Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 7. Synthèse de polybutadiènes: Études cinétiques

It could be shown that radical polymerizations of butadiene in methanol, initiated by hydrogen peroxide, cleaved in two hydroxyl radicals by thermal reaction, give three types of products: oligomers formed predominantly during the two first hours, polymers formed by an autoacceleration phenomenon, mainly during the two first hours, and polymers of high molecular weight, formed after two hours of reaction. The results show that the reaction order is about 1,6. In addition, thermal initiation was also observed.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 9. Synthèse de polybutadiènes: étude des microstructures

Butadiene polymerization with hydrogen peroxide resulted in the simultaneous formation of oligomers, polymers, and high polymers. Analyses of their microstructures showed that oligomers have a higher content of 1,2-structures (28%) than the polymers (22%). The nature of the chain ends was determined with low molecular weight compounds. The content of 1,2-units is distinctly higher in the oligomers, which shows that initiation takes place preferably in 1,2- and propagation in 1,4-position. Besides hydroxyl end groups, other functional groups were detected in small quantities in the low molecular weight products: aldehydes, ketones, acids, hydroperoxides, and epoxides. These functions result from secondary reactions such as transfer, initiation, or termination reactions with alcohol releasing radicals.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 2 Synthèse de polybutadiènes

The polymerization of butadiene with aqueous hydrogen peroxide as initiator in an alcoholic medium, gives oligomers of low molecular weight (≈500) and liquid polymers with hydroxy end groups and average molecular weights between 1500 and 11000. The obtained products show that the monomeric units have mainly 1,4 structures (trans). The polymers contain two or three, in certain cases up to six hydroxy groups per molecule. Systematic studies were carried out varying the proportions of alcohol, hydrogen peroxide, and monomer in the reaction mixture.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 1, synthèse de polyisoprènes

Aqueous hydrogen peroxide decomposes by heat into two hydroxyl radicals which initiate the polymerization process. With isopren as monomer, two main products are obtained: liquid hydroxytelechelic polymers (1,4, principally trans) and oligomers composed of dimers, trimers and tetramers. The addition of alcohol to the polymerization medium modifies deeply the conversion yield in oligomers and polymers, and the molecular weight. The kinetics and the influence of the temperature of the reaction are studied.     

Synthèse et propriétés d'oligomères dièniques partiellement et totalement hydrogénés

Hydrogenations of several hydroxy-terminated low molecular weight polybutadienes (PB) or non functional PB and one polyisoprene by homogeneous catalysis were studied. Hydrogenation of 1,4-polybutadienes gave solid crystalline polymers. In the case of hydrogenated 1,2-polymers a decrease of the glass transition temperature was noted, the hydrogenation leading to amorphous polymers. The rheological behaviour of oligomers was found to be Newtonian at low shear rates (≤ 100 s^?1). The viscosity at T_g+100°C increased in every case with the hydrogenation rate. It was found that hydrogen bonding induced by hydroxyl groups has a great effect on the glass transition temperature but does not change the viscosity at T_g + 100°C.     

Synthèse de polymères ω-hydroperoxyde

The general conditions are described for the synthesis of ω-hydroperoxy polymers by reaction of oxygen with C? Li bonds of anionic living polymers. Secondary reactions as interchain coupling and the formation of alcohols are also discussed. In order to obtain a quantitative hydroperoxydation the following experimental parameters must be observed: (a) slow addition of the living solution to a polar solvent saturated by oxygen; (b) low concentration of living ends; (c) bulky terminal units; (d) lowest possible temperature.     

Synthèse et étude de copolymères sequencés photochromiques

New photochromic polymers were prepared by deactivating living homo or block copolymers with various 2H-chromene-2-spiro-2′-indolines ( 3a–3d ). Classical anionic polymerization was used throughout this work. By varying the chemical nature of the blocks as well as that of the photochromic units, a series of novel materials was obtained and their structure and behaviour were characterized.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 5. Polymérisation du méthacrylate de méthyle sous rayonnement ultraviolet

Hydrogen peroxide is cleaved by UV irradiation (253,7 nm) into two hydroxyl radicals which can be used as initiators of polymerization, in order to give hydroxytelechelic polymers. Yields and number average molecular weights are influenced by the presence of an alcohol in the reaction medium, and the results depend on the solubility of the polymer in the alcohol used. The polymerisation of methyl methacrylate in methanol, being a non-solvent for the polymer, is described in the present paper. The characteristics of the polymers obtained are studied: distribution of molecular weights, microstructures, proportion of hydroxyl groups per macromolecule; the influence of several parameters—reaction time, proportion of hydrogen peroxide, and nature of the reaction medium—is also studied.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 3. Synthèse de poly(acétate de vinyle)

On heating, hydrogen peroxide is cleaved into hydroxyl radicals, which can be used as initiators of polymerization in order to give hydroxylated polymers of low molecular weight. The conversion and the number average molecular weights are influenced by the presence of an alcohol in the reaction medium, and the results depend on the solubility of the polymer in the applied alcohol. The following characteristics of the polymerisation of vinyl acetate in methanol are studied: distribution of molecular weights, microstructures, proportion of hydroxyl groups in the macromolecule. The influence of several parameters as reaction time, temperature, proportion of hydrogen peroxyde and solvent, is also investigated.     

Synthèse de polysiloxanes téléchéliques, 2. Synthèse de diamines aromatiques

Telechelic aromatic diamines ( 11 ) containing an oligo- or polysiloxane chain were prepared in a 4-step synthesis. In the first step 1-allyloxy-4-nitrobenzene ( 6 ) was synthesized and subsequently hydrosilylated with chlorodimethylsilane. In the third step the product ( 7 ) was hydrolyzed or condensed with α-hydro-β-hydroxyoligo- or polydimethylsiloxane ( 9a or 9b ). In the last step the nitro groups were reduced into amino groups. The steps were controlled by means of ¹H and ²⁹Si NMR spectroscopy.     

Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalène carbonyloxyméthyles

In 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.     

Synthèse de polymères étoiles par réaction de polymères ω-fonctionnels sur des polyisocyanates

The present investigation was undertaken to study further the synthesis of networks with viscoelastic properties. This involves two stages: synthesis of functional polymers with reactive chain ends and selective condensation reaction with polyfunctional crosslinking agents. In order to determine the conditions of crosslinking reaction, a preliminary study was realised on the branched star polymer synthesis. These polymers are obtained by reaction of ω-functional polymer with tri-, tetra-, and pentaisocyanates. Polymers used in this work were polyisoprene, polybutadiene, polystyrene, block copolymers from diene and styrene with hydroxylic end groups. The reaction of the liquid polymer having hydroxylic end groups with isocyanates leads to a branched star polymer with formation of an urethane group, the average branching depending on the functionality of the polyisocyanates. Structures of this star polymer are confirmed by NMR analysis and by determination of the rel. mol. mass.     

Synthèse de composé photoréticulables, 9. Modification du polybutadiène carboxytéléchélique par des monomères acryliques

The addition of mercaptoacetic acid upon radical initiation onto carboxytelechelic polybutadienes ( 1 ) which have an average mass M?_n = 4400 gives polyacids having about twelve carboxylic groups. The reaction is followed by ¹³C NMR, ¹H NMR and by GPC. The thiol disappears according to a first order law. Besides, the value of the modification rate obtained from acido-basic titration confirms that obtained from NMR. In a second step, 2,3-epoxypropyl methacrylate is added to the acid groups to obtain an insaturated and carboxylated polydienic oligomer 5 . An application of these oligomers processed with a reactive diluter shows their high cross-linking ability under UV irradiation and confirms the improvement of the flexibility properties compared to those of traditional insaturated oligomers.     

Synthèse de polystyrènes chlorométhylés renfermant de nouveaux groupements tétrathiafulvalénylcarbonyloxyméthyles

In order to conserve high contrast while improving the sensitivity of microlithographic resins made up of polystyrene bearing tetrathiafulvalene (TTF) units, we prepared new polystyrenes containing tetrathiafulvalenylcarbonyloxymethyl groups which are methylated or non-methylated. The polymers were synthesized by reaction of poly[styrene-co-(p-chloromethyl-styrene)] with the corresponding caesium tetrathiafulvalenecarboxylate. To optimize this grafting reaction, preliminary reactions were carried out with model molecules.     

Synthèse de polyquinazolones à chaîne latérale fluorée

Bis(4H-3,1-benzoxazin-4-one) substituted in 2- and 2′-position with ? CH₂CH₂R_F, where R_F is a perfluorinated alkyl group, have been prepared. Polycondensation with 4,4′-oxydianiline and with 4,4′-methylenedianiline led to polyquinazolones which have different inherent viscosities according to the solvent of polycondensation and to the proportions of reactants used. The thermal behavior of these polymers characterized by differential scanning calorimetry or thermogravimetry was studied. The polyquinazolones are thermostable and exhibit a fluorine content of 50 mass-%.     

Synthèse des polyglutarimides à partir de PMMA et de cyclohexylamine, 4 Nouvelles voies de synthèse des polyglutarimides à partir des polysels d'ammonium

In this fourth paper, a new method for the preparation of polyglutarimides was studied. In order to avoid the use of a free amine at high temperature and contrary to the classic imidization reaction from PMMA and cyclohexylamine or methylamine, the amine function was introduced in the backbone on the polymer thanks to ammonium salts. They were incorporated by radical copolymerization between methacrylic monomers (methyl methacrylate, methacrylic acid) and cyclohexylammonium methacrylate or by salification of a methacrylic acid homopolymer with cyclohexylamine. After a thermal treatment at 250°C, the properties of these (co)polymers were compared (composition, glass temperature transition) with the materials obtained from the classic method.     

Synthèse de polymères α,ω-bifonctionnels par réaction de métathèse. Méthodologie d'approche des différences de réactivité des sites carbéniques en présence

The results of studies of co-metathesis reactions of 1,5-cyclooctadiene ( 1 ) with dimethyl 3-hexenedioate ( 2a ) and for comparison, with 4-octene ( 2b ) and 1,5-hexadiene ( 2c ) are analyzed in order to approximate the relative reactivities of the carbene species and of the different types of double bonds. To this end, the experimental distributions of the first telomers are compared with theoretical ones calculated on the one hand allowing equal probability of arrangement of alkylidene groups and on the other hand allowing a kinetic control of propagation and transfer reactions. In other respects, the possibilities of mass control of the products obtained by the same co-metathesis or by degradation of 1,4-polybutadiene are studied. The results show that the reactivity of the 1,5-cyclooctadiene double bonds is higher than that of the other types of double bonds, this being in agreement with the hypothesis of stabilization of the β-carbomethoxycarbene species by carbene/ester complexation. This stabilization allows us to explain the distribution of α,β-difunctional oligomers in agreement with the hypothesis of kinetic control. The distribution of non-functional oligomers agrees with a random combination of alkylidene groups. This stabilization is compatible with the controlling method of molecular weights in the products obtained by polymerization of cyclooctadiene and also by degradation of 1,4-polybutadiene in the presence of 2a .     

Synthèse de polysiloxanes téléchéliques, 1. Synthèse de diols et diépoxydes

Telechelic poly(dimethylsiloxane)s ( 4, 5, 6 ) with acetoxy, hydroxyl or 2,3-epoxypropoxy functions as end groups were synthesized. As starting materials chloro-3-acetoxy-[or 3-(2,3)-epoxypropoxy]-propyldimethylsilanes ( 2 and 3 ) were prepared by hydrosilylation of the corresponding allylic derivatives with chlorodimethylsilane, and subsequently condensed with α-hydro-ω-hydroxyoligo- (or poly-) dimethylsiloxanes ( 1b – d ) in the presence of pyridine. The hydroxyl derivatives 5a – d were obtained by hydrolysis of the acetoxy derivatives, and the 3-(2,3-epoxypropoxy)propyl derivatives 6a, b by reaction of the diols with 1-chloro-2,3-epoxypropane.     

Synthèse et greffage de polymères bioactifs sur des surfaces en titane pour favoriser l’ostéointégration

Titanium is widely used in orthopedic and dental implants for its excellent resistance to corrosion and its biocompatibility. In order to improve the long-term osteointegration of titanium, bioactive polymers bearing ionics groups such as sulfonates (sodium polysytrene sulfonate, polyNaSS) are grafted by a covalent way onto titanium surface. The surface is chemically modified and then bioactive polymers are grafted by radical polymerization. The chemical composition of grafted surfaces is given by ATR/FTIR and XPS which certified the presence of sulfonate groups at the surface of grafted titanium. Quantitative grafting of polyNaSS is determined by a colorimetric method and evaluated at 5 μg/cm².

In vitro study is performed in order to see the effect of these bioactive polymers on the mineralization of human osteoblast (line MG63). After 28 days of cultured cells on grafted titanium surfaces and non-grafted ones, the amount of calcium onto surfaces is quantified. The results show that the mineralization of these cells is improved with the presence of polyNaSS. The amount of calcium is increased on grafted surfaces compared to non-grafted ones. Cell adhesion was evaluated. Cells were seeded onto grafted and non-grafted titanium and then subjected to detachment forces. The results show that the attachment of human osteoblasts-like cells is increased for grafted titanium with polyNaSS. A study on titanium surface grafted by polymers bearing ionics groups such as carboxylate and phosphate is in progress.     

Synthèse, étude physicochimique et diélectrique de poly(acétoxyméthylstyrène)s

Various 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.