Controlled Synthesis of Fluorinated Copolymers via Cobalt-Mediated Radical Copolymerization of Perfluorohexylethylene and Vinyl Acetate
Résumé
: Designing novel polyfluoropolymer architectures
is attractive for the development of new applications, such as
advanced coatings, purification membranes, or materials for
energy. Nevertheless, controlling the radical polymerization of
fluoroalkenes is very challenging due to the high reactivity of the
propagating fluorinated macroradicals. This study aims at
exploring the controlled copolymerization of perfluorohexylethylene
(PFHE) and vinyl acetate (VAc) in order to
prepare a range of well-defined statistical poly(PFHE-stat-VAc)
copolymers with different compositions. Cobalt-mediated radical
polymerization demonstrated to be active at 40 °C starting from
an alkylcobalt(III) initiator, and copolymers with a fluorinated monomer content as high as ca. 80 wt % were successfully
prepared. Reactivity ratios were determined to be rVAc = 0.18 and rPFHE = 0 at 40 °C and emphasized a clear tendency for
alternation. Unprecedented PFHE/VAc containing block copolymers were also prepared via a single-step approach or through
sequential copolymerizations. Finally, hydrolysis of the pendant ester groups of these copolymers led to the corresponding
fluorinated copolymers bearing vinyl alcohol (VOH). A preliminary solution behavior study, carried out by dynamic light
scattering and transmission electron microscopy on block copolymers composed of PFHE and VAc or VOH units, evidenced a
marked amphiphilicity of the copolymer composed of an extremely hydrophobic PFHE block associated with a highly
hydrophilic PVOH segment.