bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyoxirannes et polythiirannes comportant un centre chiral dans la chaîne latérale, 3. Polymérisation de (2RS,3S)‐ et (2R,3S)‐épithio‐1,2 méthyl‐3 pentanes
Authors: Goguelin Michel , Sepulchre Maurice 
Published: April 2003

AbstractDifferent mixtures of (2R,3S)‐ and (2S,3S)‐1,2‐epithio‐3‐methylpentanes (1) were polymerized using anionic (sodium), stereoselective (ZnEt2/H2O, cadmium tartrate) and stereoelective (ZnEt2/R(−)‐3,3‐dimethyl‐1,2‐butanediol (R(−)DMBD)) initiator systems. In all cases a preferential consumption of the (2R,3S)‐diastereoisomer was observed. The reactivity ratios of the two diastereoisomers (2R,3S) and (2S,3S) in the copolymerization, initiated with sodium, were determined: r1 = 1,40 ± 0,08 and r2 = 0,54 ± 0,05. A low but significant diastereoisomeric enrichment was observed in stereoselective polymerization. It results from different consumption rates for the two diastereoisomers on enantiomorphic sites of the initiator. The election obtained with a stereoelective system is much higher. It is, however, not very different from that observed with isopropylthiiranne, which does not bear an additional chiral center in the alkyl substituant.
Study of exchange reactions in polycarbonate/polyarylcarboxylate mixtures with model compounds
Authors: Devaux Jacques , Devaux Pierre , Godard Pierre 
Published: April 2003

AbstractThe exchange reaction between a polycarbonate and a polyarylcarboxylate, both based on bisphenol A, was simulated by studying the reaction between the polycarbonate and diphenyl terephthalate or isophthalate used as model compounds of a polyarylcarboxylate. The kinetic results indicate the presence of a transesterification reaction occurring without any catalyst. Some results from reactions in the melt between both polymers also point to an exchange reaction.
A non‐linear approach to the Kuhn‐Mark‐Houwink‐Sakurada equation
Authors: Jadraque Daniel , Pereña José M. 
Published: April 2003

AbstractIntrinsic viscosities and molecular weights were evaluated to obtain Kuhn‐Mark‐Houwink‐Sakurada (KMHS) relationships for some selected polymers by means of a non‐linear regression analysis. The proposed method yields unbiased values of the KMHS parametersaandK, improves the fitting and shows that KMHS relationship must be considered as a simple correlation with two interdependent parameters,aandK.
Polymer conformation and viscometric behaviour, 3. Synthesis, characterization and conformational studies in poly(mono‐n‐octyl itaconate)
Authors: Gargallo Ligia , Radić Deodato , León Arturo 
Published: April 2003

AbstractThe unperturbed dimensions and the steric factor σ of poly(mono‐n‐octyl itaconate) (poly‐(1‐carboxy‐1‐octyloxycarbonylmethylethylene)) were determined from the intrinsic viscosities in two solvents, using the semiempirical equation of Stockmayer and Fixman. Evidence for the existence of specific effects was found. The irregular behaviour observed, can be interpreted in terms of conformational changes and conformational transitions of the polymeric chain, induced both by solvent and temperature. The effect of the structure of the monomeric unit on the flexibility of the macromolecule is discussed.
Synthèse, étude physicochimique et diélectrique de poly(acétoxyméthylstyrène)s
Authors: Amadei Henri , Monthéard Jean‐Pierre , Boiteux‐Steffan Gisèle , Lucas Jean‐Michel , Seytre Gérard 
Published: April 2003

AbstractVarious poly(acetoxymethylstyrene)s were synthesized. Examination of the physicochemical properties of the polymers as a function of the type of substitution revealed the influence of the position of polar groups on the thermal (glass transition temperature) and electrical (dielectric constant and loss factor) characteristics of the polymers. Because of their good solubility and their electrical properties over a wide range of temperatures and frequencies the polymers proved to be interesting materials for dielectric films.
Studies on functional diene oligomers with an amino end group, 2. Reaction mechanism of the isoprene oligomerization
Authors: Nagasaki Yukio , Yoshino Norio , Tsuruta Teiji 
Published: April 2003

AbstractLithium diisopropylamide, in the presence of diisopropylamine, initiates the polymerization of isoprene to form oligomers having one diisopropylamino end group. These oligomers 1 a, formed in the early stages of the reaction, are considered to carry out the chain termination (or metalation) reaction. Results of mechanistic studies of the chain termination (or metalation) reaction in isoprene oligomerization in the presence of various types of allylamine homologues, as low molecular weight model compounds for 1 a are presented. The presence of a cis‐methyl group with respect to the amino methylene group was found to be essential for the low molecular weight model compounds to exhibit large reactivity in the chain transfer reaction. Oligomers with amino end groups neither have to possess a cis‐methyl group nor an allylamine structure to be active. A number of results showed that the driving force for the metalation reaction of oligomers with amino end groups is different in nature from that of the lowmolecular‐weight allylamine homologues. A possible mechanism for the metalation reaction of these oligomers is discussed in terms of a hydrophobic interaction with the growing chain.
Action du sec‐butyllithium sur le bis(isopropényl‐4 phényl)‐1,1 phényl‐1 tridécane en milieu solvant non‐polaire
Authors: Beinert Gérard , Zilliox Jean‐Georges , Herz Jean 
Published: April 2003

AbstractThe reaction of sec‐butyllithium with 1,1‐bis(4‐isopropenylphenyl)‐1‐phenyltridecane (3) yields carbanionic species which are soluble in a non‐polar solvent. The long hydrocarbon “tail” of the molecule and the tendency of the organolithium compounds to associate may be the reason for the high solubility, possibly due to micel‐formation. In the absence of any sidereaction, the addition reaction should lead to a difunctional organolithium compound. However, UV spectrometric measurements and characterization by size exclusion chromatography of the species obtained after protonation of the anionic sites, show that oligomerization accompanies the di‐addition reaction with formation of principally dimeric and a small fraction of trimeric molecules. This implies the existence of di‐, tri‐ and tetracarbanionic species in the “living” reaction media.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 14. Synthèse de copolymères butadiène‐vinylferrocène
Authors: Brosse Jean‐Claude , Folliot Véronique , Legeay Gilbert , Raynal Serge , Doriath Gérard 
Published: April 2003

AbstractHydrogen peroxide, thermally cleaved into hydroxyl radicals, was used as initiator of butadiene‐vinylferrocene copolymerization. The influence of different parameters like temperature, pressure, proportion of hydrogen peroxyde and addition of a solvent with weak transfer capability was studied.
Immobilization of α‐chymotrypsin on poly(methyl methacrylate‐co‐acrylic acid) core‐shell latex
Authors: Bahadur Anita , Bahadur Pratap , Riess Gérard 
Published: April 2003

AbstractCore‐shell latex of poly(methyl methacrylate‐co‐acrylic acid) with surface containing functional carboxylic acids, was prepared by seed polymerization and characterized. α‐Chymotrypsin was immobilized on the surface of these latex particles by chemical bonding in aqueous medium, using a water soluble carbodiimide as coupling agent. The latex particles size before and after the attachment of the enzyme was determined using photon correlation spectroscopy. The activities of free and immobilized enzyme were studied as a function of temperature, reusability and pH. The activity for the immobilized enzyme was highest at a pH slightly higher than the optimum pH of free enzyme, which could be explained due to the polyanionic matrix as well as due to the variation in the size of latex at higher pH, which provided more mobility to the enzyme, and thus a higher activity.
Kinetik der copolymerisation von styrol und p‐jodstyrol
Authors: Braun Dietrich , Chaudhari Dinkar , Czerwinski Wojciech 
Published: April 2003

AbstractA study of the copolymerization behaviour of styrene (M1) and p‐iodostyrene (M2) was carried out at 50°C in bulk with azoisobutyronitrile as initiator. The monomer reactivity ratios calculated according to Kelen‐Tüdős are r1 = 0,629 ± 0,109; r2 = 0,965 ± 0,153. Kinetic measurements were performed dilatometrically. Contraction constants for both homopolymerizations were determined to be K11 = 0,172 and K22 = 0,130. The applicability of the Wittmer method for contraction constant calculations was verified. The contraction constants for the alternating copolymerization step was estimated to be K12 = 0,132. Contraction constants calculated with this value are very adequate to the experimental data. Kinetic homopolymerization constants δ = k11//kp were found by molecular weight measurements as δ1 = 60,99 and δ2 = 11,40 (mol · s/1)1/2, respectively. Initiator efficiency factors are f = 0,60 (for M1) and 0,25 (for M2). The Polymerization rate can be described as a function of the composition of monomer mixture by the classical Melville equation with cross termination constant Φ = 0,338.
Cinétiques de télomérisation, 6. Détermination des degrés de polymérisation a partir de la répartition moléculaire
Authors: Boutevin Bernard , Maliszewicz Marc , Piétrasanta Yves 
Published: April 2003

AbstractIt is shown that the kinetic laws established for polymerization reactions can be applied for telomerization reactions provided the number‐average degrees of polymerization DPn are greater than ten. For DPn > 10 it is necessary to calculate the molecular distributions. Values of DPn obtained with the method of Mayo and the molecular distribution method are compared and an experimental application is given by the radical‐initiated telomerization of glycidyl methacrylate (2,3‐epoxypropyl methacrylate) with bromotrichloromethane.
Ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane
Authors: Endo Takeshi , Yako Naoto , Azuma Kazumi , Nate Kazuo 
Published: April 2003

AbstractPhotochemical and radical polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane (1) were carried out leading to the same polyester 2. By radical copolymerization of 1 with methyl methacrylate using various mole ratios of the monomers, the corresponding copolymers with various contents of ester groups in the backbone were obtained.
Polyene formation and crosslinking during the thermal degradation of poly(vinyl chloride)
Authors: Leijenaar Steven R. , van den Heuvel C. Jurriaan M. , Huysmans Willem G. B. 
Published: April 2003

AbstractPolyvinyl chloride (PVC) was degraded at processing temperatures in an inert atmosphere. The samples were analyzed by means of a size exclusion chromatograph equipped with a differential refractometer and a photo‐diode array UV‐visible detector. This enabled us to record online the presence of polyenes at different positions along the molecular weight distribution of the degraded polymer. Polyenes proved to be concentrated on the low molecular weight side of the distribution and, more specifically, on the high molecular weight side, which had been broadened upon degradation. The results indicate that low molecular weight PVC degrades relatively fast and that PVC molecules containing polyenes crosslink easily.
Study of photopolymers, 25. Photochemical reaction of dilute solutions of polymers containing pendant cinnamic ester moieties and photosensitizing groups
Authors: Nishikubo Tadatomi , Uchida Jiro , Takahashi Eiji , Iizawa Takashi 
Published: April 2003

AbstractRates of photochemical reactions of polymers containing pendant cinnamic ester moieties and photosensitizing 4‐nitrophenoxy or 4‐nitro‐1‐naphthyloxy groups were determined in dilute benzene and tetrahydrofuran solutions. The rate of photodimerization of the polymers obeys first order kinetics in diluted solution and is affected by the type and content of pendant photosensitizing groups and by the structure of the polymer skeleton. By comparison of the rate of photodimerization of three homopolymers and six copolymers, it could be concluded that the polymers consisting of flexible segments have a higher rate of photodimerization than those made of rigid segments.
Polyarylenealkenylenes and polyheteroarylenealkenylenes, 17. Syntheses of alkoxylated poly(2‐nitro‐1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s and poly(2,5‐dimethoxy‐1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s, and study of their electrical conductivity
Authors: Koßmehl Gerhard , Samandari Massoud 
Published: April 2003

AbstractThe influence of different substituents (nitro and methoxy groups) on the physical properties — fusibility and solubility — and the electrical conductivity of alkoxylated poly(1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s (9, 10, 12 and 13) and of the corresponding model compounds (15, 16, 18 and 19), were studied. The conductivity at room temperature, σ298K, was found to be generally increased for polymers with nitro substituents by 2–3 orders of magnitude and for dimethoxy substituted polymers up to 4 orders of magnitude, as compared with the unsubstituted polyvinylenes. Iodine doped polyvinylenes show as an average d. c. electrical conductivities 2 orders of magnitude higher than those of the original polymers.
Benzil/triethylamine combination as photoinitiator for methyl methacrylate polymerization
Authors: Sengupta Pranab Kumar , Modak Sadhan Kumar 
Published: April 2003

AbstractPhotopolymerization of methyl methacrylate (MMA) in bulk and in solution was studied using the combination benzil (BZL)/triethylamine (TEA) as photoinitiator. The initiation was found to occur through photoreduction of the ketone in presence of an amine via exciplex formation. A kinetic study of the polymerization showed that both carbonyl groups of benzil are involved in exciplex interaction, resulting in diradical formation. An analysis of the initiator dependent termination process revealed that primary radical termination is predominant in the particular system compared to the degradative initiator transfer. A kinetic scheme was designed to account for the various wastage reactions occurring in the polymerization system.
Biocide polymere, 12. Synthese und hydrolyseverhalten von copolymeren aus methacryl‐ und acrylsäure sowie 1‐methacryloyl‐ und 1‐acryloyl‐3‐methylpyrazol
Authors: Hartmann Manfred , Bauer Hans‐Jürgen , Fritzsche Antje , Wermann Kurt 
Published: April 2003

AbstractThe radical copolymerization of 1‐acryloyl‐ and 1‐methacryloyl‐3‐methylpyrazole (1a and 1b) with acrylic acid or methacrylic acid in solution was studied. Copolymers containing carboxyl as well as 3‐methyl‐1‐pyrazolylcarbonyl groups as side chains were prepared via the reaction of 3(5)‐methylpyrazole with activated poly(acrylic acid)s of various molecular weights. The hydrolysis data suggest that the release rates of the biocide 3(5)‐methylpyrazole from the investigated copolymers vary significantly depending on the content of carboxyl groups and their change during the hydrolysis.
Synthesis and characterization of a rubber incorporated polyamideimide
Authors: Sen Debasish , Bhakta Ramesh C. , Maiti Mrinal M. , Maiti Sukumar 
Published: April 2003

AbstractA new flexible and crosslinkable copolyimide was prepared by low temperature polycondensation between bis [4‐(4‐chloroformylphthalimido)phenyl] ether (1), bis(4‐aminophenyl) ether and liquid α,ω‐bis[2‐(4‐piperazinyl)ethylaminocarbonyl]poly(butadiene‐co‐acrylonitrile) in DMAc solution. The polymer is soluble in DMF, DMAc, NMP, m‐cresol, DMSO and concentrated sulfuric acid. On heating with or without dicumyl peroxide the polymer was crosslinked.
Photostability of trityl salts with different anions in vacuo
Authors: Toncheva Veska D. , Velichkova Rumyana S. 
Published: April 2003

AbstractThe visible light‐induced photolysis of trityl salts with different anions was investigated in vacuo. The following order of photostability, determined from the rates of decoloration of the dichloroethane solutions of these salts, was found: (C6H5)3C+PF6− > (C6H5)3C+AsF6− > (C6H5)3C+BF4− > (C6H5)3C+SbCl6− ≥ (C6H5)3C+FeCl4−. By model reactions it was proved that the 9‐phenylfluorenyl cation, formed on irradiation as a main product in the early stage of the photolysis, takes part in the regeneration of (C6H5)3C+. The changes in electronic spectra, as well as the composition of the reaction mixtures after photolysis and the model reactions, confirm some stages of the earlier proposed scheme.
Influence of electron‐donor‐acceptor complex formation on the melt viscosity of some poly(dimethylsiloxane)s
Authors: Zentel Rudolf , Wu Jishan , Cantow Hans‐Joachim 
Published: April 2003

AbstractA series of poly(dimethylsiloxane)s was synthesized containing either electron donor or electron acceptor groups, statistically arranged along the polymer chain or only at the chain ends (telechelic polymers). Blending of the donor and acceptor modified statistical copolymers led to a strong increase of the melt viscosity as a consequence of complex formation. In contrast to this, complex formation had no significant influence on the viscosity in blends from telechelic polymers. This different behaviour seems to be caused by the different molecular architecture favouring crosslinking by complex formation for the statistical copolymers and a linear chain extension for the telechelic polymers.
1H NMR study of the chitin dissolution mechanism
Authors: Vincendon Marc 
Published: April 2003

AbstractThe 1H NMR spectra of N‐acetyl‐D‐glucosamine (1) and methyl‐B‐D‐chitobioside (2), the monomer and dimer of chitin, respectively, were determined in the aprotic solvents, N,N‐dimethylacetamide (DMA) and DMA containing lithium chloride. It could be shown that dissolution of 1 and 2 in DMA/LiCl proceeds via interaction of one LiCl molecule with each labile proton (OH or NH). Observation of the temperature‐dependent hydroxyl proton chemical shift revealed the particular behaviour of the OH3 hydroxyl of 2. This dependence was assigned to the existence of an intramolecular hydrogen bond between OH3 and O5′ (the heterocyclic atom) of the other D‐glucopyranosyl unit. Similar results were found for chitin in DMA/LiCl solution.
Light scattering and viscosity studies of poly(2‐vinylpyridine 1‐oxide) in some organic solvents at 25°C
Authors: Sakamoto Noriyuki , Tanaka Hitoshi , Yamaguchi Katsuya , Yoshida Masafumi , Arichi Shizuo 
Published: April 2003

AbstractLight scattering in 2‐propanol and viscosity measurements in six good solvents were carried out at 25°C for fourteen fractions of poly(2‐vinylpyridine 1‐oxide) (P2VPO) with molar mass of (1,3–34,4) · 104 g · mol−1, which were synthesized by oxidizing poly(2‐vinylpyridine) with H2O2. The numerical values of the Mark‐Houwink‐Sakurada constants K′ and a and of the parameters K and B from the plots of Kamide‐Kawai, Kurata‐Stockmayer and Inagaki‐Ptitsyn as well as Stockmayer‐Fixman, were determined as well. The averaged characteristic ratio C∞ and steric factor σ for this polymer are 8,58 and 2,07, evaluated from K in each solvent except benzyl alcohol with the last plot. The value in benzyl alcohol is rather large and clearly shows the solvent dependence in K. Comparing this average value with those of similar polymers, it is concluded that the P2VPO chain acquires a compact coil structure. The solvent power was found to increase in the following sequence: chloroform < 2‐propanol < 1‐propanol < methanol ≤ 1‐butanol < benzyl alcohol, as judged from the B values.
Model compounds of poly(methyl methacrylate). Conformational structure of the dimethyl esters of 2,2,4‐trimethyl‐ and of 2‐methoxymethyl‐2,4‐dimethylglutaric acid. 13C NMR, 1H NMR and vibrational spectroscopic study
Authors: Doskočilová Danica , Schneider Bohdan , Štokr Jan , Ševčík Stanislav , Přádný Martin , Lochmann Lubomír 
Published: April 2003

AbstractThe conformational structure of the dimethyl esters of 2,2,4‐trimethylglutaric acid, and of the erythro‐ and threo‐isomers of 2‐methoxymethyl‐2,2,4‐dimethylglutaric acids was studied by NMR and vibrational spectroscopic methods. Conformational structure generated by rotation about skeletal bonds was determined by analysis of vicinal coupling in 1H and 13C NMR spectra. The results are discussed in relation to the conformational structure of PMMA.
Deformation mechanisms of isotactic poly(1‐butene)
Authors: Yang Yong‐Chin , Geil Phillip H. 
Published: April 2003

AbstractThe deformation of thin films of poly(1‐butene) (PB) occurs by micronecking. In both fresh (From II crystal structure) and aged (Form I) films finite blocks are drawn off the edge of the microneck, the detailed mechanisms depending on the orientation of the original crystalline ribbons comprising the spherulites with respect to the draw direction. Deformation of fresh thick and thin PB films is accompanied by a transformation to a Form I which melts ca. 5°C lower than that obtained by aging alone (124 vs. 129°C); in thick films the molecular axes in the Form I crystals are oriented in a cone at about 30° to the draw direction until deformation is nearly complete, after which they align in the draw direction. Tensile properties depend on the crystal form, fresh samples having a considerably lower modulus and higher elongation to failure.
Polymerization of lactams, 75. Behaviour of the polymerization mixture prepared by the non‐activated polymerization of 2‐pyrrolidone above the limit polymerization temperature, 2
Authors: Fries Tomáš , Nováková Olga , Roda Jan , Králíček Jaroslav 
Published: April 2003

AbstractThe behaviour of the polymerization mixture of 2‐pyrrolidone (PD), i.e. of the mixture of polymer, monomer, and their potassium salts, obtained by non‐activated polymerization, was studied in the temperature region 170–180°C. Poly(2‐pyrrolidone) (PPD) was found to completely disappear at this temperature from the mixture, leading again to PPD under optimal polymerization conditions. The cycle, degradation‐polymerization, can be repeated without a substantial loss of the polymerization activity. A model polymerization mixture comprising PD, Potassium salt of PD and PPD, prepared beforehand, behaves similarly as the proper polymerization mixture.
Bifunctional anionic initiators: A critical study and overview
Authors: Bandermann Friedhelm , Speikamp Hans‐Dieter , Weigel Ludwig 
Published: April 2003

AbstractThe suitability of several dilithio compounds as initiators for the anionic polymerization of dienes was tested in view of the following criteria: quantitative reaction of diolefins withsec‐butyllithium within reasonable periods of time, precipitation of dilithio compounds in a heptane/toluene mixture, sufficient solubility of the dilithio compounds in toluene, rapid initiation of polymerization and small dispersion index of the polymer, low cost of the preparation of the diolefins and the dilithio initiators. The results show that with respect to the diolefins investigated the bifunctional initiator derived from 1,4‐bis(4‐(1‐phenylvinyl)phenyl)‐butane is most suited for the preparation of diene blocks in ABA‐triblock copolymers.