ABSTRACT
This chapter shows the route to make high molecular mass poly lactic acids (PLAs) with exploitable mechanical properties is referred to as ring opening polymerization (ROP) of cyclic dimers of lactic acid named lactides. Many PLA stereocopolymers with other chiral unit distributions and chain ends can be obtained depending on the polymerization mechanism. The interest of these PLAs is primarily academic. The fact that unit distributions that depend on the monomer feed and on the mechanism of polymerization can be dramatically modified when PLA sterocopolymers are processed above 120°C because of transesterifaction reactions that cause unit interchanges. Combined with the general effects of molecular mass, molecular mass polydispersity, and chirality-related configurational structures, morphology is a factor that conditions PLA's properties. The degradability, the bioresorbability, and the biocompatibility of PLA-type polymers are proved by many applications in humans, including for the PLA98 stereocopolymer.
