Study on synthesis of monomers of D, L-lactide and polylactide

The poly(D,L-lactide)(PLA) was synthesized from D,L-lactide(LA) by bulk ring-opening polymerization with the stannous octoate as the catalyst. The effect of temperature, quantity of ZnO on the yield of lactide, the relationship between the temperature of polymerization, catalyst content and the relative molecular weights of PLA were discussed in detail. The lactide and the polylactide were characterized by infrared spectroscopy(IR) and nuclear magnetic resonance(~1H-NMR). The degradation of PLA has been investigated in 0.01mol/L NaOH solution. The results showed that the synthetic methods of the LA and PLA are simple and effective and the yield of LA preponderated over 24% within 3 hours and the Mv of PLA which was polymerized within 5 hours under the normal pressure reached 6.3×10~4.