Synthesis of novel fluorine-containing poly(aryl ether ketone)s

The high-performance fluorinated polymers have been receiving considerable attention as interesting advanced materials. The incorporation of fluorine atoms into polymer chains leads to polymers with increased solubility, flame resistance, thermal stability and glass transition temperature while also leading to decreased color crystallinity, dielectric constant and moisture absorption. 2,3,4,5,6-Pentafluorobenzoic acid (PFBA) is a valuable intermediate for pharmaceuticals, pesticides, perfumes, cosmetics and so on, and it is available as a commercial product. However, the polymers derived from PFBA have not been reported so far. In this paper, we report the synthesis and characterization of novel fluorinated poly(aryl ether ketone)s (PEKs) containing 2,3,5,6-tetrafluoro-1,4-phenylene moieties derived from PFBA. Novel fluorinated PEKs are prepared from PFBA by aromatic nucleophilic substitution reaction, of which M-n values range from 2.28 x 10(4) to 1.04 x 10(5). They have all para connected linear structures. The aromatic fluorine of the para position to the carbonyl groups of monomers is preferentially substituted by phenoxide and this para orientation is mainly attributed to the steric effect rather than pi -electron density. The obtained PEKs except 8F-PEKEK (BP) show excellent solubilities in common solvents and can be cast into tough transparent films. They also exhibit high glass transition temperatures depending on the structures and outstanding thermal stabilities. Furthermore, these fluorine-containing PEKs exhibit low dielectric constants from 2.87 to 3.52 at I MHz. Copyright (C) 2000 John Wiley & Sons, Ltd.