The present invention provides compositions that enable excellent hardness and UV resistance in coating applications, the compositions containing one or more acrylic-urethane block copolymer having as copolymerized units one or more acrylic monomer, which acrylic monomers are polymerized into a polyurethane backbone polymer. The compositions may be ambient curable. The invention also provides methods to obtain such acrylic-urethane block copolymers, which methods include the incorporation of an initiating species into the polyurethane backbone polymer, and subsequent polymerization of acrylic monomers in the presence of both the initiating species attached to the polyurethane polymer and a reducing agent.