Novel polymers having high activity as cationic surface-active agents are prepared by the addition polymerization of ethylenically unsaturated aromatic sulfonium salts, e.g., ##STR1## When such polymers are heated and/or dried, they are irreversibly converted to inert, nonionic residues without the elimination of odorous by-products.The novel sulfonium salt polymers having relatively low molecular weight and low charge density are particularly useful as surfactants or emulsifiers in the emulsion polymerization of ethylenically unsaturated monomers such as styrene, butadiene, alkyl acrylates and the like. The polymers having high molecular weight and high charge density are useful as thickeners and flocculants.