Studies On The Preparation And Degradation Of Polylactide And Copolymers

It is well known that polylactide (PLA) is a kind of much better biocompatible and biodegradable polymer and is being increasingly used in medicine and organic fields. In this paper, many affecting factors during the synthesis of D, L-lactide (D, L-LA), PLA, the block copolymers of PLA-PEG-PLA and PLA-PVP copolymer were studied in detail. The degradation behaviours of polylactide and copolymers based on lactide were also investigated. The main conclusions can be drawn as follows:Firstly, D, L-lactide monomer was synthesized from lactic acid with the ZnO as catalyst; the polylactide, PLA-PEG-PLA and PLA-PVP were synthesized from D, L-lactide by bulk ring-opening polymerization with the stannous octoate as catalyst in vacuum. The results showed that the synthetic methods are simple and effective and the yield of LA was over 24%; the molecular weight of PLA was 6.3×104.Secondly, the studies on degradation behaviours of PLA and copolymers were carried out among four kinds of media. The results showed that PLA was degraded more rapidly in NaOH solution and PLA with lower molecular weight was degraded more rapidly than that with high molecular weight in the same medium. Finally, Compared with PLA, degradation speed of the copolymers was much fast. While the degradation speed of PLA-PEG-PLA with the same length of PEG block is decreased with increasing mole ratio of the lactide to PEG. Compared PLA-PEG-PLA with PLA-PVP,degradation rate of PLA-PVP was much higher.