Synthesis and Characterisation of Poly[oligo(ε-caprolactone)L-malate-graft-poly(L-lactide)]

Graft copolyesters with a PCL backbone and PLLA side chains were successfully prepared in three steps avoiding transesterification. First epsilon-caprolactone was polymerised with 1,6-hexane diol as initiator to obtain hydroxytelechelic oligo(epsilon-caprolactone)s. These diols were then subjected in the second step to polycondensation with L-malic acid yielding in linear poly[oligo(epsilon-caprolactone)L-malate] having secondary hydroxyl functions in the side chain. For both reactions scandium triflate Sc(OTf)(3) was used as a catalyst. In the third step various amounts of L-lactide were grafted from the polymer backbone using Zn(oct)(2) as catalyst. The successful reaction was confirmed by NMR and SEC (size exclusion chromatography) analysis. Further the thermal properties of the graft copolymers with different graft lengths were determined via differential scanning calorimetry.