Polymères thiocarboxyliques, 1. Synthèse et étude de la polymérisation radicalaire de monomères dithiocarboxyliques

The syntheses and free-radical polymerizations of methyl and carboxymethyl 4-vinyldithiobenzoates are described as well as various copolymers. Copolymerisation parameters were determined for the copolymerizations of the methyl dithioester with styrene and with methyl methacrylate.     

Polymères photoréticulables à unités cinnamiques, 2. Synthèse par modification chimique et par polycondensation

Polymers containing cinnamic acid units were obtained by chemical modification of poly(vinyl alcohol) by cinnamic acid derivatives with a carbon-carbon double bond in para position. The reactivity of the acid chloride is lowered by the inductive effect of the double bond. Polycondensation of these derivatives, when difunctional, leads to low-molecular-weight polyamides and polyesters with good yields. The introduction of acrylic or methacrylic groups on photosensitizers has also been studied, leading to monomers which can be polymerized by a radical process, or copolymerized with the previous monomers, the polymer bearing then the photosensitizer and the cinnamic double bond on the same chain.     

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, 14. Synthèse de copolymères butadiène-vinylferrocène

Hydrogen 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.     

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 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 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 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.     

Polymères photoréticulables à unités cinnamiques, 1 Synthèse des monomères et polymérisation

The synthesis of cinnamic acid derivatives with a carbon-carbon double bond in para position was studied by a Knoevenagel reaction with p-chloromethylstyrene. The latter was obtained via a several-step reaction from 2-phenylethanol. The monomers can be polymerized by a free-radical process without affecting the cinnamic group. Copolymerization is effective only with monomers such as maleic anhydride, p-vinylbenzaldehyde or methyl methacrylate, having a π-acid character like the cinnamic acid derivatives used in our study.     

Polymères thiocarboxyliques, 5. Synthèse de poly(oxyéthylène)s à fonction dithioester terminale. Application au traitement de cellules d'électrophorèse

Poly(oxyethylene)s with dithioster end groups were obtained from mono- and dihydroxyl terminated commercial polymers by reaction with dimethyl chloroacetamide, subsequent thionation of the amide group, and usual conversion of the thioamides into the dithioesters 14, 15 and 20, 21 . The best results were obtained in the syntheses of the S-carboxymethyl dithioesters ( 15 and 21 ). The resulting reactive poly(oxyethylene)s were grafted upon silica tubes and electrophoresis cells, previously activated by aminopropylsilanization. These graftings result in lowering of the surface potential of the tubes and in suppression of the electro-osmosis flow in an electrophoresis cell tested with a TiO₂ standard sample.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées 4. Polymérisation et copolymérisation de butènes

The homopolymerization of 1-butene, 2-butene, and isobutene in methanol initiated by hydrogen peroxide affords low molecular weight hydroxylated oligomers in low polymerization yields. The copolymerization of these monomers with a diene monomer such as butadiene can easily be carried out. The reactivity ratios were found to depend on the structure of the monomers; the polymerization and copolymerization rate of 2-butene being higher than those of isobutene, but lower than those of 1-butene.     

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 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, 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, 6. Etude des réactions de transfert

Radical polymerizations in an alcohol, initiated by hydrogen peroxide were found to afford polymers with hydroxyl end groups. The constants of chain transfer to the initiator and to the alcohol were determined for the polymerization of vinyl acetate, isoprene, and butadiene. The results show the influence of the initiator and the nature of the alcohol in the polymerization mechanism.     

Terpolymérisation acrylonitrile-styène-acrylate de méthyle, 2. Synthèse de terpolymères homogènes en composition par polymérisation en émulsion

Previous Kinetic studies of the emulsion polymerisation of the three component system acrylonitrile (A) — styrene (S) — methyl acrylate (M) have shown that S is much more reactive than A and M, which have practically the same reactivities. As a consequence, in batch process a large copolymer composition drift is observed versus conversion. To avoid this damageable drift, two techniques were investigated, to get homogeneous macromolecules. (1) Application of the well known “semi-continuous technique” which appeared not to be totally satisfactory, since the initial batch polymer fraction generally has a composition different from the further polymer when the monomer feed is added under starving conditions; a mixture of various macromolecules is the result. (2) The use of the composition controlled reactor, developed in this laboratory, which consists in a continuous monitored readjustment of monomer feed composition. However, due to the heterogeneous medium of an emulsion copolymerization, the copolymer exerts a small chemical heterogeneity which may be practically negligible at high monomer/water ratio. It is finally proposed that a thermodynamic approach might overcome such a behaviour and insure an actual control of the copolymer composition.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 8. Synthèse de polybutadiènes: Etude de différents paramètres influençant la polymolécularité

It was shown that radical polymerization of butadiene in 1-butanol and 2-butanol, initiated by hydrogen peroxide cleaved into two hydroxyl radicals by heat, leads to three types of polymers according to their respective polydispersity. It was found that the formation of these products — oligomers, polymers, and high polymers — can be influenced by modifying the experimental conditions. Thus, it is possible to obtain selectively oligomers free of polymers and polymers free of low molecular weight oligomers.     

Application de la réaction de métathèse à la synthèse de prépolymères α,ω-bifonctionnels, 2. Etude de possibilitiés d'application à la synthèse de prépolymères α,ω-dichlorés

The capability of chloroalkenes to undergo cometathesis with alkenes was investigated with the intention to check the possibility of applying the principle of the synthesis of α,omega;-difunctional polybutadienes to α,omega;-dichloropolybutadienes. The results obtained from the analysis of the reaction products resulting from 1,6-dichloro-3-hexene ( 1 )/4-octene ( 2 ) systems and WCl₆/EtAlCl₂ were compared with those obtained from 1-chloro-3-hexene ( 8 ) alone, 1 /1,5-cyclooctadiène ( 13 ), 5-chloro-1-pentene ( 6 )/ 2 , and 1,4-dichloro-2-butene ( 10 )/ 2 systems in the presence of WCl₆/EtAlCl₂. It was found that it is possible to apply the synthetic principle to α,omega;-bis-(δ-chloroalkenyl)polybutadienes.     

Synthèse et caractérisation de copolymères coordinés par des sels métalliques

The anionic block copolymerisation of isoprene and 2-vinylpyridine (2VP) followed by a coordination with iron (III) chloride, leads to thermoreversibly crosslinked copolymers. These copolymers are character+ed by a low polydispersity (M?_w/M?_w≈1,1) between the coordination nodules of poly(2-vinylpyridine). The study of the swelling ratio at the equilibrium in benzene shows that such a polymeric network does not reach the equilibrium state expected from the thermodynamic analysis of the system. The presence of 2VP in the copolymer induces a screening effect which prevents the solvent diffusion through the polyisoprene network.     

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.