe paper is concerned with light scattering studies on solutions of ultrahigh molecular weight random copolymers of methyl methacrylate and styrene (50:50 mol/mol). The dependence of the radius of gyration and of the second virial coefficient on the weight‐average molecular weight of the copolymers was established. The value of the steric factor of the copolymer compared to those of the corresponding homopolymers confirms the random character of the copolymer chain. The interpenetration function Ψ(Z), calculated on the basis of different theoretical approximations, is discussed for the expansion factor αs3 > 7.
Degradation and depolymerization of poly(propylene carbonate) by diethylzinc
Authors: Kuran Witold , Górecki Piotr 
Published: April 2003

AbstractPoly(propylene carbonate) (PPC) was treated with diethylzinc in 1,4‐dioxane solution at 30°C, Zn(C2H5)2 being used in excess or defficiency with regard to carbonate units. PPC was found to undergo degradation and depolymerization reactions, which were followed via the polymer intrinsic viscosity and the propylene carbonate yield. A model reaction between diethyl carbonate and diethylzinc was carried out too. From the results, a mechanistic view for both pathways, degradation and depolymerization, is proposed.
Synthesis, polymerization, and copolymerization of lactams containing vinyl groups
Authors: Samyn Celest , Smets Georges 
Published: April 2003

AbstractTwo new lactam monomers containing vinyl groups were synthesized, namely 1‐benzyl‐3‐methylene‐5‐methyl‐2‐pyrrolidone (1) and 5‐oxo‐2‐pyrrolidinylmethyl methacrylate (2). Their homopolymerization and copolymerizations with methyl methacrylate (MMA), styrene, or methylacrylate were studied. The copolymerization parameters r1 and r2 were also evaluated. Poly(1) is a stable polymer which decomposes at ≈ 300°C under nitrogen and at 250°C in air. Its pyrrolidone ring is resistant towards acids and bases.
Characterization of polyesters resulting from 1,2‐propanediol and phthalic anhydride and their model compounds by 1H and 13C NMR spectroscopy
Authors: Judas Didier , Fradet Alain , Maréchal Ernest 
Published: April 2003

AbstractIn order to study the side reactions taking place during the synthesis of polyesters, the structures of several model compounds were determined. Diesters or polyesters from 1,2‐propanediol and phthalic acid were used as models. Their synthesis and characterization are described. The interpretation of their 1H and 13C NMR spectra is reported; resonances due to the various end groups could be fully assigned.
Chemical modification of polydienes, 1. Grafting of chlorohydrinated polybutadiene and nitrile rubbers with poly(tetrahydrofuran)
Authors: Cameron G. Gordon , Duncan Alexander W. S. 
Published: April 2003

Abstractcis‐1,4‐Polybutadiene and nitrile rubbers were functionalised with chlorohydrin groups up to levels of 10 mol‐% in a two‐stage process. In the first stage epoxide groups were introduced by reaction of the rubber with m‐chloroperbenzoic acid and in the second stage the epoxide ring was opened by reaction with hydrochloric acid to yield chlorohydrin groups. Both steps in the process are clean and virtually quantitative. Graft chains of poly(tetrahydrofuran) were introduced by coupling the hydroxyl groups with living poly(tetrahydrofuran) cations. The lengths of the graft chains were determined by the time between initiation (by the action of silver perchlorate on ethyl bromide in tetrahydrofuran solution) and the coupling step with the functionalised rubber.
Kinetik der radikalischen polymerisation und copolymerisation von N‐vinyl‐N‐methylacetamid
Authors: Fischer Johannes Paul , Rösinger Sigurd 
Published: April 2003

AbstractIn order to get information on the kinetics of free radical polymerization of N‐vinyl‐N‐methylacetamide (VIMA) polymerizations of the purified monomer were performed in dilatometers using the temperature range from 25 to 70°C, monomer concentrations of 10 to 100% in methanol, and initiation either by γY‐irradiation or by radical initiators. Molecular weight meassurements of the polymer were calibrated by light scattering determinations of Mw according to the following equation at 30 °C in methanol: [η]/(ml/g) = 5,02 · 10−3 · Mw0,7946. Normal kinetics of free radical polymerization were found to be valid and Arrhenius parameters were calculated for the ratio kp2/kt of the propagation rate constant kp and the termination rate constant kt as well as for the monomer transfer constant CM and for the efficiency of initiation f. For copolymerizations of N‐vinyl‐N‐methylacetamide with different comonomers the mean Q‐e‐values were calculated as follows: QVIMA ≅ 0,06; eVIMA ≅ − 1,8.