NOVELTY - Functionalizing a preformed aromatic polymer involves: providing the preformed aromatic polymer into a reactive medium; within that reactive medium providing a borylation reagent and a catalyst for C-H borylation; and catalytically borylating a C-H position on an aromatic ring on the preformed aromatic polymer with the borylating agent to form a borylated aromatic moiety on the preformed aromatic polymer with a boryl functionality.    USE - For forming incorporation of a functionality, particularly a boryl functionality selected from boronic acid, potassium trifluoroborate, haloborane or borane onto a preformed aromatic polymer selected from polysulfone or polystyrene (claimed). The functionalized polystyrene- and polysulfone-based materials are useful in applications including active filtration media in chromatographic systems, recoverable/recyclable polymer-metal catalyst systems, polymer supports, (either soluble or insoluble) in organic reactions, combinatorial chemistry, and drug discovery development, additives to polymer blends, membrane materials for fuel cells, biofuel production, water purification, water electrolysis, gas/liquid separation, ion transportation, ion conducting actuator, engineering plastics with robust mechanical strength and high thermal and chemical stability, and in precursor polymers for the creation of various functionalized aromatic polymers.    ADVANTAGE - The process avoids undesirable side reactions such as cross-linking and chain scission, which can alter the molecular weight and reduce the favorable properties of polysulfone. The process can be applied to any aromatic polymer system, either soluble or insoluble polymer, as long as the structural unit has at least some aromatic rings. The major advantage of this post-functionalization process is that various functional groups with specific concentrations can be incorporated into the aromatic ring of the polymer main chain under mild conditions without causing chain cleavage or cross-linking of polymer chains. Because various functional groups can be attached to aromatic polymer in a convenient way, the scope of materials that can be prepared by this method is enormously broad. Moreover, this process proceeds without negatively affecting polymer chain length and this highly efficient and mild post-functionalization method allows the convenient preparation of a new family of functionalized polysulfones, which can ultimately find broader applications as new high-performance engineering plastic materials.