The self-assembly of amphiphilic block copolymers has been widely studied as an approach for engineering nano-objects. A variety of different features, including spherical micelles, cylindrical or worm-like micelles, toroids, and vesicles result from the self assembly of linear amphiphilic block copolymers by manipulating the ratio of dissimilar blocks, solvent quality, and coronal interactions. Aside from the possibilities enabled by chemical diversity, aggregate structure can also be manipulated through kinetic features of the assembly process. Unlike linear amphiphiles, the morphological determinants of solution assemblies from more complex macromolecular building blocks, such as graft copolymers, are far less explored. In terms of morphological diversity and control over the characteristic sizes of self-assembled objects, there exists a lack of work showing the equivalence between graft copolymers and their linear analogs.
Herein, we show the formation of a variety of self-assembled structures through manipulation of the amphiphilic character of a series of PLA/PEG-grafted molecular brushes, the morphological transitions of which were shown to parallel those of linear diblock amphiphiles. The combination of shear effects and a rapid and large change in solvent quality resulted in self-assembled structures distinct from those achieved under equilibrium conditions. More importantly, we report on the first known examples of toroid formation from the self-assembly of molecular brush amphiphiles and the molecular and process parameters involved in their formation, demonstrating how kinetic features of the assembly process can be used to direct the formation of unique morphologies from architecturally complex macromolecules.
Related
- Toroidal structures from brush amphiphiles (ChemComm DOI: 10.1039/c3cc46834h)