Abstract:Polylactic acid is a widely used biodegradable material, which, together with its copolymers, are now among the most important biomedical materials. There are two main methods for synthesizing homopolymer of lactic acid: the ring-opening polymerization and the direct polycondensation. The direct polycondensation method includes the direct melt polycondensation and the solution polycondensation. In accordance with the reaction mechanism, the ring-opening polymerization includes the anionic ring-opening polymerization, the cationic ring-opening polymerization and the ring-opening polymerization of coordination. In this paper, the polymerization mechanism and the research progress of different polymerization methods are discussed. The high cost in synthesizing lactic acid homopolymer, the low molecular weight of products and its hydrophobic, brittle performance have limited its applications. The current study of polylactic acid is mainly concentrated in the modification. The latest research progress on chemical and physical modifications are reviewed, such as copolymerization, cross-linking, surface modification, blends, fiber composites and so on. Synthesis and modification of polylactic acid are discussed. Synthesis conditions should be improved. Non-toxic or low-residue catalysts should be used.