Radical Terpolymerization of 1,1,2-Trifluoro-2-pentafluorosulfanylethylene and Pentafluorosulfanylethylene in the Presence of Vinylidene Fluoride and Hexafluoropropylene by Iodine Transfer Polymerization

Abstract

Iodine transfer terpolymerization of two monomers bearing an SF 5 group, i.e. 1,1,2-trifluoro-2-pentafluorosulfanylethylene (F 2 C=CFSF 5) and pentafluorosulfanylethylene (H 2 C=CHSF 5), with 1,1-difluoroethylene (or vinylidene fluoride, VDF) and hexafluoropropylene (HFP) is presented. These pentafluorosulfanyl monomers present a peculiar reactivity. They do not homopolymerize by conventional radical polymerization, but they co-and terpolymerize with the above fluorinated olefins. The resulting fluorinated terpolymers were characterized by 19 F and 1 H NMR spectroscopies which enabled the assessment of the molar percentages of the three comonomers. Size exclusion chromatography and NMR characterizations were also used to assess the molecular weights, M n , ranging between 260 and 8 400 g/mol. Interestingly, both these pentafluorosulfanyl monomers exhibit different behaviors in that radical terpolymerization in the presence of C 6 F 13 I as a degenerative chain transfer agent. Thus, CF 2 CFSF 5 can be terpolymerized with VDF and HFP with a good control of molecular weight leading fluoropolymers bearing SF 5 groups with low polydispersity index (PDI). Unexpectedly, only two iodide functionalities of the terpolymers namely two end-groups (-CH 2 CF 2 I and-CF 2 CH 2 I) were observed and their proportions were influenced by the number of VDF units. Indeed,-CH 2 CF 2 I functionality decreased when the number of VDFs per chain increased. In contrast to 1,1,2-trifluoro-2-pentafluorosulfanyl ethylene, H 2 C=CHSF 5 could not be terpolymerized by ITP but led to C 6 F 13-[(CH 2 CF 2)-(CH 2 CH(SF 5)] n-I alternating cooligomers of low molecular weight in poor yields (10-20%). The formation of by-product (C 6 F 13 CH=CHSF 5 monoadduct obtained by dehydrofluorination) was also observed, which corresponds to the elimination of HI from the 1:1 adduct. In the last part, the thermal properties were discussed. The presence of SF 5 group decreases the Tg of fluoropolymers whereas the thermal stabilities depended on the molecular weights.

Vinylidene fluoride telomers for piezoelectric devices

“…As a result, the reaction may display a pseudoliving behavior. [12][13][14][15][16] As in any radical-based process, termination occurs through the coupling of VDF macroradicals (step e), as reported by Timmerman and Greyson. 20 However, to preserve living or controlled behavior, termination must be negligible compared with chain transfer.…”

“…was not observed in the 19 F NMR spectrum (Figure 2, upper spectrum) of the telomer, indicating that the ÀCF 2 CF 2 I group of R F I underwent a high field shift to À112.0 p.p.m. Moreover, the characteristic signals of C 3 F 7 (or C 5 F 11 ) end groups [13][14][15][16]22 were observed in the spectra. Namely, the peaks centered at À82.0, À124.0, À126.0 (and À128.0 p.p.m.)…”

“…10,[13][14][15][16][21][22][23] The multiplet centered at À38 p.p.m. was indicative of -CH 2 CF 2 I end groups, 10,[13][14][15][16]22 and the signal at À108.0 p.p.m. was attributed to difluoromethylene in -CH 2 CF 2 ÀCF 2 CH 2 I, which arise from reverse addition followed by a chain transfer.…”

“…Iodine transfer polymerization 12 of VDF is a degenerative transfer process [13][14][15][16] that requires an alkyl iodide as the CTA. In this study, 1-iodoperfluoroalkane (perfluorobutyl or perfluorohexyl iodide) was used as the CTA.…”

“…The radical telomerization of VDF with various chain transfer agents (CTAs) has been recently summarized. 11 Moreover, studies on the iodide transfer polymerization 12 of VDF in the presence of perfluoroalkyl iodides (R F I) [13][14][15][16] revealed that controlled polymerization could be achieved when R F I (CTA) possessed a CF 2 I end group.…”