Novel copolymers of poly(ether ether ketone) containing ring trifluoromethyl groups have been synthesized by starting with trifluorobenzophenone monomers. Unlike poly(ether sulfone) analogues, it is possible to prepare copolymers which contain CF3 groups ortho to the ether bridges. The CF3 unit decreases the crystallinity of the polymer, with 50% and 100% copolymers being amorphous. This is accompanied by a rise in the glass transition temperature, although the thermal stability, mechanical properties and hydrophobicity of the polymer are largely unaffected.