Détermination des masses et des distributions moléculaires d'un poly(aryléthercétone-co-sulfone) semi-cristallin (HTX) à l'aide d'une méthode de dérivatisation chimique, 1. Caractérisation moléculaire du HTX en solution dans l'acide sulfurique concentre

HTX, a poly(aryletherketone-co-sulfone), is characterized in solution in concentrated sulfuric acid. Upon dissolution in concentrated H₂SO₄, HTX is chemically modified by sulfonation of phenyl rings. The modification of the chemical structure is studied with a model compound by means of IR spectroscopy. The increase of the molar mass corresponding to a complete sulfonation is determined by means of mass spectrometry. Light scattering and ¹⁹F NMR measurements are performed in order to obtain the weight- (M?_w)_s and number-average (M?_n)_s molar masses of sulfonated HTX samples. (M?_w)s values allow the determination of the Mark-Houwink-Sakurada relationship for HTX in 99,5% H₂SO₄ at 25°C.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 12. Etude de la copolymérisation du méthacrylate de méthyle avec divers acrylates et méthacrylates. Détermination des microstructures

Methyl methacrylate was copolymerized with butyl or isobutyl acrylates, and butyl, isobutyl, or 2,3-epoxypropyl methacrylates, by hydrogen peroxide, in the presence of ethanol under UV irradiation (at 254 nm) at room temperature. The analysis of the microstructures was based on resonance splitting of the methoxy protons of MMA, depending on their environment. This splitting was not obtained with isobutyl and 2,3-epoxypropyl methacrylates. All the products were found to be predominantly syndiotactic.     

Etude par 1H NMR des groupements chlorométhyles du poly(chlorure de vinyle), 2. Etude par écho de spin et comparaison avec des modèles moléculaires

In order to assign all ? CH₂Cl resonances observed by ¹H NMR in poly(vinyl chloride), (PVC), a preliminary study of the diastereoisomers of molecular models for the groups CH₂Cl? CHCl? [II] and is used, in conjunction with spin echo experiments. The complex region [3,5–4,0 ppm] which corresponds to saturated ? CH₂Cl chloromethyl protons is completely assigned. A separate evaluation of ? CHCl? CH₂Cl [II], ? CH₂? CH₂Cl [III] and is proposed and tested on raw PVC samples. The main interest of this ¹H NMR determination is the fact that raw PVC can be used and that it gives the ratio [II]/[III] which is not accessible by ¹³C NMR on reduced samples.     

Catalyse de transformation des oléfines par les complexes du tungstène, 4. Evolution de la distribution des masses moléculaires au cours de la polymérisation des cyclooléfines

The molecular weight distribution of polypentenamer and polyoctenamer prepared in the presence of tungsten catalysts, was studied by GPC, as a function of reaction time. Polypentenamer shows a single distribution, the maximum and width of which decrease with increasing conversion. Polyoctenamer prepared either from cyclooctene or from a polymer of high molecular weight, shows a bimodal distribution which may be considered as the sum of two single distributions. The relative proportions of these two distributions are independent of the conversion. Each distribution finally becomes “log-normal” at high conversion. The cyclopentene-cyclooctene copolymer also shows a bimodal distribution. The oligomers possess octenamer as well as pentenamer units. The simultaneous formation of polymers of high molecular weight and of oligomers is explained in terms of a polyaddition reaction at the bond between the metal and the carbeneresidue with intramolecular chain transfer.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 11. Etude de la copolymérisation du méthacrylate de méthyle avec divers acrylates et méthacrylates. Détermination des rapports de réactivité

Methylmethacrylate (MMA) was polymerized in an oxygen or argon atmosphere with butyl or isobutyl acrylates, and butyl, isobutyl, or 2,3-epoxypropyl methacrylates, by hydrogen peroxyde in the presence of ethanol under UV irradiation (254 nm) at room temperature. The reactivity ratios were determined. MMA shows a higher reactivity than its comonomers, in good agreement with the results of the literature, except for isobutyl and 2,3-epoxypropyl methacry-lates.     

Polyméres porteurs de dérivés du glycérol, 3. Modification chimique du méthacrylate d′époxy-2,3 propyle et de son polymére par i′acide phényl-2 butyrique

The influence of time, temperature, and concentration on the addition rate of 2-phenylbutyric acid (1) to 2,3-epoxypropanol (4), 2,3-epoxypropyl methacrylate (2) , and its polymer 3 was studied in chloroform and 1, 4-dioxane. The variation of the yeld with time and concentration of catalyst (tetramethyl ammonium salt of 1 ) can be fairly well represented by the equation v = k [Acid] · [Epoxide] · [Catalyst], with k ～ 0,6 to 0,8 1² · mol ^-2 ·h^-1 at T = 60°C and [Acid] ≈ 1 mol · 1^-1. The Arrhenius activation energy was found to be 70 to 80 kJ · mol^-1. With variation of the epoxide and acid concentrations, deviations were observed.     

Réactivité du groupement N-(époxy-2,3 propyl)-N-méthylamino vis-à-vis d'amines aromatiques à l'état fondu. Etude des mécanismes et des chemins réactionnels

Mechanism and kinetics of the reactions of N-(2,3-epoxypropyl)-N-methylaniline ( 1 ) with aniline or 4,4′-sulfonyldianiline ( 3 ) were investigated using high performance liquid chromatography and ¹³C FT NMR under different conditions (110–172°C). Comparison of 1 with its derivatives shows that the activity of the 2,3-epoxypropyl group in such epoxides depends on the structure and the substituents at the benzene ring; etherification may occur already before the secondary amine is consumed.     

Etude par 1H NMR des groupements chlorométhyles du poly(chlorure de vinyle), 1. Synthèse et étude de modèles moléculaires chloro-4 chlorométhyl-3 heptane et trichloro-1,2,4 pentane

4-Chloro-3-chloromethylheptane ( 2 ) and 1,2,4-trichloropentane ( 3 ) were synthesized and analysed by means of ¹H NMR. These compounds — with two asymmetric carbon atoms — are models for two types of structure involving chloromethyl groups present in poly(vinyl chloride): short chloromethyl branches and chain end groups resulting from reinitiation by a chlorine atom. The spectra of these compounds allow a better understanding of the corresponding resonance region observed in standard PVC.     

Thermo-rétraction et orientation moléculaire du poly(téréphtalate d'éthylène) soumis a une déformation uniaxiale homogène et plastique

A study of molecular orientation in drawn and shrunk poly(ethylene terephthalate) was undertaken at 80°C and 120°C for samples drawn at (i) 80°C (homogeneous deformation) and (ii) two-stage drawing: a homogeneous pre-orientation at 80°C, followed by cold drawing at 20°C. The results (birefringence, residual shrinkage ratio, crystallinity) are discussed in terms of molecular disorientation in the noncrystalline region which occurs upon the shrinkage process.     

Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25°C: Étude en solution aqueuse avee amorçage par radiolyse du solvant. II. Arguments pour un mécanisme monomoléculaire de décomposition des radicaux peroxyles

Cationic copolymerizations of furfural were carried out with several vinyl monomers. No copolymers were obtained with some hydrocarbon comonomers. At low temperatures furfural copolymerized with vinyl ethers selectively through the aldehyde group. On the other hand, deeply-colored copolymers of complex structures were formed at higher temperatures (ca. 0°C). Three typical vinyl ethers (p-tolyl vinyl ether, dihydropyran, and divinyl ether) were selected as comonomers, and their copolymerization behaviour studied in detail. The monomer reactivity ratios for furfural (M₁) and p-tolyl vinyl ether (M₂) were r₁ = 0,15 ± 0,15, r₂ = 0,25 ± 0,05. The furfural (FF) contents were fairly independent of the monomer feeds when dihydropyran (DHP) and divinyl ether (DVE) were used as comonomers: 37–47% for FF-DHP copolymers and 40–50% for FF-DVE copolymers. More than half of the second vinyl groups were consumed in the FF-DVE copolymers indicating the formation of 1,3-dioxane rings as in the case of benzaldehyde-DVE copolymers.     

Préparation,polymérisation et réticulation du méthacrylate de (diméthyl-2,2 dioxolann-1,3 yle-4) méthyle. Hydrolyse des polymères obtenus

The preparation of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate is carried out using the reaction between a mixture of methacrylic acid and thionyl chloride with 2,3-O-isopropylideneglycerol in an HMPT/ether medium. Anionic polymerization of the obtained monomer yields linear polymers of low polydispersity, provided the experimental conditions are satisfactory. Using anionic block copolymerization, model-networks of poly[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate] [poly( 4 )] have been obtained with ethylene dimethacrylate as bifunctional second monomer. The obtained gels are characterized by the quasi-constant molecular weight of the elastic chains between two successive branch points. The acidic hydrolysis of the acetal functions of the linear poly( 4 ) yields poly(2,3-dihydroxypropyl methacrylate).     

Apport de la méthode des ondelettes continues à l'analyse du signal ultrasonore rétrodiffusé par des suspensions de globules rouges agrégésContribution of the continuous wavelet method to the analysis of the ultrasound signal backscattered from suspensions of aggregated red blood cells

Many studies have already been conducted to better understand blood flow in human vessels. Various techniques, in particular ultrasonic methods such as ultrasonic imaging and Doppler velocimetry have been used. Some microcirculatory disturbances found in human being could be explained by a bad distribution of blood in the capillary network, due to an increase of aggregation and a decrease of deformability of red blood cells (RBC). In the present work, the structure of aggregated RBC suspensions were approached by processing of the ultrasonic backscattering signal using the continuous wavelet transform (CWT) method. Under our experimental conditions, the CWT provides three types of parameters: first, a characteristic time of sedimentation of red blood cells and aggregates, second, characteristic frequencies of fluctuations of the number and density of red blood cells and, third ponderation coefficients of the wavelet transform. Ponderation of the wavelet coefficients was used to calculate the first four statistical moments providing information on the aggregate geometry. Experiences providing from suspensions of normal red blood cells, for various hematocrit from 5% to 35%, aggregated by using dextran 70 (70,000Da) at concentration of 30 g l^–1, show that the calculated statistical moments are useful to characterize the size distribution of aggregates.     

Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 4 Discussion du schéma réactionnel

Results from previous publications of the series are interpreted and discussed in terms of a reaction scheme. Probabilities of the different non-terminating reactions of α-alkoxyalkylperoxy radicals during the autoxidation of solutions of poly(oxytetramethylene) 10^?2 g cm^?3 ≤ c ≤ 6.10^?2 g cm^?3 were determined as follows: for the H atom abstraction = 0,2–0,4, for the monomolecular decomposition (reference) = 1, and for the non-terminating bimolecular reaction = 7–10.     

Polymères porteurs de dérivés du glycérol, 10. Fixation de l'acide naphtyl-1 acétique sur le poly(acide méthacrylique)

Glycidyl (2,3-epoxypropyl) esters are convenient reagents for the fixation of carboxylic acid moieties on polymeric support of the polyacid type. This way of synthesis was applied to 1-naphthylacetic acid on poly(methacrylic acid). Esterification of 1-naphthylacetyl chloride by glycidol (2,3-epoxy-1-propanol) and addition of 1-naphthylacetic acid on epichlorohydrin (1-chloro-2,3-epoxypropane) with subsequent reformation of the oxirane ring have been used for the synthesis of the glycidyl ester but the reaction of the potassium salt of the acid with epichlorohydrin leads to a better yield. Addition of 1-naphthylacetic acid on glycidyl acetate was studied in N,N-dimethylformamide (DMF) and acetonitrile. The best results were obtained in DMF. The reaction is of first order with respect of epoxide, but 2nd order applies when the solvent is acetonitrile. The same reaction conditions as for glycidyl acetate were used for the chemical modification of poly(methacrylic acid) with glycidyl 1-naphthylacetate except that methanol was used as the solvent.     

Éthers-oxydes polymères des composés azoïques. Hétéropolycondensation du azodiphénolate-4,4′ de sodium avec des dérivés bis(chlorométhylés) du benzène

This publication deals with the polycondensation of disodium 4,4′-azodiphenolate ( 1 ) with bis(chloromethyl)benzene compounds ( 2a, b and 4 ) in a heterogeneous phase. The resulting products are linear polymers with a yellow colour and a low solubility in organic solvents. They are analysed by spectroscopic (UV, visible, IR) and thermogravimetric methods.     

Cryométhodes en microscopie électronique à balayage en transmission (MEBT) appliquées a l'analyse cellulaire à l'échelle submicrométrique : mesure locale en eau par imagerie en champ sombre quantitative afin de déterminer des concentrations élémentaires dans l'état physiologique

Nous exposons une méthode qui permet une mesure de la teneur en eau à l'échelle des compartiments cellulaires. Cette méthode est basée sur la mesure de l'intensité en champ sombre sur des cryocoupes lyophilisées en microscopie électronique à balayage en transmission. La teneur en eau est déduite de la teneur en masse seche par son complément à 100 %. À l'aide de cryocoupes de solutions étalons d'un composé macromoléculaire, nous établissons une relation linéaire entre la teneur en masse sèche restante clans l'échantillon lyophilisé et l'intensité en champ sombre.Nous présentons ensuite les différentes étapes des cryométhodes : cryofixation, coupe à froid, observation à froid après lyophilisation. Nous appliquons ce protocole au cas des cellules isolées (érythrocytes) et des cellules en monocouche (ostéoblastes). L'utilisation des cryom6thodes et de la mesure locale de la teneur en eau couplée à la microanalyse X permet, en outre, d'accéder aux mesures de concentrations élémentaires dans l'état physiologique (exprimées en mmol/L) dans les tissus biologiques.