An Innovative Trifluoromethyl Radical from Persistent Radical as Efficient Initiator for the Radical Copolymerization of Vinylidene Fluoride with tert-butyl α-Trifluoromethacrylate
Résumé
A persistent perfluoroalkyl radical (PPFR), perfluoro-3-ethyl-2,4-dimethyl-3-pentyl, was shown to be a good source of *CF3 radicals able to initiate the radical copolymerization of vinylidene fluoride (VDF) with tert-butyl α-trifluoromethacrylate (MAF-TBE). Three copolymerizations of VDF with MAF-TBE were performed at 90 °C and at different concentrations of PPFR to examine the effect on molecular weights, end groups, degrees of polymerization, yields, chains defects and degradation temperatures of the resulting copolymers (Table 1). NMR characterizations of the resulting poly(VDF-co-MAF-TBE) copolymers showed that copolymerization was exclusively initiated by *CF3 radicals, as evidenced from the thermal decomposition of PPFR at T > 80 °C. The addition of *CF3 radical onto VDF/MAF-TBE system was regioselective leading to CF3-CH2-CF2* radical that further cross propogated onto MAF-TBE unit and the α,-trifluoromethyl groups acted as an efficient label to assess the molecular weights of the resulting copolymers by 19F NMR spectroscopy. Three [PPFR]0/([VDF]0+[MAF-TBE]0)initial molar ratios (0.5, 1.0 and 2.0 %) led to various molecular weights ranging from 10,000 to 20,000 g.mol-1. When that ratio decreased, both the molecular weights and the thermostability of these original poly(VDF-co-MAF-TBE) copolymers increase. reference P. Yogesh, T. Ono and B. Ameduri submitted to ACS Macro Letters (in press)