Bromomethyl poly (aryl ether ether ketone) has been prepared from methyl poly (aryl ether ether ketone) (MePEEK) and has been used as the precursor to many forms of functionalized PEEK. MePEEK was brominated directly with bromine. Bromination takes place exclusively at the methyl group. The reaction conditions for bromination have been studied. The bromination level can be controlled by the amount of bromine used, up to 90% of the methyl groups can be brominated to mono-bromo and di-bromo methyl PEEK. Modification reactions have been carried out on the brominated methyl PEEK. The bromomethyl group has been converted to different functional groups, such as - CH2OH, - CH2OCH3, -COOCH3, -CH2 ($) under bar CN, -CH2COOH, -CH2OCOCH3, -CH2N+H (CH2CH3Br-,-CH2N(CH2CH3)(2), -CH2N+(CH2CH3)(3) Br-.