Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s

The dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioketalization, dithioketal-ketal exchange, ketal hydrolysis, and redithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.