Synthesis And Properties Of Polylactide Block Copolymers Of Esters And Polyethylene Glycol

This paper reviews recent research work and application of polylactide and its copolymers, especially involoving polylactide-poly(ethylene glycol) block copolymers. Polylactide -poly(ethylene glycol) block copolymers are amphiphilic polymers and have good water-absorbability and degradability. These materials will be widely used in biomedical fields and tissue engineering. The OH-terminated PLA-PEG-PLA triblock copolymers was synthesized by the ring-opening polymerization of L-lactide(L-LA)and the poly(ethylene glycol) (PEG) with the low molecular weight (Mn=1000 or 2000), using the stannous octanoate as the catalyst. And then a series of PLA-PEG multiblock copolymers films with different mechanical property was synthesized by the chain extension of the PLA-PEG-PLA trimers, using hexamethylene diisocyanate (HDI). The optimum conditions in the reaction of chain extension were confirmed when the the PLA-PEG multiblock copolymers films had the best mechanical property. The crystallization structures and melting temperature was characterized by X-ray diffraction analysis and differential scanning calorimetry (DSC). Water absorption and degradation was tested. The results show that as PEG increasing, the crystallizibility and melting temperature was decreased. Meanwhile, mechanical property, water absorption and degradability of PLA-PEG multiblock copolymers was remarkablely changed with the content and molecular weight of poly(ethylene glycol).