Homochiral “8″-shaped nanotoroids assembled from polypeptides

Figure eight-shaped ("8"-shaped) nanotoroids have been observed in DNA and proteins, however, they are rarely reported in synthetic polymer systems. Reported here is the formation of homochiral "8"-shaped nanotoroids from poly(γ-benzyl glutamate) (PBG) homopolymers. The L-type and D-type PBGs, i.e., PBLG and PBDG respectively, form right-handed and left-handed "8"-shaped chiral nanotoroids. The formation of the nanotoroids is achieved in a two-step route. Nanofibers are first self-assembled by the PBG homopolymers, which, with changing solvent nature, break into short nanofibers and twist into "8"-shaped nanotoroids. In such processes, the pendant phenyl groups of PBGs change from an extended to a contract form, which generates the internal stress driving the transition of nanofibers to "8"-shaped nanotoroids. This work not only enriches the topology and preparation method of nanotoroids, but also enhances our ability in controlling polymer nanostructures.