Processus de photopolymerisation du methacrylate de methyle en presence de chlorure de zinc

The photopolymerization of methylmethacrylate in solution or in bulk, initiated by DMPA (2,2-dimethoxy-2-phenylacetophenone) and BP (benzophenone), has been investigated in the presence of ZnCI₂ as a complexing agent. We have studied the steady state polymerization (measurement of R, and OT) and the behaviour of the excited states by laser spectroscopy. We have shown the following points: R_p and DP increase with [ZnCI₂]; the rate constant for propagation increases with [ZnC12]; the rate of initiation remains constant in presence of BP-ZnCl₂ but increases with DMPA-ZnCl₂. The results are accounted for by the results of laser spectroscopy.     

Etude de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse

Original mass spectra of uracil and thymine derivatives are presented with the corresponding fragmentation schemes. In the first series of spectra, the fragmentations of thymine derivatives, including ¹⁴C-2-thymine, dimers, and bromo thymines, confirm the basic retro Diels-Alder mechanism. The second series includes dihydro 5,6-derivatives of uracil (hydroxy and bromo substituents). The behaviour of these molecules is quite different; they are more sensitive to the substituents and a part of the fragmentation is often explained by protonated molecular ions.     

Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation

Different transformations of the functions fixed on a heterocyclic molecule were made. It is thus possible to quickly determine the number of functions of each type present in the molecule: e.g. (i) all the functions are silylated and (ii) the alcohols are acetylated whilst the sulfates and acids are silylated. Mass spectra of atractylate, apoatractylate and gummiferine have been studied and the substituents are counted and enumerated.     

Synthese regioselective de bases de mannich de cetones dissymetriques

Methods for the regioselective synthesis of Mannich bases starting from unsymmetrical ketones are described. The Mannich base on the more substituted carbon is obtained by reaction with (CH₃)₂N⁺CH₂,CF₃CO₂^- in CF₃CO₂H and its isomer on the less substituted carbon with (iPr)₂N⁺CH₂,ClO₄^- in CH₃CN. In the first case, the orientation corresponds to a non-selective attack of the immonium salt on a mixture of enols in which the more-substituted isomer is predominant. In the second ease, use of a bulky immonium salt induces a selectivity favoring the less-substituted enol.     

Fragmentation de derives phenyles de l'isobenzofuranne et de l'isoindole

The fragmentation patterns of two paris of heterocycil compounds are investigated in order to discuss the effect of the nature of the heteroatom.     

Mecanismes de Fragmentation de l'Oxazole

The fragmentation mechanisms of oxazole have been studied in detail on using various experimental techniques (refocusing of metastable ions, deuteration, AP measurements) and by theoretical calculations.     

Elaboration de capteurs de gaz a partir de ceramiques conductrices ioniques de type NaSICON

The elaboration of Na⁺ super-ionic conductor (NaSICON) ceramics is studied in this work. These solid electrolytes can be used as sensor for detection of polluted gases in air. Two sorts of ceramics with different chemical compositions are synthesised by soft chemistry route: a zirconium-based NaSICON and a hafnium-based NaSICON. DTA-TG and temperature depending X-ray diffractometry were used to follow the thermal decomposition of the precursor phases. The electrical properties of these ceramic sodium ionic conductors are investigated by complex impedance spectroscopy (CIS). The substitution of the zirconium by the hafnium increases the ceramic conductivity and decreases the activation energy E ^a (from 0.29 to 0.12 eV). This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence de la Structure de Diverses Fonctions sur l'Evaluation de l'Energie de Correlation

The influence of various correlation functions, multiplying the monoelectronic space function, is studied and applied to the Helium atom and its isoelectronic series. We used Slater-type basis orbitals and the ground and first excited states have been studied, taking into account the virial and cusp conditions. In the ground state, a very good value for the correlation energy is obtained, using a function of the type For the excited states, this type of function overestimates the assumed value of the correlation energy.     

Modification chimique de polyisoprenes et de polybutadienes de faible masse par addition de trichlorosilane

The addition of trichlorosilane to carbon-carbon double bonds of low molecular weight polyisoprenes and polybutadienes has been studied with hexachloroplatinic acid as catalyst. The reaction was carried out in benzene as solvent, at 110, under nitrogen pressure. The reaction rate decreases as the carbon-carbon double bond substitution increases. In most cases, addition of trichlorosilane is accompanied by cyclization reactions more or less important depending on the polymer structure, except for 1,2-polybutadiene. Trichlororosilyl groups have been modified to trimethyl and trimethoxy derivatives.     

Synthese de polyacrylamides porteurs de groupements iminodiacetate et etude de leur pouvoir de complexation vis-a-vis de quelques cations metalliques

Water soluble polymers were prepared by topochemical reaction of sodium iminodiacetate with polymethylolacrylamide. Their complexing properties towards some metallic cations were investigated by potentiometric and spectroscopic techniques and compared with the complexing properties of iminodiacetic acid and of a model molecule of the polymer ionic unit. The results showed that polymer and model 1-1 chelates are stronger than iminodiacetic complexes. We explain this difference by participation of the amide group in the coordination of cation by the two first ligands.     

Etude par microcalorimetrie de la reactivite de deux ammoniacates de chlorure de manganese

The reaction [Mn(NH₃)₂]Cl₂+ 4NH₃ [Mn(NH₃)₆]Cl₂, which is of potential use in chemical heat pumps, was studied by means of differential scanning calorimetry. The thermodynamic conditions, the enthalpy of the reaction, and the heat capacity values for MnCl₂, [Mn(NH₃)₂Ch and [Mn(NH₃)₆Cl₂ were measured. The influence of the reaction kinetics of the experimental procedure and some parameters such as sample temperature, ammonia pressure and scanning rate was examined.

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Zusammenfassung Mittels DSC wurde die Reaktion [Mn(NH₃)₂]Cl₂+4 NH₃ [Mn(NH3_{) 6}]Cl₂ untersucht, die von potentieller Verwendung für chemische WÄrmepumpen ist. Thermodynamische Bedingungen, die Reaktionsenthalpie und WÄrmekapazitÄtswerte für MnCl₂, [Mn(NH₃)₂]Cl₂ und [Mn(NH₃)₆]Cl₂ wurden gemessen. Weiterhin wurde der Einflu\ des Versuchsablaufes und einiger Parameter, wie Probentemperatur, Ammoniakdruck und Scanning-Geschwindigkeit auf die Reaktionskinetik untersucht.

     

Cinetique de polymerisation de monomeres complexes par des acides de Lewis. Etude du systeme methacrylate de methyl-chlorure de zinc-azobisisobutyronitrile

The polymerisation of methyl methacrylate (MMA) initiated by azo-bis-isobutyronitrile (AIBN) in the presence of ZnCl₂ as complexing agent has been investigated. Increase of the polymerisation rate and a minimum in the average polymerisation degree were observed by increasing the ZnCl₂ concentration. By assuming the existence of complexes {AIBN · ZnCl₂} and {MMA · ZnCl₂}, a kinetic scheme is proposed; it is in good agreement with the experimental results and allows calculation of the characteristics of the system.     

Etude de stabilisation de verres a base de YF3

New fluoride glasses were obtained in the InF₃-BaF₂-YF₃ system. Evidence for phase separation was found in this basic ternary system, suggesting that glasses based on yttrium fluoride could be formed. Indeed such glasses could be prepared by fast cooling. The mean sample thickness was 2–3 mm. Glass transition, crystallization and melting temperatures were measured.     

Regioselectivite de la reduction de tropones de la quinoxaline

The reduction of quinoxalinotropones by some borohydrides is studied. We calculate the electronic structures, ab initio STO 3G method, of the various possible complexes and compare to the α-enones. It is demonstrated that the borohydride reduction of these tropones is under orbital frontier control and that the important element is carbonyl complexation by the cation.     

Etude de l'incorporation de l'oxyde de cuivre dans le reseau de l'oxyde de nickel par traitement thermique

NiO prepared at 950° has been impregnated with a solution of copper nitrate and heated at 300°. The incorporation of CuO issued from this treatment in the lattice of NiO during sintering at 450–1100° has been studied by DTA and TG, and chemical analysis. A few experiments by radiocrystallographic analysis and electron diffraction have also been done. The process of incorporation begins at about 600° and is nearly complete at 900°. A sample elaborated at 1100° is homogeneous in the mass but presents in the surface an excess of copper ions which seems to be located at certain points.

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Zusammenfassung Bei 950° erzeugtes NiO wurde mit Kupfer(II)nitratlösung impregniert und auf 300° erhitzt. Der Einbau von CuO (5 %) in das NiO-Netz bei thermischer Behandlung von zwischen 450–1100° wurde durch DTA, TG und chemische Analyse untersucht. Einige Proben wurden auch einer Prüfung durch Radiokristallographie und Elektronendiffraktion unterworfen. Der Einbau beginnt bei 600° und ist bis 900° praktisch vollendet. Eine bei 1100° erzeugte feste Probe, obzwar homogen in der Masse, zeigt an der Oberfläche einen Überschuß von an gewissen Stellen lokalisierten Kupferionen.

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Résumé NiO préparé à 950° a été imprégné par une solution de nitrate cuivrique et chauffé à 300°. L'incorporation de CuO (5 %), ainsi engendré, dans le réseau de NiO, lors de traitements thermiques à 450–1100° a été étudiée par ATD, ATG et analyses chimiques. Quelques essais d'analyses radiocristallographiques et de diffraction électronique ont également été effectués. Le processus d'incorporation se manifeste à partir de 600°. Il est pratiquement complet vers 900°. Un solide élaboré à 1100°, bien qu'homogène dans la masse, présente, en surace, un excédent d'ions Cu^{+ +} qui semble localisé en certains points. , 950°, 300°. , , , 450° 1100°. . 600° 900°. , 1100°, , .

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Nous tenons à exprimer nos remerciements à Messieurs H. Urbain et R. Bacaud, à Mesdames G. Dalmai-Imelik, C. Leclerq et M. A. Gresteau, et à Monsieur A. Renouprez pour leur contribution à cette étude.     

Etude par spectroscopie de photoelectrons (XPS) de la surface de profiles a base de PVC

Variations of the surface composition (over a thickness of 50 Å) of stabilized and rigid PVC for outdoor applications and of pure moulded PVC resin have been investigated by photoelectron spectroscopy (ESCA or XPS) after extrusion, outdoor and accelerated ageing and photooxidation. Extrusion is accompanied by a pronounced migration of lead thermal stabilizers and of calcium stearate, used as an external lubricant, towards the outer surface. This treatment however, induces neither significant oxidation nor formation of a great quantity of ionic chloride. Natural and accelerated weathering were compared and were characterized by a large decrease in the lead surface concentration. The surface of this material is unaffected when exposed to air in a closed vessel and protected from external radiations. Finally, surface photooxidation by u.v. exposure has been evaluated and compared for the stabilized material and for the pure resin. This treatment involves formation of carbonyl and carboxylic groups. ESCA spectroscopy, a speedy and non-destructive surface analytical method, is well suited for study migration of stabilizers and lubricants.     

Quelques caracteristiques morphologiques de melanges de polymeres a base de propene et de butene

This paper reports a study of the morphology of blends of polypropene with polybutene as a function of composition. Techniques such as differential thermal analysis, thermomechanical analysis and dilatometry were used. The “compatibility” of these polyolefines is considered. Glass transition temperatures of the homopolymers are detectable when using the various techniques.     

Spectres de vibration de l'acide cyclopropane dicarboxylique-1.1 et de ses sels de potassium en solution aqueuse

Raman and infrared spectra of the cyclopropane-1.1 dicarboxylic acid and its potassium salts in aqueous solution were recorded from 100 to 4000 cm⁻¹. An assignment of the observed lines as fundamentals is proposed. The analysis of the polarization of the Raman lines indicated that the salts belong to the C₂ group. The intramolecular hydrogen bonds which exist in the acid, persist in aqueous solution in both the acid and the acid salt.     

Spectres de vibration de pigments rouges de la famille des quinacridones

The i.r. and Raman spectra of various crystalline phases of the trans linear quinacridone and some methylated and chlorinated derivatives have been investigated between 4000 and 200 cm⁻¹. Each of these pigments has been characterized spectroscopically and an assignment for intramolecular fundamentals is given in terms of group frequencies. The strength and length of NH ⋯ O hydrogen bonds have been assessed from the vNH frequency and correlated with the pigment colour which is principally determined by intermolecular interactions rather than by the substituent hypso(batho)chromic effect. The NH ⋯ O distance increases from 2.87 Å for the red compounds to 2.93 Å for the purple ones.