As a kind of important biodegradable material

polylactic acid (PLA ) has been extensively applied in many fields such as biomedicine

fiber

and plastics.In order to improve the properties of PLA

more and more researches on the modification of PLA via the direct copolymerization without lactide intermediate

especially the direct melt copolymerization method for its simpler operation

lower economical cost and better practical result have been reported.Classified as different functional group compounds used in the direct copolycondensation

and combining with the author group’s work on the direct melt copolycondensation of LA

the recent new progress on the direct copolycondensation of LA

especially the direct modification of PLA by small organic molecules with different functional groups

organic macromolecules and inorganic materials is reviewed.In the future

in order to obtain PLA copolymer with desirable and controllable molecular weight

properties and structure

it is a key to make the reaction mechanism of the direct melt polycondensation of LA clear in the research on the direct synthesis of PLA copolymer.