[L]-Lactide ([L]-LA)/ethylene oxide (EO) ring-opening copolymerizations were successfully carried out by using various catalysts including isobutylaluminoxane (IBAO), in situ AlR3 . 0.5H(2)O systems (R = ethyl, isobutyl) and Sn-Al bimetallic catalysts. Analysis of products by H-1 NMR showed that methanol insoluble copolymer fractions had multiblock structures. The multiblock segment length and molecular weight of the copolymers were regulated by a variation in the reaction temperature, reaction time, reaction medium, and the catalyst structure. An increase in the reaction temperature was used to obtain shorter segment block lengths. Bulk reactions at elevated temperatures gave shorter block lengths than those of corresponding polymerizations conducted in solution (xylene). Differential scanning calorimetry (DSC) results showed two melting transitions corresponding to poly(ethylene oxide) (PEG) and [L]-polylactide ([L]-PLA) crystalline phases. The melting temperature and enthalpy of fusion for the phase-separated [L]-PLA crystalline phase was "tailored" by modulating the copolymer composition and the [L]-PLA block length. Blends with PW were prepared by substituting poly(ethylene glycol) (PEG) with a high EO content [L]-PLA/EO multiblock copolymer. The idea explored was that the multiblock copolymers would be expected to leach into aqueous environments at a slower rate than PEGs. Substitution of the [L]-PLA/EO copolymer in place of PEG resulted in important increases in the film modulus and yield strength without loss in elongation at yield, break stress, and elongation at break. Thus, we demonstrated a versatile route to important new multiblock [L]-PLA/EO copolymers which have excellent potential to be useful for a wide range of biomedical applications including bioresorbable implant materials and tissue engineering. Furthermore, the synthetic methods developed herein provide routes which will be useful in "fine-tuning" product physicomechanical properties and degradation rates.