bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fixation d'amines pharmacologiquement actives sur les polyphosphonates, 1. Etude sur molécule modèle
Authors: Brosse Jean‐Claude , Fontaine Laurent , Derouet Daniel , Chairatanathavorn Supachat 
Published: April 2003

AbstractChemical modification of poly(alkylene phosphonate)s via the Atherton‐Todd reaction was investigated with diethyl phosphonate (3) as a model molecule. The study of the reaction showed that in the presence of a sufficiently basic tertiary amine, the reaction with carbon tetrachloride leads to an intermediate chlorophosphate. The variation in phosphorylation yields with the pKa of the primary amine highlights the role played by the basicity of the reaction medium.
Fixation of pharmacologically active amines on polyphosphonates, 2. Application to benzocaïne and phenethylamine
Authors: Brosse Jean‐Claude , Derouet Daniel , Fontaine Laurent , Chairatanathavorn Supachat 
Published: April 2003

AbstractThe Atherton‐Todd reaction was used for the preparation of a new class of hydrophilic drug carriers with an organic polyphosphate main chain. Chemical modification of poly(propy1ene phosphonate) (3) and poly(3,6,9‐trioxaundecamethylene phosphonate) (4) with benzocaine (ethyl 4‐aminobenzoate) (1) and phenethylamine (2) led in one step to polyphosphoramidates 7a, b and 8a, b bearing pharmacologically active amines in the side chain with modification yields of 60 to 75%.
Synthèse de molécules fonctionnelles deutérées sélectivement
Authors: Pichon Hervé , Laguerre Albert , Durand Dominique , Rabadeux Jean‐Claude 
Published: April 2003

AbstractFor the study of the orientational order in strained polyurethane elastomers, selectively deuterated molecular probes were synthetized. End‐deuterated poly(propylene oxide)s were obtained using deuterated methanol as initiator. Coupling of theses prepolymers with hexamethylene diisocyanate led to products deuterated at both ends. To obtain derivatives deuterated in the centre of the chain, various deuterated hexamethylene diisocyanates were synthetized and coupled with poly(propylene oxide) containing one hydroxyl end group.
Ring‐opening polymerization of norbornene initiated by tungsten alkylidene complexes. Activation by AlCl3
Authors: Leymet Isabelle , Siove Alain , Parlier Andrée , Rudler Henri , Fontanille Michel 
Published: April 2003

AbstractAddition of aluminium compounds to the stable metal‐carbene complex tetracarbonyl[4–5‐η‐1‐methoxy‐4‐pentenylidene]tungsten (1), showing an intramolecular coordination of double bond to the transition metal, leads to highly active catalytic systems in the polymerization of norbornene. It is shown that, in optimal conditions, AlCl3 is more efficient than AlEt3 for cyclo‐olefin polymerization. From spectroscopic studies (UV‐visible, 1H and 13C NMR) of the activated system 1‐AlCl3, a mechanism of activation by AlCl3 is proposed involving a modification of the nature of carbene 1 by the Lewis acid.
Synthesis of telechelic polysiloxanes, 3. Synthesis of aliphatic diamines and diimides
Authors: Boutevin Bernard , Guida‐Pietrasanta Francine , Robin Jean‐Jacques 
Published: April 2003

AbstractTelechelic oligo(dimethylsiloxane)s 6 and 7 with chloro‐, cyano‐ or aminopropyl end groups were synthesized from the corresponding chlorodimethylsilanes 2a–c and α‐hydro‐ω‐hydroxyoligo(dimethylsiloxane)s 4 and 5. The ω‐cyano derivatives 6b and 7b were reduced to the 4‐aminobutyl derivatives 8a and 8b with LiAlH4. 8a was subsequently transformed into 1,7‐bis(4‐maleimidobutyl)‐1,1,3,3,5,5,7,7‐octamethyltetrasiloxane (10) by reaction with maleic anhydride, via the intermediate dimaleamic acid 9. The products were characterized by IR, 1H, 29Si, and 13C NMR spectroscopy.
New monofunctional derivatives of poly(ethylene glycol)s via monotrityl intermediates
Authors: Pozzo Alma Dal , Vigo Angelo , Donzelli Giovanni 
Published: April 2003

AbstractFour new monofunctional poly(ethylene glycol)s (PEGs) and one new monofunctional poly(propylene glycol) (PPG) were prepared and characterized. Monosubstitution of the dihydroxyfunctional PEGs was achieved through an intermediate PEG protected at one end‐function with a trityl group. These polymers are proposed as pro‐moieties for the synthesis of pro‐drugs.
Fourier transform infra‐red spectroscopy of atactic polystyrene in the glass transition region
Authors: Magonov Sergei N. , Shen Deyuan , Qian Renyuan 
Published: April 2003

AbstractFourier transform infra‐red (IR) studies on samples of atactic polystyrene with different thermal history, i.e. quenched from the melt (QM), quenched from the rubbery state (QR), slowly cooled (SC), and sub‐glass‐transition (sub‐Tg) annealed (AN), were carried out in the absorption region from 500 to 600 cm−1 with gradually increasing temperatures through the glass transition region at 100°C. The heights of the positive peak (532 cm−1) and the negative peak (566 cm−1) appearing in the temperature difference spectra, T‐60°C, are considered to be a measure of the amount of frequency shifts for the 540 cm−1 and 557 cm−1 bands in the conformationally sensitive spectral range of atactic polystyrene. These bands show a continuously increasing low‐frequency shift with increasing temperature, except for sample QM, the 557 cm−1 band of which shows an inappreciable frequency shift in the range 60 < T/°C < 100. The different temperature behaviour of these shifts for samples QM, QR, SC and AN is due to changes in their intermolecular interactions. Sub‐Tg annealing of the sample QM is shown to shift the frozen high‐temperature state of the quenched sample to the temperature‐defined equilibrium. For all samples of different thermal history the difference in their IR spectra vanish at temperatures above Tg.
Stereospecific polymerization of higher α‐olefins with the solvay type catalyst TiCl3/Cp2Ti(CH3)2
Authors: Soga Kazuo , Lee Dong Hee , Shiono Takeshi , Kashiwa Norio 
Published: April 2003

AbstractPolymerizations of higher α‐olefins (C10–C20) were carried out at 40°C in heptane, using the following three catalysts which differ in the isospecificity for propene polymerization: Solvay type TiCl3/Cp2TiMe2((A) highly isospecific), Solvay type TiCl3/AlEt3((B) isospecific) and TiCl3.3Py/MgCl2/AlEt3((C) aspecific). The isospecificity of the catalysts was found to decrease in the following order: (A) ≫ (B) ≫ (C), which agrees well with the results obtained in propene polymerization. The crystallinity of these polymers is discussed in brief.
Group transfer polymerization of methyl acrylate in tetrahydrofuran with tetrabutylammonium fluoride trihydrate and tetrabutylammonium cyanide as catalysts
Authors: Schubert Walter , Bandermann Friedhelm 
Published: April 2003

AbstractGroup transfer polymerization (GTP) of methyl acrylate (MA) with 1‐methoxy‐1‐propenyloxytrimethylsilane (MTP) as initiator and tetrabutylammonium fluoride trihydrate and tetrabutylammonium cyanide as catalysts in tetrahydrofuran was investigated. Tetrabutylammonium fluoride trihydrate turned out to be absolutely unsuited as GTP catalyst, since its crystal water destroys the initiator and the active centres. Furthermore, in side reactions between the initiator and the catalyst, the concentrations of both are diminished. Tetrabutylammonium cyanide is a powerful catalyst of GTP of MA, leading to complete conversion of the monomer, but initiates an anionic polymerization of MA too, which, however, is of minor importance in the main part of the reaction. Reaction rates may easily be controlled by the catalyst concentration. Number‐average molecular weights are dependent on initiator concentration. They are lower as well as higher than those expected for a really living system, pointing to a rather complicated overall reaction.
Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalène carbonyloxyméthyles
Authors: Fabre Jean‐Marc , Giral Louis , Montginoul Claude , Mungroo Aumduth , Sagnes René , Schué François 
Published: April 2003

AbstractIn order to solve the problem of polymer swelling, which limits the resolution for negative resists, new resists were developed which show no swelling. The undesirable swelling can be suppressed by converting nonpolar crosslinked polymers into polar ones, which are soluble after irradiation. This aim was attained by mixing a polystyrene bearing tetrathiafulvalenyl (TTF) groups with 1,2‐dibromo‐1,1,2,2‐tetrachloroethane. For our study, we applied resists including poly(4‐chloromethylstyrene)s containing tetrathiafulvalenecarbonyloxymethyl groups (1 and 2). Poly(4‐chloromethylstyrene)s (4) or poly[styrene‐co‐(4‐chloromethyl)styrene]s (5) with a variety of controlled molecular weights and molecular weight distributions were prepared by radical chain polymerization. The reaction of cesium tetrathiafulvalenecarboxylate (3) with 4 or 5 was carried out and the resultant substituted polymers 1 and 2 were characterized.
Crystallization of the γ‐form of isotactic poly(propylene)
Authors: Marigo Antonio , Marega Carla , Zannetti Roberto , Paganetto Guglielmo , Canossa Enrica , Coletta Flaviano , Gottardi Francesca 
Published: April 2003

AbstractThe pure γ‐form of isotactic poly(propylene) can be obtained by melt‐crystallization starting from a fraction of a random ethylene‐propene copolymer (ethylene content 4 wt.‐%) soluble in p‐xylene at 28°C. Some structural models previously reported are tested by comparing calculated wide‐angle X‐ray diffraction patterns with the experimental ones. A method for the quantitative determination of the γ‐form crystallinity by X‐ray line profiles is proposed. The original copolymer and its fractions are characterized by differential scanning calorimetry and 13C NMR techniques.
Molecular weight and temperature dependence of the cold‐drawing behavior of ethylene‐tetrafluoroethylene copolymer
Authors: Gundert Friedhelm , Smith Paul 
Published: April 2003

AbstractThe temperature dependence of the cold‐drawing behavior of melt‐crystallized films of ethylene‐tetrafluoroethylene copolymer (E/TFE) was investigated by tensile deformation from medium to ultrahigh molecular weight (UHMW), with the draw ratio at break λ as the crucial quantity. From meltrheological measurements at T = 300°C, the weight‐average of molecular weight (M̄w) is calculated to be in the range of 100 to 17000 kg/mol (zero‐shear viscocity η0 = 104–1010 Pa. s). The results of tensile experiments are discussed in comparison to polyethylene (PE) within the scope of a model of entanglement kinetics for tensile deformation presented by Termonia and Smith recently. In contrast to PE, the values of the maximum draw ratio at break λmax are low and increase with M̄w(λmax = 4,5–6,5; for PE λmax = 30–10 for M̄w = 125–1500 kg/mol). Also different to PE is the lack of correlation of Tmax (T at λmax) with melting point Tm in the case of UHMW‐E/TFE (Tmax ≈ 180°C < Tm = 280°C; for PE Tmax ≡ Tm). These findings are explained by the transition from orthorhombic crystal phase to hexagonal mesophase in E/TFE, which was reported to occur at Tα ≈ 100°C by Tanigami et al. On the molecular scale the onset of this order‐disorder transition is described as a drastic increase of chain slippage in the crystallites during deformation and cannot be compensated by entanglements in amorphous regions, which act as transient crosslinks.
Liquid‐crystalline elastomers with cholesteric and chiral smectic C* phases
Authors: Zentel Rudolf , Reckert Gertrude , Bualek Sauvarop , Kapitza Heinrich 
Published: April 2003

AbstractA series of 9 new chiral and crosslinkable liquid‐crystalline copolymers were synthesized and transformed into liquid‐crystalline elastomers by crosslinking using a hydrosilylation reaction. Both the soluble copolymers and the elastomers show cholesteric, smectic A and chiral smectic C* phases, which are not affected by the crosslinking procedure. First measurements show that the helical superstructure of elastomers with cholesteric and chiral smectic C* phases can be reversibly untwisted by stretching. Thereby a cholesteric structure can be transformed into a nematic structure and a chiral smectic C* structure into a smectic C one.
Photooxidation of poly(diacetylene) single crystals
Authors: Poole Nicholas J. , Day Richard J. , Smith Brian J. E. , Batchelder David N. , Bloor David 
Published: April 2003

AbstractSingle crystals of poly(diacetylene) 1a with p‐tosyloxymethyl side groups undergo photooxidation when irradiated with visible light of wavelength 520 nm or less. The presence of molecular oxygen adsorbed on the surface of the crystals and its subsequent photochemical reaction with the polymer were monitored using resonance Raman spectroscopy and the formation of holographic gratings. Reaction products which were identified include hydroperoxy groups, p‐toluenesulfonic acid and poly(diacetylene) oligomers. The photooxidation reaction appears to proceed by the “ene” mechanism; the polymer reacts with singlet oxygen produced by energy transfer with the photoexcited poly(diacetylene) backbone.
Vergleichende berechnungen an stereoisomeren modellverbindungen des polyacrylnitrils und polyvinylchlorids
Authors: Röttger Jutta , Pittel Bernd , Michels Gisbert , Korte Siegfried , Süling Carlhans 
Published: April 2003

AbstractZusammenfassend läßt sich sagen, daß sich die Modelle für die Diastereomere des PAN in ihren Stabilitäten und Reaktivitäten noch weniger unterscheiden als die entsprechenden PVC‐Modelle. Daraus läßt sich der Schluß ziehen, daß eine Beeinflussung der Stereoregularität des PAN allein durch Erniedrigung der Polymerisationstemperatur nicht zu erreichen ist.
New polymer syntheses, 40. Syntheses of substituted polybenzodioxazoles from aryloxyterephthalic acids
Authors: Kricheldorf Hans R. , Engelhardt Jürgen 
Published: April 2003

AbstractSubstituted polybenzodioxazoles were synthesized from silylated 2,5‐diaminohydroquinone (5) and various aryloxyterephthaloyl dichlorides (6). Either a “one‐pot procedure” or a two step procedure was used. In the latter case the silylated monomer was condensed with a terephthaloyl dichloride at −15°C in 1‐methyl‐2‐pyrrolidone and the isolated polymer 8 was cyclized at 350°C in an inert reaction medium. The optimum reaction conditions were determined for a low‐molecular‐weight model and the reaction products were characterized. The substituted polybenzodioxazoles are soluble in dichloromethane/trifluoroacetic acid mixtures, yet, they do not form a mobile melt up to 600°C.
Synthesis and properties of model oligomers of poly(naphthylenevinylene)s
Authors: Stenger‐Smith J. D. , Lenz Robert W. , Enkelmann Volker , Wegner Gerhard 
Published: April 2003

AbstractModel compounds for poly(1,4‐naphthylenevinylene) (1) and poly(2,6‐naphthylenevinylene) (2) were synthesized by the Wittig synthesis and studied by UV/VIS spectroscopy and cyclic voltammetry. The values of 2,0 eV for the band gap edge and 0,7 V vs. the saturated calomel electrode for the oxidation potential, which were estimated by an extrapolation of the band gap edge and oxidation potential of model dimer and trimer of 1, are in excellent agreement with the literature values for the polymer. A value of 2,3 eV for the band gap edge of 2 was found by extrapolating the band gap edge of a model dimer and trimer, but the oxidation potential of polymer 2 could not be estimated, because the model trimer was not sufficiently soluble in solvents used. The stoichiometries of the radical cation salts of the model compounds, which were prepared by electrocrystallization, were evaluated from elemental analysis. A single crystal, radical cation salt was obtained for the model dimer of polymer 2.
Thermotropic polyesters, 5. Liquid‐crystalline segmented polyesters containing non‐rigid mesogenic units with variable geometry
Authors: Bilibin Alexander Yu. , Tenkovtsev Andrey V. , Piraner Olga N. 
Published: April 2003

AbstractThermotropic liquid‐crystalline polyesters, containing the 3,3′‐biphenylylene unit as part of a conformationally mobile mesogenic group, were synthesized. Preliminary investigation of polymers as to their ability for manifesting liquid‐crystalline properties was carried out by polarizing microscopy and DSC.
Hydrogen peroxide formation by using redox resins containing nitroxyl radical groups
Authors: Dulog Lothar , Valet Andreas 
Published: April 2003

AbstractCrosslinked copolymers from styrene, divinylbenzene and maleic anhydride were reacted with 4‐amio‐2,2,6,6‐tetramethylpiperidine to form imides, then oxidized to form polynitroxyles, and reduced to polyhydroxylamines. These resins form hydrogen peroxide when oxygen is blown through an aqueous slurry. The highest yield was found at 80°C.
Thermal degradation of polybutadiene, 1. Reactions at temperatures lower than 250°C
Authors: Chiantore Oscar , di Cortemiglia Maria Paola Luda , Guaita Marino , Rendina Gabriele 
Published: April 2003

AbstractThe thermal degradation of polybutadiene (PB) samples having different initial contents of cis‐1,4‐, trans‐1,4‐ and 1,2‐units were investigated at temperatures lower than 250°C, where cyclization, cross‐linking and cis‐trans isomerization occur without depolymerization. Changes of the cis‐trans content and decrease of double bonds in the polymers were measured at different temperatures. The rates of double bond loss were found to follow the order: trans‐1,4 > 1,2 > cis‐1,4, whereas the opposite occurred for the isomerization process. The reactions responsible for the structural changes of PB at temperatures lower than 250°C are reviewed and discussed.
Transition temperatures of thermotropic liquid‐crystalline copolyesters
Authors: Zhang Hongzhi , Zhang Zhibin 
Published: April 2003

AbstractA series of thermotropic copolyesters with glass transition temperatures (Tg) ranging from 70°C up to 180°C based on terephthaloyl chloride (1), chlorohydroquinone (2a) or hydroquinone (2b), 4,4′‐isopropylidenediphenol (bisphenol‐A) (3) and ethylene glycol (4) was synthesized. The mesomorphic properties of the copolyesters were examined by visual observation of stiropalescence and birefringence under a polarizing microscope. The Tg values of the copolyesters depend mainly on the composition of non‐mesogenic or spacer segments and are practically independent of the content of mesogenic units. The structure of mesogenic units also shows a relatively small influence on the Tg behaviour.
13C NMR spectroscopical sequence analysis of poly(ethylene terephthalate‐co‐oxybenzoate)s
Authors: Jancke Harald , Böhme Frank , Graßhoff Karin , Rätzsch Manfred , Rafler Gerald 
Published: April 2003

AbstractThe sequence distribution of liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s was determined by 13C NMR spectroscopical investigations of samples with different compositions. All possible oxybenzoate‐ and terephthalate‐centered triads could be identified and assigned. The analysis of NMR substituent effects confirms the assignment. The comparison of the calculated statistical with the experimentally determined triad distribution shows a tendency for the formation of oxybenzoate blocks in the polymer chain.
In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 4. Influence of a lateral methyl substituent on monomer and oriented polymer network properties of a mesogenic diacrylate
Authors: Broer Dirk J. , Hikmet Rifat A. M. , Challa Ger 
Published: April 2003

AbstractMesomorphism and the molecular orientation of 1,4‐phenylene bis{4‐(6‐(acryloyloxy)hexyloxy)benzoate} (1) and its derivative with a methyl‐substituent in the central phenylene group (2) are studied. The methyl group affects the transition temperatures and the thermodynamic parameters, but not the order parameter of the monomers. The photoinitiated polymerization of the diacrylate monomers in their uniaxially oriented state leads to highly oriented and densely crosslinked polymer networks. The order parameter of these networks depends on the polymerization temperature, but becomes nearly temperature‐independent after polymerization. The presence of the methyl group leads to a significant lower degree of order in the polymeric state. In addition, data are presented on the monomeric viscosity of 2 and on the tensile moduli, glass transitions and refractive indices of the oriented polymer networks. In order to extend the mesomorphous temperature range, mixtures of 1 and 2 are also investigated.
Living cationic polymerization of isobutyl vinyl ether, 1. Initiation by hydrogen iodide/tetraalkylammonium salts
Authors: Nuyken Oskar , Kröner Hubertus 
Published: April 2003

AbstractAddition of hydrogen iodide to isobutyl vinyl ether (1) yields 1‐(1‐iodoethoxy)‐2‐methylpropane (2). The cationic polymerization of 1 initiated by 2/tetraalkylammonium salts (R4N+A−) shows the characterstics of a living polymerization. Different tetraalkylammonium salts were investigated. The coinitiator R4N+A− has no effect on the molar mass and the molar mass distribution of the resulting polymers. However, the rate of polymerization depends heavily on the nature and concentration of the coinitiator. The effect of the coinitiator is discussed on the basis of a special salt effect.
Studies in ring‐opening polymerisation, 10. Pyridine‐initiated polymerisation of cyclic anhydrocarboxylates of α‐mercapto acids
Authors: Ali M. Mobarak , Ammas Allan J. , Tighe Brain J. 
Published: April 2003

AbstractThe kinetics of the pyridine‐initiated polymerisation of simple 1,3‐oxathiolan‐2,5‐diones (3a–c) in nitrobenzene was studied at various temperatures. Results show that, although the substituents in 4‐position have a marked effect on rate of polymerisation, the polymerisation of the three monomers studied is linked by a common mechanism. Thus, the pyridine, nucleophile attacks the carbonyl in 5‐position and forms a charge transfer complex which decomposes to form a highly reactive α‐thiolactone intermediate 8 together with carbon dioxide and pyridine. Chain addition continues by the direct attack on the thiolactone by the terminal‐SH group of traces of parent acid. The reaction of each of the three monomers with pyridine was found to show first order kinetic dependence on both monomer and pyridine, although the initiator (i.e. pyridine) is not consumed. The resultant polymers (molecular weight typically around 20000) are highly crystalline and relatively insoluble in common organic solvents.
Synthesis and characterization of substituted aromatic polyesters derived from phenoxy‐ and tert‐butylhydroquinone
Authors: Heitz Walter , Nießner Norbert 
Published: April 2003

AbstractAromatic polyesters 5 and 6 were synthesized from tert‐butyl‐ and phenoxyhydroquinone (4a and 4b) and terephthalic acids 3a–e. The introduction of substituents reduces the phase transition temperature and increases the solubility of the corresponding polyesters in common solvents. As a result, soluble, amorphous and liquid‐crystalline aromatic polyesters were obtained. Unexpectedly, the phenoxyhydroquinone moiety suppresses the formation of a mesophase in some polyesters.
Miscibility behavior in blends of poly(2,6‐dimethylphenylene oxide) and random or block copolymers of styrene with methyl methacrylate
Authors: Kressler Jörg , Kammer Hans‐Werner , Morgenstern Ute , Litauszki Beata , Berger Werner , Karasz Frank E. 
Published: April 2003

AbstractThe Miscibility in blends of poly(2,6‐dimethylphenylene oxide)Systematic IUPAC name: poly[oxy(2,6‐dimethyl‐1,4‐phenylene)].
(PPO) with random or block copolymers of styrene and methyl methacrylate (MMA) was studied by light microscopy and glass transition temperature measurements. Blends of PPO and the random copolymers were found to be miscible up to a copolymer content of 18 wt.‐% MMA. The transition from miscibility to immiscibility in these blends in independent of temperature in the range 100 to 350°C. From these data, the segmental interaction parameter between units of the homopolymer and MMA, χPPO/PMMA is estimated to be about 0,5. Blends of PPO and the block copolymers of styrene and MMA used behave essentially as the corresponding homopolymers in terms of miscibility.