The present invention is directed towards a polymerization process for the preparation of block copolymers. In an embodiment, the polymerization process may comprise low levels of catalyst in an oxidized state that react with a reducing agent to form an active catalyst. Embodiments of the process surprisingly use low levels of catalysts and allow formation of the all blocks with the same catalyst. The catalyst may be deactivated and reactivated to form each block. In one embodiment of the invention, the catalyst is oxidized to the deactivator state when the desired degree of polymerization of a polymer segment or block is reached. The first monomer may be removed prior to addition of the second monomer. The catalyst may then be reactivated for preparation of a second block. A further embodiment may include addition of second radically polymerizable monomer to provide efficient initiation of the macroinitiator to transition from polymerization of the first block or segment to polymerization of a second block or blocks.