Dr. Gerald Guerin
University of Toronto, Ontario
Block copolymers self-assemble in a selective solvent (i.e., good for one block and poor for the second block) to form micellar structures. The morphology of these micelles strongly depends on the block ratio of the copolymer. When the two blocks are amorphous, the main structure obtained are spheres with an insoluble core and a solvent swollen corona. However, if the core forming block is semi-crystalline, its crystallization highly influences the morphology of the micelles formed. For example, poly(ferrocenylsilane-b-isoprene) (PFS-b-PI) block copolymer self-assembles in alkane solvents to form one-dimensional micelles.
Here, I will show how PFS based block copolymers self-assemble by a nucleated “living polymerization” mechanism. New macromolecules selectively condense on the ends of existing seeds, leading to the formation of structures of controlled size and morphology. Using electron microscopy and light scattering techniques, we can unravel important information about the fragmentation and dissolution of these fibrillar structures, allowing us to prepare even more sophisticated structures.
Transposition of crystallization-driven self-assembly to non PFS based copolymers remains, however, very difficult. In the last part of my talk, I will present an alternative approach to form nanostructures of control morphology and size that can be used for biomedical applications.