Synthesis of poly[oligo(hexafluoropropylene oxide) perfluoroisopropenylether (PIPE)] graft copolymers with vinylidene fluoride (VDF) using CF3 radicals

Abstract

The synthesis of poly(vinylidene fluoride)-graft-oligomeric hexafluoropropylene oxide graft copolymers [poly[VDF-g-oligo(HFPO)-PIPE] is presented, where VDF, HFPO, and PIPE stand for vinylidene fluoride (CH₂CF₂), hexafluoropropylene oxide (CF₃CFCF₂O) and, perfluoroisopropenylether (–OC(CF₃)CF₂), respectively. First, an 82% isolated yield of oligo(HFPO)-PIPE macromonomer was achieved by using oligo(HFPO) primary iodide as the starting reagent. Then, the radical copolymerization of VDF with the PIPE comonomer, initiated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical (PPFR), was studied under various conditions. The PPFR initiator, stable at room temperature, was able to release a ˙CF₃ radical starting from 80 °C. The resulting poly[VDF-g-oligo(HFPO)-PIPE] graft copolymers were produced in good isolated yields (76 to 97%). The molar percentages and molar masses of such graft copolymers were assessed by ¹⁹F-NMR spectroscopy using the CF₃– end-group label. The molar percentages of VDF and oligo(HFPO)-PIPE comonomers reached up to 99% and 20%, respectively, while the molar masses ranged between 7500 and 42 600 g mol⁻¹. Their thermal properties showed: (i) fair to satisfactory thermostability (T^5%_d) showing up to 271 °C under nitrogen, (ii) glass transition (T_g) ranged from −81 to −82 °C while (iii) their melting temperature (T_m) ranged between 150 and 163 °C. Moreover, the synthesized copolymers were demonstrated to be highly omniphobic (i.e., simultaneously hydrophobic and oleophobic), showing a water contact angle of ca. 133°, a hexadecane contact angle ca. 70°, and a surface energy as low as 12 mN m⁻¹.