The control of surface segregation of blend films using stereocomplex formation between enantiomeric polylactide chains

This study investigated the stereocomplex-induced surface structure of enantiomeric poly(lactide) (PLA) blend films by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The design of the blend systems was based on the principle of surface segregation of a modified component with a low surface energy, fluorine-end-capped PLLA (F-PLLA). Analysis of F-PLLA/PDLA and F-PLLA/PLLA blends, yielded a difference in the ion beam-induced behavior between fluorine and lactide groups. In addition, a completely phase-separated sample of PLLA with the fluorine end-capping agent cast onto the surface was used for a real analysis of peak intensities from the two components, simulating bulk compositions. The two blend systems, uncomplexed (F-PLLA/PLLA) and complexed (F-PLLA/PDLA) blends, showed quite different surface structures: namely, a higher fluorine concentration was observed in the uncomplexed blends while the complexed blends showed a wider range of fluorine concentrations, depending on the degree of complexation. This indicates that the complexed blends offer a greater level of control over the surface fluorine concentration because this concentration changes more significantly with the blend composition (or the degree of complexation).