This invention relates to block polymers containing both crystalline and elastomeric blocks, the block copolymer having an A block and a B block. The A block is a polyethylene or an ethylene polymer optionally containing an alpha-olefin and optionally a non-conjugated diene, and is generally crystalline. The B block is an ethylene, .alpha.-olefin copolymer. Also disclosed is a process for manufacture of the block copolymers and methods for coupling the block copolymers. Coupled block copolymers are useful as thermoplastic elastomers exhibiting physical properties approaching those of crosslinked EP or EPDM elastomers, but showing thermal processability after coupling. The block copolymers of the present invention may also be used as a lubricant or fuel additive, as a plastics blend component, and as a component in hot melt adhesives.