A curable ambient cure high-solids coating composition including (a) an epoxy resin; (b) an amphiphilic block copolymer containing at least one epoxy resin miscible block segment and at least one epoxy resin immiscible block segment; wherein the immiscible block segment comprises at least one polyether structure provided that the polyether structure of said immiscible block segment contains at least one or more alkylene oxide monomer units; such that when the epoxy resin composition is cured, the toughness of the resulting cured epoxy resin composition is increased; and (c) a sufficient amount of a nitrogen-containing curing agent to cure the coating composition at ambient temperature of less than about 60° C.