Synthesis and characterization of biodegradable multiblock copolymers of L-lactide, -caprolactone and poly(ethylene glycol)

Two multiblock copolymers of polyethylene glycol (peg), l-lactide (lla) and-caprolactone (cl) were synthesized and characterized. triblock prepolymers were rstsynthesized using peg with molecular weight (mn) of 15,000 daltons, -caprolactone orl-lactide in the presence of sn(oct)2 as catalyst. the triblock pcl-b-peg-b-pcl prepolymerwith two hydroxyl functional groups was subjected to further block copolymerizationwith l-lactide in the presence of sn(oct)2 as catalyst. similarly, the triblock plla-b-pegb-plla prepolymer was subjected to further block copolymerization with -caprolactonein the presence of the same catalyst. the molecular structures of the copolymers werecharacterized by 1h nmr and 13c nmr analyses. the thermal behavior and thermalstability of these copolymers were evaluated by dsc and tga thermograms, respectively.finally, the eect of each discrete block on thermal behavior and stability was studied inthe typical pentablock copolymers.