Surface-Compartmentalized Micelles by Stereocomplex-Driven Self-Assembly

• Applicant: Dr. Holger Schmalz
• Subject Area: Polymer Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 498593608

The unique corona structure of surface-compartmentalized polymeric micelles (patchy or Janus-type micelles) makes these materials highly interesting for a number of applications, like as efficient particulate surfactants/compatibilizers or as supports for catalytically active nanoparticles. In contrast to spherical patchy or Janus micelles, surface-compartmentalized micelles with an anisotropic shape (cylindrical (1D), disc- or platelet-like (2D)) have been considerably less studied owing to the fact that they are more difficult to realize via self-assembly of amorphous block copolymers. Besides, crystallization-driven self-assembly of block copolymers bearing a crystallizable block is one of the few methods to prepare patchy micelles, yet limited to polyethylene or poly(ferrocenyl dimethylsilane) as crystallizable blocks and to cylindrical micelles. Consequently, there is a substantial need for new concepts to realize shape anisotropic surface-compartmentalized micelles to harness their unique properties, like for example superior interfacial activity of 1D patchy and Janus micelles compared to their spherical analogues.Thus, the aim of this project is to develop an efficient method for the production of shape anisotropic (1D and 2D) patchy as well as Janus micelles and to study their interfacial activity and applicability as nanoparticle templates. Our approach is based on stereocomplex-driven self-assembly (SCDSA) of diblock copolymer mixtures bearing enantiomeric poly(L-lactide) and poly(D-lactide) blocks, as well as highly incompatible amorphous blocks. Shape anisotropic patchy micelles will be realized by SCDSA of racemic mixtures of diblock copolymers directly in solution, whereas for the production of Janus micelles films with lamella-cylinder (lc) and lamella-lamella (ll) morphologies will be cast from solution first. Subsequently, the bulk morphologies can be dissolved yielding the respective cylindrical (lc) or platelet-like (ll) Janus micelles. For both routes the formation of semicrystalline and thus insoluble polylactide stereocomplexes is the driving force for self-assembly into defined crystalline-core micelles or bulk morphologies. The incompatibility of the employed amorphous blocks (e.g. poly(tert-butyl methacrylate) (PtBMA)/polystyrene, PtBMA/poly(2-vinylpyridine)), will assure microphase separation for moderate degrees of polymerization resulting in patch-like (solution approach) or Janus (bulk approach) micelles. This modular approach will open access to shape anisotropic surface-compartmentalized micelles with tailored corona properties (e.g. amphiphilicity, anchor groups for nanoparticles) with potential applications as highly active surfactants or as nanoparticle supports in heterogeneous catalysis.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Matthias Karg