RAFT Polymerisation of Trifluoroethylene: The importance of understanding reverse additions

International audience; This article is the first report of the RAFT polymerisation of trifluoroethylene (TrFE). Trifluoroethylene is a rare but very important fluoromonomer, as it allows the preparation of materials endowed with unique electroactivity via copolymerisation with vinylidene fluoride (VDF) and other fluoromonomers. RAFT polymerisations carried out using O-ethyl-S-(1-methoxycarbonyl) ethyldithiocarbonate as a chain transfer agent and a thermal initiator were carefully examined. The polymerisation, its kinetics and the chain-end evolution were investigated by GPC, 1H{19F} and 19F{1H} NMR spectroscopy as well as MALDI-TOF mass spectrometry. Similar to the RAFT polymerisation of VDF, irreversible transfer reactions and reverse additions significantly affect the control of the polymerisation as well as the chain-end functionality. However, in contrast to VDF, unusual reverse propagation of TrFE, although limited to a few monomer units, was evidenced thanks to a combined NMR spectroscopy and DFT calculation approach. RAFT polymerisation afforded relatively well-defined PTrFE with a crystalline structure consistent with previous reports.