Synthesis and copolymerization of vinylidene fluoride (VDF) with Trifluorovinyl Monomers, 11

Radical copolymerization of chlorotrifluoroethylene with 4‐bromo‐3,3,4,4‐tetrafluorobut‐1‐ene

“…) display also various signals in the 0.5 to 1.4 ppm range attributed to the end‐groups that arise from TBPPi initiator. Indeed, it has been previously reported that when heated at 74 °C, tert ‐butylperoxypivalate undergoes a homolytic scission that generates two radicals (Scheme ) . One is able to rearrange into a methyl radical and acetone while the other one may go through a decarboxylation to give rise to a tert ‐butyl radical …”

Radical Copolymerization of Vinylidene Fluoride with 8‐Bromo‐1H,1H,2H‐perfluorooct‐1‐ene: Microstructure, Crosslinking and Thermal Properties

“…[56] Nevertheless, according to Table 1, it can be clearly observed that BDFO is reactive enough to be incorporated in sufficient amounts into poly(VDF-co-BDFO) copolymers. In addition, three statements can be deduced from these first results: (1) the radical copolymerizations of both comonomers were successfully achieved (yield > 50%) for copolymerization when the molar ratio of BDFO in the feed was lower than 10%, as evidenced by the presence of the characteristic 19 F and 1 H NMR signals of the expected groups attributed to both monomers; (2) the fluorinated side chain kept its bromine end atom (-CF 2 -Br) in the course of the copolymerization; (3) comparing the integrals of the triplet of triplets located at À43.2 ppm (assigned to -CF 2 -CH 2 -CF 2 -Br [45] ) with that of the triplet centered at À64.9 ppm (attributed to the Rf-CF 2 -Br of BDFO), the percentage of transfer to the -R f -Br side chain of BDFO comonomer could be assessed using Equation (2). % of transfer to BDFO ¼ I À43:2 ðI À43:2 þ I À64:9 Þ Â 100 ¼ 3%…”

“…[33,42] This end group could result from the direct initiation of CH 3 8 onto the methylene side of VDF, and that radical may arise from the decomposition of the initiator: at 134 8C, DHBP undergoes a thermal decomposition by homolytic cleavage of the O-O bonds, generating t-BuO8 radicals which produce CH 3 8 radicals and acetone after rearrangement. [42][43][44][45] Interestingly, the quasi absence of the triplet of triplets located at 6.3 ppm ( 3 J HF ¼ 55.2 Hz and 3 J HH ¼ 4.4 Hz) confirmed that CH 2 CF 2 H end groups resulting from transfer reactions were negligible. Figure 2 represents the 19 F NMR spectrum of a poly(VDF-co-BDFO) copolymer from a feed content of VDF/BDFO with the molar ratio 90.8/9.2 (run #3 in Table 1).…”

“…The signal located at À43.2 ppm was attributed to -(CH 2 -CF 2 )-[CH 2 -CH(C 6 F 12 -CH 2 -CF 2 -Br)]-resulting from the insertion of VDF after cleavage of the C-Br bond of BDFO under radicals. [37,45] However, the amount of transfer was low (3%). As expected, the difluoromethylene side group adjacent to CH in the backbone led to an AB system, since both fluorine atoms are anisochronous (d 1 ¼ À116.5 and d 2 ¼ À120.0 ppm), with a slight overlap with the signals centered in the À117.1 to À123.1 ppm range (attributed to the characteristic difluoromethylene groups in the pendant chain of the BDFO units).…”

“…Nevertheless, this amount of transfer is low since the telomerization of VDF has already been reported with brominated transfer agents, [3,37,39,45] such as BrC 2 F 4 Br [37,39] or BrCF 2 CFClBr, [45] in good yields. The authors assessed the molecular weights of the telomers by 19 F NMR, size exclusion chromatography and elemental analysis and estimated them from about 3 000 g Á mol À1 .…”