Controlled Radical Copolymerization of Vinylidene Fluoride and perfluoromethyl vinyl ether to obtain well-Architectutred Crosslinked High Performance Elastomers
Résumé
Two major strategies were applied to obtain poly(VDF-co-PMVE) copolymers based diols as precursors of bis(acrylate)s containing various spacer lengths between hydroxyl (or ester functions) and the poly(VDF-co-PMVE) oligomeric chain. The first approach involved quantitative ethylene end-capping of telechelic diiodo poly(VDF-co-PMVE) copolymer and subsequent hydrolysis to form diols with ethylene spacers (C2) between -OH moieties and the fluorinated oligomeric chain. The second pathway to obtain fluorinated diols involved the radical addition of telechelic poly(VDF-co-PMVE) copolymer onto allyl alcohol to obtain bis(iodohydrine), the iodine atoms of which were further reduced to yield fluorinated diols (85 % yield) that bear three methylene groups (C3) as the spacer. Acrylation of C2 diol was optimized from various acrylating agents and catalysts (75 % yields) and was monitored by IR spectroscopy. The acrylation of C3 diols was carried out using acryloyl chloride and taking into account the results from C2 optimization (85 % yields). UV curing of C2 and C3 telechelic bis(acrylate)s led to crosslinked films4, the gel contents, flexibilities (via the assessment of their glass transition temperatures that ranged between -53 and -30 °C) and thermal behavior (their 10 wt.% losses were ranging between 240 and 360 °C, under air) were investigated. The thermal properties of the resulting materials exhibit better thermal stability than those of the telechelic poly(VDF-co-PMVE) copolymers.