Disclosed are uses of polyaniline homopolymer or copolymer prepared by preparing a solution of a polyaniline precursor having at least one aromatic 5 amine group and at least one carboxylic acid group (eg. 2-aminobenzoic acid, 3-aminobenzoic acid or 4-aminobenzoic acid) in a solvent selected from aqueous methanesulfonic acid or aqueous ammonia and optionally one or more additional polyaniline precursors (such as aniline) and oxidatively polymerising the polyaniline precursor or precursors, as an antimicrobial and/or free radical scavenger
