Enantioselective assembly of amphipathic chiral polymer and racemic chiral small molecules during preparation of micro-scale polymer vesicles.

Abstract

Enantioselective assembly is observed during preparation of vesicles from a solution mixture of an amphipathic block copolymer bearing pendent chiral L- or D-phenylalanine groups in hydrophobic segments and racemic chiral small molecules. Primary experimental results reveal that racemic chiral small molecules have been enantioselectively encapsulated into the hydrophobic shells of assembled vesicles with homochiral bilayer membrane structure, showing reverse CD signals compared with the original vesicles. A further study shows that the enantiomeric excess obtained through the enantioselective assembly is directly dependent on the molecular weight of the hydrophobic chiral chain segments, implying both the hydrophobic interaction and chirality are key points during the assembly of vesicles. Other factors, such as hydrogen-bonding interactions and π-π stacking interaction, are also found to be responsible for the enantioselective assembly phenomenon during the formation of the vesicles.