The steric effect of bulky groups of the catalyst can kinetically suppress the transesterification reactions by screening linear polymer chains from the active center during the polymerization of epsilon-caprolactone (CL) with rare earth alkoxide. Therefore, isopropoxy rare earth diethyl acetoacetate ((EA)(2)LnOiPr Ln = Nd, Y) and Nd(OiPr)(3)-donor adducts (1,10-phenanthroline, 2,2’-bipyridyl, 18-crown-6 ether) are excellent catalysts for the living polymerization of epsilon-caprolactone, giving poly(epsilon-caprolactone) (PCL) with a narrow molecular weight distribution. Block copolymerizations of epsilon-caprolactone with trimethylene carbonate (TMC) and D,L-lactide (LA) have been attained successfully using (EA)(2)LnOiPr as catalyst. The characterizations by GPC, NMR, DSC, and polarizing microscope showed that the block copolymers, P(CL-b-TMC) and P(CL-b-D,L-lactide), have well-controlled sequences without random placement.