Synthesis of multiblock poly(l-lactide)-co-poly(ε-caprolactone) from hydroxy-telechelic prepolymers prepared by using neodymium tetrahydroborate

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(ε-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.