PERFLUOROCYCLOBUTANE AROMATIC POLYETHERS - SYNTHESIS AND CHARACTERIZATION OF NEW SILOXANE-CONTAINING FLUOROPOLYMERS

The synthesis and characterization of siloxane-containing pefluorocycl obutane (PFCB) aromatic polyethers, a new class of fluorosiloxane poly mers possessing a well-defined linear structure of alternating disilox anyl-p-phenylene (cis/trans)-1,2-disubstituted perfluorocyclobutyl eth er linkages with known fluoroolefin end groups, is described. The unex pected formation of an aryl Grignard reagent from 4-[(trifluorovinyl)o xy]bromobenzene (2) allowed for the high-yield synthesis of 4- [(trifl uorovinyl)oxy] phenyldimethylsilane (3) which was dehydrogenatively hy drolyzed in situ and condensed to rovinyl)oxy]phenyl]]-1,1,3,3-tetrame thyldisiloxane monomer(4). Thermal cyclopolymerization in the bulk pro duces l-p-phenylene-1-oxaperfluorocyclobutylene-2-oxa-p- phenylene) (5 ) as a clear, flexible, and thermally stable elastomeric film. Copolym erization of 4 with a trifunctional PFCB monomer gives a toughened the rmoset with good thermal stability. Monomers and polymers were charact erized by H-1, C-13, and F-19 NMR and FTIR spectroscopy. Number-averag e molecular weights were determined by gel permeation chromatography a nd, when possible, quantitative F-19 NMR end group analysis. Synthesis , characterization, thermal analyses, and current scope of PFCB polyme r chemistry are discussed.