Alberto Fontana

Radical additions to 1,2-dichlorodifluoroethene

Abstract Fluorine containing alcohols, esters and ethers have been obtained by peroxide induced radical addition of alcohols, esters and ethers to 1,2-dichlorodifluoroethene. The influence of the kind and amount of the peroxide has been studied and the reactivity of alcohols, esters and ethers compared.

Radical reactions of 1,1-difluoroethene

Radical reactions of 1,1-difluoroethene (VDF) in the presence of halogenated telogens RX have been widely investigated in the literature; they give products of general formula R(CH2CF2)nX where n ranges mainly from 2 to 8 [1]. The present work is concerned with the study of peroxide induced telomerization of vinylidene difluoride in the presence of bromofluoroethanes as CF3CF2 Br, CF3CFBr2 and CF2BrCF2Br. Reactions were carried out at 150°C in the presence of di-tert-butylperoxide (0.5–40 mol % based on VDF) with telogen/VDF molar ratios ranging from 1/20 to 5/1. Liquid, waxy and solid telomers are obtained with n < 30. The different behaviour of the telogens is also reported and discussed. For instance in the same reaction conditions CF3CF2Br gives n values higher than CF2BrCF2Br. The structure of the telomers has been determined by 19F and 1H NMR spectroscopy. Glass transition temperatures of the telomers are reported and discussed.

Phase transfer catalysis in reactions of vinylidene fluoride-hexafluoropropene copolymers

Phase transfer catalysis (PTC) in dehydrofluorination of polyvinylidene fluoride (PVDF) has been recently investigated. Operating at 70–90°C on powder or film PVDF with aqueous NaOH 4–5 N and a PTC catalyst an amount of 9–100% of unsaturation was obtained [1] . No information was given about degradation of the polymer that likely seems to occur in these conditions. Aim of this work is a preliminary study on the PTC dehydrofluorination of vinylidene fluoride-hexafluoropropene copolymers in a wide range of composition (HFP from 0 to 40 mol %) and operating in milder conditions than above (T = 25–50°C, NaOH < 0.5 N, with a ratio meq base/g polymer ranging from 1 to 3). The level of unsaturation was detected by F− analysis in the aqueous phase on the assumption that the elimination of one HF affords one unsaturation in the polymer chain. The resulting structure has been studied by I.R. and N.M.R. spectra. Polymer degradation, indicated by the decrease of the intrinsic viscosity, seems to occur only by strong alkaline treatment. In our reaction conditions no change of the intrinsic viscosity is observed with unsaturation content up to 4%. The ability to give unsaturation has been related to the HFP content in the copolymer. The results show an increase of the rate of dehydrofluorination with increasing HF content.