Self-assembly of chiral block and gradient copolymers

Chiral micelles have a high potential for targeted drug delivery or chiral separation applications. In this contribution the self-assembly of chiral amphiphilic copolymers into chiral structures was investigated. Gradient copolymers could be obtained by statistically copolymerizing the hydrophilic 2-ethyl-2-oxazoline (EtOx) with the hydrophobic chiral R-2-butyl-4-ethyl-2-oxazoline (R-BuEtOx) or racemic RS-BuEtOx monomers. Self-assembly of the gradient enantiopure copolymers was studied by both cryogenic transmission electron spectroscopy (cryo-TEM) and dynamic light scattering (DLS) revealing the formation of spherical micelles in aqueous solution. Additionally, amphiphilic block copolymers were synthesized in a 1-pot-2-step manner. The type of self-assembled structure could be controlled by varying the hydrophobic to hydrophilic ratio within the block copolymer from spherical and cylindrical micelles to sheets and vesicles. When the enantiopure block was replaced by the corresponding racemic block, only spherical micelles could be observed, while the chiral block copolymers with similar hydrophobic content revealed cylindrical micelles.