A copolymer having utility in coating compositions comprises the addition polymerization product of an alpha-olefin monocarboxylic acid having at least 8 carbon atoms (particularly undecylenic acid) and a mono- or di-ester of an unsaturated dicarboxylic acid or anhydride (e.g., dialkyl maleat). The copolymer may be provided with hydroxy functionality by reacting the carboxylic acid functionality with an epoxy compound to permit use in curable coatings. Alternatively the copolymer may be base neutralized to serve as a surfactant in aqueous dispersion polymerization.