Recent Advances in PLA Stereocomplexes: Synthesis, Modification, and Applications

Stereocomplexes derived from natural polylactides are an important class of renewable plastics. Although neat polylactides generally exhibit low elongation at break and low Young's modulus, stereocomplex formation significantly enhances their thermal resistance and stiffness (rather than toughness), dimensional stability, and controlled degradability, compared with simple polylactides. Consequently there has been significant research efforts to discover improved uses of these stereocomplexes-formed when the two enantiomers are combined-reported in many previous reviews. Here, we discuss improvements in them reported in the last five years, including a wide range of applications from simple packaging to biomedical aids, which make use of polylactide biodegradability, and self-assembing micelles, with quite complex structures, that are used for drug delivery and agricultural uses. We also noted that many general claims for degradability in PLA based polymers need to be qualified: the polymers will degrade, but very slowly in normal, low humidity conditions. However, degradation may be accelerated by heat, moisture, and enzymes-and also by fabricating with functional groups.