Chromatographic separation of polylactides by stereochemical composition

Polylactides exist in different stereochemical compositions, as pure l-(PLLA), pure d-(PDLA), or mixtures containing the two enantiomeric forms in varying amounts. Polylactides of different stereochemical compositions differ in their solubility in THF. Based on the difference in solubility a gradient chromatographic method was developed allowing separation of polylactides differing in their stereochemical compositions (excess of enantiomers, e.e.). Moreover, blends composed of polylactides having different stereochemical purity could be separated into their individual components. However, for mixtures of PDLA with PLLA an additional peak was observed at higher elution volume. Since this peak cannot be attributed to any of the individual components, this peak might result from the formation of the stereocomplex described in literature.