Synthesis and characterization of biodegradable methoxypoly(ethylene glycol)-poly(ε-caprolactone-co-L-lactide) block copolymers

A series of methoxypoly(ethylene glycol) (MPEG)-poly(ε-caprolactone- co-L-lactide) (PCLA) diblock copolymers were synthesized by ring-opening polymerization of a mixture of c-caprolactone and L-lactide with different ratios in the presence of Sn(Oct)₂. The characterization of MPEG-PCLA diblock copolymers were examined by ¹H-NMR, GPC, DSC, and XRD. Kinetic study on ring-opening polymerization of monomer mixtures was carried out in various conditions such as a variation with polymerization time, amount of catalyst, and temperature. The highest conversion obtained in 1.2 ratio of initiator versus catalyst at 110 °C. The biodegradable characterization of MPEG-PCLA diblock copolymers in aqueous solution was carried out by using GPC for 1-14 weeks. The biodegradability of MPEG-PCLA diblock copolymers increased as the X-lactide content of diblock copolymers increased. In conclusion, we confirmed the dependence of polymerization rate according to various conditions. In addition, we can control the biodegradability of MPEG-PCLA diblock copolymers by changing the ratio of PCL and PLA block segment.