Linear polyetherketones containing both aromatic rings and icosahedral carborane (C2B10) cages in the main chain have been synthesized by superacid-promoted polycondensation between bis(4-phenoxyphenyl derivatives of ortho- or meta-carborane and aromatic or aliphatic dicarboxylic acids. Under strictly anhydrous conditions, polymers of high molecular weight (M-w > 150 000) are readily obtained. These new materials are amorphous and readily soluble in organic solvents, to give solutions from which strong, transparent films may be cast. Poly(aryletherketonecarborane)s are characterized by very high mass-retention (up to 93%) on thermolysis under nitrogen to 850 degrees C, and demonstrate extreme resistance to combustion, losing as little as 3% of their mass on pyrolyis at 850 degrees C in air. A new type of ionomer, based on the [-C2B9H10-](-) sub-unit, is obtained by deboronation of poly(aryletherketone-ortho-carborane)s under strongly basic conditions.