Telechelic Diiodopoly(VDF-co-PMVE) Copolymers by Iodine Transfer Copolymerization of Vinylidene Fluoride (VDF) with Perfluoromethyl Vinyl Ether (PMVE)

Abstract

The synthesis and the characterization of fluoroelastomers, based on vinylidene fluoride (VDF) and perfluoromethyl vinyl ether (PMVE), poly(VDF-co-PMVE) copolymers, by iodine transfer copolymerization are presented. These statistic poly(VDF-co-PMVE) copolymers were prepared in the presence of a perfluoromonoiodo functional chain transfer agent (CTA), C6F13I, or telechelic diiodoperfluoroalkane CTAs, IC6F12I and IC4F8I, using an emulsion process without any surfactant. Quasi-optimal conditions were found to lead to poly(VDF-co-PMVE) copolymers in satisfactory yields. The copolymer compositions, the molecular weights, and end-groups of these random-type copolymers were assessed by means of 19F NMR spectroscopy. Model molecules containing only one PMVE unit were synthesized by the radical addition of different CTAs (ICl, ICF2I, CF3I) onto PMVE to help in the assignments by 19F NMR spectroscopy of the characteristic signals of the end-group, i.e., −CF2CF(OCF3)I and −CF(OCF3)CF2I. Indeed, only −CH2CF2−I (major amount) and −CF2CH2−I end-groups of these poly(VDF-co-PMVE) copolymers were noted, showing the high reactivity of PMVE−I in the iodine transfer polymerization of VDF. The CTA concentration enabled one to control the molecular weights of the resulting telechelic diiodopoly(VDF-co-PMVE) copolymers ranging from 1000 to 18 000 g mol−1 (assessed by 19F NMR), produced for the first time. It was also noted that the higher the molar masses, the higher the amount of −CF2CH2−I end-group. The controlled behavior of that polymerization was also evidenced by the absence of the reversed −CH2CF2−CF2CH2− VDF dyads, narrow polydispersity indices (<1.75), and the linear “molar mass versus monomer conversions” relationship. Finally, the thermal properties, i.e., the glass transition temperatures (T g) and degradation temperatures, of these copolymers were assessed and were found to depend on the molecular weights and on the monomer composition of the copolymers. These fluoroelastomers had T gs ranging from −63 to −35 °C according to their molecular weights and the contents of both comonomers, with decomposition temperatures greater than 250 °C under air.

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.…”