Methylated and pegylated PLA-PCL-PLA block copolymers via the chemical modification of Di-hydroxy PCL combined with the ring opening polymerization of lactide

Methylated and pegylated poly(lactide)-block-poly(epsilon-caprolactone)-block-poly(lactide) copolymers, PLA-P(CL-co-CLCH3)-PLA and PLA-P(CL-co-CLPEG)PLA, were prepared in three steps: combining the formation of carbanion-bearing dihydroxylated-PCL, the coupling of iodomethane or bromoacetylated alpha-hydroxyl-omega-methoxy-poly(ethylene glycol) onto the carbanionic PCL, and finally the ring opening polymerization Of DL-lactide initiated by the preformed grafted diOH-PCL copolymers. The resulting block copolymers exhibited lower crystallinity, melting temperature, and hydrophobicity with respect to the original PCL. Degradation of the grafted copolymers was investigated in the presence of Pseudomonas cepacia lipase and compared with that of the triblock copolymer precursor. It is shown that the presence of the grafted substituents affected the enzymatic degradation of PCL segments. (c) 2005 Wiley Periodicals, Inc.