Patchy stereocomplex micelles as efficient compatibilizers for polymer blends

Surface-compartmentalized polymer micelles (Janus and patchy micelles) have gained increasing attention as their unique properties open the way for various applications. While Janus micelles have been extensively studied, e.g. as compatibilizers in polymer blends, there are hardly any reports on the use of patchy micelles. In this study, we show that spherical micelles with a polylactide stereocomplex (SC) core and a patch-like microphase separated polystyrene/poly(tert-butyl methacrylate) (PS/PtBMA) corona are efficient compatibilizers for highly immiscible PS/PtBMA blends. The patchy SC micelles, prepared by stereocomplex-driven self-assembly (SCDSA) of enantiomeric diblock copolymers, improved the homogeneity of the blends and led to a significant reduction of the PS droplet size. We further employed SCDSA to selectively incorporate a fluorescent dye inside the SC micelle core without changing the shape or chemistry of the patchy corona. This allows the use of confocal scanning fluorescence microscopy to localize the patchy SC micelles, being predominantly assembled at the PS/PtBMA blend interface. Interestingly, the reduction in PS droplet size was comparable for blends compatibilized with patchy SC micelles and Janus micelles, but only for patchy SC micelles a monomodal droplet size distribution could be achieved. The outstanding interfacial activity of the patchy SC micelles can be attributed to their adaptive corona structure, resulting in a selective swelling/collapse of the respective miscible/immiscible corona patches at the blend interface. Patchy spherical micelles prepared via stereocomplex-driven self-assembly are applied as efficient compatibilizers for highly immiscible polystyrene/poly(tert-butyl methacrylate) blends.