Gérard Rigal

Etude de la télomérisation et de la cotélomérisation du fluorure de vinylidéne (VF2). Part I. Cotélomérisation du VF2 avec l'acétate de vinyle et le 2-hydroxyéthylmercaptan

Abstract The radical telomerization of vinylidene fluoride (VF 2 ) and of vinyl acetate (VAc) with 2-hydroxyethylmercaptan, and the radical cotelomerization of both monomers with the same thiol have been investigated. In each case, the chemical structures and the chain lengths have been determined by various methods in order to understand the reactivity and the direction of addition of both monomers. This study indicates a greater reactivity for VAc relative to VF 2 since a twofold excess of VAc may be introduced into the cotelomers for an equimolar initial feed concentration of the monomers. Of the telomers produced, it was noted that the diadduct is HOCH 2 CH 2 SCH 2 CF 2 CH 2 CH 2 OCOCH 3 , indicating that the thiyle radical reacts preferentially with VF 2 . This study is a preliminary to obtaining curable VF2 oligomers.

Study of vinylidene fluoride (VF2) telomerization and cotelomerization. Part II. VF2 and chlorotrifluoroethylene (CTFE) cotelomerization with 2-hydroxyethylmercaptan by radical initiation

Abstract The radical telomerization of vinylidene fluoride (VF2) and of chlorotrifluoroethylene (CTFE) with 2-hydroxyethylmercaptan as the telogen was investigated. The corresponding homotelomers R-S- (CF2-CFCl)n-H (Cn) and R-- (CH2-CF2)n-H (Vn) with R =- -CH2CH2OH were synthesized and the 1:1 adducts identified. The VF2/CTFE/thiol reaction gave a mixture of the expected products, homotelomers and cotelomers. By various methods, mainly by 19F NMR spectroscopy, the chain length and tacticity of these telomers were determined. For example, after analysis, a fraction of the cotelomers was in good agreement with the general formula HO-CH2-CH2-S- (CF2-CFCl)x- (CH2-CF2)y-H, with x and y close to 4. Moreover, by comparison with the spectra of homotelomers of VF2 and CTFE, it was shown that these cotelomers exhibit an alternating structure.

Influence des alcools dans les réactions de télomérisation du chlorotrifluoroéthylène par catalyse rédox

Abstract The influence of alcohols, particularly of methanol and isopropanol has been studied in Redox catalyzed telomerization of trifluorochloroethylene and carbon tetrachloride. The nature of the by-products strongly favours participation of these alcohols during the transfer step. Results support formation of a reagent-metal complex during the course of the reaction. The latter does not follow as in the classical free radical telomerization.

TÉLOMÉRISATION ENÉMULSION DU STYRÈNE AVEC LES MERCAPTANS

Abstract The telomerization in emulsion of styrene is studied with two transfer agens: thioglycolic acid and 1,1,2,2-tetrahydro perfluorooctane thiol. The influence of the telogen-amount vs the degree of telomerization, that of the surfactant concentration and that of the nature of the initiator are investigated. The telomerization of this monomer with these aliphatic mercaptans is possible in aqueous medium whatever the solubility of the thiols in water. Transfer constants of both these mercaptans were determined as 1.60 and 1.16 for thioglycolic acid and the fluoronated thiol, respectively.