A variety of diblock copolymers containing a high density polyethylene block were synthesized directly by a transformation reaction from an anionic to a Ziegler-Natta type polymerization. A wide range of reaction parameters were investigated and optimized. Efficiencies of conversion of the anionic first block to diblock were as high as 33% (100% normalized), consistent with the known 3/1 Li-R/Ti relationship in the active catalyst species. The activity of the polymeric Li-R/Ti catalyst with regards to ethylene polymerization was as high as 40000 g of polymer per mole Ti. Molecular characterization of the resultant polymers is consistent with diblock copolymer structures, especially the characteristic microphase-separated structure exhibited in transmission electron micrographs. Detailed microscopic and X-ray analyses show distinct differences, however, between the morphological behaviour of these materials and the now well established morphological behaviour of amorphous-amorphous diblock copolymers. These differences are readily explained by consideration of the interactions between the competing thermodynamic processes of microphase separation and crystallization in these copolymers.