bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymérisation anionique de l'acroléine, 2. Influence de la nature du contre‐ion et de la température sur la cinétique de la réaction
Authors: Gulino Danièle , Golé Jean , Pascault Jean Pierre 
Published: April 2003

AbstractIn tetrahydrofuran, with Na+ and Li+ as counter‐ions, the kinetic order of the anionic polymerization of acrolein is unity for monomer and for initiator. These results indicate that the living ends are not associated at the studied concentrations of initiator. The polymerization rate depends on the nature of the counter‐ion. Transfer reactions to monomer do not affect the polymerization rate but greatly change the molecular weights Mn of polyacroleins. The experimental M are much lower than the theoretical M. The propagation constants kpr and the transfer constant hm are determined using these experimental values of M. From these results, we can conclude that with Li+ as counter ion, transfer reactions are much more numerous than with Na+. Furthermore, the polymerization rate increases with temperature. The activation energies of the propagation (Ea,pr) and transfer reactions (Ea,t) can be determined separately. When the temperature increases the propagation reaction is promoted in comparison to the transfer reaction to monomer, and simultaneously transfer reactions to polymer take place. This last phenomenon restricts the upper value of the polymerization temperature.
The polymerisation of styrene by trifluoroacetic acid
Authors: Obrecht Werner , Plesch Peter H. 
Published: April 2003

AbstractThe polymerisation of styrene (St) by trifluoroacetic acid (TFA) in methylene chloride was studied by high‐vacuum dilatometry at 40°C with specially purified reagents. Drying increases rates, changes the internal orders, and changes the MWD in that with undried TFA the MWD is bimodal, with the driest TFA it is unimodal. For undried TFA, the whole reaction cannot be represented by a single, simple equation; with dried TFA, —d[St]/dt = kv [St]2[TFA]3. When polymerisation is complete the solutions contain free TFA and polystyryl trifluoroacetates. 1‐Phenylethyl trifluoroacetate itself is not an initiator, it yields oligostyrene if treated with TFA, and if present in a reaction mix of St + TFA it retards the polymerisation, is consumed, and causes a distinctly bimodal MWD. The relation of our results to those of Sawamoto et al is discussed.
Thermodynamic studies of DNA‐dye complexes, 2. DNA‐methylene blue and DNA‐thionine systems
Authors: Tanaka Shigeyuki , Baba Yoshihiro , Kagemoto Akihiro 
Published: April 2003

AbstractThe interaction between DNA and various dyes (methylene blue (1), and thionine (2)) was studied by means of the heat of mixing. From the results, the thermodynamic quantities were estimated for the DNA‐dye system by an intercalation process. The free energy change of the system DNA‐2 was found to be nearly equal to that of the system DNA‐1, but the absolute value of the heat of interaction of the system DNA‐2, which has amino groups, is higher than that of the system DNA‐1. These facts are comparable with those previously found for the systems DNA‐proflavine and DNA‐acridine orange. However, the locations of 1 and 2 intercalated into DNA may be different from those of acridine orange and proflavine because the enthalpy changes for the systems DNA‐1 and DNA‐2 are higher than those of the systems DNA‐acridine orange and DNA‐proflavine, respectively. These facts showed that the location of the intercalated dye depends on the presence of amino groups in 3‐position of the dye.
Der einfluß von D‐alanin auf das konformative verhalten von kollagenmodellpeptiden
Authors: Roth Werner , Heidemann Eckhart 
Published: April 2003

AbstractWith the help of equilibrium measurements on covalently bridged collagen model peptides of the sequence D,L‐Ala‐Gly‐L‐Pro it was shown that the thermostability of the tertiary structure of these peptides is strongly influenced by the D‐Ala contents. The conformational behaviour of the peptides was studied by measurements of circular dichroism in methanol at various temperatures.
Préparation et identification de copolyamides alternés du type ω‐aminoacide
Authors: Tran Ngoc‐Mai , Carrière François , Sekiguchi Hikaru 
Published: April 2003

AbstractThe hydrochlorides of p‐nitrophenyl 6‐aminocaproate (4a), p‐nitrophenyl 12‐aminododecanoate (4b), and p‐nitrophenyl 12‐(6‐aminocaproylamino)dodecanoate (6) were prepared and polycondensed in 1,2,4‐trichlorobenzene in the presence of tributylamine under different conditions. The polycondensation of 6 at 128°C gave the alternating copolyamide (PA 6, 12). The polymers were identified by DTA and by 13C NMR.
Etude 13C NMR d'alcanes ramifiés, 1. n‐alkyl‐12 tricosanes. Application aux polyéthylènes basses densités
Authors: Freche Patrick , Grenier‐Loustalot Marie‐Florence , Metras Franck , Gascoin Alain 
Published: April 2003

AbstractA series (8 compounds) of mono‐branched alkanes (12‐n‐alkyl‐tricosanes) as models for polyethylene was prepared. The results obtained from 13C NMR show in particular the dependence of the chemical shifts (Δδ ≈ 0,05 p.p.m.) on T in the temperature range 37°C ≤ T ≤ 100°C but that the branches remain identifiable in this range of temperature. By mixing different tricosanes we simulated various branched polyethylenes. The chemical shifts observed at 100°C with some corrections complete the incremental system of Grant and Paul as modified by Randall for the effect of temperature.
A functional styrene monomer having a hexylamino group. Synthesis and polymerization
Authors: Li Xue‐fen , Maeda Mizuo , Tsuruta Teiji 
Published: April 2003

AbstractSynthesis and polymerization of N‐hexyl‐N‐[2‐(4‐vinylphenyl)ethyl]amine (5) are reported. To elucidate the reaction mechanism for the monomer synthesis, kinetic studies are carried out on the lithium catalyzed amination reaction of styrene (3) and of 1,4‐divinylbenzene (1) with hexylamine (2). The reaction rate, v, was found to be expressed as v = k [3] [2] [CH3(CH2)5NHLi], where k is the rate constant. Methods for selective synthesis of 5 are considered on the basis of results of the kinetic studies. Polymerization and copolymerization behavior of 5 shows that 5 has characteristics similar to 3 in radical polymerization.
Versuche zur copolymerisation deuterierter monomerer copolymerisation styrol/deuterostyrol und methylmethacrylat/deuteromethylmethacrylat
Authors: Wittmer Paul , Böck Harald , Naarmann Herbert , Schmitt Burghard J. 
Published: April 2003

AbstractIn free radical copolymerization of styrene with completely deuterated styrene and methyl methacrylate with completely deuterated methyl methacrylate no isotope effects upon the copolymerization parameters were observed. However, isotope effects were found in the rates of copolymerization Rp. In the case of styrene Rp decreases monotonically from a higher level for the deuterated monomer to a lower level for the [1H]‐monomer. For the case of methyl methacrylate Rp again is higher for the deuterated monomer than for the [1H]‐monomer, but there is a minimum in the curve Rp vs. monomer mixture composition.
Dégradation photochimique de polymères cétoniques, 2. Etude sur modèles de la photodégradation de copolymères cétoniques à groupes carbonyles en chaǐne
Authors: Bonnans‐Plaisance Chantal , Casals Pierre‐François , Levesque Guy 
Published: April 2003

AbstractThree linear phenyl ketones, 4‐methyl‐1,7‐diphenyl‐3‐heptanone (6a), 2,8‐diphenyl‐4‐nonanone (6b), and 5‐methyl‐2,8‐diphenyl‐4‐nonanone (6c), and four cyclic ketones, 1‐phenethyl‐2‐(3‐phenylpropionyl)cyclopentane (4a), 1‐(3‐phenylbutyryl)‐2‐(2‐phenylpropyl)cyclopentane (4b) and their cyclohexane homologues (5a and 5b), were synthesized as models of styrene copolymers bearing carbonyl groups in the chain, and their photochemical degradation was studied in various solvants at wavelengths > 280 nm. This study has shown that both Norrish mechanisms, i.e., the type I scission in α‐position of the carbonyl and the type II photoelimination, which occur with the models, take place in a similar fashion with the copolymers. The relative part and the efficiency of each photodegradation depend on the solvent, the linear or cyclic character of the chain, as well as on the substitution. Photodegradation studies of the models have also allowed us to explain the photochemical behaviour of the particular copolymers and especially the faster fragmentation of linear chains, and to elucidate the mechanisms involved in the degradation of these polymers.
Darstellung von Oligo[(hydroxy‐1,3‐phenylen)methylen]en mit Hydroxynitrophenylen‐ und Alkylhydroxyphenyleneinheiten
Authors: Böhmer Volker , Lotz Werner , Pachta Jiri , Tütüncü Suat 
Published: April 2003

AbstractPossibilities to synthesize substituted oligo[(hydroxy‐1,3‐phenylene)methylene]s containing hydroxynitrophenylene and alkylhydroxyphenylene units are discussed. The only successful way to introduce the hydroxynitrophenylene unit consists in the condensation of chloromethylated nitrophenols with an excess of alkylphenols. The resulting compounds can be prolonged stepwise at the alkylhydroxyphenylene end group by alternating hydroxymethylation and further condensation with alkylphenols. Thus, including the hydroxymethylated compounds, 11 dinuclear, 17 trinuclear, and 5 tetranuclear compounds were obtained for the first time. Some of them were characterized by their acetyl derivatives.
Molecular association in aqueous solutions of high molecular weight poly(N‐vinyl‐2‐pyrrolidone)
Authors: Güven Olgun , Eltan Ender 
Published: April 2003

AbstractA viscosimetric method was used to investigate the molecular association in aqueous solutions of poly(N‐vinyl‐2‐pyrrolidone), (PVP), of molecular weight 700 000. Limiting viscosity numbers [η] and Huggins constants kH of the polymer solutions were observed to decrease upon addition of denaturing agents such as thiourea and guanidinium sulfate. Guanidinium sulfate was found to be even more effective in its denaturing action as compared to urea and thiourea. The decrease in [η] and kH values increased with increasing concentrations of the denaturing agents. This behaviour was explained on the basis of the rupture of bridges formed by water molecules among different PVP chains, hydrogen bonding being responsible for these intermolecular associations. While no change in the [η] values was observed for PVP in 2 M thiourea solutions upon increasing the temperature from 25°C to 35 and 45°C, for the same increase in temperature the [η] values of aqueous PVP solutions showed substantial decreases. This is also attributed to the breaking of hydrogen bonds existing between PVP molecules.
Photochromic polymers: Photoinduced conformational changes and effect of polymeric matrix on the isomerization of photochromes
Authors: Matějka L. , Dušek K. 
Published: April 2003

AbstractTwo types of photochromic polymers were prepared and studied: a copolymer of maleic anhydride with styrene containing aromatic azo groups P(MAH‐STY‐AAB) and a copolymer of methacrylic acid with methacryloylamidoazobenzene, P(MA‐MAAB). The effects of the polymeric carrier, the solution viscosity, and the position of the photochrome in the chain on photochrome isomerization were determined. Investigation of the effect of radiation on the conformation of the polymer chain revealed that the copolymer P(MAH‐STY‐AAB) exhibited a pronounced photoviscosity effect in 1,4‐dioxane solution, i.e., a reversible decrease by 24–30% in the reduced viscosity of the solution after irradiation. In the case of the copolymer P(MA‐MAAB), radiation causes a destabilization of the compact conformation.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 8. Synthèse de polybutadiènes: Etude de différents paramètres influençant la polymolécularité
Authors: Brosse Jean‐Claude , Bonnier Maryvonne , Legeay Gilbert 
Published: April 2003

AbstractIt was shown that radical polymerization of butadiene in 1‐butanol and 2‐butanol, initiated by hydrogen peroxide cleaved into two hydroxyl radicals by heat, leads to three types of polymers according to their respective polydispersity. It was found that the formation of these products — oligomers, polymers, and high polymers — can be influenced by modifying the experimental conditions. Thus, it is possible to obtain selectively oligomers free of polymers and polymers free of low molecular weight oligomers.
The morphology of semicrystalline segmented poly(ether ester) thermoplastic elastomers
Authors: Zhu Li‐Lan , Wegner Gerhard 
Published: April 2003

AbstractThe supermolecular structure of melt‐crystallized segmented copoly(ether ester)s based on poly(tetramethylene terephthalate) and poly(tetramethylene oxide) is investigated by polarizing microscopy and electron microscopic techniques. Spherulites are formed on isothermal crystallization at supercoolings ΔTu < 30°C. The spherulites recrystallize to form dendritic structures on further annealing at higher temperatures. The spherulites and dendrites are builtup from lamellae which exhibit little variation concerning the thickness of their crystalline core. The internal phase boundaries in these systems are made visible with a newly developed staining method. A network of interlocked individual lamellae is formed on rapid quenching of the melt films. Row crystallization (shish‐kebabs) is observed, if the melt is sheared during the crystallization. It is concluded from these observations that the chemical structure of the segmented copolymers bears little relevance for the supermolecular structure of these materials except for the thickness of the crystalline core of the lamellae which seems to be related to the molecular length of the hard segment sequences occurring with the highest concentration in the sample.
The crystallization behavior and the mechanical properties of segmented poly(ether ester) thermoplastic elastomers
Authors: Zhu Li‐Lan , Wegner Gerhard , Bandara Upali 
Published: April 2003

AbstractThe isothermal melt crystallization of three segmented copoly(ether ester)s based on PBT as the hard and PTMO as the soft segments differing in their hard segment content was investigated. The kinetics of crystallization was studied using polarizing microscopy and DSC. Two regimes of crystallization were observed. Spherulitic structures of low crystallinity are formed via predominantly athermal nucleation in regime I at supercoolings ΔTu < 30°C. Ill‐defined aggregations of lamellae grow at ΔTu > 30°C. The crystallization follows an apparent Avrami‐equation; the Avrami‐constants cannot be explained in terms of a simple model. The structure of the samples was investigated by SAXS and compared to the structure of samples crystallized by rapid quenching and subsequent annealing. Much higher long spacings are obtained on isothermal crystallization. The long spacing increases with decreasing ΔTu. It increases at constant ΔTu with decreasing average hard segment length contrary to the samples crystallized by subsequent annealing of the quenched melt. In this case polymers differing in composition do not differ with regard to the long spacing obtained at constant ΔTu. The modulus in the Hookean‐range as derived from stress‐strain curves at T > Tg does not reflect the details of the morphology or chain architecture but it is found to depend logarithmically on the volume fraction of crystallinity in the sample. Data of pure PBT are described by the same relationship.
Chain folding in α‐methyl‐ω‐alkoxypoly(oxyethylene)
Authors: Al Kafaji Jawad K. H. , Booth Colin 
Published: April 2003

AbstractSamples of α‐methyl‐ω‐alkoxypoly(oxyethylene), with an oxyethylene block of number average molar mass M̄n = 2300 g · mol−1 and with n‐alkoxy end groups ranging from methoxy to octadecyloxy, have been prepared and characterised. Lamella spacings have been investigated by small‐angle X‐ray scattering and by Raman scattering. Melting behaviour has been investigated by differential scanning calorimetry. Crystallisation is affected by the length of the n‐alkoxy end group (nc carbon atoms) and the crystallisation temperature (Tc). Samples with small nc form extended chain lamella crystals. The formation of folded chain lamella crystals is favoured by large nc and small Tc. Folded chain lamella crystals are unstable with respect to chain unfolding above a given temperature (Tx). Annealing at temperatures lower than Tx increases the stability of the lamella crystals. All samples have been obtained in extended chain lamella crystalline form by annealing at 43,5°C. The melting points of these annealed crystals show a shallow minimum at nc ≈ 5. This effect can be explained if alkyl and oxyethylene segments are well mixed in non‐crystalline lamella‐surface layers.
Ring‐opening copolymerization of cycloalkenes investigated by 13C NMR spectroscopy
Authors: Ivin Kenneth J. , Lapienis Grzegorz , Rooney John J. 
Published: April 2003

AbstractRing‐opening copolymerization studies were made on the systems cyclopentene (CPE)/ norbornene (NBE), cyclooctene (COE)/ norbornene, 1,5‐cyclooctadiene (COD)/norbornene, cyclopentene/cycloheptene (CHP), and cyclopentene/ 1,5‐cyclooctadiene using olefin metathesis catalysts.13C NMR spectra of the copolymers permit direct determination of the reactivity ratios in most cases, as well as the proportion of cis double bonds in each type of dyad. For CPE/NBE, COD/NBE and CPE/CHP the reactivity ratios vary widely with the catalyst system and sometimes with the catalyst/cocatalyst ratio and method of mixing. There is no correlation between composition of the copolymer and cis content. The copolymers show either a random or blocky distribution of monomeric units. The results are discussed in terms of a mechanism in which the metal carbenes formed in the propagation processes are initially coordinated to the polymer chain and can add further monomeric units stereospecifically while in this form. These propagation processes compete with a relaxation process leading to a metal carbene in which the polymer chain is no longer coordinated at the vacant site and which adds monomer in a less stereospecific fashion.
Synthesis of poly(oxovinyl sulfide)s by vinylogous nucleophilic substitution polymerizations of bis(3‐chloroacryloyl) derivatives of benzene with 4, 4′‐oxydibenzenethiol
Authors: Ueda Mitsuru , Sakai Naoyuki , Komatsu Masanobu , Imai Yoshio 
Published: April 2003

AbstractPoly(oxovinyl sulfide)s 3 were prepared by vinylogous nucleophilic substitution polymerization of bis(3‐chloroacryloyl) derivatives of benzenes (1a and 1b) with 4,4′‐oxydibenzenethiol (2). The synthesis involves solution polycondensation and two‐phase polycondensation with phase transfer catalysts. Polymers having inherent viscosities in the range of 0,2–0,7 dl·g−1 were obtained quantitatively by both methods. They are soluble in concentrated sulfuric acid, dichloroacetic acid, and m‐cresol, and practically insoluble in polar aprotic solvents and common organic solvents. Thermogravimetric studies in both air and nitrogen atmospheres indicated that the decomposition temperatures for 10% weight loss of the polymers were about 400°C.
The effect of preaveraging of hydrodynamic interaction on the intrinsic viscosity and intrinsic flow birefringence of gaussian polymer chains
Authors: Fortelný Ivan 
Published: April 2003

AbstractThe intrinsic viscosities of a Gaussian chain with and without hydrodynamic interaction preaveraging and with the identification of the centre of gravity of the Gaussian coil with the chain center were calculated using Tsuda's theory. It appears that the value of the Flory constant is more affected by approximations used in the derivation of Tsuda's theory than by preaveraging of hydrodynamic interaction. Svetlov's theory was used in the calculation of the ratio of intrinsic flow birefringence to intrinsic viscosity. For unpreaveraged hydrodynamic interaction this quantity is lower by some 15–20% than for a free‐draining coil.
Polymere azomethine mit azobenzol‐einheiten
Authors: Koßmehl Gerhard , Wallis Jan 
Published: April 2003

AbstractCondensation of 4‐aminoazobenzene (1), respectively 4, 4′‐diaminoazobenzene (2), with mono‐ and dialdehydes of the benzene and thiophene series yields intensive coloured polymeric azomethines (polymeric Schiff bases) with azobenzene units, respectively model compounds. The structure of these polymers and model compounds were confirmed by elemental analyses, IR‐and electronic spectra and — in the case of the model compounds — by MS and 1H NMR spectra. The electrical conductivities of the polymers and model compounds and the thermo oxidative degradations of the polymers were studied.
Anionic polymerization of isopropenyl methyl ketone, 1. IR‐spectroscopic study of the nature of alkali derivatives of acetone and of the active centres in the anionic polymerization of isopropenyl methyl ketone
Authors: Tsvetanov Christo B. , Petrova Dobrinka T. , Panayotov Ivan M. 
Published: April 2003

AbstractThe nature of alkali derivatives of acetone (ADA) and active centres (AC) in the anionic polymerization of isopropenyl methyl ket one (IMK) was studied by means of IR spectroscopy. Solutions of ADA and of the AC of IMK in tetrahydrofuran show a characteristic absorption at 1560 – 1610 cm−1, due to the stretching vibrations of the delocalized isopropenyl oxide group. Two kinds of equimolar complexes are formed between acetone and ADA, depending on the nature of the counterion (Li+, Na+, K+, Cs+). The same interaction is observed between the AC of oligo (IMK) and the carbonyl group of the last but one monomeric unit (penultimate effect).
Aliphatic‐aromatic polyamide‐imides from diisocyanates, 1. 1H and 13C NMR study of polymer structure
Authors: Nieto José L. , de la Campa José G. , de Abajo Javier 
Published: April 2003

AbstractThe reaction of a diisocyanate and an asymmetric aliphatic‐aromatic diacid containing a preformed imide group was studied in order to obtain polyamide‐imides. It is shown in this paper that combined 1H and 13C NMR spectrometry will permit the quantitative evaluation of the proportions of head‐tail, head‐head, tail‐tail additions, provided the content of urea in the polymer is low. In order to obtain unequivocal assignments and to thoroughly characterize the NMR spectra of the polymer, several model compounds resembling the polymer backbone were synthesized. A model polymer was synthesized with the same purpose, and its 1H and 13C NMR spectra fully assigned. Unexpected chemical functions in the polymer, like urea and carboxylic acid, can also be easily detected and quantified by NMR.
Approche de la microstructure d'une résine copolymère de monomères vinyliques et diéniques
Authors: Guillot Jean 
Published: April 2003

AbstractThe present work deals with a general framework of the kinetics and the microstructure (sequence distribution of monomeric units, network parameters…) of resins constituted of vinyl and diene monomers based on the theory of Markov chain propagation. As a matter of example, calculations were applied to the copolymerization of styrene with p‐ and m‐divinylbenzene.