Perfluorocyclobutane Aromatic Polyethers. Synthesis and Characterization of New Siloxane-Containing Fluoropolymers†

The synthesis and characterization of siloxane-containing perfluorocyclobutane (PFCB) aromatic polyethers, a new class of fluorosiloxane polymers possessing a well-defined linear structure of alternating disiloxanyl-p-phenylene (cis/trans)-1,2-disubstituted perfluorocyclobutyl ether linkages with known fluoroolefin end groups, is described. The unexpected formation of an aryl Grignard reagent from 4-[(trifluorovinyl)oxy]bromobenzene (2) allowed for the high-yield synthesis of 4-[(trifluorovinyl)oxy]phenyldimethylsilane (3) which was dehydrogenatively hydrolyzed in situ and condensed to bis[1,3-[4-[(trifluorovinyl)oxy]phenyl]]-1,1,3,3-tetramethyldisiloxane monomer (4). Thermal cyclopolymerization in the bulk produces poly(1,1,3,3-tetramethyldisiloxanyl-p-phenylene-1-oxaperfluorocyclobutylene-2-oxa-p-phenylene) (5) as a clear, flexible, and thermally stable elastomeric film. Copolymerization of 4 with a trifunctional PFCB monomer gives a toughened thermoset with good thermal stability. Monomers and polymers...