Francine Guida-Pietrasanta

Grafting of ceramic membranes by fluorinated silanes: hydrophobic features

Abstract One of the application of ceramic membranes can be the transfer of a gas into a liquid or the extraction of gas from a liquid through a membrane. The problem is the hydrophilic behaviour of the oxide materials that leads to a natural and important absorption of liquid into the different layers of a membrane. Pressures required, in order to bring the liquid back out of the membrane, especially when the pore diameters of the layers become smaller, are too high and systems cannot support such pressures. Consequently, a mean of making membrane material hydrophobic is developed. The membrane was impregnated by a solution of a fluorinated product. It grafts into the membrane material. Grafting using two different fluorinated silanes, C 6 F 13 C 2 H 4 Si(OMe) 4 and C 8 F 17 C 2 H 4 Si(OEt) 3 , was investigated. First experiments were made, for instance, on microfiltration membrane with C 8 F 17 C 2 H 4 Si(OEt) 3 . Results of grafting of microfiltration and ultrafiltration membranes with different fluorinated silanes will be given and discussed.

Study of the alkylation of chlorosilanes. Part I. Synthesis of tetra(1H, 1H, 2H, 2H-polyfluoroalkyl)silanes

Abstract The synthesis and structural characterization of tetra(1 H , 1 H , 2 H , 2 H -polyfluoroalkyl)silaneswith the same or different chain lengths C n F 2 n +1 linked to Si (1⩽ n ⩽6) is reported. When the synthesis was effected from chlorosilanes and fluorinated organomagnesiumor organolithium reagents, the trialkylsilanes were obtained. The last fluorinated chainwas introduced either via a fluoroalkyllithium reagent or by hydrosilylation of thetrialkylsilanes. Some properties and characterization by 1 H, 19 F and 29 Si NMR spectroscopy of the1 H , 1 H , 2 H , 2 H -polyfluoroalkylsilanes are described.

Fluorinated oligomers, telomers and (co)polymers: synthesis and applications

Abstract An overview of the activities in fluorine chemistry at the Laboratory of Macromolecular Chemistry of the Ecole Nationale Superieure de Chimie de Montpellier is presented, ranging from the synthesis of fluorinated monomers and initiators to the properties and applications of the corresponding (co)polymers. Concerning the monomers, acrylic, vinyl, allyl, styrenic, epoxides or silicon-containing monomers have been prepared. Then, original telomers of fluoroolefins from various chain transfer agents, and their functionalizations have been described. Further, fluorinated (co)polymers have been obtained and characterized: they can be produced either from radical (co)polymerization of commercially available or synthesized fluoromonomers (e.g. acrylic, trifluorovinyl monomers), or from polycondensation (e.g. fluorinated silicones or polyimides) or from polyaddition (e.g. fluorinated polyurethanes). Finally, several properties and applications are given.

Study of the alkylation of chlorosilanes. Part II. Synthesis of (fluoroalkyl)chlorosilanes and tetra(fluoroalkyl)silanes via hydrosilylation

Abstract The hydrosilylation of various fluorinated olefins and of a diene with different chlorosilanes and with a tri(fluoroalkyl)silane, in the presence of a peroxide or a Pt catalyst, is reported. The reactivity is influenced considerably by the structure of the silane and of the fluorinated olefin. The following (fluoroalkyl)chlorosilanes and (fluoroalkyl)-α,ω-chlorodisilanes are described; C 6 F 13 (CH 2 ) n ,SiR 1 R 2 Cl where n = 2 or 3 and (ClR 1 R 2 SiC 2 H 4 C 3 F 6 ) 2 with R 1 p=R 2 =Cl, R 1 =Cl and R 2 =CH 3 or C 2 H 4 CF 3 , R 1 =R 2 =CH 3 and R 1 =CH 3 and R 2 =C 6 H 5 . Three new tetra(fluoroalkyl)silanes have also been synthesized. All the products were characterized by 1 H, 19 F and 29 Si NMR spectroscopy.

Study of the alkylation of chlorosilanes. Part III. Synthesis and reactivity of new fluorinated organolithium reagents

Abstract The effect of the structure of the fluoroalkyl group R F C 2 H 4 , where R F CF 3 , C 6 F 13 and (CF 3 ) 2 CF, on the synthesis and reactivity of organolithium reagents R F C 2 H 4 Li towards trimethylchlorosilane, (CH 3 ) 3 SiCl, and tris(fluoroalkyl)silanes, R 1 R 2 R 3 SiF, where RR F C 2 H 4 , has been studied. As a result, new fluorinated organolithium reagents have been synthesized, as well as new silanes such as a tris(fluoroalkyl)fluorosilane, [(CF 3 ) 2 CFC 2 H 4 ] 2 SiF(C 2 H 4 C 6 F 13 ), and fluorinated tetraalkylsilanes such as C 6 F 13 C 2 H 4 Si(CH 3 ) 3 and [(CF 3 ) 2 CFC 2 H 4 ] 2 Si(C 2 H 4 C 6 F 13 )(C 2 H 4 CF 3 ). All the products have been characterized by 1 H, 19 F and 29 Si NMR spectroscopy.

Physically crosslinked fluorosilicone elastomers obtained by self- assembly and template polycondensation of tailored building blocks

Self-assembly and template polycondensation of two tailor-made fluorinated oligocarbosiloxanes generated physically crosslinked elastomer-like materials (denoted here as “gelastomers”). Clustering was found to arise from phase separation between strongly aggregated, polar silanol chain-ends and highly hydrophobic fluorosilicone domains. The large concentration of silanol functions promoted a template catalyst-free co-condensation to generate chains of typically 10 000 g mol−1 after extended times. One of these gelastomers exhibited noteworthy mechanical properties, such an elongation as large as 1500% at a fair strain force (0.2 MPa).

HYDROLYSE BASIQUE DE SELS DE BISPHOSPHONIUMS [Agrave] PONT TÉTRACARBONÉ INSATURÉ

Abstract Alkaline hydrolysis of 1,3-butadien 1,4-ylene bistriphenylphosphonium dibromide Ph3P+[sbnd]CH[dbnd]CH[dbnd]CH[dbnd]CH[sbnd]P+Ph3 2 Br− 1 and 2-butyn 1,4-ylene bistriphenylphosphonium diiodide Ph3P+[sbnd]CH2[sbnd]C[dbnd]C[dbnd]CH2[sbnd]P+Ph3 2 I− 2 has been studied using sodium hydroxide in various conditions of concentration and homogeneity. Compound 1 and compound 2, which affords 1 by isomerisation, react like a vinylphosphonium salt substituted by an electron withdrawing group: their hydrolysis proceeds mainly through a nucleophilic substitution on the phosphorus atom, with anionotropic migration of a phenyl group (SNPmig) and gives the salt Ph3P+[sbnd]CH2[sbnd]CH[sbnd]CH[sbnd]CH(Ph)P(O)Ph2HBr− 3. However, as for the vinylphosphonium salts, an increase in the solvatation of the phosphorus electrophilic site can disadvantage this process, on behalf of that of “phosphonioethylation” (addition occurring then on the carbon β to the phosphonio group): Ph3P+[sbnd]CH°C(OC2H5)[sbnd]CH2[sbnd]CH2[sbnd]P...

Synthesis of tetra(fluoroalkyl)silanes from trifluorosilanes

Abstract 1. R F R′ F R″ F CF 3 2. R F R″ F CF 3 , R′FC 6 F 13 3. R F R′ F C 6 F 13 , R″ F CF 3 4. R F C 6 F 13 , R′ F (CF 3 ) 2 CF, R′ F CF 3 The fluoroalkylmonofluorosilanes IV have been obtained in good yields (50–90%) from the reaction of an excess of trifluorosilane II (prepared from the corresponding trichlorosilane I ) with a fluorinated organomagnesium reagent III . Then, substitution of the last fluorine atom has been made by reaction with the fluorinated organolithium V , and the tetra(fluoroalkyl) silanes VI have, thus, been prepared. All the products have been characterized by 1 H, 19 F and 29 Si NMR spectroscopy.

Radical crosslinking during polyhydrosilylation between fluorinated and silicone molecules: a model study

Abstract The present study deals with an explanation for crosslinking reactions that occur during the polyhydrosilylation of telechelic Si-H silicones with divinylperfluoro molecules. For a better understanding of the chemical process, a model reaction was performed and characterized by a full battery of techniques, including the different nuclei NMR analyses. Even if hydrosilylation occurs, side methyl groups on the silicon atoms also react with tert-butoxy radicals. Abstraction of a hydrogen radical from the methyl side group of the silicone chains allows the vinyl fluorinated molecules to add on polydimethylsiloxane and to bridge chains together.