A series of new polyisoprene-block-polylactide and polystyrene-block-polylactide diblock copolymers was prepared by combining the living anionic polymerization of isoprene or styrene, and the stereoselective ring-opening polymerization of rac-lactide. Aluminum and yttrium-based polystyrene or polyisoprene macroinitiators yielded isotactic-stereoblock and heterotactic-enriched polylactide segments, respectively. A strong influence of the microstructure of the polylactide block on the aggregation properties in solution and morphological behavior of the solid materials in thin films has been observed.