Ring-opening polymerization of L-lactide by a neodymium tetrahydroborate complex, Nd(BH4)(3)(THF)(3) (1, THF = tetrahydrofuran), afforded hydroxy-telechelic poly(L-lactide) (HO-PLLA-OH) in a good yield. Chain extension of the HO-PLLA-OH by hexamethylene diisocyanate (HMDI) successfully yielded poly(ester-urethane), whereas random chain extension of a mixture of HO-PLLA-OH and hydroxy-telechelic poly(e-caprolactone) afforded multiblock PLLA-co-PCL. The PCL-rich multiblock co-polymers with high molar mass exhibited high tensile modulus and extremely high elongation at break. (c) 2006 Elsevier Ltd. All rights reserved.